MCBHD

Question 1

what chromosomal abnormality is the most common

Answer 1

aneuploidies

Question 2

daughter cells of meiosis and mitosis

Answer 2

identical - mitosis

different in meiosis

Question 3

what is karyotyping good for

Answer 3

big deletions/duplications
missing/duplications chromosomes

no need to know what you are looking for

Question 4

what is FISH good for

Answer 4

micro deletions/microduplications
looking for aneuploidies

but you need to know what you are looking for

Question 5

quantitive PCR

Answer 5

only picks up aneuplodies

Question 6

array-CGH

Answer 6

no need to know what you are looking for

good for deletions/duplications

most of genome (many probes)
but produces a lot of data

not good at detecting mosaicism/detecting balanced rearrangements/where the aberration is

Question 7

aneuploidy vs polypoidy

Answer 7

aneuploidy = more than 2 copies of a chromosome

polypoidy = more than 2 sets of chromosomes

Question 8

2 ways that can result in aneuploidy

Answer 8

non-disjunction–> daughter cells having incorrect number

mosaicism

Question 9

3 common tirosomies and features

Answer 9

21 - downs
-epicanthic folds/almond eyes/flat nasal bridge/single palmar crease/sandal gap/short/hypotonia/cardiac problems

18 - edwards
-exomphalos/overlapping fingers/rocker bottom feet/heart and kidney defects

13 - patau
-midline cleft palate/scalp defects/exomphalos/polydactyl/hypotelorism close eyes/brain defects

Question 10

sex chromosome aneuploides

Answer 10

45X0 = turners

47XXY = klinefelter

Question 11

translocation types

Answer 11

reciprocal / robertsonian (2xp or 2xq)

robertsians therefore are between acrocentric chromosomes

balanced/unbalanced(missing/extra material)

Question 12

inversion types

Answer 12

paracentric - not including centromere

pericentric - including centromere

Question 13

ring chromosome

Answer 13

ends of abnormal chromosome fuse

Question 14

what kind of inheritance pattern is cystic fibrosis

Answer 14

autosomal recessive

Question 15

2 non – Mendelian Inheritance

Answer 15

mitochondrial (homo/heteroplasmy)

multi-factorial

Question 16

what is the tandem repeat at the end of chromosomes

Answer 16

TTAGGG

Question 17

5 main histone types

Answer 17

H1
H2A
H2B
H3
H4

Question 18

do histones have introns

Answer 18

no

Question 19

histone N and C terminal ends

Answer 19

N - highly basic

C - highly hydrophobic

Question 20

3 different levels of genes can be transcribed to

Answer 20

Gene 1 = genes that are highly expressed “housekeeping genes”

Gene 2 = less expressed

Gene 3 = only expressed in certain tissues
These genes also can be affected by a stimulus to start their transcription/expression

Question 21

By what mechanism does each cell in our body achieve differential gene expression

Answer 21

2 main ways:

• Regulatory transcription factors
• Chromatin remodeling

Question 22

3 types of RNA polymerase

Answer 22

I = rRNA
II = mRNA
III = tRNA

Question 23

Oestrogen responsive genes - how it brings RNA polymerase II

+ what interferes with this

Answer 23

1. oestrogen binds to oestrogen free receptor
2. they bind to TATA box
3. recruitment of general transcription factor to bind to the Tata box
4. recrutiment of RNA polymerase

Tamoxifen interferes by preventing TF from binding–> used to prevent tumours from growing

Question 24

role of acetylation of histones (chromosome remodelling)

Answer 24

histones = +vely charged (DNA = -vely)

TF recruit Histone acetylase

it neutralises the positive charge at N-terminal of histone –> no longer bind to DNA molecule

opens up the chromosome

Allows access to general TF and RNA polymerase for transcription

Question 25

what are Restriction Enzymes what 2 things do they do

Answer 25

bacteriophages (viruses that infect bacteria) These can be purified and used to digest DNA There are multiple restriction enzymes but only type II restriction enzymes are useful, because they are sequence specific. 1. recognise specific DNA sequence 2. break phosphodiester bonds

Question 26

Components of a PCR Reaction

Answer 26

Template – DNA to amplify Primers – Short pieces of ssDNA (15-30bp) Polymerase – thermostable enzyme (to about 95degrees) Nucleotides – single base mixture (dNTPs) Buffer – To maintain pH MgCl2 – Essential for polymerase activity

Question 27

PCR temperature steps

Answer 27

94-denature 60 - primer anneal 72 - extension

Question 28

equation to work out how many copies of target DNA we get with PCR

Answer 28

n=cycle number no. of copies = 2^ n-1

Question 29

what happens to pre-mRNA after transcription

Answer 29

1. methylation of 5' cap to help ribosome know where to translate from 2. poly A 3' (adding AAUAAA-U/G ---> AAUAAA-AAAA) stabilising 3. splicing (alternative splicing=> isomers) 4. TREX binds to the exon junction complexes to export mRNA to the cytoplasm for translation

Question 30

which type of chromatin is stained darker with giemsa stain

Answer 30

Heterochromatin - AT rich and it is tightly packed because here the genes are inactive (i.e. not being transcribed).