Bio 30 - Cell Division

Interphase

period of the cell cycle between cell divisions (G1, S, G2)

G1 phase

stage of interphase in which cell grows and performs its normal functions

S phase

chromosome replicate and DNA synthesizes

G2 phase

The second growth phase of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs.

Prophase

Chromosomes condense, nuclear envelop dissolves, spindle forms

Metaphase

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

Anaphase

Phase of mitosis in which the chromosomes separate and move to opposite ends of the cell

Telophase

phase of mitosis in which the distinct individual chromosomes begin to spread out into a tangle of chromatin

Cytokinesis

division of the cytoplasm to form two separate daughter cells

Haploid

cell having only one complete set of chromosomes

Diploid

cell having two sets of chromosomes or twice the haploid number

functions of mitosis

embryonic development, tissue growth, replacement of dead cells, repair of injured tissues

function of meiosis

sexual reproduction

Stages of Mitosis

Interphase, prophase, metaphase, anaphase, telophase

Stages of meiosis

Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II

Difference between Meiosis I and Meiosis II

In Meiosis I, DNA is replicated and cross over occurs; in Meiosis II, chromosome replication does NOT occur. I results in 2 haploid cells, II results in 4 haploid cells. Meiosis I separates homologous chromosomes while meiosis II separates sister chromatids.

homologous chromosomes

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

crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis. Occurs during the Prophase of Meiosis I.

spindle fibers

help pull apart the cell during replication and are made up of microtubules

histomes

the protein that the DNA strands winds up around

nuclear envelope

layer of two membranes that surrounds the nucleus of a cell

sister chromatids

joined copies of the original chromosome

Chromatin

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

Chromosomes

threadlike structures made of DNA molecules that contain the genes

Centromere

Area where the chromatids of a chromosome are attached

what undergoes crossing over?

Homologous Chromosomes

From one spermatogonia how many sperm cells do you get?

4 Sperm Cells

somatic cells

Any cells in the body other than reproductive cells. Contain double the count of chromosomes as Gametes.

Gametes

Sex cells. Contain half as many chromosomes as somatic cells

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.

Meiosis I nondisjunction

Failure of homologous chromosomes to separate

Gamete w/ 24 chromosomes has both paternal and maternal pairs. Results two gametes that lack one chromosome and two gametes with two copies of one chromosome

Meiosis II nondisjunction

tumor suppressor genes

A gene whose protein product inhibits cell division, thereby preventing the uncontrolled cell growth that contributes to cancer.

Cell that has its tumor suppressor cell deactivated and has become immortal

Cancer cell

recombinant chromatids

chromatids with a combination of DNA from both homologous chromosomes, formed by crossing over and chiasmata in meiosis.

trisomy 23 (XXY)

Klinefelter syndrome

Trisomy

a condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities.

Trimsomy 18

Edward's Syndrome

Trisomy 21

condition in which an individual has three number 21 chromosomes, resulting in Down syndrome

Trisomy 13

Patau syndrome

alteration of generations

The alteration of two or more different forms in the life cycle of a plant or animal.

identical twins

twins who develop from a single fertilized egg that splits in two, creating two genetically identical organisms

fraternal twins

twins who come from two different eggs fertilized by two different sperm.

Monosomy

Chromosomal abnormality consisting of the absence of one chromosome from the normal diploid number

Carcinogen

A cancer-causing substance, An agent that effects the genetic make-up of the cell.

Telemeres

DNA at the tips of chromosomes

Karotype

A picture of all the chromosomes in a cell arranged in pairs

independent assortment of chromosomes

The random distribution of maternal and paternal chromosomes into gametes during meiosis.

synapsis

the pairing of homologous chromosomes during meiosis

reduction division of meiosis

Reduces chromosome number from 2n to n