MGD7+8

Question 1

Where does the energy come from for DNA replication?

Answer 1

The hydrolysis of pyrophosphate

Question 2

What are the steps of initiation for DNA replication?

Answer 2

recognition of the origin of replication
recruitment of DNA polymerase
‘kick-start’ by primase
small amount of RNA made that can be extended and then RNA bit is removed

Question 3

What makes up the lagging strand?

Answer 3

Okazaki fragments

Question 4

On chromosomes, which arm is usually shorter?

Answer 4

The p arm

Question 5

What type of chromosome do humans not have?

Answer 5

Telocentric

Question 6

How long does it take a human cell to replicate all of its DNA?

Answer 6

8 hours

Question 7

What happens in telophase of mitosis?

Answer 7

nuclear membrane reforms, chromosomes decondense and spindle fibres disappear

Question 8

What happens in prophase I of meiosis?

Answer 8

homologous chromosomes find each other to form bivalents

crossing over occurs at chiasmata

Question 9

What happens in metaphase I of meiosis?

Answer 9

homologous pairs line up on equator (metaphase plate)

random assortment of chromosomes

Question 10

What happens in anaphase I of meiosis?

Answer 10

chromosomes are pulled to opposite ends of the cell

Question 11

What is the difference between meiosis I and meiosis II?

Answer 11

in anaphase II the sister chromatids are split up and pulled to opposite ends of the cell instead of the chromosomes

Question 12

How long does spermatogenesis take?

Answer 12

48 days

Question 13

What is the sequence for spermatogenesis?

Answer 13

spermatogonium (2n) -> primary spermatocyte (2n) ->

spermatids (n) -> mature sperm (n)

Question 14

What is the sequence for oogenesis?

Answer 14

Oogonium (2n) -> primary oocyte (2n) -> 
1 egg (n) + 3 polar bodies

Question 15

What does hemizygous mean?

Answer 15

can only occur in men, it means they only have 1 allele of a gene as it is on the X chromosome

Question 16

What are the most common patterns on inheritance and give an example for each?

Answer 16

autosomal recessive eg. cystic fibrosis
autosomal dominant eg. Huntington’s disease
X linked recessive eg. Haemophilia A

Question 17

What does it mean if alleles are codominant?

Answer 17

They both contribute to the phenotype

Question 18

Give an example of codominance

Answer 18

Human blood types

Question 19

Give an example of complementation

Answer 19

Albinism

Question 20

What is the basis of complementation?

Answer 20

The basis is that more than one gene can be involved in producing the phenotype.
Sometimes you have to have the mutant allele in both to have the disease.

Question 21

What are linked genes?

Answer 21

Genes on the same chromosome

Question 22

Do linked genes show independent assortment?

Answer 22

No

They are on the same chromosome so are most likely carried together.

Question 23

If 2 genes are further apart on a chromosome how does this affect the recombination frequency?

Answer 23

The recombination frequency is likely to be higher the further apart the genes are on the chromosome.

Question 24

Which enzyme catalyses DNA replication?

Answer 24

DNA polymerase