Meiosis

Question 1

Terms

Answer 1

Tetrad: structure of two homologous chromosomes getting side by side
Synapsis: pairing process of non-sister chromatids of homologous chromosomes at prophase I
Chiasma Point: exchange of non-sister chromatids of homologous chromosomes at prophase I

Question 2

Crossing Over

Answer 2

~ happens only between non-sister chromatids
~ major source of genetic diversity
~ does not have to occur at every meiosis
~ there won’t be any changes at chromosome number, gene type, gene number
~ only new gene combinations or nucleotide rearragnements occur

Question 3

Purpose of Meiosis

Answer 3

1. Genetic Diversity: sexual reproduction introduces new gene combinations and unique individuals
2. Production of female (egg) and male (sperm) gamete cells from primordial gamete cells
3. Maintenance of chromosome number stability among same species

Question 4

Reasons of Genetic Diversity

Answer 4

~fertilization of male and female gamete cells (different gene combinations occur)
~ crossing over at prophase I
~ independent lining up of chromosomes at metaphase I

Question 5

Interphase I

Answer 5

~ dna duplicates itself
~ centrosome duplicates itself
~ dna is in chromatin form
~ nuclear envelope starts to break down
(Replication only occurs at meiosis I, not again in meiosis II, so only one interphase stage)

Question 6

Prophase I

Answer 6

~ chromatins get thicker and shorter and creates chromosomes immediately
~ each chromosome has 2 sister chromatids
~ chromatids attach each other with centromeres
~ nuclear envelope fully dissappears
~ centrosomes migrate to opposite sides of the cell and spinde fiber appears
~ homologous chromosomes come together and line up side by side because of an attraction and tetrad (bivalent) occurs
~ tetrad, sinapsis, chiasma point and crossing over occurs

Question 7

Metaphase I

Answer 7

~ homologous chromosomes attach to spindle fiber by their kinetochores and line up randomly on an equatorial plate

Question 8

Anaphase I

Answer 8

~ seperation of homologous chromosomes

Question 9

Telophase I and Cytokinesis I

Answer 9

~ they perform together at meiosis I
~ two n cells are created from 2n mother
~ daughter cells are not identical with mother because there are two parents
~ spindle fibers fully dissappears at telophase I
~ animal cells divide by cleavage furrow
~ plant cells divide by cell plate

Question 10

Prophase II

Answer 10

~ centrosomes duplicates itself and and migrate opposite poles of the cell
~ chromosomes are not homologous pairs
~ if the nuclear envelope appears again in telophase I it dissappears again in prophase II (not necessary)
~ spindle fiber appears

Question 11

Metaphase II

Answer 11

~ chromosomes line up on an equatorial plate
~ chromosomes have attached fully to spindle fiber by their kinetochores

Question 12

Anaphase II

Answer 12

~ centromers of sister chromatids seperate from each other
~ sister chromatids move opposite poles of the cell
~ chromatids call chromosomes

Question 13

DNA Amount

Answer 13

G1: 2x
S: 4x
G2, P1, M1, A1, T1: 4x
Cy1: 2x
P2, M2, A2, T2: 2x
Cy2: x

Question 14

Chromosome Number

Answer 14

P1, M1, A1, T1: 2x
Cy1: x
P2, M2: x
A2: 2x
T2: 2x
Cy2: x