Unit 5 Test Prep Bio

why do cells divide?

growth, reproduction and replace old cells

chromatin

Substance found in eukaryotic chromosomes that consists of DNA tightly coiled around proteins called histones.

chromosome

Tightly wound strand chromatin (DNA)

sister chromatids

Structures that contain identical copies of DNA

homologous chromosomes

Chromosomes that occur in pairs and have the same genes arranged in the same order, but there are small variations in the DNA letters of those genes

centromere

region of a chromosome where the two sister chromatids attach

autosomes

First 22 pairs of chromosomes (non-sex chromosomes)

sex chromosomes

23rd pair of chromosomes that determine the sex of an individual.

XX: Female

XY: Male

haploid cell

1 set of chromosomes (1n)

Human haploid cells contain 23 chromosomes

diploid cell

2 sets of chromosomes (2n)

Human diploid cells contain 46 chromosomes

asexual reproduction

A reproductive process that involves only one parent and produces offspring that are identical to the parent.

sexual reproduction

A reproductive process that involves two parents that combine their genetic material to produce a new organism, which differs from both parents

Interphase

Cell grows, performs its normal functions, and prepares for division; consists of G1, S, and G2 phases

G1 phase (interphase)

The first growth phase of the cell cycle in which the cell begins to prepare for cell division.

G1 checkpoint

cell determines if DNA intact, cell is the large enough, nutrients are readily available and growth factors are present.

S phase (interphase)

DNA is replicated (copied)

S checkpoint

The cell checks to make sure the DNA is intact and two complete copies are present.

G2 phase (interphase)

Last phase of interphase in which cell organelles are duplicated and cell grows rapidly.

G2/M checkpoint

cell checks if DNA is properly replicated and cell organelles are copied.

mitosis

The division of the cell and its contents into two identical daughter cells. Used for growth and replacing old cells.

daughter cell (mitosis)

genetically identical to the parent cell

Meiosis

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

crossing over

Process in which homologous chromosomes exchange portions of their chromatids during prophase I.

independent assortment

Each homologous chromosome gets sorted into gametes independently of one another (shuffled).

Fertilization

Process in sexual reproduction in which male and female reproductive cells join to form a new cell

Zygote

a diploid cell resulting from the fusion of two haploid gametes.

Karyotype

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

Nondisjunction

An error in meiosis or mitosis in which members of a pair of homologous chromosomes or a pair of sister chromatids fail to separate properly from each other.

Monosomy

missing a chromosome

Trisomy

extra chromosome