Topic 1: Chromosomes and Cellular Reproduction Flashcards

(45 cards)

1
Q

What is the n-value

A

The number of chromosomes of a cell

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2
Q

What is the c-value

A

Amount of DNA in an individual cell

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3
Q

Diploid vs haploid cells?

A

Diploid = cells that carry two sets of genetic information (two chromosomes)
Haploid = cells that carry one set of genetic information

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4
Q

n vs 2n

A

n= haploid
2n= diploid

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5
Q

What is polyploid

A

4n, 6n (# chromosomes)
Found in plants

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6
Q

In diploid cells, chromosomes occur in…

A

homologous pairs

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7
Q

Two kinds of homologous pairs

A

Similar but not identical (same genes in same order, different alleles of those genes)

Sister chromatids (identical alleles)

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8
Q

Two ways of measuring the amount of DNA within a haploid nucleus

A

Picograms, base pairs

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9
Q

Base pairs are measured in…

A

kb = kilo base = 100
Mb = mega = 1 million
Gb = giga = 1 billion

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10
Q

Number of chromosomes in a human

A

2n = 46

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11
Q

Number of genes in a human, genome size

A

21k genes
3 Gb genome

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12
Q

What is the c-value paradox

A

The number of genes does not indicate complexity, genome size, number of chromosomes, etc

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13
Q

Types of non-gene DNA?

A

Repetitive DNA
Centromeres
Telomeres

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14
Q

Two types of repetitive DNA, describe them

A

Moderately repetitive (150-300 bps long, found in many places in the genome, transposons)

Highly repetitive (<10 bps long, microsats)

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15
Q

What are centromeres

A

constricted region of chromosome where spindle fibers attach
Moderately repetitive DNA, tandemly repeating

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16
Q

What are telomeres

A

6 bp repeats, tandemly repeating
Repetitive sequence at the end of linear chromosomes

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17
Q

What is the role of telomeres

A

Solves end replication problem
Provide stability

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18
Q

The end of the chromosome that is overhanging (longer) is the

A

G-rich strand

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19
Q

What is the T-loop

A

G-rich strand folds over and pairs with a short stretch of DNA

20
Q

What organisms are T-loops found in, what are their role?

A

In mammals, provide stability to the end of the chromosome

21
Q

What are the phases of interphase, describe them

A

G1 = cell growth/development; G1/S checkpoint
S = synthesis phase (of DNA)
G2 = prepare cell for mitosis (division); G2/M checkpoint

22
Q

What is the M phase?

A

Mitotic phase (nuclear and cell division)

23
Q

What are the major checkpoints of mitosis, what do they look for?

A

G1/S = external conditions/DNA damage
G2/M = prevent entering into mitosis if DNA is damaged
spindle assembly = all chromosomes
properly attached to spindle apparatus

24
Q

Five phases of mitosis, describe them.

A

Prophase = chromosomes start to condense, centrosomes start to find each other

Prometaphase = disintegration of nuclear envelope

Metaphase = chromosomes line up on metaphase plate individually; spindle-assembly checkpoint

Anaphase = sister chromatids separate

Telophase = chromosomes arrive at spindle poles, nuclear envelope re-forms

25
Slide 19**
Mitosis summary
26
What are the genetic consequences of the cell cycle
- produces two genetically identically cells - new cells contain full complete set of chromosome - each new cell contains half the cytoplasm of the parent cell
27
Meiosis produces...
haploid gametes (2n -> n)
28
Fertilization produces...
Fusion of two haploid cells (n -> 2n)
29
Broad phases of meiosis
Interphase (same as mitosis; G1, S, G2) Meiosis I (separation of homologous chromosomes) Meiosis II (separation of sister chromatids)
30
Describe meiosis 1, aka...
Reduction division 2n -> n Metaphase plate homologous pairs line up Different from mitosis due to change in ploidy
31
Describe meiosis 2, aka...
Equational division n -> n (no change in ploidy, similar to mitosis)
32
Three steps of prophase 1 during meiosis 1
Synapsis: homologous pairs find each other, pair up Tetrad: the chromosomes are now a tetrad Crossing over: exchange of genetic material between homologous chromsomes
33
What is the chiasmata
Forms between homologous chromosomes (links them) before crossing over; prepares for separation/reattachment
34
What happens during metaphase 1 in meiosis 1
Tetrads line up on metaphase plate
35
What happens during anaphase 1 in meiosis 1
Separation of homologous chromosomes (segregate independently)
36
What is interkinesis
Stage between M1 and M2
37
During mitosis anaphase, what does separase do? What happens after?
Cuts all the cohesins Microtubules then pull sister chromatids apart
38
What does shugoshin do
Protein that is added to cohesin to protect it from separase (only to cohesins near centromere)
39
Stages of Meiosis 2
Prophase II, Metaphase II, Anaphase II, Telophase II
40
Difference between meiosis II and mitosis
Similar, except meiosis 2 starts off with 2 haploid cells and we end up with 4 haploid cells
41
What happens during metaphase 2 in meiosis 2
Individual chromosomes line up at metaphase plate
42
What happens during anaphase 2 in meiosis 2
Separation of sister chromatids
43
Products of meiosis 2
4 haploid cells (gametes)
44
Consequences of meiosis on chromosome number
- Reduced by half - Diploid to haploid
45
Newly formed cells from meiosis are...
Genetically different from one another and from the parental cell