Genetics

Question 1

How is DNA different from RNA? (4)

Answer 1

DNA:
found in nucleus
double-stranded
deoxyribose sugar
A, G, T, C

Question 2

How is RNA different from DNA? (4)

Answer 2

RNA:
found in cytoplasm
single-stranded
ribose sugar
A, G, U, C

Question 3

How does DNA replicate?

Answer 3

Semi-conservatively

Question 4

What stages make up interphase?

Answer 4

G1, S, G2

Question 5

What happens in G0?

Answer 5

Cell cycle arrest

Question 6

What happens in G1?

Answer 6

Cellular contents (excluding chromosomes) are duplicated

Question 7

What happens in S?

Answer 7

Chromosomes are duplicated

Question 8

What happens in G2?

Answer 8

Duplicated chromosomes checked for errors, and repaired

Question 9

What are the 3 checkpoints in the cell cycle?

Answer 9

• G1 checkpoint
• G2 checkpoint
• M/ metaphase checkpoint

Question 10

Mutation in what protein can cause cancer?

Answer 10

Tumour protein p53

Question 11

What do proto-oncogenes do?

Answer 11

They code for growth factors

Question 12

What do tumour suppressor genes do?

Answer 12

Inhibit cell division of damaged cells

Question 13

When does DNA and organelles replicate?

Answer 13

Interphase

Question 14

What happens during prophase? (2)

Answer 14

Chromatin condenses into chromosomes

Centrioles move to opposite poles of the cell

Question 15

What happens during pro-metaphase? (2)

Answer 15

Nuclear envelope disappears

Spindle fibres form

Question 16

What happens during metaphase? (2)

Answer 16

Chromosomes line up along equator

Spindle fibres attach to centromeres

Question 17

What happens during anaphase? (2)

Answer 17

Centromeres split

Spindle fibres contract, pulling sister chromatids to opposite poles of the cell

Question 18

What happens during telophase? (3)

Answer 18

Chromosomes unfold into chromatin
Nuclear membrane forms
Spindle fibres disintegrate

Question 19

What happens during cytokinesis?

Answer 19

Cells form cleavage and splits into two

Question 20

What happens during meiosis 1?

Answer 20

Homologous chromosomes separate

Question 21

What happens during meiosis 2?

Answer 21

Centromeres split and sister chromatids separate

Question 22

How is genetic diversity introduced during meiosis?

Answer 22

Prophase 1: crossing over w/in homologous pairs

Metaphase 1: independent assortment of homologous chromosomes

Question 23

What condition is an example of a non-disjunction?

Answer 23

Trisomy 21 - Down’s syndrome

Question 24

What condition is associated with the genotype 45XO?

Answer 24

Turner’s syndrome

Question 25

Define gonadal mosaicism (2)

Answer 25

Germ line mutation giving rise to affected offspring from unaffected parents. Child is heterozygous in every cell

Question 26

Define somatic mutation

Answer 26

Postzygotic mutation that results in some cells being affected in the offspring

Question 27

How are the gamates in the affected individual of gonadal mosaicism affected?

Answer 27

Half carry mutation, half are don’t

Question 28

Are the gametes in the affected individual of somatic mosacism affected?

Answer 28

None of the genes carry the mutation

Question 29

Define genotype

Answer 29

Genetic makeup of an individual

Question 30

Define phenotype

Answer 30

Observable characteristic of an individual (env + genotype)

Question 31

Define locus

Answer 31

Fixed position of a gene on a particular DNA molecule

Question 32

Define allele

Answer 32

Different version of the same gene

Question 33

Define hemizygous

Answer 33

Gene carried on unpaired chromosome (eg X chromosome in male)

Question 34

Define penetrance

Answer 34

Proportion of ppl w/ a gene/genotype that show the expected phenotype

Question 35

Define variable expression

Answer 35

Individuals w/ the same genotype may show a different phenotype

Question 36

What is the reason for unaffected parents to produce affected children?

Answer 36

- Gonadal mosaicism - Mother may have reduced penetrance/ variable expression - They don’t have the genes for it

Question 37

Define lyonisation

Answer 37

Process of X chromosome inactivation in every cell in a female

Question 38

What genetic inheritance does male-to-male transmission suggest?

Answer 38

Autosomal dominant

Question 39

Define anticipation

Answer 39

Gene defects that affect successive generations earlier and more severely