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2. MCBG > 3.2 Mitosis And Meiosis > Flashcards

3.2 Mitosis And Meiosis Flashcards

1
Q

Describe the cell cycle.

A
  1. INTERPHASE (G1, S, G2)
    - G1 - all cell components except chromosomes replicate
    - S all chromosomes (23 pairs) replicate
    - G2 cell double checks for errors making any repairs
  2. DIVISION (M)
    - mitosis
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2
Q

What is G0?

A

Cell exists here in a quiescent state (not dividing nor preparing)

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3
Q

What is a telomere and its function?

A
  1. Repeated sequences (TTAGGG) at ends of chromatids
  2. Protect from degradation and fusion with other chromosomes
  3. Shorted with replication and causes senescence
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4
Q

Complete the sentence:

One chromosome is made of _______________________

A. One DNA molecule
B. Two DNA molecules
C. One or Two DNA molecules

A

C. One or Two DNA molecules

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5
Q

What are sister chromatids? (2)

A
  1. Limbs of X shaped chromosomes

2. 2 identical DNA molecules with same alleles

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6
Q

How would you identify the p and q arms?

A

P arm is short (usually top one diagrammatically), q arm is longer (usually lower one diagrammatically)

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7
Q

How are chromosomes grouped?

A
  1. According to shape and size
  2. A-G
  3. X is a C group and Y is a G group
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8
Q

What are homologous chromosomes?

A

Pair of chromosomes
Have same genes
May have different alleles

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9
Q

Define diploid and haploid.

A

Diploid - full 46 chromosomes

Haploid - 23 chromosomes

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10
Q

What is mitosis and its stages?

A
  1. Cell division for somatic cells producing two identical daughter cells
  2. Prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis
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11
Q

What happens during prophase?

A
  1. Nuclear membrane and nucleolus disappear

2. Chromosomes condense and become visible

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12
Q

What happens during Prometaphase?

A
  1. Microtubule spindle fibres move to opposite ends of the cell
  2. Kinetophores connect to chromosomes, spindle to kinetophores
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13
Q

What happens during metaphase?

A
  1. 46 chromosomes randomly line up in middle forming metaphase plate
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14
Q

What happens during anaphase?

A
  1. Centromeres divide and spindles pull each chromosome apart
  2. Chromatids (now called chromosomes) go to each pole of the cell
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15
Q

What happens during telophase?

A
  1. Spindles disappear, nuclear membranes reappear

2. Cleavage furrow forms

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16
Q

What happens during cytokinesis?

A
  1. Cytoplasm divides

2. Birth of two daughter cells

17
Q

Why cant we see the chromosomes during interphase?

A
  1. Not condensed

2. In chromatin - hetero and eu - form

18
Q

What is the function of meiosis? (4)

A
  1. One germ line diploid cell (46 chromosomes replicated (X shaped)) to 4 haploid cells (23 chromosomes (I shaped))
  2. Maintain constant chromosome number from generation to generation
  3. Genetic diversity by random assortment of chromosomes
  4. Genetic diversity by crossing over of genetic material (chiasma)
19
Q

How does meiosis I happen?

A
  1. Prophase I
    - nuclear membrane and nucleolus disappear
    - chromosomes condense and become visible
    - homologous pairs find each other and Chiasmas occur (crossing over)
  2. Metaphase I
    - homologous pairs lines up on metaphase plate
    - random assortment
  3. Anaphase I
    - microtubule spindle fibres pull one chromosomes from each pair to each pole (23 chromosomes replicated (X shaped) )
  4. Telophase I
    - spindles disappear, nuclear membrane reappears
    - cleavage furrow
    - 2 daughter cells with 23 X shaped chromosomes
20
Q

What happens during meiosis II?

A

We start with 2 daughter cells with 23 X shaped chromosomes from meiosis I

  1. Prophase II
    - nuclear membrane and nucleolus disappear
  2. Metaphase II
    - 23 chromosomes (X shaped) line up on metaphase plate
  3. Anaphase II
    - centromeres divide and spindles pull each chromosome apart
    - go to each pole of cell
  4. Telophase II
    - spindles disappear, nuclear membrane reappears
    - cleavage furrow
    - 4 haploid daughter cells :)
21
Q

How does a sperm cell develop?

A

Spermatogenesis

  1. Spermatogonium, mitosis, more spermatogonium. OR
    Spermatogonium, mitosis, 1 spermatogonium, diploid primary spermatocyte
  2. Meiosis I forms secondary spermatocyte
  3. Meiosis II forms 4 spermatids
  4. Maturation forms 4 mature sperm cells
22
Q

How does an egg cell develop?

A

Oogenesis - 1 big egg produced from one diploid cell!

  1. Oogonium goes through mitosis and forms more oogonium (before birth) but after birth forms primary oocyte
  2. Primary oocyte goes through meiosis I and pauses at prophase I
  3. Monthly, 1 primary oocyte finishes meiosis I becoming a secondary oocyte (other one from oogonium becomes a polar body)
  4. Release from ovary and fertilisation
  5. Meiosis II produces one big egg cell and one small polar body which stays attached to egg cell
  6. One daughter cell gets all of cytoplasm , containing all nutrients forming zygote
23
Q

What is a polar body?

A

Formed from oogenesis and acts as a garbage can from chromosomes that we dont want (as one oogonium diploid 2n only forms one haploid egg cell!)

24
Q

What are the effects is meiosis doesn’t occur properly?

A
  1. A third of all identified miscarriages are due to this
  2. Infertility
  3. Leading cause of mental retardation
25
Q

What is missegregation/non-disjunction?

A
  1. In metaphase, all chromosomes line up correctly
  2. In anaphase, both copies of X shaped DNA that usually splits into two I shaped, go to one pole
  3. Results in one pole having one copy too many and other pole having one copy too less
26
Q

Name two ways chromosome analysis can occur and explain briefly

A
  1. Metaphase spread - chromosomes spread on glass plate. Different stains can be used to see every chromosome.
  2. Karyotyping - number and visual appearance of chromosomes can be seen and chromosome number, sex, structural changes can all be identified
27
Q

How would you write the karyotype of i) a normal female and ii) a male with trisomy 21

A

46,XX

47,XY+21

28
Q

What are the two types of non-disjunction you can have?

A

Mitotic and meiotic

29
Q

What is aneuploidy?

A

Presence of abnormal number of chromosomes in a cell resulting from mitotic nondisjunction

30
Q

What is mosaicism and how does it happen?

A

Presence of 2 or more cell lines in an individual (throughout body or throughout a tissue)
Depends on when non-disjunction occurs (first post-zygotic division (non-mosaic!) or through later mitotic divisions (mosaic!)

31
Q

What is anaphase lag?

A

Different to non-disjunction

May lose one chromatid due to delayed movement/not attaching to spindle

32
Q

What stage does crossing over occur?

A

Prophase I

33
Q

What stage does random assortment occur?

A

Metaphase I

34
Q

What is i) monosomy and ii) trisomy?

A

Monosomy is presence of only one chromosome

Trisomy is presence of three chromosomes (Extra one appeared from non-disjunction)

35
Q

What are the four chromosome structures due to centromere placement?

A

Metacentric, submetacentric, Acrocentric and telocentric

36
Q

What happens at a cell cycle checkpoint to allow the cycle to continue?

A

Checkpoint proteins phosphorylated

2. MCBG (18 decks)

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