Mol/ med gen

Question 1

what is a gene

Answer 1

inherited units if information specifying phenotype at a gross level

Question 2

main mode of gene expression control in prokaryotes

Answer 2

dna transcription, as transcription and translation both occur almost simultaneously in the cytosol

Question 3

levels of gene expression control in eukaryotes

Answer 3

can be controlled at three levels
epigenetic (DNA uncoiling, TF binding)
post-transcriptional (RNA processing)
post translational

Question 4

differences in eukaryotic and prokaryotic promoter structures

Answer 4

prokaryote: 2 short sequences upstream of transcription site. first region = TATAAT, essential for transcription to be initiated. second is TTGACA, allows for high transcription rate
eukaryote: very diverse and complex, different regulator elements, many have TATA box

Question 5

what are epigenetic modifications

Answer 5

direct chemical modification of DNA itself and modification of proteins closely associated

Question 6

effect of DNA methylation

Answer 6

prevents gene expression

Question 7

histone tail modifications example

Answer 7

de/ methylation
de/ acetylation
Phosphorylation, ubiquitylation

Question 8

effect of histone acetylation and methylation

Answer 8

increase expression

Question 9

two genomes present in human

Answer 9

nucelar and mitochondrial
mitochondrial = only 37 genes
nuclear = about 30,000 genes

Question 10

amount of DNA that is coding

Answer 10

1.5%

Question 11

functions of non-coding DNA

Answer 11

regulation of gene expression
not fully known
most are highly repeated sequences

Question 12

single copy DNA sequences

Answer 12

represent almost half of genome

only a small fraction codes for proteins, the rest is unique intron and regulatory sequences

Question 13

multi copy DNA sequences

Answer 13

present for histone production and the genes for rRNA

repeated from a few to thousands of times

Question 14

highly repeated non-coding sequences

Answer 14

satellite = centromeres/heterochromatin
minisatellite = 10-60 bp, often at centromere
micrisatellite = less than 10 bp, at telomeres
interspersed repeats

Question 15

overall classification of highly repeated regions

Answer 15

VNTRs = variable number tandem repeats
STR = short tandem repeats

Question 16

high throughput sequencing methods

Answer 16

use different methods to act more rapidly
- massively parallel signature sequencing
- pyrosequencing
lots of regions sequenced rapidly at the same time

Question 17

what is ‘depth’ in sequencing

Answer 17

number of unique reads that include a given nucleotide in the reconstructed sequence
also called coverage
greater in whole exome than whole genome

Question 18

hardy weinburg eqbm

Answer 18

p + q = 1

p^2 + 2pq + q^2 = 1

Question 19

ethnic differences in disease frequencies

Answer 19

depends partly on open or closed populations
can also depend on consanguinity
sickly cell/ thalassaemia in mediterranean or African
amish = maple syrup urine disease, MCAD
Ashkenazi jews = tay sachs

Question 20

heterozygote advantage

Answer 20

one copy of faulty gene can be advantageous
eg. protection from malaria from sickle cell gene
can lead to differences in disease incidence between populations

Question 21

identification of a gene for a single gene defect

Answer 21

• if know protein, use cDNA (use cDNA library to isolate gene)
• other members of the family of genes when one has already been shown to cause a disease
• human homologue for a disease causing gene in an animal
• genes in a metabolic pathway linked with a specific condition
• anticipation -> expanding repeat

Question 22

what is linkage analysis

Answer 22

the mapping of a trait on the basis of its tendency to be co-inherited with polymorphic markers

Question 23

whole genome sequencing use

Answer 23

identifying monogenic traits

Question 24

genome wide association studies uses

Answer 24

identifying loci for polygenic traits
isolate candidate gene which may confer susceptibility to a condition
study genetic variants (lots of SNPs) to try and find a link with a disease