heredity study guide

Compare & contrast the following terms: Gene, allele, chromosome, homologous chromosomes, sex chromosomes, autosomes, genome

• Gene → DNA segment

• Allele → gene variation

• Genotype → genetic makeup

• Phenotype → physical trait

Know the diploid number of chromosomes & the number of homologous chromosomes present in humans

• 46 total (23 pairs)

• 22 autosomes

• 1 sex chromosome pair

• diploid number: 2n

Determine the difference between genotype & phenotype. Be able to identify an example of a genotype versus phenotype

the genotype is the set of genes, while the phenotype is the observable trait, with identical genotypes sometimes producing different phenotypes based on environmental factors.

Given an individual’s genotype, be able to determine whether their alleles are

heterozygous or homozygous.

• Homozygous → AA or aa

• Heterozygous → Aa

List & explain the three major sources of genetic variation between individuals.

1. Independent assortment

2. Crossing over

3. Random fertilization

Compare the four patterns of inheritance

• Dominant/recessive- one allele (dominant) masks (suppresses)

  expression of its recessive partner
  - Dominant trait is expressed even if other allele codes for recessive trait

• Incomplete dominance- Heterozygotes have intermediate phenotype

  or combination of both

• Multiple alleles (ABO)- Genes that exhibit more than

  two allele forms

• Sex-linked- Genes that are located on sex chromosomes- X or Y

Understand effects on gene expression outside of genotype

• Drugs (thalidomide)

• Nutrition

• Hormones