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Cell Biology And Genetics > Mitosis And Meosis > Flashcards

Mitosis And Meosis Flashcards

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1
Q

Describe the structure of a chromosome

A
  • has a Omar, ( short)
    Has a q arm ( long)

Has a telomere ( present at the end of a chromosome)

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2
Q

What is a telomere?

A

Repeated structures that are found at the end of a chromosome - they have repeated sequences.

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3
Q

What are the 4 different ways a centromere can be located in sister chromatids ?

A
  • in the middle (metacentric)
  • at the top ( telocentric - not found in humans )
  • just after the middle ( submetacentric)
  • near the top ( Acrocentric)
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4
Q

What occurs during prophase in mitosis ?

A
  • chromosones condense , becoming shorter and fatter in length.
  • nucleolus and nuclear membrane disintegrate.

-

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5
Q

What occurs in prometaphase ?

A
  • spindle fibres form.

- spindle fibres attach to the kinetochore on the centromeres.

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6
Q

What occurs during metaphase ?

A

The 46 chromosones ( with 92 chromatids ) line up at the centre of the cell called the metaphase plate.

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7
Q

What occurs during anaphase ?

A

The sister chromatids separate

With centromeres going first , each chromatid moves to opposite ends of the pole.

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8
Q

What occurs during telophase ?

A
  • nuclear envelope re appears
  • chromosomes go back to their original shape.
  • cleavage furrow forms
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9
Q

What occurs during cytokinesis ?

A
  • cytoplasm divides

-

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10
Q

When do you call chromosomes chromatids ?

A

ONCE THEY HAVE BEEN REPLICATED

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11
Q

When do you stop calling chromosomes chromatids ?

A
  • when they split during anaphase , you then go back to calling them chromosomes.
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12
Q

Define homologous chromosomes

A
    • maternal and paternal copy
  • have the same genes , but could have a different variation of alleles
  • centromere on the Same position
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13
Q

What occurs in prophase 1?

A

Homologous chromosome pairs find eachother eg chromosome 1 from paternal finds chromosome 2 from maternal. They can do this because they have similar sequences so are attracted to eachother.

  • this makes a bivalent/tetrad
  • crossing over occurs : this is where non-sister chromatids swap sections of themselves over. The chromosomes are now non-identical. A new combination of alleles.
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14
Q

What occurs during metaphase 1?

A
  • homologous pairs of chromosomes line up at the metaphase plate.
  • random assortment occurs : it is completely random at which the homologous pairs line up at the equator.
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15
Q

Is there a prometaphase stage in meiosis ?

A

No

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16
Q

What occurs during anaphase 1?

A

Homologous pairs of chromosomes separate.

17
Q

The daughter cells produced after meiosis 1 are haploid or diploid ?

A

Haploid

18
Q

What occurs during anaphase 11?

A

Chromatids separates

19
Q

What occurs during metaphase 11 ?

A

Chromosomes line up

20
Q

Outline the process of spermatogenesis

A
  • spermatogenesis is the process by which mature sperm are produced in the testes.
  • it begins with a stem cell called spermatogonium (2n) which divides by MITOSIS into primary spermatocyte (2n).
  • primary spermatocyte then undergoes meiosis 1 to form secondary spermatocytes. Meiosis 11 then occurs where the secondary spermatocyte divides into four spermatids (n). These then mature into 4 spermatozoa.
21
Q

How long does spermatogenesis take ?

A

60 days

22
Q

How long does oogenesis take ?

A

12-50 years. Oogenesis is only completed once egg has been fertilised

23
Q

Why women after the age of 45 find it difficult to get pregnant ?

A
  • this is because when babies are born - they are born with the maximum number of primary Oocytes. And so across the years , these of course deplete.
24
Q

When does meiosis 11 of secondary Oocytes begin ?

A

When fertilisation occurs - this would produce polar bodies and egg cell.

25
Q

When is meiosis 1 activated in oogenesis ?

A

When girl hits puberty

26
Q

Outline the process of oogenesis

A

1) begins with an oogonium.
2) this undergoes mitosis to produce a primary Oocyte. This occurs before birth.
3) MEIOSIS 1 of the primary Oocyte only begins once puberty is reached. This is where the primary Oocyte divides into the secondary Oocyte. ( a polar body and egg is made )
4) MEIOSIS 11 occurs only at fertilisation - this is where the secondary Oocyte divides into the egg cell and polar bodies.

Cell Biology And Genetics (22 decks)

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