Chromosomes

Question 1

Where is the heterochromatin found?

Answer 1

By the centromere and telomeres

Question 2

What are telomeres?

Answer 2

The ends of chromosomes have no space for the RNA primers to attach to hence doesn’t get replicated.
Therefore telomeres shorten throughout our lives
Must not be inappropriately degraded or repaired

Question 3

What is the centromere?

Answer 3

Holds sister chromatids together

Question 4

What is heterochromatin

Answer 4

Loped around histones and are inactive

Question 5

What direction does DNA polymerase work ?

Answer 5

3 to 5 prime

Question 6

What stitches Okazaki fragments?

Answer 6

DNA ligase

Question 7

DNA polymerase can synthesis dna de novo.
True or false

Answer 7

False it needs an RNA primer

Question 8

What is the end replication problem?

Answer 8

Shortenning of telomerres

Question 9

What is telomerase ?

Answer 9

An enzymes which adds repeats to resynthesis the telomere but it’s only present in stem or germ cells

Question 10

What are centromeres

Answer 10

Repeated DNA sequences which joins sister chromatids together.

Question 11

What is a kinetochore

Answer 11

Protein complex that binds to the microtubules on the centromere

Question 12

What form is dna when activates or transcribed?

Answer 12

Euchromatin

Question 13

What are extragenic sequences?

Answer 13

Repeated DNA sequence which have no biologically function

Question 14

What is satellite DNA?

Answer 14

In centromeres and telomeres
14 to 500 base pairs with mainly A and T

Question 15

What is minisatellite dna?

Answer 15

Present in shorter lengths
15 to 100
GC rich

Question 16

What is the use of minisatellites

Answer 16

Used for paternity tests and DNA fingerprinting

Question 17

What are the types of highly repeated interspersed DNA?

Answer 17

SINE (short interspersed nuclear elements)
LINE

Question 18

What is a nucleosome?

Answer 18

DNA wrapped around a core protein of 8 histones with a histones H1 clipping them onto the histones

Question 19

What is a solenoid structure?

Answer 19

Coiling of nucleosomes
6 nucleosomes per turn
Called a chromatin fibre

Question 20

How long is a chromatin fibre?

Answer 20

30nm

Question 21

What happens to a chromatin fibre before becoming a chromosome?

Answer 21

It joins with fibre scaffold complex to form a series of loops to form a chromatin scaffold

Question 22

When are chromosomes most condense?

Answer 22

Metaphase

Question 23

Why is heterochromatin important?

Answer 23

Negative DNA becomes neutral due to positive histones
Takes up less space
Becomes inactive as it’s inaccessible

Question 24

What is metacentric chromosomes?

Answer 24

Where the centromere is near the middle of the chromosome

Question 25

What is sub metacentric chromosomes?

Answer 25

The centromere is much hugger up the chromosomes to create a distinct p and a arm

Question 26

What is an acrocentric chromosome?

Answer 26

Where the centromere is so far up that the p arm of the chromosome has no function it is just a telomere really

Question 27

What is an example of metacentric chromosomes ?

Answer 27

Chromosome 1

Question 28

What is an example of submetacentric chromosomes ?

Answer 28

Chromosome 12

Question 29

What is an example of acrocentric chromosomes ?

Answer 29

Chromosome 21

Question 30

How are chromosomes analysed?

Answer 30

Take blood Separate out rbc Culture and incubate Colchicine added Separate WBCs Burst cells using saline Spread out chromatin on slide Stain it

Question 31

What is colchicine ?

Answer 31

Mitotic inhibitor which causes cells to accumulate at metaphase

Question 32

What is Karotyping?

Answer 32

Preparation of a complete set of metaphase chromosomes in order

Question 33

Most of our chromosomes are submetacentric. True or False

Answer 33

True

Question 34

What is FISH?

Answer 34

Fluorescence in situ hybridisation The sequence of interest is labelled with a dye

Question 35

What are the types of Fish probes?

Answer 35

Unique sequence probes Centromeres probes Telomeric probes Whole chromosome probes

Question 36

What is a unique sequence probe?

Answer 36

Unique sequences are highlighted

Question 37

What is a centromeric probe?

Answer 37

Helps determine chromosome number

Question 38

What is a telomeric probe used for?

Answer 38

Detect sub telomeric rearrangements Often in children with unexplained mental retardation

Question 39

What is a whole chromosome probe?

Answer 39

Use various probes and fluorescent dyes for each chromosome to create spectral karyotypes to detect translocation Easier to align

Question 40

FISH can be used on an intact nuclei. True or False

Answer 40

True

Question 41

What is a bivalent?

Answer 41

The sister undergo recombination

Question 42

What is recombination?

Answer 42

Exchange of parts of chromosomes between the maternal and paternal copy

Question 43

What is gametogenesis?

Answer 43

Production of gametes via meisos

Question 44

What is egg formation called?

Answer 44

Oogenesis

Question 45

What is sperm formation called?

Answer 45

Spermatogenesis

Question 46

Difference of timing of gametogenseis

Answer 46

Females are born with all their eggs in meiosis 1(primary oocytes) males make them in puberty

Question 47

What is x inactivation ?

Answer 47

Females zygotes get 2 X chromosomes one gets randomly switched off so it’s never expressed and hidden deep in heterochromatin

Question 48

What is the first enzyme needed for dna replication?

Answer 48

RNA primase To make a complementary segment of rna (a primer) It allows DNA polymerase to bind onto it

Question 49

What’s the difference between microsatellites and lines/sines?

Answer 49

Microsatellites repeats are back to back/consecutive Lines are repeats dispersed throughout the whole genome randomly (not adjacent)