Chromosomes and cell division

Question 1

What is the telomere?

Answer 1

5’-TTAGGG-3’ repeats on the end of the chromosomes to protect them

Question 2

What is the centromere?

Answer 2

Constricted region of repeating DNA joining sister chromatids together
Site of kinetochore

Question 3

What are the stages of the cell cycle and what happens in each?

Answer 3

G1- growth
S- DNA synthesis
G2- cell prepaid for mitosis
M- mitosis

Question 4

What are the stages of mitosis and what happens in each?

Answer 4

Prophase- chromosomes condense, nuclear membrane disappears, spindle fibres form
Metaphase- chromosomes align at centre of cell and spindle fibres attach
Anaphase- Sister chromatids separate longitudinally and move to opposite poles of the cell
Telophase- new nuclear membrane forms
Cytokinesis- Cytoplasm separates

Question 5

What is the kinetochore?

Answer 5

Protein complex that binds to the microtubules and is required for chromosomes

Question 6

What is heretochromatin?

Answer 6

Condensed, usually inactive form of DNA

Question 7

What is euchromatin?

Answer 7

Open, usually active genes

Question 8

What are extragenic sequences?

Answer 8

Tandemly repeated DNA sequences making up roughly 45%of the genome

Question 9

What is a nucleosome?

Answer 9

146 base pairs wrapped around 8 histone proteins

Question 10

What is the charge of DNA and histone?

Answer 10

DNA= negative
Histone= positive

Question 11

What are chromatin fibres?

Answer 11

Tightly packed nucleosomes

Question 12

What are centromeric probes useful for?

Answer 12

Determining chromosome number

Question 13

What are telomeric probes useful for?

Answer 13

Determining subtelomeric arrangements

Question 14

What are whole chromosome probes and what are they useful for?

Answer 14

Cocktail of different probes covering different parts of a particular chromosome
Determining translocations and rearrangements

Question 15

What is oogenesis?

Answer 15

Meiosis of the gremline cells to form ova

Question 16

What is spermatogenesis?

Answer 16

Meiosis of gremlin cells to form sperm

Question 17

What are the different types of chromosomal abnormalities and what are they?

Answer 17

Numerical- karyotype has wrong number of chromosomes
Structural- chromosomes rearranged
Mutational- change to DNA sequence

Question 18

What is a trisomy?

Answer 18

Muttion causing there to be 3 copes of a particular chromosome

Question 19

What does trisomy 13 cause?

Answer 19

Patau

Question 20

What does trisomy 18 cause?

Answer 20

Edwards

Question 21

What does trisomy 21 cause?

Answer 21

Downs

Question 22

What does the XXY mutation cause?

Answer 22

Klinefelter

Question 23

What does the X mutation cause?

Answer 23

Turner

Question 24

How many gametes would be affected by a problem with disjunction in meiosis 1?

Answer 24

All

Question 25

How many gametes would be affected by a problem with disjunction in meiosis 2?

Answer 25

2

Question 26

Why are mutations more likely in older mothers?

Answer 26

Disjunction becomes less accurate the longer eggs sit having completed meiosis 1 and not 2

Question 27

What are the types of translocation mutation?

Answer 27

``` Deletion Insertion Inversion Balanced Unbalanced ```

Question 28

What is a reciprocal translocation?

Answer 28

Involving breaks in two chromosomes with formation of two new derivative chromosomes

Question 29

What is a Robertsonian translocation?

Answer 29

Twi afrocentric chromosomes are fused but no genetic material is lost

Question 30

What is an inversion translocation?

Answer 30

2 breaks in chromosome repaired incorrectly so all information is present but in wrong order Not normally harmful unless it involves centromere

Question 31

What is polymorphism?

Answer 31

Differences in genetic code between individuals that doesn't cause abnormality

Question 32

What are the types of coding mutations?

Answer 32

Silent Missense Nonsense Frameshift- insertion, deletion

Question 33

What is used to detect genetic mutations?

Answer 33

Polymerase chain reaction Gel electrophoresis Restriction fragment length polymorphism analysis Amplification refractory mutation system

Question 34

What is the amplification refractory mutation system used to detect?

Answer 34

Single base changes or small deletions

Question 35

What is a disadvantage of the amplification refractory immune system?

Answer 35

Nature of mutation must be known