Molecular Biology

Question 1

What is the nature of mutations?

Answer 1

Changes to the genetic material of a cell or virus (with genetic material being DNA or RNA.

Question 2

What creates spontaneous mutation?

Answer 2

Created by anything but exogenous agents, for example DNA errors made during replication or repair or recombination

Question 3

Why are most mutations silent?

Answer 3

A change to one base pair often does not affect the amine group therefore having no affect on the phenotype.

Question 4

What is a nonsense mutation?

Answer 4

Changes in the codon resulting in a stop codon.

Question 5

What is a missense mutation?

Answer 5

Changes in a codon leading do a different amino acid in the polypeptide chain.

Question 6

How do you calculate net mutation?

Answer 6

DNA damage- repair

Question 7

Give examples of some origins of mutations.

Answer 7

Mutagens in food/ exposure to toxins/ radiation / rDNA damage during recombination (form of spontaneous mutation)

Question 8

Do germ-line or somatic cells have higher mutation rates?

Answer 8

Somatic cells, due to more replication occurring.

Question 9

How does a mutation affect a phenotype?

Answer 9

Mutation must alter a exon, therefore altering a section of DNA which affects

Question 10

What is meant by frameshift?

Answer 10

The insertion or deletion of one base pair, therefore altering all subsequent codons.

Question 11

What is the difference between conservative missense mutation and non-conservative missenses mutation?

Answer 11

Conservative missense occurs when an amino acid is replaced by another amino acid with similar structures however non-conservative missense is when a new amino acid is introduced with different properties.

Question 12

What does the term analogy mean?

Answer 12

Mutation in a protein-coding region.

Question 13

How do recessive mutations affect the phenotype?

Answer 13

Usually recessive mutations result in a loss of function e.g. Albinism is a recessive mutation where less melanin is produced due to reduced enzyme activity, which increases the risk of skin cancer.

Question 14

How dominant mutations affect phenotype?

Answer 14

Through a gain in function for example Achdroplasia, where the enzyme which inhibits growth is ‘locked’ in the active form therefore preventing bone growth.

Question 15

How do we determine if an allele is dominant or recessive?

Answer 15

By looking at the protein pool and its behaviour.

Question 16

List some main features of the human genome.

Answer 16

diploid (2 copies of every gene) // contains introns (non-coding genes) and exons (coding genes)

Question 16

How does the human genome differ between poeple.

Answer 16

Spontaneous mutations/ mutations due to exogenous factors all create variations in individuals genomes. INDELS (insertions and deletions )n of base pairs can alter an individuals genome.

Question 17

Roughly how many genes does a eukaryote have?

Answer 17

6,000

Question 18

What is meant by orthologs?

Answer 18

Genes from a common descendent which share the same function. these genes are often separated through speciation events

Question 19

What is meant by paralogs?

Answer 19

Genes with different functions separated by duplicate events(SAME GENE SAME SPECIES)

Question 20

What are SNPs?

Answer 20

Single nucleotide polymorphism, meaning a change to a single base position on DNA .

Question 21

What is the effects of SNPs?

Answer 21

If they occur on protein-coding regions of DNA, they can affect the protein product, they can also be used for biological markers

Question 22

What is ORF (open reading frame)

Answer 22

The protein coding region of a gene.

Question 23

How do you calculate allele frequency?

Answer 23

number of alleles divided by total alleles

Question 24

Define evolution in molecular terms

Answer 24

Is a change in allele frequency in a gene pool over time.

Question 25

When using the hard-Weinberg equilibrium what is assumed?

Answer 25

Alleles are stable/there is homozygous populations/ there is random mating/ all genotypes are equally ‘fit’/ mutations between alleles occur at low frequencies/ natural selection is not occurring/ THE POPULATION IS NOT EVOLVING AND ALLELE FREQUENCY REMIANS THE SAME.

Question 26

What is the hardy-Weinberg equation?

Answer 26

p^2 +2pq q^” = 1 // p^2 = frequency of homozygous dominant (AA)// q^2= frequency of homozygous recessive (aa)// pq= frequency of heterozygous (Aa)

Question 27

What is analogy ?

Answer 27

Mutations Within a protein coding region

Question 28

What is the chemical PTC (phenylthiocarbmide)?

Answer 28

A chemical which tastes bitter to the majority of the population, it is found in many vegetables and the bitter taste of it is detected by the TAS2R38 gene.

Question 28

How do we taste bitterness in our foods?

Answer 28

We have taste receptor cells on the roof of our mouth which create a chemical cascade releasing neurotransmitters which are recognised by the brain.// the TAS2R38 gene encodes for these protein receptors.

Question 28

What are the 3 stages of PCR (polymerase chain reaction) ?

Answer 28

1. Denature , 94degrees - DNA double strands are separated into single strands as the hydrogens bonds break // 2. Annealing, 55degrees- A primer is added, tis is a complimentary DNA strand which is complimentary to the template strands of DNA// 3. Extension, 72degrees - Taq DNA polymerase is added, an enzyme which joins single stranded DNA.

Question 28

How do SNPs affect the TAS2R38 gene?

Answer 28

There are 3 SNPs, at position 145, 785 and 886 which create a change at the gene level, leading to a change in protein therefore changing the phenotype of taste.

Question 29

Why is Taq DNA polymerase used not human DNA polymerase?

Answer 29

Due to the high temperatures and Taq polymerase coming from a thermophilic bacteria meaning the enzyme will not denature.

Question 29

After PCR what is done to find the genotype of bitter tasting perception?

Answer 29

Fn4H1, a restriction enzyme is introduced, this enzyme is complimentary to the specific sequence- GCNGC, therefore the enzyme will only create a change when this sequence is present.

Question 29

What is meant by a restriction enzyme?

Answer 29

An enzyme which is restricted to being active in the presence of a specific sequence// the enzyme ‘cuts’ DNA.

Question 30

What is albinism?

Answer 30

A recessive disease which is due to a lack of melanin production from tyrosine. Thus increasing the risk of skin cancer (many types OCA1, OCA2, OCA3, OCA4, with 1 being most sever and 4 being weakest form of the disease

Question 31

What is haplosufficiency?

Answer 31

When one working allele is enough to maintain normal function

Question 32

Give an example of a dominant disease.

Answer 32

Huntington’s - a neurodegenerative disease resulting in a loss of muscular control

Question 33

What is the difference between treatments for recessive and dominant disease?

Answer 33

Recessive focus on replacing missing gene product or correcting the gene through gene therapy// dominant focus on symptom management and targeting effects of the domain

Question 34

What the main features of the genome which makes individuals unique?

Answer 34

epigenetic markers / SNPs - single nucleotide polymorphisms / independent mutations / mitochondrial DNA

Question 35

What are some uses of SNPs?

Answer 35

Genetic associated studies/ genome-wide associated studies/ personalised medicine /