AP BIO UNIT 5

What is the result of meiosis?

4 haploid cells (gametes)

Name some key differences between mitosis and meiosis?

Mitosis has 1 division, and meiosis has two. Meiosis produces NEW cells with a novel set of genes, while mitosis produces original copies.

What are homologous chromosomes?

Homologous chromosomes are a pair of a particular type of chromosomes that carry genes controlling the same characteristics

What occurs in prophase 1?

Crossing over occurs, which is when certain proteins break apart the DNA of nonsister chromatids at exactly the same location. This location is refered to as the chiasmata. The spindle forms and the nucleus comes apart.

What are recombinant chromosomes?

Recombinant chromosomes are chromosomes that have undergone genetic recombination, typically through the process of crossing over during meiosis. This results in a mix of genetic material from both parents, leading to genetic diversity among offspring.

What happens in metaphase 1?

Homologous Chromosomes line up at the metaphase plate (the middle of the cell) in a line.

What happens in anaphase 1?

Homologues get pulled apart (each complete with both sister chromatids)

What happens in telophase 1?

The nuclear membrane reforms, cytokinesis occurs, and 2 haploid cells are created

What happens in meiosis II?

It is basically the same as mitosis except for the fact that chromatids are not identical due to crossing over from prophase 1, and the chromatids line up on the metaphase plate instead of the homologous pairs.

What is complete dominance?

Presence of a dominant trait that is always expressed.

What is Codominance?

Both dominant traits are expressed at the same time

What is incomplete dominance?

Hybrid offspring phenotype will be a blend of parental phenotypes (think interracial couples = mix of colors)

What is non disjunction?

The failure of chromosomes to separate during meiosis

What times can nondisjunction occur?

When sister chromatids fail to separate in meiosis II OR when homologous chromosomes fail to separate in meiosis.

What can nondisjunction cause?

If the homologous chromosomes fail to separate, gametes will have incorrect number of chromosomes. If sister chromatids fail to separate, 2 gametes will have correct number of chromosomes, and 2 will have an incorrect number (missing or more)

What is the law of segregation?

Each gamete must have an allele from each parent

What is the law of independent assortment?

alleles from two or more different genes get sorted into gametes independently of one another.

What is sickle cell anemia and tay sachs disease caused by?

Due to a missense mutation, which is a single change in DNA sequence.

What is Huntington disease caused by?

35+ CAG a repeat that overwhelms proteins and causes neurons to degenerate over time