Biology- Cell Reproduction

Chromosomes

threadlike structures made of DNA molecules that contain the genes

Histone

protein molecule around which DNA is tightly coiled in chromatin

Chromatid

one of two identical "sister" parts of a duplicated chromosome

Centromere

Area where the chromatids of a chromosome are attached

Chromatin

Clusters of DNA, RNA, and proteins in the nucleus of a cell

Autosome

Any chromosome that is not a sex chromosome

Sex Chromosome

Chromosomes that determine the sex of an individual

Homologous Chromosome

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

Karyotype

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

Diploid (2n)

contain 2 copies of each chromosome

Haploid (1n)

one copy of each chromosome

Mitosis

part of eukaryotic cell division during which the cell nucleus divides

Binary Fission

A form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size

Asexual Reproduction

process of reproduction involving a single parent that results in offspring that are genetically identical to the parent

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.

Gametes

sex cells

Interphase

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

Cytokinesis

division of the cytoplasm

Prophase

Chromosomes become visable, nuclear envelop dissolves, spindle forms

Spindle Fibers

Protein structures which move the chromosomes during cell division.

Metaphase

second phase of mitosis, during which the chromosomes line up across the center of the cell

Anaphase

the third phase of mitosis, during which the chromosome pairs separate and move toward opposite poles

Telophase

the final phase of cell division, between anaphase and interphase, in which the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed.

Cell Plate

In a plant cell, midline of dividing cells. Becomes the cell wall eventually.

Synapsis

Pairing of homologous chromosomes

Tetrad

structure containing four chromatids that forms during meiosis

crossing over

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

genetic recombination

The regrouping of genes in an offspring that results in a genetic makeup that is different from that of the parents.

Spermatogenesis

Formation of sperm

independent assortment

Independent segregation of genes during the formation of gametes

Oogenesis

Egg production

polar bodies

each of the small cells that bud off from an oocyte at the two meiotic divisions and do not develop into ova.

Sexual Reproduction

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

Meiosis I

The first division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.

Meiosis II

the second phase of meiosis consisting of chromatids separating, along with the two diploid cells splitting in two

Trisomy 21 (Down Syndrome)

A human genetic disorder resulting from the presence of an extra chromosome 21