Chapter 2 Mitosis and Meiosis

What is the genetic material contained in all living organisms except viruses?

DNA (deoxyribonucleic acid)

What are the two processes involved in genetic continuity of nucleated cells in eukaryotes?

Mitosis and Meiosis

Mitosis

Produces two daughter cells, each with the same number of chromosomes as the parent cell (2n).

Meiosis

Produces sex gametes with half the number of chromosomes (n).

What are chromosomes visible as during mitosis and meiosis?

Condensed structures.

Uncoiled chromosomes within the nucleus

Chromatin.

What is the diploid number of chromosomes in humans?

46 chromosomes (2n).

What is the haploid number of chromosomes?

Half the normal amount of chromosomes (23 in humans)

biparental inheritance

Inheritance from two parents, resulting in two copies of each gene.

Allele

Alternative forms of the same gene.

What are the four types of centromere placements?

Metacentric, submetacentric, acrocentric, and telocentric.

Metacentric

centromere in middle

submetacentric

centromere between middle and end

acrocentric

centromere close to end

telocentric

centromere at end

Sex-determining chromosomes of Males

XY

Sex-determining chromosomes of Females

XX

What is the purpose of meiosis?

To produce gametes or spores and enhance genetic variation.

What are the two divisions involved in meiosis?

Meiosis I (reductional division) and Meiosis II (equational division).

Prophase I of meiosis

Homologous chromosomes pair up (synapsis) to form bivalents.

Bivalent

a pair of single strand homologous chromosomes

Number of bivalents

equal to the haploid number

Synapsis

Pairing of homologous chromosomes

Chiasma

The region where chromatids are intertwined and have undergone genetic exchange during crossing over.

Tetrad

structure containing 4 chromatids that forms during meiosis

chromatids

Identical halves of a duplicated chromosome.

Metaphase I of meiosis

Tetrads align at the metaphase plate, and terminal chiasmata hold nonsister chromatids together.

Disjunction in anaphase I

The separation of homologous chromosomes, with half of each tetrad (dyad) pulled to opposite poles.

Telophase I of meiosis

Reappearance of the nuclear membrane around dyads, leading to a short interphase.

What is the result of cytokinesis after meiosis II

Four haploid gametes from a single meiotic event.

What is spermatogenesis?

The symmetrical production of male gametes (sperm) in the testes.

What is oogenesis?

The non-symmetrical production of female gametes (eggs) in the ovaries.

Crossing over during meiosis

It results in genetic exchange between homologous chromosomes, creating genetic variation.

What is a locus (loci plural)?

A specific location on a chromosome where a gene is found.

Centromere

It is the constricted region of a chromosome that plays a crucial role in the movement of chromosomes during cell division.

Homologous chromosomes

Chromosomes that have the same sequence of genes and the same structure

Nonhomologous chromosomes

Chromosomes that do not match because they have different sets of genes (sex chromosomes)