Meiosis APBio

What is meiosis?

the process of gamete formation.

What does meiosis do to the number of chromosome sets?

It reduces the number of sets of chromosomes.

What are the ploidy levels of sperm and egg cells?

haploid (n).

What is the ploidy level of a zygote?

diploid (2n).

How many chromosomes do humans have?

46

How many chromosomes does each parent contribute?

one copy of 23 chromosomes.

What defines diploid cells?

two complete sets of chromosomes.

What defines haploid cells?

one complete set of chromosomes.

What happens when two haploid cells combine?

They form a diploid zygote.

What are homologous chromosomes?

Chromosomes that are the same but have different alleles.

What are sister chromatids?

Exact copies of the same chromosome.

What are nonhomologous chromosomes?

Different chromosomes that do not share the same genes.

What is the purpose of meiosis?

To take a diploid somatic cell and form a haploid gametic cell.

What are somatic cells?

Body cells that are diploid.

What are gametic cells?

Sex cells that are haploid.

What happens in the G1 phase

The cell gets the signal that gametes need to be formed.

What occurs during the S phase

DNA replicates.

What happens in the G2 phase

The cell prepares to divide.

What are the key events of Meiosis I?

Independent Assortment and Crossing Over.

What is produced at the end of Meiosis I?

2 haploid cells.

What transitions occur immediately after Meiosis I?

The cell immediately moves into Meiosis II.

How many haploid cells are produced at the end of Meiosis II?

4 haploid cells.

What is Independent Assortment?

Nonhomologous chromosomes line up independently of each other.

What occurs during crossing over in meiosis?

Nonsister chromatids swap information, producing new allelic combinations.

How do chromosomes line up differently in Mitosis vs Meiosis?

Mitosis lines up chromosomes one by one, while Meiosis pairs homologous chromosomes together.

What is the significance of homologous pairing in meiosis?

It allows for genetic diversity as the two resulting cells are different and haploid.

What is the role of alleles in homologous chromosomes?

They are different versions of genes located on the same chromosome.

What happens to the chromosome number during fertilization?

It returns to diploid as two haploid cells combine.

What do somatic cells consist of?

They consist of two sets of chromosomes inherited from both parents.

How does meiosis contribute to evolution?

By introducing genetic variation through sexual reproduction.

What does crossing over produce?

Chromosomes with a different combination of alleles than either parent.

How many divisions occur in meiosis?

Two

How does meiosis differ from mitosis in terms of genetic outcome?

Meiosis produces genetically diverse cells, while mitosis produces identical cells.