Genetics 1

Question 1

do DNA strands pair up in parallel or antiparallel fashion?

Answer 1

antiparallel

Question 2

in what direction does DNA replicate?

Answer 2

5’ –> 3’ direction

Question 3

which base is different in RNA vs DNA?

Answer 3

thymine in DNA

uracil in RNA

Question 4

other molecules in DNA?

Answer 4

nitrogen
carbon
hydrogen
oxygen
phosphorus

Question 5

how does DNA form chromosome?

Answer 5

associates with proteins (including histones) and wound into chromosome

Question 6

how many bases and genes in human genome?

Answer 6

3,000,000 bases
30,000 genes
(2 copies per cell)

Question 7

stages of cell cycle?

Answer 7

M > G1 > G0 > S > G2 > M etc

Question 8

what happens at each stage in cell cycle?

Answer 8

M = mitosis
G1 = cell growth
G0 = cell is resting
S = DNA synthesis
G2 = cell growth and preparation for division

Question 9

how can DNA be damaged during replication?

Answer 9

DNA strand breaks
UV or chemical crosslinking
mismatched base

Question 10

1st vs 2nd meiotic division?

Answer 10

1st = diploid cell replicates DNA and divides into 2 diploid cells, crossing over occurs
2nd = diploid cells divide into 2 haploid cells each (don't replicate DNA)

Question 11

RNA backbone is made of what?

Answer 11

ribose

Question 12

which parts of DNA are removed (spliced) when it is transcribed to mRNA?

Answer 12

introns

exons left in

Question 13

what determines the amount of protein produced?

Answer 13

rate of transcription to pre-mRNA
rate of splicing of pre-mRNA to mRNA
half life of mRNA
rate of processing of polypeptide

Question 14

how are humans all so different when they have almost the same genome?

Answer 14

polymorphisms and muations

Question 15

what differences are seen in the genome between people?

Answer 15

sequence variations within gene
- changes in promotor sequence, changes in exon sequences from ones that sequence amino acids to ones that don’t

sequence changes in DNA between genes
- single nucleotide polymorphisms, larger deletions or duplications

Question 16

what is a polymorphism?

Answer 16

any variation in the human genome that has a population frequency of greater than 1%
or
any variation in the human genome that doesn’t cause a disease in its own right however may predispose to a common disease

Question 17

what is a mutation?

Answer 17

a gene change that causes a genetic disorder
or
any heritable change in the human genome

Question 18

how is crossing over involved in the variation between each copy of the human genome?

Answer 18

bc of crossing over during meiosis, the variants all segregate independently of each other (unless they are very close together on the chromosome)

Question 19

how are different chromosomes recognised?

Answer 19

banding pattern with specific stains
length
position of centromere

Question 20

parts of chromosome?

Answer 20

telomeres at each end
centromere in middle
long and short arm

Question 21

what is an acrocentric chromosome?

Answer 21

centromere is so far to one end that the short arm is almost non-existant and doesn’t really matter

Question 22

what chromosome changes can cause disease?

Answer 22

balanced chromosome rearrangement (all chromosome material is present)
unbalanced (extra or missing chromosomal material, usually 1 or 3 copies of some of the genome)

Question 23

what is aneuploidy?

Answer 23

whole extra or missing chromosome

Question 24

what is a robertsonian translocation?

Answer 24

where 2 acrocentric chromosomes are stuck end to end

increases chance of trisomy in pregnancy (down syndrome)

Question 25

risk of down syndrome recurrence if mother already has a child with down syndrome?

Answer 25

around 1% if child has primary trisomy 21

higher risk if caused by robertsonian translocation

Question 26

what is trisomy 18?

Answer 26

Edward syndrome

Question 27

what is 45 X?

Answer 27

turner syndrome

Question 28

what is 47 XXY?

Answer 28

kleinfelter syndrome

Question 29

what is a reciprocal translocation?

Answer 29

chromosome abnormality caused by exchange of parts between non-homologous chromosomes
2 detached fragments of 2 different chromosomes are switched

Question 30

how does FISH work?

Answer 30

probe DNA labelled with fluorescent dye

DNA is denatured and hybridized

Question 31

genome wide cytogenetics?

Answer 31

array comparative genomic hybridisation (aCGH)

Question 32

specific loci or chromosome specific cytogenetics?

Answer 32

quantitative PCR

Question 33

what is microarray CGH?

Answer 33

first line chromosome test which detects any missing or duplicated piece of chromosome
DNA based
can find polymorphisms
e.g - digeorge syndrome can be seen as half as much DNA being present indicating a deletion

Question 34

what is mosaicism?

Answer 34

different cells have a different genetic constitution

mosaicism = when a person has 2 or more sets of genetically different cells in their body

Question 35

what is somatic mosaicism?

Answer 35

mosaicism which is derived from a post-zygotic mutation rather than inherited
may only affect part of the body and isn’t passed on

Question 36

how can chromosome changes cause cancer?

Answer 36

can activate an oncogene or delete a tumour suppressor

Question 37

what is the Philadelphia chromosome?

Answer 37

abnormally short chromosome 22 which is involved in a translocation with chromosome 9
causes chronic myeloid leukaemia