week 4 GID Flashcards
In DNA structure what carbon does not have the OH group?
carbon 2
what additional group does RNA have and why is it less stable than DNA?
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
what direction is DNA and RNA synthesised?
5 to 3 direction
what stage does DNa replication take place in the cell cycke?
it takes place in the S phase before mitosis occurs
how many genes does one hapliod genome contain?
3000 MB
how much of the genome is non coding gene?
90%
how many protein coding genes are there?
20000
what are the different types of gene sequencing in the genome?
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
which part of the gene is coding for protein and what is non functioning?
exons –> coding
introns –> non coding
what is the importance of the poly A tail?
helps with protection of the mRNA moving out into the nucleus and directing the mRNA to the appropiate part of the ribosome.
how is more types of protein produced than the number of genes?
different type of splicing –> alternative splicing –> different exons come together which form different proteins –> increase the variation
what two factors play a key in the grouping of genes into familis?
the duplication and divergence of genes over the years
what causes divergence?
a mutation in a gene
what is pseudogenes and whats causes it?
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
what is a common area on a chromosome to find satellite DNA and what is the differenation between these blocks in the DNA?
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
what is the uniqueness of alphoid DNA?
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
what is alphoid DNA used for?
to identify specific chromosomes with the individual stains
what is ALU repeat a example of ?
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
What is retrotranspoisition?
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.
when does alignment/recombination of chromosomes occur?
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.
what is the consquences of large deletion or insertion?
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)
what is the cause of heamophilia A
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
what is a silent point mutation and what could be the possible consequence?
when a mutation has no affect and if it occurs in more than 1% of the population –> polymorphism
what are the outcome of a missense point mutation?
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.
what is the most common mutation and what is the cause?
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
what is a nonsense point mutation?
it causes the formation of a stop codon and therefore a truncated protein –> shortened protein
what is the cause of frameshift mutation?
is it the deletion or insertion of a base that causes the shift of the sequence –> can cause formation of truncate protein
how can a pathogenic mutation of a non coding gene caues a disease?
the introns is involved in the strucutre of the coding gene and therefore affects the splicing of the gene
if you loose function what type of inheritance is it usually?
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
what is the cause of dominant inheritance?
the gain or alteration of a gene function not a loss of function –> achondroplasia –> short limbs –> the same mutation every time
what is polyglutamine repeat?
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
what type of mutation is fragile X syndrome?
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.
what is a processed gene
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)
