Meiosis and Genetic Inheritance

Meiosis

A type of cell division that reduces the chromosome number by half, resulting in the production of gametes.

Meiosis I

The first round of cell division in meiosis, consisting of phases: Prophase I, Metaphase I, Anaphase I, Telophase I.

Prophase I

The longest phase of meiosis where homologous chromosomes pair up and exchange genetic material.

Crossing Over

The process during Prophase I where homologous chromosomes exchange genetic material.

Metaphase I

The stage of meiosis where paired chromosomes line up at the center of the cell.

Anaphase I

The stage in meiosis where paired chromosomes separate and homologous chromosomes move to opposite poles.

Telophase I

The stage in meiosis where chromosomes uncoil and the nuclear envelope reforms.

Meiosis II

The second round of cell division in meiosis, consisting of Prophase II, Metaphase II, Anaphase II, and Telophase II.

Prophase II

The stage of meiosis II where chromosomes condense again and the nuclear envelope breaks down.

Metaphase II

The stage in meiosis II where chromosomes line up at the center of the cell.

Anaphase II

The stage in meiosis II where sister chromatids separate and move to opposite poles.

Telophase II

The final stage in meiosis II where chromosomes uncoil and the nuclear envelope reforms.

Nondisjunction

The failure of homologous chromosomes to separate properly during meiosis, leading to abnormal gametes.

Anaphase I failure effects

Results in 4 abnormal gametes due to nondisjunction.

Anaphase II failure effects

Results in 2 abnormal gametes due to nondisjunction.

Gene

A piece of DNA that codes for a product, including regulatory elements.

Allele

A version of a gene.

Trait

A physical characteristic determined by a gene.

Polymorphic

A trait that comes in several forms.

Polygenic

A trait determined by several genes.

Classical Dominance

A type of inheritance where one allele is completely dominant over another.

Homozygous dominant

An individual with two copies of the dominant allele.

Homozygous recessive

An individual with two copies of the recessive allele.

Heterozygous

An individual with one copy of each allele.

Incomplete Dominance

A type of inheritance where heterozygous offspring display a blended version of the parental phenotype.

Example of Incomplete Dominance

Red flowers (RR) and white flowers (rr) produce pink flowers (Rr).

Codominance

A type of inheritance where both alleles are expressed independently, at the same time.

Example of Codominance

Human ABO blood group gene.

Epistasis

A type of inheritance where one gene affects the expression of another gene.

Testcross

A cross between an unknown dominant and a homozygous recessive individual.

Law of Segregation

Alleles are separated during gamete formation.

Law of Independent Assortment

How one pair of alleles separates is independent of how other pairs separate.

Rule of Multiplication

The probability of two events occurring together is the product of their individual probabilities.

Rule of Addition

The probability of two events occurring is the sum of their individual probabilities, minus the probability of both events occurring together.

Probability of having a son with specific traits

1/4 for Jane and Bob's son to have brown eyes and brown hair.

Linked Genes

Genes found close together on the same chromosome that might not sort independently.

Recombination Frequency (RF)

A measure of the likelihood of recombination occurring between two genes.

Recombination Frequency Meaning 0%

Genes are completely linked.

Recombination Frequency Meaning 50%

Genes are completely unlinked.

Recombination Frequency Meaning 0-50%

Genes are partially linked.

Hardy-Weinberg Equilibrium

Allele frequencies within a population do not change from generation to generation.

Hardy-Weinberg Equation for allele frequency

p + q = 1.

Hardy-Weinberg Equation for genotype frequency

pp + 2pq + qq = 1.

5 Conditions for Hardy-Weinberg Equilibrium

No mutations, no natural selection, random mating, large population, no migration.

Disturbance Recovery Time to New Equilibrium

One generation.

Types of Selection

Various mechanisms that drive evolution through natural selection.

Speciation

The formation of new and distinct species.

Barriers to Speciation

Factors that prevent populations from interbreeding.

Anatomical Terminology

Terms used to describe the structures of organisms.