Flashcards in Clinical Genetics Deck (46)
T/F A significant portion of the genome codes for proteins
False, very little of the genome actually codes for proteins
What is the main role of heterochromatin region?
protect integrity of DNA
What are some of the regulatory products coded by the genome?
tRNA, rRNA, non-coding RNAs
Which process complex is responsible for the splicing of RNA?
Slicesosomes, important for generating diversity
How does histone regulate expression?
it winds more or less tightly via acetylation and methylation, allowing or denying access of replicating machinery
the open conformation of chromosome (heterochromatin is closed)
What is DNA methylation associated with?
What is the CpG region also known as?
CpG islands, because they are rich around promotor regions
How is CpG island related to silencing of the genome
when it's hyper-methylated + low acetylation of histone, the gene is silenced
T/F Euchromatins have hypermethylated CpG islands
False, euchromatins are open, allowing replication. So CpGs are lacking methylation, while histones are hypermethylated
What are some ways of generating genome and protein diversity?
having more than one promotor on one gene
alternative splicing from the same transcript
What are some roles of non-coding RNAs?
act as decoy
guide transcription factor
What are short interfering RNAs made from?
double stranded RNAs
What is the action of short interfering RNA
Interact with RNA-induced silencing complex to increase degradation of mRNA
What is the function of micro-RNAs?
interact with RISC to repress translation rather than degrade mRNAs
What is bi-allelic expression?
Where both maternal and paternal copy need to transcribe equal amount of proteins at a time
What is trisomy 21 also known as?
What are the symptoms of down syndrome?
congenital heart disease, GIT disease, increased risk of leukemia, early onset Alzheimer
What is trisomy 18 also known as?
Edwards Syndrome, with severe mental disability, limb and heart defects
What are some autosomal recessive conditions?
cystic fibrosis, sickle cell anaemia, thalassaemia, haemochromatosis
What is haplo-insufficiency?
When there is only one copy of the chromosome and not enough protein is produced.
Autosomal dominant condition
When does X-chromosome inactivation occur?
around 8 cell stage
What is the Barr body?
condensed chromosome on X-inactivation
How does X-inactivation occur?
due to non-coding RNA Xist expression, which creates a wave of hyperchromatin in both directions
What is Turner syndrome?
45X, where one X is missing. There are a few genes that must remain active
Which genes of the inactivated X genes must remain active?
genes that cluster at the ends of the chromosome, homologous to the Y chromosome
What are genomic imprinted genes?
genes that are expressed in parent-specific manner. The maternal and paternal genes come together during fertilisation
What is parthenogenesis and androgenesis?
parthenogenesis = all maternal origin chromosomes
androgenesis = all paternal origin chromosomes
T/F Maternal genes tend to conserve resource for the mother