Download Mendelian Genetics

Mendelian
Genetics
How Genetics Began
● Gregor Mendel
● Father of genetics
● Austrian monk & plant breeder
● In 1866, published findings on the method of inherence
in garden pea plants.
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Genetics: The science of heredity.
Heredity: The passing of traits of the next
generation.
● Mendel studied pea plants
● Pea plants consistently produce off-spring with only
one form a trait.
● Pea plants reproduce by self-fertilization.
● Mendel noticed that some pea plants always produced
green seeds, while others always produced yellow
seeds.
● Mendel performed cross-pollination by transferring
male gametes from the flower of a green-seed plant
to the female organ of a flower from a yellow- seed
plant.
● He called the green-seed plant & the yellow seed
plant the parent generation, also known as the P
generation.
The Results
● The resulting offspring had yellow seeds. The
offspring from this first cross are called the first filial
generation (F1).
● Mendel wanted to know: is the green-seed trait gone,
or is it just hidden?
● Allowed the plants to grow & self-fertilize. This
generation of seeds is called the second filial
generation. (F2)
Results
● 3:1 Ratio of yellow to green seeds.
Mendel’s Conclusions
● 2 forms of the seed trait in the pea plants (yellow-
seed & green-seed).
● Each form is controlled by a factor called an allele.
● Allele: An alternative form of a single gene passed
from generation to generation.
● The gene for yellow seeds & the gene for green seeds
are different forms of a single gene.
Vocabulary
● Dominant: Form of the trait that appeared. (Yellow-
seeds in the F1 generation). Represented by a capital
letter. (A)
● Recessive: Form of the trait that was masked.
(Green-seeds in the F1 generation). Represented by a
lower case letter. (a)
Vocabulary
● An organism that has 2 of the same alleles for a
particular trait is homozygous for that trait. (AA or
aa)
● An organism that has 2 different alleles for a
particular trait is heterozygous for that trait.(Aa). The
dominant allele is observed.
Vocabulary
● Genotype: The organism’s pair of alleles. (AA, Aa,
aa)
● Phenotype: The observable characteristics of an
allele pair.
● AA = Yellow-seed
● Aa= Yellow- seed
● aa = Green-seed