Animal Genetics:Animal Genetics:Dominant vs.

Recessive Traits

Intro to Agriculture Science

GOALS:GOALS:Explain the difference between

dominant and recessive genes.

Use a Punnett Square to predict genotypic and phenotypic ratios of offspring.

What do we What do we alreadyalready know? know?review…

PhenotypePhenotypeAppearance! Result of GenotypeExample:

Bw = Black Coat

Because

B is dominant

GenotypeGenotypeThe genetic makeup! Alleles from parentsWhat you can’t see

Example:

Alleles that code for good milk production.

AllelesAllelesA pair of genesThat code for the same trait

Example:

Hair ColorEye Color

Height

What do we What do we need toneed to know?know?

vocabulary…

Dominant GenesDominant GenesDetermine what the offspring will

look like!Expressed as capital lettersMask recessive genes.Example:

B=Black w=White

Dominant Allele = B

Recessive GenesRecessive GenesSometimes determine what the

offspring will look like.Expressed as lowercase letters

Example:B=Black w=White

Recessive allele = w

What is it called What is it called when both when both allelesalleles are the are the

same?same?

Homozygous

ExampleExample

AA or aa

Identify... Dominant & Identify... Dominant & RecessiveRecessive

AA or aa

? ?

AA or aa

Homozygous

Dominant

Homozygous

Recessive

What is it called What is it called when both when both allelesalleles are are

different?different?

Heterozygous

ExampleExample

Aa

Lets Get to It!

GeneticGeneticCrossesCrosses

MonohybriMonohybrid Crossesd Crosses

Punnett Punnett SquaresSquaresGeneticGenetic

CrossesCrosses

Punnett Punnett SquaresSquares

MonohybriMonohybrid Crossesd Crosses

What the What the heckheck are they? are they?Punnett squares are genetic crosses

used by biologists to predict the probability that certain traits will be inherited by offspring.

What do they What do they looklook like? like? Punnett Square:

MONOHYBRID CROSSMONOHYBRID CROSS

A Punnett Square

Using one pair of contrasting traits

Ex: hair color

Example #1:Example #1:Homozygous vs. Homozygous

Example #1:Example #1:

A White Sow (ww)

crossed with

A Black Boar (BB)

B

B(BB)

w w

(ww)

Bw Bw

Bw Bw

Homozygous vs. Homozygous

Example #2:Example #2:Homozygous vs. Heterozygous

Example #2:Example #2:

A White Sow (ww)

crossed with

A Black Boar (Bw)

B

w(Bw)

w w

(ww)

Bw Bw

ww ww

Homozygous vs. Heterozygous

Example #3:Example #3:Heterozygous vs. Heterozygous

B

w(Bw)

B w

(Bw)

BB Bw

Bw ww

Heterozygous vs. Heterozygous

Result…Result…

Try it!Try it!cfu…