Animal Genetics: Animal Genetics: Dominant vs. Recessive Traits Intro to Agriculture Science

GOALS:  Explain the difference between dominant and recessive genes.  Use a Punnett Square to predict genotypic and phenotypic ratios of offspring.

What do we already know? review…

Phenotype  Appearance!  Result of Genotype Example: Bw = Black Coat Because B is dominant

Genotype  The genetic makeup!  Alleles from parents  What you can’t see Example: Alleles that code for good milk production.

Alleles  A pair of genes  That code for the same trait Example: Hair Color Eye Color Height

What do we need to know? vocabulary…

Dominant Genes  Determine what the offspring will look like!  Expressed as capital letters  Mask recessive genes. Example: B=Black w=White Dominant Allele = B

Recessive Genes  Sometimes determine what the offspring will look like.  Expressed as lowercase letters Example: B=Black w=White Recessive allele = w

What is it called when both alleles are the same?  Homozygous

Example AA or aa

Identify... Dominant & Recessive AA or aa ? ?

Homozygous Dominant Homozygous Recessive

What is it called when both alleles are different?  Heterozygous

Example Aa

Lets Get to It! Genetic Crosses Monohybrid Crosses Punnett Squares Genetic Crosses Punnett Squares Monohybrid Crosses

What the heck 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 look like?  Punnett Square:

MONOHYBRID CROSS  A Punnett Square  Using one pair of contrasting traits  Ex: hair color

Example #1:  Homozygous vs. Homozygous

Example #1:  A White Sow (ww) crossed with  A Black Boar (BB)

B B (BB) ww (ww) Bw Homozygous vs. Homozygous

Example #2:  Homozygous vs. Heterozygous

Example #2:  A White Sow (ww) crossed with  A Black Boar (Bw)

B w (Bw) ww (ww) Bw ww Homozygous vs. Heterozygous

Example #3:  Heterozygous vs. Heterozygous

B w (Bw) Bw BB Bw ww Heterozygous vs. Heterozygous

Result…

Try it! cfu…