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Medical Cell Biology & Genetics > Cell Division > Flashcards

Cell Division Flashcards

1
Q

What is the difference between mitosis and meiosis?

A

Mitosis produces 2 identical daughter cells, while meiosis produces 4 daughter cells (gametes) with genetic variation

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2
Q

How many chromosomes, chromatids, and DNA molecules are there after S phase and during G2 phase of mitosis?

A

There are 46 chromosomes, 92 chromatids, and 46 DNA molecules

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3
Q

What are centrosomes?

A

Centrosomes are structures made of y-tubulin, that migrate to opposite ends of the cell and make it bi-polar - from here, mitotic spindles segregate the chromatids into seperate daughter cells to ensure there are 46 chromosomes per cell

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4
Q

How have taxols proved successful in targeting cancer cells?

A

Taxols disrupt the growth of the microtubules, meaning that they cannot pull sister chromatids apart and so cannot form 2 viable daughter cells

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5
Q

What is interesting about the number of centrosomes in a cancer cell?

A

They usually have more than 2

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6
Q

How may a cancer cell propagate in spite of having more than 2 centrosomes?

A

They cluster the spare centrosomes in other compartments of the cell, which do not interfere with cell division

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7
Q

How have modern therapeutic techniques been able to target the increased number of centromeres in a cancer cell? Why does it not affect normal cells?

A

Modern drugs may inhibit centrosome clustering, meaning that cancer cells will not be dividing into viable daughter cells and will die - this doesn’t affect normal cells as they have 2 centrosomes, and will continue to divide normally

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8
Q

What are the cell cycle checkpoints? Where do they occur?

A

The cell cycle check points are points that assess environmental factors, ensuring they are appropriate before beginning the next stage of the cell division cycle - they occur towards the end of G1 & G2

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9
Q

What is the function of cohesin?

A

Cohesin holds the homologous sister chromatids together, ensuring they do not become seperated before they are moved into their respective daughter cells

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10
Q

How many sub-units comprise cohesin?

A

4

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11
Q

What is the difference between homozygous and heterozygous?

A

Homozygous states that the 2 alleles of a gene inherited by an individual are the same, while heterozygous states that the 2 alleles of a gene inherited by an individual are different

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12
Q

What is hemizygous?

A

There is only one allele of a gene, on the X chromosome (therefore only males express this type of inheritance)

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13
Q

In a heterozygote, how is it determined which allele is expressed?

A

Now allele is dominant, while the other is recessive

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14
Q

What is co-dominance?

A

This relates to heterozygotes where neither allele is dominant or recessive, and so both alleles are expressed

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15
Q

What is the risk percentage of 2 carriers of a recessive disease having a child has the disease phenotype?

A

25%

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16
Q

In a heterozygous recessive disease, how many alleles are required for an individual to exhibit the disease phenotype?

A

Both alleles (2)

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17
Q

In a heterozygous dominant disease, how many alleles are required for an individual to express the disease phenotype?

A

Just 1 (the disease) dominant allele

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18
Q

Name 1 disease that is the result of a recessive allele. What is the mutation that occurs?

A

Cystic fibrosis - a mutation in the CFTR gene - F508 is the most common mutation, which leads to the loss of a phenylalanine at position 508 of the CFTR protein

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19
Q

What can you say about the parents of an individual with an autosomal dominant disease?

A

At least one of the parents will also express the disease phenotype

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20
Q

Why are X-linked recessive diseases more common in males?

A

They only need to inherit 1 allele (as they only inherit 1 maternal X chromosome) in order to inherit the disease

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21
Q

Can males with an X-linked recessive disorder pass it on to their sons? Why?

A

No - they will only pass their Y chromosome to their sons - the sons won’t inherit an X chromosome from their father

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22
Q

What is the chance the a heterozygous female carrier of an X-linked recessive disorder will pass the disorder onto their male offspring? Why?

A

50% - there is a 50% chance the son will inherit either allele (as they will also inherit their Y chromosome from their father)

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23
Q

How may you be able to infer whether is X-linked or not by a brief look at a pedigree diagram?

A

An unequal distribution of the disorder between males and females

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24
Q

What does whether a disorder is monogenic or polygenic refer to?

A

Whether the disorder is directly the result of a singular genetic abnormality or whether multiple genetic abnormalities result in a disorder

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25
Q

How are mitochondrial diseases inherited?

A

Maternally (through the mother)

26
Q

In what manner is albinism inherited? Is it monogenic or polygenic?

A

In a recessive manner - it is apolygenic disorder

27
Q

What makes some disorders more likely to be the result of polygenic inheritance?

A

Their proximity (i.e. how close they are) of the genes on a particular chromosome

28
Q

What are 2 homologous chromatids called?

A

Sisters

29
Q

What is the short arm of a chromosome referred as? What is a long arm referred as?

A

The short arm is called the p arm - the long arm is called the q arm

30
Q

What repeat sequence is associated with telomeres?

A

TTAGGG

31
Q

What are the 4 types of centromere? Describe their position in regards to the centre of the chromosome.

A
  • metacentric - directly in the centre
  • submetacentric - just off-centre
  • acrocentric - grossly off-centre
  • telocentric - at the telomere
32
Q

What links the p and q arms of a chromosome?

A

A centromere

33
Q

List the stages of cell division in chronological order.

A
  • prophase
  • prometaphase
  • metaphase
  • anaphase
  • telophase
34
Q

What is cytokinesis?

A

Cytokinesis is the physical process of cell division, which divides the cytoplasm of a parent cell into 2 daughter cells

35
Q

What occurs in prophase of mitosis?

A

The nuclear membrane dissolves, and the chromosomes condense

36
Q

What is the kinetochore?

A

The part of the chromosome (more specifically the part of the centromere) that the microtubules connect to

37
Q

What occurs at prometaphase of mitosis?

A

Microtubules connect to the kinetochore

38
Q

What occurs in metaphase of mitosis?

A

The 46 chromosomes (92 chromatids) line up at the midline of the cell

39
Q

What occurs in anaphase of mitosis?

A

The kinetochore fibres pull the homologous chromatids to opposite parts of the cell

40
Q

What occurs during telophase of mitosis?

A

The kinetochore fibres disintegrate and the nuclear membrane(s) reappear

41
Q

Where are the chromosomes during interphase?

A

Chromosomes are not condensed during interphase so you cannot see them - they do not exhibit their classic X shape in this phase

42
Q

What is a variant of the same gene called?

A

An allele

43
Q

Everybody has 2 copies of a chromosome - are chromatids on two different chromosome 1 molecules sisters? Do they contain the same genes?

A

They are not sisters, but will contain the same genes (but will probably contain different alleles of these genes)

44
Q

Are gametes diploid of haploid?

A

Haploid

45
Q

How do chromosomes line up in metaphase I of meiosis?

A

They line up with their homologous pair

46
Q

What is crossing over? When in cell division does this occur?

A

Crossing over is the genetic exchange of material between 2 homologous chromosomes, creating genetic variation - this occurs in prophase I

47
Q

What is a chiasmata?

A

The point at which 2 homologous chromosomes exchange genetic material during crossing over in prophase I of meiosis

48
Q

How many chromatids are lined up next to each other in metaphase I of meiosis? What is this called?

A

4 chromatids are lined up - this is called a tetrad

49
Q

At the end of telophase I of meiosis, how many chromosomes are in each daughter cell?

A

23 (but 46 chromatids are in each daughter cell)

50
Q

What does the random assortment of chromosomes refer to?

A

The random order in which paternal and maternal chromosomes line up at the midline in metaphase I

51
Q

What cell gives rise to mature sperm?

A

A spermatogonium - this produces a primary spermatocyte, which go on to form primary sperm

52
Q

What gives rise to an ovum?

A

An oogonium - this differentiates into a primary oocyte, which mature into an ovum

53
Q

During which phases of the cell cycle are chromosomes heavily condensed?

A

Prophase, anaphase, and metaphase

54
Q

During which phase of the cell cycle are chromosomes replicated?

A

S phase

55
Q

What is the nucleolus?

A

The nucleolus is an unbound area of the nucleus where it is responsible for the creation of ribosomes, containing various rRNAs

56
Q

When in the cell cycle is the nucleolus normally present?

A

During interphase

57
Q

During meiosis I, how do homologous chromosomes find each other at the midline?

A

Due to the similarity in the regions of the genes they share

58
Q

How do the sex chromosomes find one another?

A

Through PAR regions

59
Q

What is aneuploidy?

A

An error in cell division, resulting in an abnormal number of chromosomes in the daughter cell after division

60
Q

Why does aneuploidy of the sex cells have fewer consequences than aneuploidy of other cells?

A

The sex cells contain less genetic information, meaning that genes necessary for viability are not lost

61
Q

What is anaphase lag? Why might it occur, and what are its consequences?

A

Anaphase lag describes a delayed movement during anaphase - this may be because a kinetochore spindle has failed to attach to the kinetochore of the chromatid is tardily drawn to its polar region - this will result in aneuploidy

Medical Cell Biology & Genetics (11 decks)

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