Lecture 4b- Mitosis and Meiosis

Question 1

Meiosis

Answer 1

The process sexually-reproducing organisms use to create gametes with half the required genetic material to create a zygote

Question 2

Bivalent and Tetrad

Answer 2

A bivalent is one pair of chromosomes (homologous chromosomes) in a tetrad. A tetrad is the association of a pair of homologous chromosomes (4 sister chromatids) physically held together by at least one DNA crossover

Question 3

Crossing-over

Answer 3

Genetic recombination that occurs during meiosis, leading to novel forms

Question 4

Chiasmata

Answer 4

A point at which paired chromosomes remain in contact during the first metaphase, and at which crossing over and exchange of genetic material occur between the strands

Question 5

Recombination

Answer 5

The mixing of genetic material from different strands of DNA

Question 6

Synapsis

Answer 6

An event that occurs during meiosis in which homologous chromosomes pair with their counterparts and remain bound due to the exchange of genetic information

Question 7

Synaptonemal Complex

Answer 7

A protein and RNA structure that aids in forming the connections during synapsis of homologous chromosomes

Question 8

The stages of Meiosis

Answer 8

• In the first cell division (meiosis I), homologous chromosomes separate
• Meiosis I results in 2 haploid daughter cells with replicated chromosomes
• In the second cell division (meiosis II), sister chromatids separate
• Meiosis II results in 4 haploid daughter cells with unreplicated chromosomes

Question 9

The stages of Meiosis: Interphase

Answer 9

chromosomes are replicated to form sister chromatids
- the sister chromatids are genetically identical and joined at the centromere

Question 10

Division in meiosis I occurs in four phases:

Answer 10

• Prophase I
• Metaphase I
• Anaphase I
• Telophase I

Question 11

Prophase I

Answer 11

• chromosomes begin to condense
• each pair of chromosomes forms a tetrad, a group of 4 chromatids

Question 12

Metaphase I

Answer 12

-tetrads line up at the metaphase plate, with one chromosome facing each pole.

Question 13

Anaphase I

Answer 13

pairs of homologous chromosomes separate
- sister chromatids remain attached at the centromere

Question 14

Telophase I and Cytokinesis

Answer 14

Telophase I: each half of the cell has a haploid set of chromosomes (consists of 2 sister chromatids)

Question 15

prophase II

Answer 15

a spindle apparatus forms
- in late prophase II, chromosomes move toward the metaphase plate

Question 16

Metaphase II

Answer 16

sister chromatids are arranged at the metaphase plate

Question 17

Anaphase II

Answer 17

sister chromatids separate

Question 18

Telophase II

Answer 18

the chromosomes arrive at the opposite poles. nuclei form, and the chromosomes begin decondensing

Question 19

3 events unique to meiosis (meiosis I)

Answer 19

1) synapsis and crossing over in prophase I
2) there are homologous chromosomes instead of sister chromatids
3) at anaphase I, it is homologous chromosomes instead of sister chromatids