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Biology *1090 Flashcards > Lecture 2 Flashcards > Flashcards

Lecture 2 Flashcards

1
Q

What is a Ploidy?

A

The number of complete sets of chromosomes in a cell

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2
Q

What is a Cell with One complete Set of Chromosomes

A

Haploid

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3
Q

What is an Example of a Haploid Cell?

A

Sperm cell or an egg in vertebrates

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4
Q

What is a Diploid Cell?

A

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

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5
Q

What is an example of a Diploid cell?

A

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

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6
Q

What can a Haploid Cell be represented by?

A

“n”

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7
Q

What can a Diploid cell be represented by?

A

“2n”

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8
Q

What happens to a Diploid Cell after S-phase?

A

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

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9
Q

What does not change in Mitosis?

A

The Ploidy Level

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10
Q

Is meiosis a terminal event?

A

Yes. It stops.

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11
Q

Can mitosis keep happening?

A

Yes.

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12
Q

How many interphase in Meiosis?

A

1

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13
Q

What happens in the first division of Meiosis?

A

It randomly separates homologous chromosomes

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14
Q

What happens in the second division of Meiosis?

A

Results in the splitting of sister chromatids

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15
Q

What is the end result of meiosis?

A

4 genetically unique daughter cells

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16
Q

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

A

Haploid (unlike mitosis)

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17
Q

What happens at the end of mitosis?

A

2 identical daughter cells

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18
Q

What is the first stage of Prophase I

A

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

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19
Q

What is the second stage of Prophase I

A

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

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20
Q

What is the third stage of Prophase II

A

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

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21
Q

What is synapsis?

A

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.

22
Q

What is the Chiasma?

A

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.

23
Q

What is the fourth stage of prophase I?

A

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

24
Q

What happens in the fifth stage of prophase I?

A

The nuclear envelope begins to break down

25
Q

What happens in prometaphase I?

A

Spindles attach to kinetochores on chromosomes

26
Q

What happens in metaphase I?

A

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

27
Q

What happens to the spindle fibres in Mitosis?

A

Attach to kinetochores that oppose each other

28
Q

What happens to the kinetochores in Meiosis?

A

Orient side by side (mono-orientation)

29
Q

What are the three stages of Mitosis Metaphase?

A

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

30
Q

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

A

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

31
Q

What happens in Anaphase I of Meiosis?

A

Homologous chromosomes separate but sister chromatids do not separate

32
Q

What happens in Teleophase I and cytokinesis of Meiosis?

A

Daughter cells are ready to move to prophase II

33
Q

What happens after cytokinesis in Meiosis?

A

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

34
Q

What are the stages of Meiosis II?

A

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

35
Q

Prophase II?

A

The nuclear envelope breaks down and the chromosomes condense

36
Q

Prometaphase II

A

Spindle fibres attach to kinetochores on chromosomes

37
Q

Metaphase II

A

Chromosomes align in centre of cell

38
Q

Anaphase II

A

Sister chromatids separate

39
Q

Telophase II and cytokinesis

A

The nuclear envelope reforms and the cytoplasm divides

40
Q

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

A
  1. Mitotic spindles attached to both sister chromatids
  2. Separation of sister chromatids
  3. Alignment of all chromosomes along equatorial plate
41
Q

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

A
  1. Only 1 of the homologues in Metaphase II
  2. Only recombined chromosomes in Meiosis
  3. Half the number of chromosomes in Metaphase II
42
Q

How much DNA is apparent after Meiosis I?

A

I/2 DNA

43
Q

How much DNA is apparent after Meiosis II

A

1/4 DNA

44
Q

What happens in Meiosis I during each menstrual cycle?

A

Arrest is released in one or a few oocytes

45
Q

What happens in Meiosis II during menstrual cycle?

A

Arrest is released upon fertilization

46
Q

What is cytoplasmic division?

A

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

47
Q

What is an Ooocyte?

A

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

48
Q

What is a sperm cell?

A

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

49
Q

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?

A

The cell must replicate its chromosomes

50
Q

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

A

Only the G1 and G2 phases are very, very short

51
Q

What does not happen during mitosis

A

The synthesis of DNA (happens prior)

52
Q

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?

A

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

Biology *1090 Flashcards (4 decks)

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