Cell Division Flashcards
G1 (Gap 1) phase
genes are actively transcribed and translated. The duration varies among different types of cells in body
S phase
where DNA replication takes place
G0 phase
an alternative to G1 of the cell cycle entered by mature cells that generally do not divide again
G2 phase
cell prepares to divide
diploid (2n)
2 Copies of each chromosome, 2n = 46 (23 pairs) for human somatic cells
haploid (n)
A single copy of each chromosome, n = 23 for human gametes
interphase
G1 -> S phase -> G2, then cells go through mitosis
karyokinesis
divides up DNA into daughter cell nuclei
cytokinesis
divides up cytoplasm
meiosis I
homologous chromosomes separate from one another, reducing the diploid number of chromosomes to the haploid number
meiosis II
-sister chromatids separate from one another to produce four haploid gametes, each with one chromosome of the original diploid pair (similar to mitosis in a haploid cell)
What 3 hallmark events occur in meiosis I?
-1.Homologous chromosome pairing (Synapsis) in Prophase I
- 2. Crossing over between homologous chromosomes in Prophase I
- 3. Segregation (separation) of homologous chromosomes (Anaphase I), which reduces chromosomes to the haploid number
metaphase I
Tetrads (pairs of homologs) line up at the center of the cell. The homologs are oriented towards opposite poles of the cell
anaphase I
homologous chromosome disjunction (separation). (where segregation occurs)
telophase I
nuclear envelope reforms. Chromosomes may partially decondense. haploid nuclei are separated by cytokineses. No DNA replication occurs between Meiosis I and II. Meiosis I is called the reductional division.
