Genetics Made by: Nebo School District es/ppt/

What is Genetics ? All body cells contain “Blueprints” with instructions as to how an animal will look or act etc. One Gene comes from each parent (pairs) Genes are divided into sections (Chromosomes) that carry genes

Chromosomes The DNA in every cell is located in rod like segments called chromosomes Chromosomes occurs in pairs in every cell of our body except in the sperm and ovum. Chromosomes numbers are the same for each specie.

Genes Chromosomes contains several units of inheritance “genes”. Genes usually occurs in pairs, one from each parent. Some traits are inherited directly from one set of genes. Some traits are inherited through several sets of genes.

What are dominant genes? The gene that express itself, the powerful and dominant gene. It has the power to overshadow the recessive gene when there is complete dominance. Some examples are: – White faced in cattle – Polled in cattle – Black coat color in Angus cattle

What are Dominant Genes ? Dominant Genes = one gene overshadows the other Angus Cattle: black is dominant, red is not (Bb) Hereford: white face is dominant (Ww) Hampshire Hog: white belt is dominant Horns are dominant (Pp)

What are Recessive Genes ? The gene that is overshadowed by a dominant gene Recessive genes can only express themselves if both genes are recessive Polled vs Horned (Pp) (pp) Black wool vs white (Ww) (ww) Dwarfism vs normal size (dd) Albino

What are Recessive Genes ? The gene that is overshadowed by a dominant gene Recessive genes can only express themselves in the absence of the dominant gene Polled vs Horned (Pp) (pp) Black wool vs white (Ww) (ww) Dwarfism vs normal size (dd) Albino

Punnet Square P = horned p = polled If a homozygous horned cow (PP) is mated to a homozygous polled bull (pp), what percent of the calves will be horned, polled?

Punnet Square

If a homozygous horned cow (PP) is mated to a heterozygous horned bull (Pp), what percent of the calves will be polled?

Punnet Square

Angus- Black coat color is dominant. BB = Homozygous Dominant and Black Bb = Heterozygous and is black bb = Homozygous recessive and red A heterozygous bull is mated to 50 homozygous recessive cows. How many calves are black? How many calves are red? What is the genotypic and phenotypic ratios?

Punnet Square

Results 2 heterozygous = Bb 2 Homozygous Recessive bb 25 Black, 25 Red Genotypic ratio = 0:2:2 Phenotypic ratio = 2 Black: 2 Red

Genetic Terms Genotype: genetic makeup (Bb) Phenotype: physical appearance (Black) Heterosis: Genes are different, Dominant & Recessive (Bb) Homozygous: both genes are the same (BB or bb)

Terms to know Homozygous- contains 2 identical genes for the same trait, AA, BB, cc Heterozygous- contains 2 different genes for the same trait, Aa, bB, Cc Phenotype- Outward appearance of a trait, coat color, polled, horned. Genotype- Genetic classification of a gene, AA, Aa, aa. Allele- Location of a gene on the chromosome. F-one = First cross mating. F-two = Second cross mating.