Genetics- the study of heredity. Heredity is the passing of characteristics from parent to

offspring.

Gregor Mendel-Father of Genetics

Gregor Mendel- 1840’-1860’s did research on heredity.

An Austrian Monk who became the Father of Genetics. Used Pea plants to do test-crosses.

Genetic Crosses

• Parent generation (P1) the first two organisms that are crossed

• F 1 generation - offspring from first generation

• F2 generation-offspring from crossing the F 1 generation. Common in plants and animals

Seed Shape

Flower Position

Seed CoatColor

Seed Color

Pod Color

Plant Height

PodShape

Round

Wrinkled

Round

Yellow

Green

Gray

White

Smooth

Constricted

Green

Yellow

Axial

Terminal

Tall

Short

Yellow Gray Smooth Green Axial Tall

Section 11-1

Figure 11-3 Mendel’s Seven F1Crosses on Pea Plants

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Mendel’s 4 Principles

1. 1. The principle of dominance states that some alleles are dominant and some are recessive.

• 2.      The principle of probability can be used to predict offspring outcome.

• 3.      The principle of independent assortment states that alleles for different genes usually separate independently of each other.

• 4.      The principle of inheritance of biological characteristics -genes are passed from parent to offspring.

Dihybrid Crosses

When two traits that separate

independently of each other are

put into a cross you get 16

Offspring .When both individuals

are heterozygous you get a

9:3:3:1- phenotypic ratio.

(what they look like)

Section 11-3

Figure 11-10 Independent Assortment in Peas

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Beyond Simple Dominant and Recessive Alleles

Some alleles are neither dominant or recessive, and multiple alleles or multiple genes control many traits

 

   Incomplete Dominance- The phenotype of the offspring is intermediate (blend) of the parents. Example :red flowers x white flowers make pink

 .

Example Incomplete Dominance

Co-Dominance

Both alleles are expressed equally giving striping spots or checkered appearance. Example: some chickens have equal number of white and black feathers giving a checkered appearance. In cattle red cattle and white cattle make roan cattle (some red patches some white)

Multiple Alleles- In the population of organisms there are more than two

alleles for certain traits. An individual can only have 2 alleles for each trait but more can exist in

the population. Example:

Human blood type A, AB, O, B

 

Polygenic Traits

     Trait produced by the interaction of several genes. This causes a wide variation in outcomes. Example: Human skin color –controlled by 4 different genes

Sex-LinkedThe trait is on the Chromosome that determines

the sex of the offspring. Females=XX Males=XYBecause males only receive one X from their

mother if the trait is on the X it will show up even if it is recessive.

Y chromosome is very small and does not carry many traits .

Examples: Color-blindness, hemophilia