Genetics

Question 1

Each human has how many pairs of chromosomes?

Answer 1

23 pairs (46 chromosomes 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 two main methods, which are?

Answer 7

Crossing over

Independent segregation of homologous chromosomes

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

Chromosome 22 looks like a…

Answer 11

Teddy bear

Question 12

A chromosome consists of…

Answer 12

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

Question 13

A chromosome is metacentric if…

Answer 13

Both arms are roughly the same length

Question 14

A chromosome is acrocentric if…

Answer 14

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

Question 15

A chromosome is telocentric if…

Answer 15

The centromere is located at the terminal end of the chromosome

Question 16

An aneuploidy is…

Answer 16

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

Question 17

Reciprocal translocations are when…

Answer 17

Segments from two different chromosomes have been exchanged

Question 18

Robertsonian translocations are when…

Answer 18

A chromosome attaches to another chromosome at the centromere
Only occurs in acrocentric chromosomes: 13, 14, 15, 21, 22

Question 19

Monosomy of the sex chromosomes causes…

Answer 19

Turner’s syndrome

Question 20

Trisomy of chromosome 21 causes…

Answer 20

Down’s syndrome

Question 21

What is FISH?

Answer 21

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

Must know where to ‘look’

Question 22

Penetrance is defined as…

Answer 22

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

Question 23

Mendelian inheritance encompasses which disorders?

Answer 23

Autosomal dominant
Autosomal recessive
X-linked
Mitochondrial

Question 24

Autosomal dominant disease occurs when…

Answer 24

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

Question 25

Autosomal recessive disease occurs when...

Answer 25

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 26

X-linked disease occurs when...

Answer 26

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 27

Mitochondrial disease occurs when...

Answer 27

Diseased mitochondria passed from mother to child

Question 28

What is mosaicism?

Answer 28

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

Question 29

Epigenetic variation describes...

Answer 29

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

Question 30

Methylation inhibits which process?

Answer 30

DNA transcription

Question 31

What is imprinting?

Answer 31

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 32

Heteroplasmy is when...

Answer 32

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

Question 33

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

Answer 33

Between G2 and M | Between G1 and S

Question 34

What is the function of proto-oncogenes?

Answer 34

Promote cell division

Question 35

What is the function of tumour suppressors?

Answer 35

Inhibit cell division

Question 36

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

Answer 36

False | 2 copies required

Question 37

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

Answer 37

False | More usually multifactorial

Question 38

Achondroplasia. Gene? Inheritance?

Answer 38

FGFR3 | AD

Question 39

Turner Syndrome

Answer 39

45X

Question 40

How is the lagging DNA strand replicated?

Answer 40

Replicated in short Okazaki fragments in the 5' → 3'

Question 41

What percentage of the genome are exons?

Answer 41

2-3%

Question 42

What is the most common base pair mutation?

Answer 42

Cytosine to Thymine

Question 43

Why do some females develop some feature of X-linked conditions?

Answer 43

X-inactivation via methylation

Question 44

Where does methylation (to turn of genes) usually occur?

Answer 44

Cytosine bases that occur directly before Guanine

Question 45

Which targeted therapy is used for BRAF oncogene mutations?

Answer 45

Vemurafenib

Question 46

Which targeted therapy is used for HER2 oncogene mutations?

Answer 46

Trastuzumab

Question 47

Which targeted therapy is used for philadelphia chromosome mutations?

Answer 47

Imatinib - protein kinase inhibitor

Question 48

What does the Rb gene encode?

Answer 48

Tumour suppressor proteins - located at G1 checkpoint

Question 49

When is karyotyping and chromosome analysis used?

Answer 49

For large (>5 million base-pairs) balanced translocations

Question 50

When is array-aCGH used?

Answer 50

Only detects imbalance (deletions or duplications)

Question 51

What is the disadvantage of using FISH?

Answer 51

You need to know where to look for the mutation

Question 52

When is PCR and Sanger Sequencing used?

Answer 52

When very small amounts of DNA need to be multiplied and sampled

Question 53

Which type of Next Generation Sequencing is most expensive?

Answer 53

Whole Genome Sequencing

Question 54

Which transcription factor aids all RNA polymerase II transcriptions?

Answer 54

TF IID

Question 55

How is pre-mRNA modified upon completion?

Answer 55

Poly - u - tail

Question 56

How is mRNA modified upon completion?

Answer 56

Poly - a - tail and a 5'-cap

Question 57

What does the term degenerate refer to in the genetic code?

Answer 57

Many amino acids have more than one corresponding codon

Question 58

In which direction is DNA polymerase's exonuclease activity?

Answer 58

3' -> 5'

Question 59

Which enzyme binds amino acids to their specific tRNA?

Answer 59

Aminoacyl-tRNA synthetases

Question 60

Which elongation factor brings the next aminoacyl-tRNA to the ribosomal A-site?

Answer 60

EF-1a

Question 61

Which elongation factor regenerates EF-1a after it is hydrolysed to EF by GTP?

Answer 61

EFßgamma

Question 62

Which enzyme catalyses the peptide bond between amino acids in the P and A-sites?

Answer 62

Peptidyl transferase

Question 63

Which elongation factor moves the ribosome along the mRNA?

Answer 63

EF-2

Question 64

How is the the peptide chain terminated in translation?

Answer 64

A-site encounters stop codon; RF binds GTP is hydrolysed and finished protein is cleaved off