Molecular Biology Flashcards
Week 1 of lectures
What is the nature of mutations?
Changes to the genetic material of a cell or virus (with genetic material being DNA or RNA.
What creates spontaneous mutation?
Created by anything but exogenous agents, for example DNA errors made during replication or repair or recombination
Why are most mutations silent?
A change to one base pair often does not affect the amine group therefore having no affect on the phenotype.
What is a nonsense mutation?
Changes in the codon resulting in a stop codon.
What is a missense mutation?
Changes in a codon leading do a different amino acid in the polypeptide chain.
How do you calculate net mutation?
DNA damage- repair
Give examples of some origins of mutations.
Mutagens in food/ exposure to toxins/ radiation / rDNA damage during recombination (form of spontaneous mutation)
Do germ-line or somatic cells have higher mutation rates?
Somatic cells, due to more replication occurring.
How does a mutation affect a phenotype?
Mutation must alter a exon, therefore altering a section of DNA which affects proteins structure and function
What is meant by frameshift?
The insertion or deletion of one base pair, therefore altering all subsequent codons.
What is the difference between conservative missense mutation and non-conservative missenses mutation?
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.
What does the term analogy mean?
Mutation in a protein-coding region.
How do recessive mutations affect the phenotype?
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.
How dominant mutations affect phenotype?
Through a gain in function for example Achdroplasia, where the enzyme which inhibits growth is ‘locked’ in the active form therefore preventing bone growth.
How do we determine if an allele is dominant or recessive?
By looking at the protein pool and its behaviour.
List some main features of the human genome.
diploid (2 copies of every gene) // contains introns (non-coding genes) and exons (coding genes)
How does the human genome differ between poeple.
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.
Roughly how many genes does a eukaryote have?
6,000
What is meant by orthologs?
Genes from a common descendent which share the same function. these genes are often separated through speciation events
What is meant by paralogs?
Genes with different functions separated by duplicate events(SAME GENE SAME SPECIES)
What are SNPs?
Single nucleotide polymorphism, meaning a change to a single base position on DNA .
What is the effects of SNPs?
If they occur on protein-coding regions of DNA, they can affect the protein product, they can also be used for biological markers
What is ORF (open reading frame)
The protein coding region of a gene.
How do you calculate allele frequency?
number of alleles divided by total alleles
Define evolution in molecular terms
Is a change in allele frequency in a gene pool over time.
When using the hard-Weinberg equilibrium what is assumed?
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.
What is the hardy-Weinberg equation?
p^2 +2pq q^” = 1 // p^2 = frequency of homozygous dominant (AA)// q^2= frequency of homozygous recessive (aa)// pq= frequency of heterozygous (Aa)
What is analogy ?
Gene encodes for similar proteins/ structuters in differnet species
What is the chemical PTC (phenylthiocarbmide)?
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.
How do we taste bitterness in our foods?
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.
What are the 3 stages of PCR (polymerase chain reaction) ?
- 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.
How do SNPs affect the TAS2R38 gene?
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.
Why is Taq DNA polymerase used not human DNA polymerase?
Due to the high temperatures and Taq polymerase coming from a thermophilic bacteria meaning the enzyme will not denature.
After PCR what is done to find the genotype of bitter tasting perception?
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.
What is meant by a restriction enzyme?
An enzyme which is restricted to being active in the presence of a specific sequence// the enzyme ‘cuts’ DNA.
What is albinism?
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
What is haplosufficiency?
When one working allele is enough to maintain normal function
Give an example of a dominant disease.
Huntington’s - a neurodegenerative disease resulting in a loss of muscular control
What is the difference between treatments for recessive and dominant disease?
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
What the main features of the genome which makes individuals unique?
epigenetic markers / SNPs - single nucleotide polymorphisms / independent mutations / mitochondrial DNA
What are some uses of SNPs?
Genetic associated studies/ genome-wide associated studies/ personalised medicine / can act as genetic risk factor identifications
