Genetics and Inheritance Concepts

Genotypes and Phenotypes

• Genotype predicts phenotype; the genotype of parents can be used to predict the phenotype of offspring.
• Homozygous recessive offspring have the genotype pp.

Mendel's Discoveries

• Mendel discovered the principles of dominance, segregation, and independent assortment.
• Birds and mammals do not have the same sex chromosomes (false).
• An animal's genotype can be manipulated by breeding (true).

Karyotype

• A complete set of chromosomes is called a karyotype.

Chromosome Number

• All body cells, except gametes, have a diploid number of chromosomes.
• This is true.
• Down syndrome (trisomy 21) results from the failure of homologous chromosomes to separate normally during meiosis.

Predicting Offspring Genotypes

• Crossing two heterozygous parents (Yy x Yy) produces offspring with genotypes YY, Yy, and yy.

Dominance and Codominance

• Heterozygous black and white speckled chickens are an example of codominance.
• Many factors alter an animal's phenotype. This is true.

Genetic Disorders

• Gametogenesis is the term for producing sex cells.
• Only changes in chromosome structure can cause genetic disorders (false).
• Embryos have the diploid number of chromosomes, not a haploid number (false).

Mutations and Organism Survival

• Mutations can make an organism less able to survive and may cause death.

Animal Phenotypes

• Phenotypes include traits like eye color, hair color, height, and length of tail,
• Genotypes are the actual gene makeup.

Chromosomal Structure

• Chromosomes have specific shapes (metacentric, submetacentric, acrocentric, telocentric) based on centromere position.

Chromosomes and Cells

• Autosomes control somatic characteristics, while sex chromosomes control sexual characteristics.
• Two individuals with the same genotype in similar environments should have the same phenotype. (Relationship between phenotype and genotype P = G + E).

Polyploidy and Aneuploidy

• Polyploidy has a chromosomal number that is a multiple of the normal haploid number (3N or 4N).
• Aneuploidy results from the gain or loss of a single chromosome.
• Monosomy results in the loss of a single chromosome (2n—1).
• Trisomy results from the gain of a single chromosome (2n+1).

Chromosomal Variations

• Deletion, duplication, translocation, and inversion are variations in chromosome structure.

Mating Systems & Breeding

• Inbreeding increases homozygosity; line breeding is a form of inbreeding.
• Outbreeding increases heterozygosity.
• Outcrossing is outbreeding within a breed, while crossbreeding is breeding animals of different breeds.
• Domestication is the process of converting wild animals to domestic use.

Domestication Prerequisites

• Factors for domestication include animal adaptation to food types, ability to survive, and calm nature.

Animal Breeding Goals

• Breeding goals often include increasing productivity and bringing in desirable genes through methods like grading up (mating sires with commercial female grades).

Animal Health Effects

• Effects of animal breeding can include metabolic health problems for broilers, increased bone fractures in laying birds, and reduced fertility in dairy cows.