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2B: Genetics and Evolution > 9 - Mitosis and Meiosis > Flashcards

9 - Mitosis and Meiosis Flashcards

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Biology 101 flashcards
1
Q

what is ploidy?

A

number of chromosomes in a cell

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2
Q

What is G0?

A

non-replication / dividing cell s

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3
Q

that is the role of condensin?

A
  • protein complex
  • condenses chromosomes
  • binds to two points on the DNA and folds the chromatin
  • takes a helical shape
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4
Q

What is a karyotype?

A
  • photo of full set of chromosomes in homologous pairs in decreasing size
  • specific to different organisms
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5
Q

what are the male sex chromosomes?

A

XY or ZZ

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6
Q

What are the female sex chromosomes?

A

XX or ZW

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7
Q

What is the name of the chromosomes that are not sex chromosomes?

A

autosomes

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8
Q

Which chromosome is number 1?

A
  • the largest one
  • number goes up as chromosomes get smaller
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9
Q

What are centromeres?

A
  • constitutive heterochromatin repetitive DNA
  • bind to kinetichore in mitosis
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10
Q

What are telomeres?

A
  • constitutive heterochromatin
  • repetitive DNA
  • protects ends of DNA from degradation
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11
Q

describe the structure of the kinetochores

A
  • nucleosome
  • CENP-A-containing nucleosome (histone variant)
  • inner kinetochore
  • outer kinetochores
  • spindle microtubules
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12
Q

How is the kinetochore recruited to the correct region?

A
  • nucleosome at the centromere contain CENP-A (a histone variant)
  • this recruits the kinetochore
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13
Q

Explain the stages of mitosis

A

Prophase
- condensin is recruited and chromosomes condense

Metaphase
- kinetochores attach to the centromeres of each sister chromatids
- line them up at the centre

Anaphase
- spindle microtubules pull sister chromatids apart ad towards opposite poles of the cell

Telophase
- nuclear membranes form around the two groups of chromosomes

Cytokenesis
- cytoplasm splits

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14
Q

What holds sister chromatids together

A

cohesin

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15
Q

explain sister chromatid adhesion across mitosis

A

prophase
- arms are attached by cohesin

metaphase
- connected at the centromere y cohesion
- arms are separated

anaphase
- cohesin at centromere degraded
- chromatids separated

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16
Q

What are the two models cohesin function?

A
  • ring model - wraps around two strands
  • handcuff model - wraps around one strand and interlinked with another cohesin
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17
Q

Explain bacterial mitosis (binary fission)

A
  • DNA is replicated
  • cell elongates and cross wall is formed (separating cells)
  • cells divide
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18
Q

What is the differences between bacterial and eukaryotic mitosis?

A
  • no nuclear envelope
  • no spindles needed as only one chromosome
  • plasmids are also replicated
  • axsexual reproduction
19
Q

explain organelles in cell division

A
  • mitochondria and chloroplasts carry out binary fission due to bacterial origin
  • organells partitioned in mitosis
  • in meiosis only maternally inherited
20
Q

when is the germ line set aside in development?

A

week 7

21
Q

explain the stages of meiosis

A

Prophase I
- chromosomes condende
- nuclear membrane breaks

Metaphase I
- pairs of homologous chromosomes go to centre of cell

Anaphase I
- homologous chromosomes move to opposite poles of the cell

Telophase and Cytokenesis I
- cytoplasm divides

Prophase II
- new spindle forms around chromosomes

Metaphase II
- chromosomes line up at the equator

Anaphase II
- centromeres divide
- chromatids move to opposite poles of the cell

Telophase and Cytokenesis II
- nuclear envelope forms around chromosomes
- cytoplasm divides

22
Q

What is thought to be a way that homologous chromosomes pair up in meiosis?

A
  • Programmed double stranded breaks
  • reaches out for homologous chromosome
  • brings them closer together
  • forms synaptoemal complex
  • when strand is repaired SC disassembles
23
Q

What are chiasmata?

A

sites where cross overs happen

24
Q

What is a tetrad or bivalent arrangement?

A
  • arrangement of chromosomes during crossing over
25
Q

what does separation of homologous chromosomes require?

A

At least one cross over

26
Q

what is the evolutionary importance of crossing over?

A
  • leads to recombination
  • new combination of alleles
27
Q

How does recombination prevent the accumulation of deleterious mutations?

A
  • unaffected regions of chromosomes can cross over to create a mutation free chromosome
  • will allow the fixing of advantageous alleles
28
Q

What lead to the difference appearances between X and Y chromosomes?

A
  • at some point one of the chromosomes inserted
  • this prevented crossing over
  • mutations were allowed to accumulate
  • XX can still undergo recombination in females
29
Q

How can X and Y pair up if there is no recombination?

A
  • they can recombine but only at their pseudo autosomal regions (at the ends of the chromosome)
30
Q

how many gametes are produced on spermatogenesis?

A

4

31
Q

how many gametes are produced in Oogenesis?

A

gametes - 1
polar bodies - 3

32
Q

When do spermatogenesis and Oogenesis happen?

A

males - continuously
females - once a month from puberty

33
Q

can sperm cells divide mitotically?

A

yes

34
Q

What are de novo mutations?

A
  • Mutations that happen during gamete production
  • can be inherited by offspring
35
Q

how does age increase risk?

A
  • males - more mutations due to number of divisions in the germline
  • females - increases risk of chromosomal mis-segregation
36
Q

what is parasexuality?

A

reproduction in bacteria
- transduction - transfer of DNA via viruses infecting the cell
- conjugation - transfer via physical contact between two cells
- transformation - DNA is taken from surrounding environment, such as dead bacteria

37
Q

explain gene dosage in XX and XY individuals

A
  • XX - one X is inactivated
  • XY - receives same dose as XX
38
Q

explain chromosome missegregation in cancer

A
  • many tumours aneuploid
  • higher mutation rate - extensive dosage changes
  • higher division rate - accumulation of changes
39
Q

Name 2 potential causes of miss-segregation

A
  • cohesin defects
  • issues in spindle attachment
40
Q

how many gametes will be effected if aneuploidy happens in meiosis I?

A

4

41
Q

how many gametes will be effected if aneuploidy happens in meiosis II?

A

2

42
Q

What is a haplotype?

A
  • set of alleles located and inherited together
43
Q

what are mitochondrial Eve and y-chromosomal Adam?

A
  • not the first humans
  • but most successful at spreading genes

2B: Genetics and Evolution (25 decks)

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