DNA - The building blocks of all life - lecture notes from a presentation by Jill Pullan to Mansfield U3A Science and Technical group. http://www.mansfield-u3a.org.uk/.

1. DNA
The building blocks of all life
It is a known fact that the Raison d'être for all living things is to pass on their
DNA. This is what drives the urge to pro-create.
The Discovery of the Molecular Structure of DNA -
The Double Helix

2. A Scientific Breakthrough
Although we have known about ‘genes’ for quite a long time, the amazing discovery by
James Watson and Francis Crick astounded the world
It will be approximately 70 years ago last February that James Watson and Francis Crick famously burst into
the pub next to their Cambridge laboratory to announce the discovery of the "secret of life".
The sentence "This structure has novel features which are of considerable biological interest" may be one of
science's most famous understatements. It appeared in April 1953 in the scientific paper where James
Watson and Francis Crick presented the structure of the DNA-helix, the molecule that carries genetic
information from one generation to the other.
Nine years later, in 1962, they shared the Nobel Prize in Physiology or Medicine with Maurice Wilkins, for
solving one of the most important of all biological riddles. Half a century later, important new implications
of this contribution to science are still coming to light.
Francis Crick and James Watson, 1953. Maurice Wilkins.
DNA compared to RNA
DNA is defined as a nucleic acid that contains the genetic instructions used in the development and
functioning of all known living organisms. RNA molecules are involved in protein synthesis and sometimes
in the transmission of genetic information.
However unlike DNA, RNA comes in a variety of shapes and types. While DNA looks like a double helix
and a twisted ladder, RNA may be of more than one type. RNA is usually single-stranded, while DNA is
usually double-stranded. In addition, RNA contains ribose (a sugar) while DNA contains deoxyribose,
(another sugar) which has one oxygen atom less. RNA has the bases Adenine (A), Uracil (U) (instead of
Thymine in DNA), Cytosine (C) and Guanine (G).
The helix geometry of DNA is of B Form. DNA can be damaged by exposure to Ultraviolet rays. The helix
geometry of RNA is of A-Form. RNA strands are continually made, broken down and reused. RNA,
however, is more resistant to damage by Ultra-violet rays.
Functions of RNA
The main job of RNA is to transfer the genetic code need for the creation of proteins from the nucleus to the
ribosome. This process prevents the DNA from having to leave the nucleus. This keeps the DNA and
genetic code protected from damage. Without RNA, proteins could never be made.

3. What is DNA?
The work of many scientists paved the way for the exploration of DNA. Way back in 1868, almost a century
before the Nobel Prize was awarded to Watson, Crick and Wilkins, a young Swiss physician named
Friedrich Miescher, isolated something no one had ever seen before from the nuclei of cells. He called the
compound "nuclein." This is today called nucleic acid, the "NA" in DNA (deoxyribo-nucleic-acid) and RNA
(ribo-nucleic-acid).
Two years earlier, the Czech monk Gregor Mendel, had finished a series of experiments with peas. His
observations turned out to be closely connected to the finding of nuclein. Mendel was able to show that
certain traits in the peas, such as their shape or colour, were inherited in different packages. These packages
are what we now call genes.
For a long time the connection between nucleic acid and genes was not known. But in 1944 the American
scientist Oswald Avery managed to transfer the ability to cause disease from one strain of bacteria to
another. But not only that: the previously harmless bacteria could also pass the trait along to the next
generation. What Avery had moved was nucleic acid. This proved that genes were made up of nucleic acid.
Solving the Puzzle
In the late 1940's, the members of the scientific community were aware that DNA was most likely the
molecule of life, even though many were sceptical since it was so "simple." They also knew that DNA
included different amounts of the four bases adenine, thymine, guanine and cytosine (usually abbreviated A,
T, G and C), but nobody had the slightest idea of what the molecule might look like.
In order to solve the elusive structure of DNA, a couple of distinct pieces of information needed to be put
together. One was that the phosphate backbone was on the outside with bases on the inside; another that the
molecule was a double helix. It was also important to figure out that the two strands run in opposite
directions and that the molecule had a specific base pairing.
As in the solving of other complex problems, the work of many people was needed to establish the full
picture.

4. DNA's code is written in only four 'letters', called A, C, T and G. The meaning of this code lies in the sequence of the
letters A, T, C and G in the same way that the meaning of a word lies in the sequence of alphabet letters. Your cells
read the DNA sequence to make chemicals that your body needs to survive. This is where the letters come from.
Deoxyribonucleic acid (DNA) is an informational molecule encoding the genetic instructions used in the
development and functioning of all known living organisms and many viruses. Along with RNA and
proteins, DNA is one of the three major macromolecules that are essential for all known forms of life.
Genetic information is encoded as a sequence of nucleotides (guanine, adenine, thymine, and cytosine)
recorded using the letters G, A, T, and C. Most DNA molecules are double-stranded helices, consisting of
two long polymers of simple units called nucleotides, molecules with backbones made of alternating sugars
(deoxyribose) and phosphate groups, with the nucleobases (G, A, T, C) attached to the sugars. DNA is well-
suited for biological information storage, since the DNA backbone is resistant to cleavage and the double-
stranded structure provides the molecule with a built-in duplicate of the encoded information.
These two strands run in opposite directions to each other and are therefore anti-parallel, one backbone
being 3' (three prime) and the other 5' (five prime). This refers to the direction the 3rd and 5th carbon on the
sugar molecule is facing. Attached to each sugar is one of four types of molecules called nucleobases
(informally, bases). It is the sequence of these four nucleobases along the backbone that encodes
information. This information is read using the genetic code, which specifies the sequence of the amino
acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA in a
process called transcription.
Within cells, DNA is organized into long structures called chromosomes. During cell division these
chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of
chromosomes. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA inside the
cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts. In contrast,
prokaryotes (bacteria and archaea) store their DNA only in the cytoplasm. Within the chromosomes,
chromatin proteins such as histones compact and organize DNA. These compact structures guide the
interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.
DNA is a long polymer made from repeating units called nucleotides. DNA was first identified and isolated
by Friedrich Miescher and the double helix structure of DNA was first discovered by James D. Watson and
Francis Crick. The structure of DNA of all species comprises two helical chains each coiled round the same
axis, and each with a pitch of 34 ångströms (3.4 nanometres) and a radius of 10 ångströms (1.0 nanometres)
According to another study, when measured in a particular solution, the DNA chain measured 22 to
26 ångströms wide (2.2 to 2.6 nanometres), and one nucleotide unit measured 3.3 Å (0.33 nm) long

5. Although each individual repeating unit is very small, DNA polymers can be very large molecules
containing millions of nucleotides. For instance, the largest human chromosome, chromosome number 1, is
approximately 220 million base pairs long. In living organisms DNA does not usually exist as a single
molecule, but instead as a pair of molecules that are held tightly together. These two long strands entwine
like vines, in the shape of a double helix. The nucleotide repeats contain both the segment of the backbone
of the molecule, which holds the chain together, and a nucleobase, which interacts with the other DNA
strand in the helix. A nucleobase linked to a sugar is called a nucleoside and a base linked to a sugar and one
or more phosphate groups is called a nucleotide. A polymer comprising multiple linked nucleotides (as in
DNA) is called a polynucleotide.
The backbone of the DNA strand is made from alternating phosphate and sugar residues.[10] The sugar in
DNA is 2-deoxyribose, which is a pentose (five-carbon) sugar. The sugars are joined together by phosphate
groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings.
These asymmetric bonds mean a strand of DNA has a direction. In a double helix the direction of the
nucleotides in one strand is opposite to their direction in the other strand: the strands are antiparallel. The
asymmetric ends of DNA strands are called the 5′ (five prime) and 3′ (three prime) ends, with the 5' end
having a terminal phosphate group and the 3' end a terminal hydroxyl group. One major difference between
DNA and RNA is the sugar, with the 2-deoxyribose in DNA being replaced by the alternative pentose sugar
ribose in RNA.
** 5’ - 5 prime end and 3’ - 3 prime end.
A section of DNA. The bases lie horizontally between the two spiralling strands.
The DNA double helix is stabilized primarily by two forces: hydrogen bonds between nucleotides and base-
stacking interactions among aromatic nucleobases. In the aqueous environment of the cell, the conjugated
π bonds of nucleotide bases align perpendicular to the axis of the DNA molecule, minimizing their
interaction with the solvation shell and therefore, the Gibbs free energy. The four bases found in DNA are
adenine (abbreviated A), cytosine (C), guanine (G) and thymine (T). These four bases are attached to the
sugar/phosphate to form the complete nucleotide, as shown for adenosine monophosphate.
A genome is an entire set of genes.
Here is a list of DNA ‘facts’
1. DNA stands for deoxyribonucleic acid.
2. DNA is part of our definition of a living organism.
3. DNA is found in all living things.
4. DNA was first isolated in 1869 by Friedrich Miescher.
5. James Watson and Francis Crick figured out the structure of DNA.
6. DNA is a double helix.
7. The structure of DNA can be likened to a twisted ladder.
8. The rungs of the ladder are made up of “bases”
9. Adenine (A) is a base.
10. Thymine (T) is a base.
11. Cytosine (C) is a base
12. Guanine (G) is a base.
13. A always pairs with T in DNA.
14. C also pairs with G in DNA.
15. The amount of A is equal to the amount of T, same for C and G.

6. 16. A+C = T+G
17. Hydrogen bonds hold the bases together.
18. The sides of the DNA ladder is made of sugars and phosphate atoms.
19. Bases attached to a sugar; this complex is called a nucleoside.
20. Sugar + phosphate + base = nucleotide.
21. The DNA ladder usually twists to the right.
22. There are many conformations of DNA: A-DNA, B-DNA, and Z-DNA are the only ones found in
nature.
23. Almost all the cells in our body have DNA with the exception of red blood cells.
24. DNA is the “blueprint” of life.
25. Chromosomal or nuclear DNA is DNA found in the nucleus of cells.
26. Humans have 46 chromosomes.
27. Autosomal DNA is part of chromosomal DNA but does not include the two sex chromsomes – X and
Y.
28. One chromosome can have as little as 50 million base pairs or as much as 250 million base pairs.
29. Mitochondrial DNA (mtDNA) is found in the mitochondria.
30. mtDNA is only passed from the mother to the child because only eggs have mitochondria, not sperm.
31. There’s a copy of our entire DNA sequence in every cell of our body with one exception.
32. Our entire DNA sequence is called a genome.
33. There’s an estimated 3 billion DNA bases in our genome.
34. One million bases (called a megabase and abbreviated Mb) of DNA sequence data is roughly
equivalent to 1 megabyte of computer data storage space.
35. Our entire DNA sequence would fill 200 1,000-page New York City telephone directories.
36. A complete 3 billion base genome would take 3 gigabytes of storage space.
37. If unwound and tied together, the strands of DNA in one cell would stretch almost six feet but would
be only 50 trillionths of an inch wide.
38. In humans, the DNA molecule in a non-sex cell would have a total length of 1.7 metres.
39. If you unwrap all the DNA you have in all your cells, you could reach the moon 6000 times!
40. Our sex cells–eggs and sperm–have only half of our total DNA.
41. Over 99% of our DNA sequence is the same as other humans’.
42. DNA can self-replicate using cellular machinery made of proteins.
43. Genes are made of DNA.
44. Genes are pieces of DNA passed from parent to offspring that contain hereditary information.
45. The average gene is 10,000 to 15,000 bases long.
46. The segment of DNA designated a gene is made up of exons and introns.
47. Exons have the code for making proteins.
48. Introns are intervening sequences sometimes called “junk DNA.”
49. Junk DNA’s function or lack thereof is a source of debate.
50. Part of “junk DNA” help to regulate the genomic activity.
51. There are an estimated 20,000 to 25,000 genes in our genome.
52. In 2000, a rough draft of the human genome (complete DNA sequence) was completed.
53. In 2003, the final draft of the human genome was completed.
54. The human genome sequence generated by the private genomics company Celera was based on DNA
samples collected from five donors who identified themselves only by race and sex.
55. If all the DNA in your body was put end to end, it would reach to the sun and back over 600 times
(100 trillion times six feet divided by 92 million miles).
56. It would take a person typing 60 words per minute, eight hours a day, around 50 years to type the
human genome.
57. If all three billion letters in the human genome were stacked one millimetre apart, they would reach a
height 7,000 times the height of the Empire State Building.
58. DNA is translated via cellular mechanisms into proteins.
59. DNA in sets of 3 bases, called a codon, code for amino acids, the building blocks of protein.
60. Changes in the DNA sequence are called mutations.
61. Many thing can cause mutations, including UV irradiation from the sun, chemicals like drugs, etc.
62. Mutations can be changes in just one DNA base.

7. 63. Mutations can involve more than one DNA base.
64. Mutations can involve entire segments of chromosomes.
65. Single nucleotide polymorphisms (SNPs) are single base changes in DNA.
66. Short tandem repeats (STRs) are short sequences of DNA repeated consecutively.
67. Some parts of the DNA sequence do not make proteins.
68. Genes make up only about 2-3% of our genome.
69. DNA is affected by the environment; environmental factors can turn genes on and off.
70. There are many ways you can analyse your DNA using commercially available tests.
71. Paternity tests compare segments of DNA between the potential father and child.
72. There are other types of relationship testing that compares DNA between siblings, grandparents and
grandchild, etc.
73. DNA tests can help you understand your risk of disease.
74. A DNA mutation or variation may be associated with a higher risk of a number of diseases, including
breast cancer.
75. DNA tests can help you understand your family history aka genetic genealogy.
76. DNA tests can help you understand your ethnic make-up.
77. DNA can be extracted from many different types of samples: blood, cheek cells, urine.
78. DNA can be stored either as cells on a cotton swab, buccal brush, or frozen blood or in extracted
form.
79. In forensics, DNA analysis usually looks at 13 specific DNA markers (segments of DNA).
80. The odds that two individuals will have the same 13-loci DNA profile is about one in one billion.
81. A DNA fingerprint is a set of DNA markers that is unique for each individual except identical twins.
82. Identical twins share 100% of their genes.
83. Siblings share 50% of their genes.
84. A parent and child share 50% of their genes.
85. You can extract DNA at home from fruit and even your own cheek cells.
86. DNA is used to determine the pedigree for livestock or pets.
87. DNA is used in wildlife forensics to identify endangered species and people who hunt them
(poachers).
88. DNA is used in identify victims of accidents or crime.
89. DNA is used to exonerate innocent people who’ve been wrongly convicted.
90. Many countries, including the US and UK, maintain a DNA database of convicted criminals.
91. The CODIS databank (Combined DNA Index System) is maintained by the BI and has DNA profiles
of convicted criminals.
92. Polymerase chain reaction (PCR) is used to amplify a sample of DNA so that there are more copies
to analyse.
93. We eat DNA every day.
94. DNA testing is used to authenticate food like caviar and fine wine.
95. DNA is used to determine the purity of crops.
96. Genetically modified crops have DNA from another organism inserted to give the crops properties
like pest resistance.
97. Dolly the cloned sheep had the same nuclear DNA as its donor mother but its mitochondrial DNA
came from the egg mother. (Does that make any sense?)
98. Genes do not blend
99. Some genes are dominant
100. We share around 96- 98% of our DNA with the great apes
101. We share around 50% of our DNA with a banana; We share around 36% of DNA with a fruit fly;
7% with bacteria; 15% with mustard grass; 21% with the roundworm; 85% with a Zebra-fish.
102. The DNA taken from the right, upper arm bone of the Neanderthal specimen had 27 differences from
modern humans, compared to 55 differences between modern humans and chimpanzees. The Neanderthal
DNA differed just as much from modern humans from Africa and Asia as it did from modern humans from
Europe. If Neanderthals were in fact ancestors of modern humans it would figure that they would share
more genetic material with Europeans than groups from other parts of the world, but this is not case.
Mitochondrial DNA studies suggest that Neanderthals and modern humans had a common ancestor 100,000
to 500,000 years but never mixed.

8. 103. A genome is an entire set of genes.
Plummers is the most thoroughly studied island in North America. And, thanks to Kress and his colleagues,
it is the first site in the world to have all 250 of its plant species barcoded.
DNA barcoding, the brainchild of Canadian geneticist Paul Hebert, is modelled after the Universal Product
Code (UPC) found on consumer packaging. Each UPC has a number designating the manufacturer (say, a
soft drink company) and a specific product identifier (diet, caffeine-free, etc.). Hebert found a segment of
animal DNA common to all species (the manufacturing code) and varied enough to distinguish among
animal species (the product identifier). But researchers have had a harder time finding a standardized DNA
segment for plant life.

9. Starting five years ago, Kress' research team collected samples of every plant species on Plummers Island.
Then, in a botany lab, Erickson and others determined each one's DNA sequence. From there, they homed in
on three genetic zones—two genes and an "intergenic spacer" between genes—that collectively could
distinguish the plants. Along with other botanists, Kress and Erickson are in the midst of a formal process to
get the markers approved as the standard plant barcode. Kress is hoping for official acceptance within a year
from the Consortium for the Barcode of Life, a project established in 2004 to compile a reference library of
codes.
Until recently, taxonomists needed a plant's flowers or fruits to classify it, meaning they had to collect
samples at specific times of the year. But with DNA barcoding, they can use any part of the plant—seeds,
bark, roots or leaves—to identify it.
"But the biggest benefit is that you won't have to be an expert," says Kress. In the not-so-distant future, even
schoolchildren will be able to identify plants with hand-held DNA sequencers. They could then upload the
barcodes via smartphones to an online encyclopaedia with basics about the species, botanical art and
anecdotal information. The Food and Drug Administration could use barcoding to test herbal supplements;
U.S. Customs and Border Protection could use it to identify suspicious imports.
Erickson has also found plant DNA in the ground-up guts of ten different orders of insects from Plummers
Island. He wants to better understand which insects are specialists, meaning they eat certain plant species,
and which are generalists, which eat just about anything.
The genetic code had to be a "language" — using the DNA alphabet of A, T, C, and G — that produced
enough DNA "words" to specify each of the 20 known amino acids. Simple math showed that only 16 words
are possible from a two-letter combination, but a three-letter code produces 64 words. Operating on the
principle that the simplest solution is often correct, researchers assumed a three-letter code called a codon.
Research teams at University of British Columbia and the National Institutes of Health laboriously
synthesized different RNA molecules, each a long strand composed of a single repeated codon (A sequence of
three nucleotides which together form a unit of genetic code in a DNA or RNA molecule) . Then, each type of
synthetic RNA was added to a cell-free translation system containing ribosomes, transfer RNAs, and amino
acids. As predicted, each type of synthetic RNA produced a polypeptide chain composed of repeated units of
a single amino acid. Several codons are "stop" signals and many amino acids are specified by several
different codons, accounting for all 64 three-letter combinations.
The famous "molecule of life", which carries our genetic code, is more familiar to us as a double helix.
But researchers tell the journal Nature Chemistry that the "quadruple helix" is also present in our cells, and
in ways that might possibly relate to cancer.
They suggest that control of the structures could provide novel ways to fight the disease.
"The existence of these structures may be loaded when the cell has a certain genotype or a certain
dysfunctional state," said Prof Shankar Balasubramanian from Cambridge's department of chemistry.
"We need to prove that; but if that is the case, targeting them with synthetic molecules could be an
interesting way of selectively targeting those cells that have this dysfunction," he told BBC News.
Tag and track
It will be exactly 60 years ago in February that James Watson and Francis Crick famously burst into the pub
next to their Cambridge laboratory to announce the discovery of the "secret of life".
What they had actually done was describe the way in which two long chemical chains wound up around
each other to encode the information cells need to build and maintain our bodies.

10. Today, the pair's modern counterparts in the university city continue to work on DNA's complexities.
Balasubramanian's group has been pursuing a four-stranded version of the molecule that scientists have
produced in the test tube now for a number of years.
It is called the G-quadruplex. The "G" refers to guanine, one of the four chemical groups, or "bases", that
hold DNA together and which encode our genetic information (the others being adenine, cytosine, and
thymine).
The G-quadruplex seems to form in DNA where guanine exists in substantial quantities.
And although ciliates, relatively simple microscopic organisms, have displayed evidence for the incidence of
such DNA, the new research is said to be the first to firmly pinpoint the quadruple helix in human cells
'Funny target'
The team, led by Giulia Biffi, a researcher in Balasubramaninan's lab, produced antibody proteins that were
designed specifically to track down and bind to regions of human DNA that were rich in the quadruplex
structure. The antibodies were tagged with a fluorescence marker so that the time and place of the structures'
emergence in the cell cycle could be noted and imaged.
This revealed the four-stranded DNA arose most frequently during the so-called "s-phase" when a cell
copies its DNA just prior to dividing.
Prof Balasubramaninan said that was of key interest in the study of cancers, which were usually driven by
genes, or oncogenes, that had mutated to increase DNA replication.
If the G-quadruplex could be implicated in the development of some cancers, it might be possible, he said,
to make synthetic molecules that contained the structure and blocked the runaway cell proliferation at the
root of tumours.
"We've come a long way in 10 years, from simple ideas to really seeing some substance in the existence and
tractability of targeting these funny structures," he told the BBC.
"I'm hoping now that the pharmaceutical companies will bring this on to their radar and we can perhaps take
a more serious look at whether quadruplexes are indeed therapeutically viable targets."
****Guanine /ˈɡwɑːnɨn/ (G, Gua) is one of the four main nucleobases found in the nucleic acids DNA and
RNA, the others being adenine, cytosine, and thymine (uracil in RNA). In DNA, guanine is paired with
cytosine. With the formula C5H5N5O, guanine is a derivative of purine, consisting of a fused pyrimidine-
imidazole ring system with conjugated double bonds. Being unsaturated, the bicyclic molecule is planar.
The guanine nucleoside is called guanosine.
Adenine is a nucleobase with a variety of roles in biochemistry including cellular respiration, in the form of
both the energy-rich adenosine triphosphate and the cofactors nicotinamide adenine dinucleotide ...
Formula: C5H5N5
IUPAC ID: 9H-purin-6-amine
Molar mass: 135.13 g/mol
Density: 1.60 g/cm³
Melting point: 360 °C
QUADRA-HELIX

11. Scientists at Cambridge University have found four-stranded DNA in human cells for the first time. "If you've ever
studied genetics in school or college, you'll know that the structure of DNA is a double helix. You likely know that DNA
carries all of our genetic code. While traditionally we think of only double helix DNA, scientists from Cambridge
University in England have made an interesting discovery. According to the researchers, a quadruple helix is also
present in some cells and is believed to relate to cancer in some ways. According to the researchers, controlling these
quadruple helix structures could provide new ways to fight cancer. The scientists believe the quadruple helix may
form when the cell has a certain genotype or operates in a certain dysfunctional state. Scientists have been able to
produce quadruple helix material in test tubes for years. The material produced is called the G-quadruplex. The G
refers to guanine, which is one of the base pairs that hold DNA together. The new research performed at the
University is believed to be the first to firmly pinpoint quadruple helix in human cells."
Cambridge University scientists say they have seen four-stranded DNA at work in human cells for the first
time.
Here is a list of 70 DNA ‘facts’
1. DNA stands for deoxyribonucleic acid.
2. DNA is part of our definition of a living organism, and is found in all living things.
3. DNA was first isolated in 1869 by Friedrich Miescher.
4. James Watson and Francis Crick figured out the structure of DNA. – the double helix, which can be
likened to a twisted ladder. The rungs of the ladder are made up of “bases”
5. Adenine (A) is a base: ; Thymine (T) is a base. Cytosine (C) is a base: Guanine (G) is a base.
6. A always pairs with T in DNA. C also pairs with G in DNA.
7. The amount of A is equal to the amount of T, same for C and G. A+C = T+G
8. Hydrogen bonds hold the bases together.
9. The sides of the DNA ladder are made of sugars and phosphate atoms.
10. Bases are attached to a sugar; this complex is called a nucleoside.
11. Sugar + phosphate + base = nucleotide.
12. The DNA ladder usually twists to the right.
13. Almost all the cells in our body have DNA with the exception of red blood cells.
14. DNA is the “blueprint” of life.
15. Chromosomal or nuclear DNA is DNA found in the nucleus of cells.
16. Humans have 46 chromosomes.
17. Autosomal DNA is part of chromosomal DNA but does not include the two sex chromsomes –
X and Y.

12. 18. One chromosome can have as little as 50 million base pairs or as much as 250 million base pairs.
19. Mitochondrial DNA (mtDNA) is found in the mitochondria and mtDNA is only passed from the
mother to the child because only eggs have mitochondria, not sperm.
20. Our entire DNA sequence is called a genome.
21. There’s an estimated 3 billion DNA bases in our genome.
22. One million bases (called a megabase and abbreviated Mb) of DNA sequence data is roughly
equivalent to 1 megabyte of computer data storage space.
23. Our entire DNA sequence would fill 200 1,000-page New York City telephone directories.
24. A complete 3 billion base genome would take 3 gigabytes of storage space.
25. If unwound and tied together, the strands of DNA in one cell would stretch almost six feet but would
be only 50 trillionths of an inch wide.
26. In humans, the DNA molecule in a non-sex cell would have a total length of 1.7 metres.
27. If you unwrap all the DNA you have in all your cells, you could reach the moon 6000 times!
28. Our sex cells –eggs and sperm– have only half of our total DNA.
29. Over 99% of our DNA sequence is the same as other humans’.
30. DNA can self-replicate using cellular machinery made of proteins.
31. Genes are made of DNA.
32. Genes are pieces of DNA passed from parent to offspring that contain hereditary information.
33. The average gene is 10,000 to 15,000 bases long.
34. The segment of DNA designated a gene, is made up of exons and introns.
35. Exons have the code for making proteins.
36. Introns are intervening sequences sometimes called “junk DNA.” Junk DNA’s function or lack
thereof is a source of debate. Part of “junk DNA” may be to help to regulate the genomic activity.
37. There are an estimated 20,000 to 25,000 genes in our genome.
38. In 2000, a rough draft of the human genome (complete DNA sequence) was completed. And in 2003,
the final draft of the human genome was completed.
39. If all the DNA in your body was put end to end, it would reach to the sun and back over 600 times
(100 trillion times six feet divided by 92 million miles).
40. If all three billion letters in the human genome were stacked one millimetre apart, they would reach a
height 7,000 times the height of the Empire State Building.
41. DNA is translated via cellular mechanisms into proteins.
42. DNA in sets of 3 bases, called a codon, code for amino acids, the building blocks of protein.
43. Changes in the DNA sequence are called mutations. Many things can cause mutations, including
UV irradiation from the sun, chemicals like drugs, tobacco etc.
44. Mutations can be changes in just one DNA base. However, Mutations can involve more than one
DNA base. Mutations can involve entire segments of chromosomes.
45. Genes make up only about 2-3% of our genome.
46. DNA is affected by the environment; environmental factors can turn genes on and off.
47. There are many ways you can analyse your DNA using commercially available tests.
48. Paternity tests compare segments of DNA between the potential father and child.
49. There are other types of relationship testing that compares DNA between siblings, grandparents and
grandchild, etc.
50. DNA tests can help you understand your risk of disease. A DNA mutation or variation may be
associated with a higher risk of a number of diseases, including breast cancer.
51. DNA tests can help you understand your family history aka genetic genealogy, and can help you
understand your ethnic make-up.
52. DNA can be extracted from many different types of samples: blood, hair, cheek-cells, urine.
53. DNA can be stored either as cells on a cotton swab, buccal brush, or frozen blood or in extracted
form.
54. In forensics, DNA analysis usually looks at 13 specific DNA markers (segments of DNA).
55. The odds that two individuals will have the same 13-loci DNA profile is about one in one billion.
56. A DNA fingerprint is a set of DNA markers that is unique for each individual except identical twins.
57. Identical twins share 100% of their genes, Siblings share 50% of their genes. A parent and child
share 50% of their genes.

13. 58. DNA is used to determine the pedigree for livestock or pets, and DNA is used in wildlife forensics to
identify endangered species and people who hunt them (poachers).
59. DNA testing is used to authenticate food like caviar and fine wine, and to determine the purity of
crops.
60. DNA is used in identify victims of accidents or crime. Conversely, DNA is used to exonerate
innocent people who’ve been wrongly convicted.
61. Many countries, including the US and UK, maintain a DNA database of convicted criminals.
62. We eat DNA every day.
63. Genetically modified crops have DNA from another organism inserted to give the crops properties
like pest resistance. – very controversial
64. Dolly the cloned sheep had the same nuclear DNA as its donor mother but its mitochondrial DNA
came from the egg mother. (Does that make any sense?)
65. Genes do not blend
66. Some genes are dominant
67. We share around 96- 98% of our DNA with the great apes
68. We share around 50% of our DNA with a banana; We share around 36% of DNA with a fruit fly;
7% with bacteria; 15% with mustard grass; 21% with the roundworm; 85% with a Zebra-fish.
69. The DNA taken from the right, upper arm bone of the Neanderthal specimen had 27 differences from
modern humans, compared to 55 differences between modern humans and chimpanzees. The
Neanderthal DNA differed just as much from modern humans from Africa and Asia as it did from
modern humans from Europe. If Neanderthals were in fact ancestors of modern humans it would
figure that they would share more genetic material with Europeans than groups from other parts of
the world, but this is not case. Mitochondrial DNA studies suggest that Neanderthals and modern
humans had a common ancestor 100,000 to 500,000 years but never mixed.
70. A genome is an entire set of genes.