MASTERING meiosis

Meiosis

A type of cell division that results in four genetically different cells with half the chromosomal number of the original cell.

Chromosome

A structure made up of DNA and proteins that carries genetic information.

Gametes

Sex cells (sperm and egg) that contain half the number of chromosomes.

Somatic cells

Normal body cells that contain the full set of chromosomes.

Karyotype

The number and appearance of chromosomes in the nucleus.

Diploid

A cell condition where there are two sets of chromosomes (2n), typical of somatic cells.

Haploid

A cell condition where there is one set of chromosomes (n), typical of gametes.

Crossing over

The exchange of genetic material between homologous chromosomes during meiosis.

Non-disjunction

The failure of homologous chromosomes or sister chromatids to separate properly during cell division.

Aneuploidy

A condition in which an organism has an abnormal number of chromosomes.

Trisomy

A condition in which an extra copy of a chromosome is present in the cell nuclei.

Monosomy

A condition where there is only one chromosome instead of the normal diploid pair.

Polyploidy

The condition of having more than two complete sets of chromosomes.

Autosomes

The 22 pairs of non-sex chromosomes in humans.

Gonosomes

The sex chromosomes, which determine the sex of an individual.

Chiasmata

The points where crossing over occurs between homologous chromosomes.

Variation

Differences in traits among individuals of the same species due to genetic differences.

Spermatogenesis

The process of sperm cell production in males.

Oogenesis

The process of egg cell production in females.

Diploid number (2n)

The total number of chromosomes in a somatic cell, which in humans is 46.

Haploid number (n)

The total number of chromosomes in a gamete, which in humans is 23.

Zygote

The fertilized egg that forms when a sperm cell and an egg cell unite.

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

What is prophase I of meiosis?

The first stage of meiosis where chromosomes condense, homologous chromosomes pair, and crossing over occurs.

What occurs during metaphase I of meiosis?

Homologous chromosomes line up along the equatorial plane of the cell.

What happens in anaphase I of meiosis?

Homologous chromosomes are pulled apart to opposite poles of the cell.

What is telophase I?

The final stage of the first meiotic division where the cell divides and two haploid cells are formed.

What is prophase II of meiosis?

The stage where the chromosomes condense again and the nuclear envelope begins to break down in the two haploid cells.

What occurs during metaphase II?

Chromosomes line up along the equatorial plane again, but this time individual sister chromatids align.

What happens in anaphase II?

Sister chromatids are pulled apart and move toward opposite poles of the cell.

What is telophase II?

The final stage where the cells divide to form a total of four haploid daughter cells.

What is the importance of crossing over in prophase I?

Crossing over increases genetic variation by exchanging DNA between homologous chromosomes.

How does meiosis differ from mitosis?

Meiosis results in four genetically different haploid cells, while mitosis results in two identical diploid cells.