meiosis

Flashcards covering the key concepts of meiosis, including ploidy, stages of meiosis, genetic diversity, and nondisjunction.

What is ploidy?

The number of chromosome sets in a cell.

What is a haploid cell?

A cell with one set of chromosomes (n).

What is a diploid cell?

A cell with two sets of chromosomes (2n). (1 from mom 1 from dad)

ex) cabbage 2n=18 (9mom/9dad)

horses 2n=64 (32mom32dad)

homologous chromosomes are present

What are homologous chromosomes?

Matching pairs of chromosomes, one from each parent.

What are autosomes?

Not a sex chromosome.

What are sex chromosomes?

Chromosomes that determine an individual’s sex.

F (XX) M (XY)

What is a germ cell?

A diploid cell that undergoes meiosis to produce gametes.

What is a gamete?

Haploid sex cell for sexual reproduction.

What is the role of meiosis?

cell division to generate gametes

One diploid germ cell goes through meiosis to produce four haploid cells.

What happens in Meiosis I?

Homologous chromosomes separate during this stage.

What happens in Meiosis II?

Sister chromatids separate during this stage.

What happens during Prophase I?

Homologous chromosomes pair up (synapsis) and crossing over occurs within tetrads

condensation of chromosomes occur

why? results in more genetic diversity of gametes

What is a chiasma?

Location where parts of non-sister chromatids exchange genetic material.

where synapsis occurs during crossing over.

What are recombinant chromatids?

Chromatids containing maternal and paternal DNA due to crossing over.

What happens during metaphase I?

Tetrads line up along the metaphase/equatorial plate

independent assortment occurs

resulting in increased genetic diversity of gametes.

Define Nondisjunction.

Occurs when chromosomes aren’t separated properly during Meiosis I or II, resulting in daughter cells having incorrect numbers of chromosomes. ex) 24/22 rather than 23

What is the result of Meiosis?

4 genetically different haploid cells

What is the function of Meiosis?

Produce gametes for sexual reproduction

what is karyotype

describes # and appearance of autosomes and sex chromosomes in cell

genome

collection of genetic info of an organism

genes

hereditary units of DNA that encode info for proteins

what is the role of meiosis

production of gametes

happens in germ-line cells

produce 4 haploid daughter cells (gametes) genetically distinct to each other and the parent cell.

what happens during anaphase 1

Homologous chromosomes are separated and pulled to opposite poles of the cell.

what happens during anaphase 2

Sister chromatids are separated and pulled to opposite poles of the cell.

what happens during telophase 1

Nuclear envelope reforms, cytokinesis begins

what happens during prophase 2

nuclear envelope may break down

spindles begin to form

condensation of chromosomes

what happens during metaphase 2

chromosomes align at the cell's equatorial plane

spindle fibers attach to kinetochores

telophase 2

nuclear envelope forms

chromosomes loosen back into chromatin

cytokinesis begins