Mitosis and Meiosis Flashcards
What are the 4 phases of cell cycle?
G1, S, G2, M
G1, S, and G2 are the interphase
How much time does a cell spend in the interphase?
90%
What is a chromosome?
A molecule of DNA and the associated proteins
What is a chromatid? What are sister chromatids?
One of the duplicated copies of DNA. Sister chromatids are identical to each other
How many chromosomes are in a pair of sister chromatids?
1
What is a centromere?
Region of DNA where sister chromatids are attached
What is the kinetochore?
The proteins attached to the centromere
What is a karyotype? What distinguishes chromosomes?
An image of chromosomes during metaphase. Size, centromere position, secondary constriction, and banding patterns
What are the 3 centromere positions?
Metacentric: in the middle
Acrocentric: not in the middle, one arm is shorter than the other
Telocentric: at the telomere
What is a secondary constriction?
Places where transcription is occurring, but RNA and proteins aren’t on the karyotype
What is mitosis?
An equational division that gives two daughter cells with the same ploidy as the original cell
What are the phases of mitosis?
Prophase, metaphase, anaphase, telophase, cytokinesis
What happens in prophase of mitosis?
Sister chromatids condense, mitotic spindle begins to form, the mass of chromatin becomes distinguishable chromosomes
What occurs in prometaphase of mitosis?
The nuclear envelope breaks apart, sister chromatids finish condensing, mitotic spindle finishes, microtubules attach to the kinetochores
What occurs in metaphase of mitosis?
Chromosomes line up along the metaphase plate in the middle of the cell
What occurs in anaphase of mitosis?
Sister chromatids separate, the microtubules attached to the kinetochores pull each sister chromatid to opposite ends of the cell
What occurs in telophase of mitosis?
Nuclear envelope reforms around each set of chromosomes, chromosomes decondense, mitotic spindle is disassembled
What occurs in cytokinesis of mitosis?
The cell membrane pinches inward at the cleavage furrow and the cytoplasm divides
What is the ploidy, chromosome number (in human cells), and DNA content in each phase of of the cell cycle of a diploid cell?
G1: 2n, 46, 2c
S: 2n, 46, 4c
G2: 2n, 46, 4c
M: 2n, 46, 2c
What is the ploidy, chromosome number (where n=8), and DNA content in each phase of the cell cycle of a haploid cell?
G1: n, 8, c
S: n, 8, 2c
G2: n, 8, 2c
M: n, 8, c
What is meiosis?
Two successive rounds of nuclear division, with the first being reductional and second equational
Where does meiosis occur? What are the products?
In specialized meiocytes in diploid organisms. Results in 4 gametes or spores that are genetically different from the parent cell
What is the difference between meiosis 1 and meiosis 2?
Meiosis 1 is a reductional division, meiosis 2 is an equational division
What is a dyad?
A pair of sister chromatids
What are phases of meiosis 1?
Prophase 1, metaphase 1, anaphase 1, telophase 1
What occurs in prophase 1 of meiosis?
Chromosomes become highly condensed, homologous chromosomes synapse and form a bivalent. Crossing over can occur
What are chiasmata?
The visual manifestation of the place where the chromatids cross over
What is synapsis?
A very tight association between non-sister chromatids of homologous chromosomes
What occurs in metaphase 1 of meiosis?
Bivalents align along the metaphase plate independently of each other and in a random orientation
What occurs in anaphase 1 of meiosis ?
Ploidy is reduced, spindle fibres pull apart the bivalent and pull one pair of sister chromatids to each end of the cell
What occurs in telophase 1 of meiosis?
Nucleus reforms at each pole, chromosomes decondense. Each new cell has one of the homologous chromosomes
How does meiosis 2 proceed? What kind of division occurs?
Proceeds like mitosis. Is an equational division
What occurs in prophase 2 of meiosis?
Chromosomes recondense
What occurs in metaphase 2 of meiosis?
Chromosomes align along metaphase plate, individually this time
What occurs in anaphase 2 of meiosis?
Sister chromatids are pulled apart by the mitotic spindle
What occurs in telophase 2 of meiosis?
Chromosomes decondense, nucleus reforms around each set of chromosomes, cytokinesis occurs
What is the ploidy, chromosome number (in a 2n=8 cell), and DNA content in each phase of meiosis 1 and 2?
Prophase 1: 2n, 8, 4c Metaphase 1: 2n, 8, 4c Anaphase 1: n, 4, 2c Telomere 1: n, 4, 2c Prophase 2: n, 4, 2c Metaphase 2: n, 4, 2c Anaphase 2: n, 4, c Telophase 2: n, 4, c
