BSC2010C Exam 5

Homozygous Dominant

AA

Homozygous Recessive

aa

Heterozygous

Aa

Genotype

Alleles

Phenotype

What we see (eye color, height, length)

Dominant Allele

Uppercase, RR/Rr. Takes priority in pheno/geno

Recessive

Lowercase, rr. Never first letter with a dominant allele

Monohybrid Crosses

Focuses on 1 trait, 2×2 punnett square. EX: Rr x rr. Phenotype ratio is typically 3:1

Dihybrid Crosses

Focuses on 2 traits (ex: height and color). Uses FOIL Method. RrAA x rrAa. Phenotype ratio is typically 9:3:3:1

Punnett Squares

Female on top, Male on the side

Male in a Pedigree

Square

Female in a Pedigree

Circle

Affected Individual in a Pedigree

Shaded square/circle

Mating in a Pedigree

Horizontal line between 2 individuals

Offspring in a Pedigree

Vertical line between 2 individuals

Multiple Alleles

Blood types: A, AB, B, O

How many genotypes of blood are there?

6: IA IA, IA i, IB IB, IB i, IA IA, i i

Multiple Alleles works closely with what?

Codominance

Rh Factor

The different antigens on the blood (+ or -) inherited by mendelian genetics

Rh Positive

+-/++

Rh Negative

--

Codominance

Offspring of true breeding parents display both phenotypes.

BB x WW leads to all checkered offspring

B → Black

W→ White

Incomplete Dominance

“In between Phenotype”

Dominant allele is not completely expressed when the recessive allele is around.

rr x RR leads to pink flowers

rr→ White

RR→ Red

Pleiotrophy

Multiple traits affect 1 gene. Frizzle gene in chickens affect their 1. Feathers and 2. Metabolism

Polygeny

Multiple genes affect 1 trait. Height, skin color, hair color, eye color

Epistasis

When 1 gene depends on another gene for it to be expressed (1 gene alters the affect of a 2nd gene). Example includes pigment in animals.

Homo Recessive? No Pigment no matter what!

SRY Gene

Sex Determining Region on Y Chromosome

Y chromosome has this gene that is responsible for the development of the testes

SRY Gene Present (+)?

Gonads develop into testes (XY+)

SRY Gene Not Present (-)?

Gonads develop into ovaries (XX-)

Male Sex Chromosomes

XY

Female Sex Chromosomes

XX

Do Males get X and all of its genes from Mom or Dad?

Mom

Do Males get Y and all of its genes from Mom or Dad?

Dad

True or False: In mammals, are genes on the Y chromosome sex linked?

True

True or False: The X chromosome has many genes and all are related to sex

False

X Inactivation

Females inherit 2 X chromosomes, while males inherit 1.

Mammalian Females can do what

Inactive 1 X chromosome in every somatic cell

When does X Inactivation happen

Embryonic Development

The X that is inactivated is random and independent. What happens to the inactivated X?

Becomes a Barr Body and gets reactivated in the ovaries during Meiosis

How does Inactivation occur?

By methylating the DNA of 1 X chromosome

What is an example of X Inactivaiton?

Tortoiseshell fur in cats