Chapter 8 Cell Reproduction

Chromosomes

In a eukaryotic cell, a rod-shaped structure in a cell's nucleus that are made up of DNA and proteins; in a prokaryotic cell, the main ring of DNA

Histones

Proteins which help maintain the shape of the chromosomes and help in the tight packing of DNA

Chromatid

Half of a chromosome, identical to the other half

Centromere

The point at which a chromosome's two chromatids are connected

Chromatin

A complex of proteins and DNA strands that are loosely coiled so that translation and transcription can occur

Sex Chromosomes

Chromosomes that determine the sex of an organism, and they may also carry genes for other characteristics

Autosomes

All the chromosomes in an organism besides the sex chromosomes

Homologous Chromosomes

The two copies of each chromosome an organism recieves from each of its parents

Karyotype

A photomicrograph of the chromosomes in a normal dividing cell found in a human

Diploid

Describes cells that have two sets of chromosomes

Haploid

Describes cells that have one set of chromosomes

Binary Fission

The division of a prokaryotic cell into two offspring cells

Mitosis

A type of cell division that results in new cells with genetic material identical to that of the original cell

Asexual Reproduction

The production of offspring from one parent

Meiosis

A process in cell division in which the number of chromosomes decreases to half the original number by two divisions of the nucleus, which results in the production of sex cells

Interphase

The time between cell divisions, during which a cell grows to mature size, its DNA is copied, and it prepares for cell division

Cytokinesis

The division of a cell's cytoplasm

Prophase

The first stage of mitosis, where a cell's chromosomes condense, its nucleolus and nuclear membrane break down and disappear, centrosomes move to opposite ends of the cell, and spindle fibers radiate from them in preperation for metaphase

Metaphase

The second phase of mitosis, where a cell's chromosomes move toward its center and are held in place by the spindle fibers

Anaphase

The third phase of mitosis, where the chromatids of each of a cell's chromosomes seperate at the center of the cell and move toward opposite ends of the cell

Telophase

The final phase of mitosis where a cell's chromosomes reach opposite ends of the cell, its spindle fibers dissasemble, chromosomes turn back into chromatin (less tightly coiled chromosomes) and a nuclear envelope forms around each of the chromosome sets,

Cell Plate

Formed during plant cell division; eventually the cell wall forms from it, dividing the cell into two

Cell Growth (G1) Checkpoint

Proteins at this checkpoint control whether the cell will divide; if the cell is healthy and has grown to a suitable size, the proteins will initiate the S phase

DNA Synthesis (G2) Checkpoint

DNA repair enzymes check the results of DNA replication, and if the checkpoint is passed, proteins will signal the cell to begin molecular processes that will allow the cell to divide mitotically

Mitosis Checkpoint

If a cell passes this checkpoint, proteins will signal for the cell to exit mitosis, and it will then enter into the G1 phase again

Synapsis

The pairing of homologous chromosomes which occurs only in meiosis

Tetrad

A pair of homologous chromosomes

Crossing-over

A process in which portions of chromatids may break off and attach to adjecent chromatids on its homologous chromosome pair

Genetic Recombination

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

Independant Assortment

The random seperation of homologous chromosomes during anaphase I of meiosis

Spermatogenesis

The production of sperm cells

Oogenesis

The production of mature egg cells

Sexual Reproduction

The production of offspring through meiosis and the union of a sperm and an egg