Clinical Genetics

Question 1

T/F A significant portion of the genome codes for proteins

Answer 1

False, very little of the genome actually codes for proteins

Question 2

What is the main role of heterochromatin region?

Answer 2

condensing DNA
gene regulation
protect integrity of DNA

Question 3

What are some of the regulatory products coded by the genome?

Answer 3

tRNA, rRNA, non-coding RNAs

Question 4

Which process complex is responsible for the splicing of RNA?

Answer 4

Slicesosomes, important for generating diversity

Question 5

How does histone regulate expression?

Answer 5

it winds more or less tightly via acetylation and methylation, allowing or denying access of replicating machinery

Question 6

What’s euchromatin?

Answer 6

the open conformation of chromosome (heterochromatin is closed)

Question 7

What is DNA methylation associated with?

Answer 7

Silencing genes

Question 8

What is the CpG region also known as?

Answer 8

CpG islands, because they are rich around promotor regions

Question 9

How is CpG island related to silencing of the genome

Answer 9

when it’s hyper-methylated + low acetylation of histone, the gene is silenced

Question 10

T/F Euchromatins have hypermethylated CpG islands

Answer 10

False, euchromatins are open, allowing replication. So CpGs are lacking methylation, while histones are hypermethylated

Question 11

What are some ways of generating genome and protein diversity?

Answer 11

having more than one promotor on one gene

alternative splicing from the same transcript

Question 12

What are some roles of non-coding RNAs?

Answer 12

act as decoy
scaffold,
guide transcription factor
enhancer

Question 13

What are short interfering RNAs made from?

Answer 13

double stranded RNAs

Question 14

What is the action of short interfering RNA

Answer 14

Interact with RNA-induced silencing complex to increase degradation of mRNA

Question 15

What is the function of micro-RNAs?

Answer 15

interact with RISC to repress translation rather than degrade mRNAs

Question 16

What is bi-allelic expression?

Answer 16

Where both maternal and paternal copy need to transcribe equal amount of proteins at a time

Question 17

What is trisomy 21 also known as?

Answer 17

Down syndrome

Question 18

What are the symptoms of down syndrome?

Answer 18

mental disability

congenital heart disease, GIT disease, increased risk of leukemia, early onset Alzheimer

Question 19

What is trisomy 18 also known as?

Answer 19

Edwards Syndrome, with severe mental disability, limb and heart defects

Question 20

What are some autosomal recessive conditions?

Answer 20

cystic fibrosis, sickle cell anaemia, thalassaemia, haemochromatosis

Question 21

What is haplo-insufficiency?

Answer 21

When there is only one copy of the chromosome and not enough protein is produced.

Autosomal dominant condition

Question 22

When does X-chromosome inactivation occur?

Answer 22

around 8 cell stage

Question 23

What is the Barr body?

Answer 23

condensed chromosome on X-inactivation

Question 24

How does X-inactivation occur?

Answer 24

due to non-coding RNA Xist expression, which creates a wave of hyperchromatin in both directions

Question 25

What is Turner syndrome?

Answer 25

45X, where one X is missing. There are a few genes that must remain active

Question 26

Which genes of the inactivated X genes must remain active?

Answer 26

genes that cluster at the ends of the chromosome, homologous to the Y chromosome

Question 27

What are genomic imprinted genes?

Answer 27

genes that are expressed in parent-specific manner. The maternal and paternal genes come together during fertilisation

Question 28

What is parthenogenesis and androgenesis?

Answer 28

``` parthenogenesis = all maternal origin chromosomes androgenesis = all paternal origin chromosomes ```

Question 29

T/F Maternal genes tend to conserve resource for the mother

Answer 29

True

Question 30

What are the four causes of imprint disorders?

Answer 30

large deletion/duplication of chromosomes with imprint genes Uniparental disomy Epimutation DNA mutation

Question 31

What is uniparental disomy?

Answer 31

extra chromosome from either mother or father

Question 32

What is Beckwith-Widemann syndrome?

Answer 32

overgrowth due to mostly sporadic epimutation on maternal allele

Question 33

What is Prader-Willi syndrome?

Answer 33

Overgrowth due to 1) deletion of paternally inherited C15 2) maternal uniparental disomy

Question 34

What is Angelman syndrome due to?

Answer 34

deficiency in maternally-imprinted genes

Question 35

What is the first step of prenatal testing?

Answer 35

take a 3 generation family history to look for any inherited condition, recurrent miscarriages, or unexplained perinatal deaths

Question 36

When does the risk of down syndrome increase in relation to maternal age

Answer 36

30

Question 37

What is the reason for prenatal testing?

Answer 37

Offer choice in order to help patients make better decisions

Question 38

What does the first trimester screen involve?

Answer 38

Biochemical test at 10 weeks, ultrasound at 11-13 weeks, and nuchal translucency

Question 39

What is nuchal translucency?

Answer 39

Fluid behind baby's neck. Thick fluid is not normal

Question 40

What does 1st and 2nd trimester screening look for?

Answer 40

Trisomy 21 and 18 | Down syndrome and Edwards syndrome

Question 41

What does the 2nd trimester screening involve?

Answer 41

blood test at 15-17 weeks + maternal age to work out risk algorithm

Question 42

What is the 2nd trimester a good screening tool for?

Answer 42

neural tube defect

Question 43

What are the diagnostic tests offered to women with high risk of birth defect?

Answer 43

Chorionic villus sampling at 11 weeks | Amniocentesis at 15 weeks

Question 44

What does Chorionic villus sampling involve?

Answer 44

insert needle into placenta to get tissue from embryonic placenta

Question 45

What is fluorescence in situ hybridisation for?

Answer 45

test on the cells collected by CVS and amniocentesis

Question 46

What are the three ways of analysing collected tissue from CVS and amniocentesis

Answer 46

FISH Karyotype Microarray