2. • Cells can contain 6-96-9 feet of DNA. If all the DNA in your body
was put end to end, it would reach to the sun and back over
600600 times.
• DNA in all humans is 99.999.9 percent identical. It is about one
tenth of one percent that makes us all unique, or about 3
million nucleotides difference.
• DNA can store 2525 gigabytes of information per inch and is the
most efficient storage system known to human. So, humans
are better than computers!!
• In an average meal, you eat approximately 55,000,00055,000,000 cells or
between 63,000 to 93,00063,000 to 93,000 miles of DNA.
• It would take a person typing 60 words per minute, eight hours
a day, around 5050 years to type the human genome.

3. ANSWER THE FOLLOWING (HW)
1.What is DNA?
2. What are nucleotides?
3. What are the 4 bases of
nucleotides?
4. How do bases pair in DNA
strands?
5. What are the consequences of erros
when bases do not pair correctly?
6. What is the function of DNA?
7. Illustrate the DNA double helix

4. 1. Represent and explain DNA structure

5. DNA is composed of units called NUCLEOTIDESNUCLEOTIDES, which are
composed of three sub-molecules:
1. Pentose SugarPentose Sugar (deoxyribose)
2. PhosphatePhosphate
3. Nitrogen BaseNitrogen Base (purine or pyrimidine)

6. DNA is composed of two
complimentarycomplimentary strands of nucleotides
joined by hydrogen bondshydrogen bonds::
AdenineAdenine with ThymineThymine (A-T or T-A)
They join with 22 hydrogen bonds
CytosineCytosine with GuanineGuanine (C-G or G-C)
They join with 33 hydrogen bonds
DNA twists into a double helixdouble helix

8. 1. DNA directs thedirects the machinery of a cell to make specificcell to make specific
proteinsproteins, and, therefore, DNA indirectly controls all of the
functioning of all living things.

9. 2. DNA stores the hereditary informationstores the hereditary information of an individual

10. 3. DNA has the ability to mutatehas the ability to mutate (change). This allows for
new characteristics and abilities to appear which may help
an individual to survive and reproduce (EVOLUTIONEVOLUTION).

11. 4. Self replication: DNA has the ability to
make copies of itselfmake copies of itself

12. 1. DNA replication is called ‘semi-conservativesemi-conservative’.
2. Semi-conservative replication is the process in which the
original strandsoriginal strands of DNA remain intactremain intact and act as
templatestemplates for the synthesis of duplicate strands of DNA.

13. 3. One copy of a DNA molecule will split apart to make twotwo
complete copies of itself. Each new DNA molecule is
made up of half of the oldhalf of the old molecule and half of a newhalf of a new
molecule.

14. 1.1. UNZIPPINGUNZIPPING: The DNA molecule ‘Unzips’
as the hydrogen bondshydrogen bonds between the base
pairs are brokenbroken. The enzyme
HELICASEHELICASE causes this unzipping to occur.

15. 2. COMPLEMENTARYCOMPLEMENTARY
BASE PAIRINGBASE PAIRING:
Complementary
nucleotides move intonucleotides move into
positionposition to bond with the
complementary bases on
the DNA chain.

16. 3. FORM NEW SUGAR PHOSPHATE BACKBONENEW SUGAR PHOSPHATE BACKBONE: The
nucleotides join as the sugars and phosphates bond to
form a new backbone. This process occurs due to the
enzyme DNA POLYMERASEDNA POLYMERASE which also checks for
mistakesmistakes as it goes.

17. 4. This process continues along the primary chain until we
have 2 IDENTICAL STRANDS2 IDENTICAL STRANDS of DNA molecules
(assuming there have been no errors made).

18. 1) Mutations can occur
naturallynaturally or through
environmentalenvironmental factors.
Environmental mutagensmutagens
include some chemicalschemicals
(food additives, pesticides,
plastics) and radiationsradiations
(X-rays to UV light).

22. 2) A gene mutationgene mutation is a change of one or more
nucleotidesnucleotides in a single gene. There are 3 types.

23. GENE MUTATIONS
DeletionDeletion: one nucleotide base is left out. All of the amino acids after
a deletion will be wrong, so SHAPE and FUNCTION of protein are
altered. Serious.
AdditionAddition: one extra nucleotide base is added. This will also change
the entire amino acid sequence of the protein, so SHAPE and FUNCTION
of protein are altered. Serious.

27. SubstitutionSubstitution: when single bases or short pieces are replaced with
one another.
Example: Sickle-Cell Anemia, only one nucleotide base is switched.
This causes only 1 amino acid to change, but it is an important one.
This type of mutation is usually not as seriousnot as serious as the 1st
two. It just
depends on which amino acid is affected (does it have an ‘R’ group with
a +,-, or S group?)

30. 3. Chromosomal mutationsChromosomal mutations: a mutation of all or partall or part
of a chromosome. These affect many genesaffect many genes.
Example #1: crossingcrossing
overover where one part of a
chromosome changes
places with another.
This can cause extra
pieces, missing pieces, or
the exchange of pieces of
chromosomes.

31. Charlotte has Cri du
Chat syndrome.
Cri du Chat Syndrome
("Cry of the cat" in French) is a genetic
disorder caused by the loss or
misplacement of genetic material
from the 5th
chromosome.
Cri du Chat causes a varied level of
mental handicap. The majority of the
children need more specialized education.
It was first identified in 1963 by Professor
Lejeune. He described the syndrome after
the sound that many of the babies and young
children make when crying.

32. Example #2:
non-disjunctionnon-disjunction = extra
chromosomes or missing
chromosomes due to
mistakes made during
meiosis.

34. Down Syndrome occurs in approx. 1 in 700 births in Canada. A person
with Down Syndrome has 47 chromosomes in each cell instead of 46. The
chance of having a baby with Down Syndrome increases significantly with
age; for example, between 20 and 24 years of age, the chance of conceiving
a child with Down syndrome is 1 in 1,450, while at age 45 this probability
increases to 1 in 32.

35. WHAT IS KLINEFELTER SYNDROME? Discovered
in 1942 by Dr. Harry Klinefelter. He studied 9 men who
had enlarged breasts, sparse facial and body hair, small
testes, and an inability to produce sperm.
By the late 1950s, it was discovered that men with
Klinefelter syndrome, had an extra sex chromosome,
XXY instead of the usual male arrangement, XY.

37. WHAT IS TURNER’S SYNDROME? A disorder that
results from a non-disjunction of the X
chromosomes during meiosis = X0 instead of XX.
Individuals are short and stocky; also sterile.

39. Definition: combining the DNA of two species.combining the DNA of two species.
1. Gene displacing: add an extra copy of a gene (cows
with huge teats to make double the milk) or deleting
genes (removing the rotting hormone from tomatoes).
2. Gene modification: repairing a gene (as in gene
therapy).
3. Gene transformation: inserting genes from a different
species to give a new function (as in making goats with
spider proteins in their milk or making bacteria that create
human insulin).

40. Recombinant DNA
refers to DNA which
has been altered
by joining genetic
material from two
different sources!