Genetics

Question 1

Each human has how many pairs of chromosomes?

Answer 1

23 pairs in total

22 autosomal pairs, 1 sex-linked pair

Question 2

G0 phase of the cell cycle

Answer 2

Most cells are resting, carrying out their normal function

Question 3

G1 phase of the cell cycle

Answer 3

1st growth phase as chromosomes become ready to be replicated

Question 4

S phase of the cell cycle

Answer 4

DNA replication occurs

Question 5

G2 phase of the cell cycle

Answer 5

2nd growth phase involving proteins etc.

Question 6

M phase of the cell cycle

Answer 6

Mitosis - mechanical separation of cell into two daughter cells
Two daughter cells are identical, diploid cells

Question 7

Variation occurs during meiosis by which method?

Answer 7

Crossing over

Question 8

In meiosis, one diploid cell becomes…

Answer 8

Four haploid daughter cells

Question 9

Examples of sequence variations between genes?

Answer 9

Single nucleotide polymorphisms (SNPs)

Deletions/duplications

Question 10

A polymorphism is…

Answer 10

A change in the genome that does not cause disease in its own right, but can predispose to a common disease

Question 11

A chromosome consists of…

Answer 11

Telomeres at each end
Short arm (p)
Centromere
Long arm (q)

Question 12

A chromosome is metacentric if…

Answer 12

Both arms are roughly the same length

Question 13

A chromosome is acrocentric if…

Answer 13

The p (short) arm is so short it is hard to observe

Question 14

A chromosome is telocentric if…

Answer 14

The centromere is located at the terminal end of the chromosome

Question 15

An aneuploidy is…

Answer 15

An abnormal number of chromosomes
Monosomy - missing chromosome from one pair
Trisomy - extra chromosome in a pair

Question 16

Reciprocal translocations are when…

Answer 16

Segments from two different chromosomes have been exchanged

Balanced translocation

Question 17

Robertsonian translocations are when…

Answer 17

Two afrocentric chromosomes stuck end to end

Question 18

45 X causes …

Answer 18

Turner’s syndrome

Question 19

Trisomy of chromosome 21 causes…

Answer 19

Down’s syndrome

Question 20

What is FISH?

Answer 20

DNA probes specifically bind to areas of individual chromosomes and apply a fluorescein stain to make the chromosome visible
Useful for detecting aneuploidies

Question 21

Penetrance is defined as…

Answer 21

The likelihood of having the disease given you have the genetic mutation

Question 22

Mendelian inheritance encompasses which disorders?

Answer 22

Autosomal dominant
Autosomal recessive
X-linked
Mitochondrial

Question 23

Autosomal dominant disease occurs when…

Answer 23

There is one faulty copy of the gene
Seen in all generations
50% risk of affected child if parent affected

Question 24

Autosomal recessive disease occurs when…

Answer 24

There are 2 faulty copies of the gene
Often only one generation affected
25% risk of affected child if parents are carriers
Increased likelihood if parents are related

Question 25

X-linked disease occurs when...

Answer 25

The disease is carried on the X-chromosome only 50% of male children of a female carrier affected 50% of female children of a female carrier affected All male children of a male carrier normal All female children of a male carrier will be carriers

Question 26

Mitochondrial disease occurs when...

Answer 26

Diseased mitochondria passed from mother to child

Question 27

What is mosaicism?

Answer 27

Occurs when cells within the same person have a different genetic makeup

Question 28

Epigenetic variation describes...

Answer 28

Functional modifications to the genome that do not involve a change in the nucleotide sequence

Question 29

Methylation inhibits which process?

Answer 29

DNA transcription

Question 30

What is imprinting?

Answer 30

Variation in gene expression depending on which parent you inherit the gene from e.g. in Angelman's syndrome, mother's UBE3A works fine but father's is methylated

Question 31

Heteroplasmy is when...

Answer 31

Different daughter cells contain different proportions of mutant mitochondria (similar to mosaicism)

Question 32

Where are the 2 checkpoints in the cell cycle where DNA can acquire mutations?

Answer 32

Between G2 and M | Between G1 and S

Question 33

What is the function of oncogenes?

Answer 33

Promote cell division

Question 34

What is the function of tumour suppressors?

Answer 34

Inhibit cell division

Question 35

Only one copy of the tumour suppressor gene is required to be mutated for cancer to occur. True/False?

Answer 35

False | 2 copies required

Question 36

Cancer is most often inherited as a high penetrance Mendelian disorder. True/False?

Answer 36

False | More usually multifactorial