Gregor Mendel was an Austrian monk who is considered the father of genetics. He conducted experiments with pea plants in which he studied 7 different traits. Through his experiments, Mendel discovered the principles of heredity, including that traits are passed from parents to offspring through discrete units called genes, and that some genes are dominant while others are recessive. When Mendel crossed plants with different traits, he found that the offspring expressed the traits of only one parent, not a blend, and that recessive traits could reappear in later generations. This led Mendel to propose that genes segregate and assort independently during the formation of gametes.

1. Introduct
ion to
Genetics

2. Genetics
The scientific study of
heredity

3. Gregor Mendel
Father of Genetics! Austrian Monk - worked at
monastery and taught high school
Grew peas and became interested in the traits
that were expressed in different generations of
peas

4. True breeding
Each and every offspring
(produced through self
fertilization) have exactly the
same traits as the parents – also
known as purebred
He was also able to cross breed
peas for different traits

5. Self Fertilization
Plants have both male and female parts so they
are able to fertilize themselves
Cross Pollination
 When male parts from one plant are dusted with
pollen from another plant thus crossing the
pollen!

6. Genes and Dominance
Mendel studied seven
different pea plant traits
Each trait he studied had a
contrasting form

7. Pea Plant Traits

8. Genes and Dominance
The offspring of crosses between
parents with different traits are called
Hybrids
When Mendel crossed plants with
different traits he expected them to
blend, but that’s not what happened at
all.
All of the offspring had the character
of only one of the parents

10. Mendel drew two conclusions
1. Inheritance is determined by
genes that are passed from
generation to generation

11. Mendel’s 2 conclusion
nd
2. The Principal of Dominance
Some alleles are dominant and
some are recessive

12. Alleles
Different forms of a gene
Either dominant or recessive

13. dominant
Covers up the recessive form
– gene that if present, is
always expressed (Capital
letter!)
Ex.) T = tall

14. recessive
Gene that gets covered up if
there is a dominant allele
present (lower case letter)
Ex.) t = short

15. Mendel wanted to know Q: Had the recessive alleles
disappeared?
 To find out, Mendel mated the
F1 plants to produce an F2
generation! (grand kids! )

16. P1 Parental
Tall
Short
F1
All Tall
F2
3 tall : 1 short
75% tall
25% short

17. The F1 Cross
The recessive traits
reappeared!
Roughly 1/4 of the F2 plants
showed a recessive trait (tt)

18. Segregation
Ratio 3:1
At some point, the allele for
shortness had been separated from
the allele for tallness.
This occurred during the formation of
SEX CELLS (when moms egg and dad’s
sperm are produced)

20. Punnett Square Vocab
If you do not know the
following vocabulary words
you will fail miserably

21. Punnett Square
Diagram used to determine
genetic crosses

22. Probability
The likelihood that a
particular event will occur
Random

23. Homozygous
Organisms that have 2
identicle alleles for a trait
Ex.) TT , tt

24. Heterozygous
Have two different alleles for
a trait
Ex.) Tt

25. Phenotype
Physical characteristics – The
thing you see
WORDS
Ex.) Tall

26. Genotype
Genetic make-up
LETTERS
Ex.) Tt, TT, tt

27. Mendel wondered if alleles segregate
during the formation of gametes
independently
Does the segregation of one pair of
alleles affect the segregation of another
pair of alleles?
For example, does the gene that
determines whether round or wrinkled in
shape have anything to do with the gene
for color?
Must a round seed also be yellow?

28. All heterozygous
9:3:3:1 Ratio

29. Independent Assortment
Genes that segregate
independently do not
influence each others
inheritance

30. Incomplete Dominance
When one allele is not dominant
over another
Four o’clock flowers
The heterozygous phenotype is
somewhat blended between the
two homozygous phenotypes

32. Codominance
When both alleles contribute
to the phenotype of an
organism
Ex.) Speckled
Chickens

33. Multiple Alleles
When more than two possible
alleles exist in a population
Ex.) blood type
IA
Dominant
IB
i
Recessive

34. Human Blood Types
Phenotype
A
Genotype
IAIA or IAi
B
IBIB or IBi
AB
IA I B
O
ii

35. Polygenic Traits
Traits controlled by two or
more genes
Ex.) eye color, skin color

36. Genetics and the Environment
Some characteristics are determined
by interactions between genes and
the environment
Ex.) genes may affect a plants
height but the same characteristic is
influenced by climate, soil conditions
and availability of water

37. Do Now
Human hair is inherited by
incomplete dominance. Human
hair may be curly (CC) or
straight (cc). The heterozygous
genotype (Cc) produces wavy
hair. Show a cross between
two parents with wavy hair

38. Mendel’s principles of genetics
require at least 2 things
1. Each organism must inherit a single
copy of every gene from each of its
parents
2. When an organism produces its own
gametes these two sets of genes
must be separated from each other
so that each gamete contains just
one set of genes

39. Homologous
Chromosomes that each have
a corresponding chromosome
from the opposite sex parent