Topic 1: Chromosomes and Cellular Reproduction

Question 1

What is the n-value

Answer 1

The number of chromosomes of a cell

Question 2

What is the c-value

Answer 2

Amount of DNA in an individual cell

Question 3

Diploid vs haploid cells?

Answer 3

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

Question 4

n vs 2n

Answer 4

n= haploid
2n= diploid

Question 5

What is polyploid

Answer 5

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

Question 6

In diploid cells, chromosomes occur in…

Answer 6

homologous pairs

Question 7

Two kinds of homologous pairs

Answer 7

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

Sister chromatids (identical alleles)

Question 8

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

Answer 8

Picograms, base pairs

Question 9

Base pairs are measured in…

Answer 9

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

Question 10

Number of chromosomes in a human

Answer 10

2n = 46

Question 11

Number of genes in a human, genome size

Answer 11

21k genes
3 Gb genome

Question 12

What is the c-value paradox

Answer 12

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

Question 13

Types of non-gene DNA?

Answer 13

Repetitive DNA
Centromeres
Telomeres

Question 14

Two types of repetitive DNA, describe them

Answer 14

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

Highly repetitive (<10 bps long, microsats)

Question 15

What are centromeres

Answer 15

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

Question 16

What are telomeres

Answer 16

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

Question 17

What is the role of telomeres

Answer 17

Solves end replication problem
Provide stability

Question 18

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

Answer 18

G-rich strand

Question 19

What is the T-loop

Answer 19

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

Question 20

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

Answer 20

In mammals, provide stability to the end of the chromosome

Question 21

What are the phases of interphase, describe them

Answer 21

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

Question 22

What is the M phase?

Answer 22

Mitotic phase (nuclear and cell division)

Question 23

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

Answer 23

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

Question 24

Five phases of mitosis, describe them.

Answer 24

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

Question 25

Slide 19**

Answer 25

Mitosis summary

Question 26

What are the genetic consequences of the cell cycle

Answer 26

- produces two genetically identically cells - new cells contain full complete set of chromosome - each new cell contains half the cytoplasm of the parent cell

Question 27

Meiosis produces...

Answer 27

haploid gametes (2n -> n)

Question 28

Fertilization produces...

Answer 28

Fusion of two haploid cells (n -> 2n)

Question 29

Broad phases of meiosis

Answer 29

Interphase (same as mitosis; G1, S, G2) Meiosis I (separation of homologous chromosomes) Meiosis II (separation of sister chromatids)

Question 30

Describe meiosis 1, aka...

Answer 30

Reduction division 2n -> n Metaphase plate homologous pairs line up Different from mitosis due to change in ploidy

Question 31

Describe meiosis 2, aka...

Answer 31

Equational division n -> n (no change in ploidy, similar to mitosis)

Question 32

Three steps of prophase 1 during meiosis 1

Answer 32

Synapsis: homologous pairs find each other, pair up Tetrad: the chromosomes are now a tetrad Crossing over: exchange of genetic material between homologous chromsomes

Question 33

What is the chiasmata

Answer 33

Forms between homologous chromosomes (links them) before crossing over; prepares for separation/reattachment

Question 34

What happens during metaphase 1 in meiosis 1

Answer 34

Tetrads line up on metaphase plate

Question 35

What happens during anaphase 1 in meiosis 1

Answer 35

Separation of homologous chromosomes (segregate independently)

Question 36

What is interkinesis

Answer 36

Stage between M1 and M2

Question 37

During mitosis anaphase, what does separase do? What happens after?

Answer 37

Cuts all the cohesins Microtubules then pull sister chromatids apart

Question 38

What does shugoshin do

Answer 38

Protein that is added to cohesin to protect it from separase (only to cohesins near centromere)

Question 39

Stages of Meiosis 2

Answer 39

Prophase II, Metaphase II, Anaphase II, Telophase II

Question 40

Difference between meiosis II and mitosis

Answer 40

Similar, except meiosis 2 starts off with 2 haploid cells and we end up with 4 haploid cells

Question 41

What happens during metaphase 2 in meiosis 2

Answer 41

Individual chromosomes line up at metaphase plate

Question 42

What happens during anaphase 2 in meiosis 2

Answer 42

Separation of sister chromatids

Question 43

Products of meiosis 2

Answer 43

4 haploid cells (gametes)

Question 44

Consequences of meiosis on chromosome number

Answer 44

- Reduced by half - Diploid to haploid

Question 45

Newly formed cells from meiosis are...

Answer 45

Genetically different from one another and from the parental cell