Mitosis and Meiosis I + Meiosis II (+ extra terms )

Chromatid

1 of 2 identical halves of a replicated chromosome

Sister Chromosome

2 identical copies of the same chromosome formed by DNA replication, attached by a centromere

Centromere

holds 2 sis chromosomes tgt, serves as point of attachment for spindle fibers

Homologous Chromosomes

Pairs of chromosomes sharing similar genes, made of one from the father and one from the mother

Autosomal Chromosomes

non-sex chromosomes, in humans 22 of 23 pairs are autosomal

Sex Chromosomes

Chromosomes that determine the sex of an individual, typically X and Y in humans.

Gamete

Sex cells produced through meiosis, egg (ovum) + sperm

Diploid

Full set of chromosomes (2n), all cells in organism are diploid except gametes

Haploid

½ the # of chromosomes (n), only haploid cells in organisms are gametes

What are the two parts of teh cell cycle?

Interphase (normal cell function) and the mitotic phase (cell division).

What are the parts of Interphase?

G1: cell growth, S: DNA synthesis, G2: preparation for mitosis.

G1: Gap or growth phase

longest phase, cell grows, organelles double, metabolism carried out

S: Synthesis

Dna replication takes place in nucleus

G2: Gap or growth phase

shortest phase, chromatin condenses —> chromosomes, centrioles duplicate

Mitosis

Occurs in non-sex cells, single cell divides into identical daughter cells for growth and repair, # of chromosomes don’t change

Prophase (Preparation)

First step of mitosis. Chromatin condenses into visible chromosomes, centriole pairs migrate to opp. poles, spindle fibers begin to form, nuclear envelope breaks down

Metaphase (Middle)

Second stage. Spindle fibers fully formed, sister chromatids migrate to middle of cell and align @ equator

Anaphase (Apart)

Third stage. Sister chromatids divide into indiv. chromosomes, pulled to opp. poles of cell, cell elongates and pinches

Telophase (Two cells)

Final stage of mitosis where chromosomes arrive at opposite poles, nuclear envelopes reform, and the cell starts to divide into two

Cytokinesis

Division of cytoplasm resulting in 2 daughter cells, occurs after mitosis or meiosis

Meiosis

Involves Meiosis I and Meiosis II, occurs in gamete producing cells. Produces 4 haploid daughter cells (unique)

Prophase I

First stage of meiosis where homologous chromosomes pair up forming tetrad (synapsis), crossing-over may occur, and the nuclear envelope begins to break down.

Metaphase I

Homologous chromosomes (tetrads) align at the cell's equator in random manner ensuring genetic variation

Anaphase I

Homologous chromosomes separate to opposite poles, sister chromatids remain attached

Telophase I + Cytokinesis

Dyads reach opp. poles, nuclear envelop reforms, cell elongates and pinches, spindle fibers fragment, cleavage furrows

Interkinesis

A short resting phase between Meiosis I and Meiosis II.

Meiosis II

Similar to Mitosis, split chromatids joined at centromere

Prophase II

Chromosomes condense, the nuclear envelope breaks down, and spindle fibers form for dyad attachment

Metaphase II

Dyads aligned @ equator, fully formed spindle fibers, centrioles @ opp. poles

Anaphase II

Dyads separate into indiv. chromosomes—> pulled to opp. poles

Telophase II + Cytokinesis

chromosomes gather @ opp. poles, nuclear envelop reforms, spindle fibers break down, 4 haploid cells formed, cleavage furrow —> cytokinesis, chromosomes de-condense—> chromatin

Synapsis

Homologous chromosomes align closely tgt, only in Meiosis I

Crossing over

Exchange of genetic material between homologous chromosomes during meiosis I

Independent Assortment

The random distribution of homologous chromosomes during meiosis I.