Lecture 2

Question 1

What is a Ploidy?

Answer 1

The number of complete sets of chromosomes in a cell

Question 2

What is a Cell with One complete Set of Chromosomes

Answer 2

Haploid

Question 3

What is an Example of a Haploid Cell?

Answer 3

Sperm cell or an egg in vertebrates

Question 4

What is a Diploid Cell?

Answer 4

Has two complete sets of chromosomes (one from mother and one copy from the father)

Question 5

What is an example of a Diploid cell?

Answer 5

A somatic cell such as a leaf cell, skin cell or a stem cell in your colon

Question 6

What can a Haploid Cell be represented by?

Answer 6

“n”

Question 7

What can a Diploid cell be represented by?

Answer 7

“2n”

Question 8

What happens to a Diploid Cell after S-phase?

Answer 8

The amount of DNA has doubled (4 complete set of chromosomes)

Question 9

What does not change in Mitosis?

Answer 9

The Ploidy Level

Question 10

Is meiosis a terminal event?

Answer 10

Yes. It stops.

Question 11

Can mitosis keep happening?

Answer 11

Yes.

Question 12

How many interphase in Meiosis?

Answer 12

1

Question 13

What happens in the first division of Meiosis?

Answer 13

It randomly separates homologous chromosomes

Question 14

What happens in the second division of Meiosis?

Answer 14

Results in the splitting of sister chromatids

Question 15

What is the end result of meiosis?

Answer 15

4 genetically unique daughter cells

Question 16

What is each genetically unique daughter cell at the end of meiosis?

Answer 16

Haploid (unlike mitosis)

Question 17

What happens at the end of mitosis?

Answer 17

2 identical daughter cells

Question 18

What is the first stage of Prophase I

Answer 18

Chromosomes first become visible as thin threads. DNA replication is already complete.

Question 19

What is the second stage of Prophase I

Answer 19

Homologous chromosomes continue to condense and undergo synapsis (gene for gene pairing)

Question 20

What is the third stage of Prophase II

Answer 20

When synapsis is complete, each pair of homologous chromosomes forms a bivalent. Each chromosome consists of two chromatids.

Question 21

What is synapsis?

Answer 21

The pairing of two chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them.

Question 22

What is the Chiasma?

Answer 22

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

Question 23

What is the fourth stage of prophase I?

Answer 23

The chromosomes continue to shorten and thicken and the chiasmata between non-sister chromatids become apparent

Question 24

What happens in the fifth stage of prophase I?

Answer 24

The nuclear envelope begins to break down

Question 25

What happens in prometaphase I?

Answer 25

Spindles attach to kinetochores on chromosomes

Question 26

What happens in metaphase I?

Answer 26

Homologous pairs line up in centre of cell, with bivalents oriented randomly with respect to each other

Question 27

What happens to the spindle fibres in Mitosis?

Answer 27

Attach to kinetochores that oppose each other

Question 28

What happens to the kinetochores in Meiosis?

Answer 28

Orient side by side (mono-orientation)

Question 29

What are the three stages of Mitosis Metaphase?

Answer 29

1.) All 46 chromosomes aligned in one plane 2.) Mitotic spindles attached to kinetochores orientated opposite each other on both sister chromatids 3.) No recombination

Question 30

What are the three stages of Metaphase 1 in Meiosis 1?

Answer 30

1.) 23 pairs of homologous chromosomes aligned in one plane 2.) Mitotic spindle attached to mono-orientated kinetochores on the sister chromatids 3.) Recombination occurring between homologous chromosomes

Question 31

What happens in Anaphase I of Meiosis?

Answer 31

Homologous chromosomes separate but sister chromatids do not separate

Question 32

What happens in Teleophase I and cytokinesis of Meiosis?

Answer 32

Daughter cells are ready to move to prophase II

Question 33

What happens after cytokinesis in Meiosis?

Answer 33

The cell went from diploid "2n" to haploid "n" and we are only half way through meiosis

Question 34

What are the stages of Meiosis II?

Answer 34

Prophase I Prometaphase II Metaphase II Anaphase II Telophase II and Cytokinesis

Question 35

Prophase II?

Answer 35

The nuclear envelope breaks down and the chromosomes condense

Question 36

Prometaphase II

Answer 36

Spindle fibres attach to kinetochores on chromosomes

Question 37

Metaphase II

Answer 37

Chromosomes align in centre of cell

Question 38

Anaphase II

Answer 38

Sister chromatids separate

Question 39

Telophase II and cytokinesis

Answer 39

The nuclear envelope reforms and the cytoplasm divides

Question 40

Similarities between Mitosis (Metaphase) and Meiosis II (Metaphase II)

Answer 40

1. Mitotic spindles attached to both sister chromatids 2. Separation of sister chromatids 3. Alignment of all chromosomes along equatorial plate

Question 41

Differences between Mitosis (Metaphase) and Meiosis II (Metaphase II)

Answer 41

1. Only 1 of the homologues in Metaphase II 2. Only recombined chromosomes in Meiosis 3. Half the number of chromosomes in Metaphase II

Question 42

How much DNA is apparent after Meiosis I?

Answer 42

I/2 DNA

Question 43

How much DNA is apparent after Meiosis II

Answer 43

1/4 DNA

Question 44

What happens in Meiosis I during each menstrual cycle?

Answer 44

Arrest is released in one or a few oocytes

Question 45

What happens in Meiosis II during menstrual cycle?

Answer 45

Arrest is released upon fertilization

Question 46

What is cytoplasmic division?

Answer 46

The cytoplasm of a single eukaryotic cell divides into two daughter cells.

Question 47

What is an Ooocyte?

Answer 47

A cell in an ovary which may undergo meiotic division to form an ovum.

Question 48

What is a sperm cell?

Answer 48

Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction.

Question 49

Paramecium is a single cell eukaryotic organism that can reproduce by mitotic cell division. Prior to the M phase of the cell cycle, what must occur?

Answer 49

The cell must replicate its chromosomes

Question 50

In the early zebrafish embryo undergoes cell division every 20 minutes, what do you think is happening with the cell cycle?

Answer 50

Only the G1 and G2 phases are very, very short

Question 51

What does not happen during mitosis

Answer 51

The synthesis of DNA (happens prior)

Question 52

Given that the correct number of chromosomes is vital to the proper functioning of a cell, what happens when a cell passes from G1 phase to S phase in the cell cycle?

Answer 52

The cell completes the process of cell division or it dies.