week 4 GID

Question 1

In DNA structure what carbon does not have the OH group?

Answer 1

carbon 2

Question 2

what additional group does RNA have and why is it less stable than DNA?

Answer 2

It has a hydroxyl group on carbon 2 –> this makes the structure less stable as it causes a neutrophlic attack on the phosphate back bone –> split of the backbone

Question 3

what direction is DNA and RNA synthesised?

Answer 3

5 to 3 direction

Question 4

what stage does DNa replication take place in the cell cycke?

Answer 4

it takes place in the S phase before mitosis occurs

Question 5

how many genes does one hapliod genome contain?

Answer 5

3000 MB

Question 6

how much of the genome is non coding gene?

Answer 6

90%

Question 7

how many protein coding genes are there?

Answer 7

20000

Question 8

what are the different types of gene sequencing in the genome?

Answer 8

single gene sequences and this is usually genes that code for a protein –> just one sequence of gene per hapliod.
Have interspersed sequences –> multiple copies of the same gene sequences but scattered around the genome –> ALU repeat is common
satellite DNA –> large blocks of continuation of same gene repeat

Question 9

which part of the gene is coding for protein and what is non functioning?

Answer 9

exons –> coding

introns –> non coding

Question 10

what is the importance of the poly A tail?

Answer 10

helps with protection of the mRNA moving out into the nucleus and directing the mRNA to the appropiate part of the ribosome.

Question 11

how is more types of protein produced than the number of genes?

Answer 11

different type of splicing –> alternative splicing –> different exons come together which form different proteins –> increase the variation

Question 12

what two factors play a key in the grouping of genes into familis?

Answer 12

the duplication and divergence of genes over the years

Question 13

what causes divergence?

Answer 13

a mutation in a gene

Question 14

what is pseudogenes and whats causes it?

Answer 14

pseudogenes is a gene that was once functional and useful but no longer is. This is due to a mutation that has occured in the gene that makes the function of it not benificial and no longer needed. However they can be very close in sequencing to functional genes which clinically is a problem

Question 15

what is a common area on a chromosome to find satellite DNA and what is the differenation between these blocks in the DNA?

Answer 15

around the centromere of the chromosomes is several million DNA base pairs –> alphoid DNA–> each satellite DNA stains differently –> have a different polymorphism and therefore different staining

Question 16

what is the uniqueness of alphoid DNA?

Answer 16

It is a type of satellite DNA that is required for the assembly of centromere of the chromosome –> it is unique to each chromosome beacuse of different repetitive sequence –> shows chromosome-specific sequence variation –> 171 BP repeat unit

Question 17

what is alphoid DNA used for?

Answer 17

to identify specific chromosomes with the individual stains

Question 18

what is ALU repeat a example of ?

Answer 18

it is a interspersed repeat of DNA pieces–> 500000 copies of it –> 5% of the genome –> can be within or between genes and can help with forming the structure of the gene. It is disperesed by retrotransposition throughout the genome

Question 19

What is retrotranspoisition?

Answer 19

it is a type of transposition throughout the genome –> similar to retrovirus. The DNA is transcribed back into RNA and then rerves transcribed back to DNA and inesrted in a different site of the Genome.

Question 20

when does alignment/recombination of chromosomes occur?

Answer 20

occurs in miosis when gametes are forming between the maternal and paternal chromosomes. Identical sites on the two chromosomes switch –> have to have the correct sequences or it does not work –> if this process does not occur then the whole process stops.

Question 21

what is the consquences of large deletion or insertion?

Answer 21

effects may not be visilbe to PCR because it has not changed the sequences except for the breacking points so hard to identify –> affect could vary –> examples Duchenne muscle dystrophy –> deletion
Charcot-Marie-Tooth disease (genome duplication)

Question 22

what is the cause of heamophilia A

Answer 22

it is a gross recombination and is a X linked disease –> males get it as they only have one X. It is a absence of the cogulation factor 8 –> there is a inversion of a segment and therefore the factor 8 does not work properly

Question 23

what is a silent point mutation and what could be the possible consequence?

Answer 23

when a mutation has no affect and if it occurs in more than 1% of the population –> polymorphism

Question 24

what are the outcome of a missense point mutation?

Answer 24

if conservative with a small C therefore amino acid that is a base is changed for another that is a base then the outcome is not that significant however if it is non consevative then outcome more significant. For example change of base that is base for aromatic group.

Question 25

what is the most common mutation and what is the cause?

Answer 25

CG to TG and this is caused by deammination of CpG. However methylation of CpG increase the susceptibility of deamination of the C and therefore changing it. –> causing mismatch repair

Question 26

what is a nonsense point mutation?

Answer 26

it causes the formation of a stop codon and therefore a truncated protein –> shortened protein

Question 27

what is the cause of frameshift mutation?

Answer 27

is it the deletion or insertion of a base that causes the shift of the sequence –> can cause formation of truncate protein

Question 28

how can a pathogenic mutation of a non coding gene caues a disease?

Answer 28

the introns is involved in the strucutre of the coding gene and therefore affects the splicing of the gene

Question 29

if you loose function what type of inheritance is it usually?

Answer 29

it is usually recessive because usually you can cope with losing 50% of gene function–> examples beta thalesemmia and CF –> thousands of different types of mutation

Question 30

what is the cause of dominant inheritance?

Answer 30

the gain or alteration of a gene function not a loss of function –> achondroplasia –> short limbs –> the same mutation every time

Question 31

what is polyglutamine repeat?

Answer 31

it is the large repetition of the codon CAG that codes for glutamine –> common to have repition but only to a certain extent –> cause neurodegenaritive disorders –> Huntington’s disease –> AD disease

Question 32

what type of mutation is fragile X syndrome?

Answer 32

mutation in the FMR1 gene –> CGG expansion –> the repition of CGG out of the normal range of 5-20 means that it turns off (silences) the FMR1 gene which is used to produce the protein FMRP.

Question 33

what is a processed gene

Answer 33

is a copy of a functional gene somewhere in the genome but it has lost its introns –> not next to their parent gene. The RNA has been spliced and then reversed transcibed back into DNA and then reentered into the DNA. The product is usually pseudogenes but can get functioning genes –> PGK2 (testis-specific)