Lecture 12 - Mitosis and Meiosis : Simon Whitehall

Question 1

What are the 5 stages of Mitosis?

Answer 1

Prophase
Prometaphase
Metaphase
Anaphase
Telophase

Question 2

What is the G0 state?

Answer 2

A non dividing senescent state.

Question 3

What is a kinetochore?

Answer 3

Protein structure located at the centromere that serves as attachment point for mitotic spindles.

Question 4

What is a centriole?

Answer 4

Cytoplasmic organelle composed of 9 groups of microtubules that act as foci for creating mitotic spindle fibres.

Question 5

What is a centrosome?

Answer 5

Region of cytoplasm containing pair of centrioles.

Question 6

What is a centromere?

Answer 6

The centre of the chromosome, where the 2 sister chromatids join.

Question 7

What happens in G2 of interphase?

Answer 7

Chromosomes extend

Question 8

What happens during Prophase?

Answer 8

Chromosomes condense and the centrioles divide and move apart.

Question 9

What happens during prometaphase?

Answer 9

Centrioles reach the opposite poles.

Spindle fibres form and attach to the kinetochore.

Question 10

What happens during metaphase?

Answer 10

Centromeres align on the metaphase plate along the midline of the cell., nuclear envelope breaks down.

Question 11

What happens during anaphase?

Answer 11

Centromeres split (once all have lined up on the spindle) and daughter chromosomes migrate to opposite poles as they are pulled by the mitotic spindles.

Question 12

What happens during Telophase/Cytokinesis?

Answer 12

Daughter chromosomes arrive at poles.

Chromosome de-condenses

Nuclear envelope reforms

Cell division occurs.

Question 13

What is a chiasma?

Answer 13

A physical connection between non sister chromatids. This leads to crossing over.

Question 14

What are the sub-stages of Prophase I?

Answer 14

Leptonema
Zygonema
Pachynema
Diplonema
Diakinesis

Question 15

What happens during Leptotene?

Answer 15

Duplicated chromosomes start to condense.

Question 16

What happens during Zygotene?

Answer 16

Synapsis begins, the chromosomes start to join (bivalent forming)

Question 17

What happens during Pachytene?

Answer 17

Synapsis is complete, and crossing over occurs.

Question 18

What happens during Diplotene?

Answer 18

Synaptonemal complex disappears, and the chiasma is visible.

Question 19

What happens during Diakinesis?

Answer 19

Nuclear envelope fragments, and the bivalent chromosomes are ready for metaphase.

Question 20

What is the synaptonemal complex?

Answer 20

A nucleoprotein zipper that forms between the paired homologous chromosomes. It looks like a backbone with lateral elements with chromatin attached to the sides.

It plays an important role in crossing over, and suggests an important role in the formation of chiasmata.

Question 21

What is the metaphase plate?

Answer 21

Where all the chromosomes line up on the horizontal axis.

Question 22

What are asters?

Answer 22

Very short microtubules.

Question 23

_______ do not act independently in Meiosis.

Answer 23

Non-Sister chromatids.

Question 24

What does Bivalent/Tetrad mean?

Answer 24

2 pairs of non sister chromatids joined together.

Question 25

What is a dyad?

Answer 25

One half of the tetrad.

Question 26

What can happen , and what will not happen between Meiosis I and Meiosis II?

Answer 26

There can be a short interphase, but no DNA replication and no chiasmata formation or crossing over.

Question 27

What is the pathway for the development of gametes in a male?

Answer 27

``` Spermatogonium -> Growth Primary spermatocyte -> Meiosis I 2 secondary Spermatocytes ->Meiosis II 4 Spermatids -> Differentiation 4 Spermatazoa ```

Question 28

What is the pathway for development of gametes in a female?

Answer 28

``` Oogonium -> Growth Primary oocyte -> Meiosis I Secondary Oocyte + polar body -> Meiosis II *of 2ndry oocyte* Oootid -> Differentiation Ovum ```

Question 29

What happens during meiosis in a female?

Answer 29

During development 1st oocyte division takes place but pauses at prophase I. Meiosis resumes many years later (prior to ovulation) and 2nd division only completed after fertilization.

Question 30

What is Aneuploidy, and how does it develop?

Answer 30

Chromosome number is not an exact multiple of the haploid number. Nondisjunction results in aneuploid gametes.

Question 31

What is Trisomy?

Answer 31

3 copies of a particular chromosome.

Question 32

Where do Meiosis and Mitosis occur?

Answer 32

Meiosis occurs in a diploid cell Mitosis can occur in haploid and diploid cells.

Question 33

Where does meiosis take place in higher eukaryotes?

Answer 33

Testis and Ovary

Question 34

What are some human syndromes associated with trisomies?

Answer 34

``` Down Syndrome Edwards Syndrome Warkany Syndrome 2 Patau Syndrome Chronic Lymphocytic Leukaemia ```

Question 35

How do you calculate no. of variations of gametes diploid organisms can produce?

Answer 35

2^number of homologous chromosomes.