Genetics

Question 1

what is Mendelian inheritance

Answer 1

Mendelian inheritance refers to patterns of inheritance that are characteristic of organisms that reproduce sexually.

Question 2

autosomal Mendelian inheritance

Answer 2

eg sickle cell or cystic fibrosis

Question 3

autosomal recessive Mendelian inheritance

Answer 3

eg sickle cell or cystic fibrosis

Question 4

autosomal dominant medelian inheritance

Answer 4

eg achondroplasia, Huntingtons disease, Duchenne muscular dystrophy, haemophilia

Question 5

sex linked Mendelian inheritance

Answer 5

haemophilia, colour blindness

Question 6

autosomal dominant medelian inheritance

Answer 6

eg achondroplasia, Huntingtons disease, Duchenne muscular dystrophy

Question 7

mechanisms of non mendelian inheritance

Answer 7

environmental factor, variants from parents, extranuclear inheritance eg mitochondria mutations, multi genic risk, anticipation eg triplet repeat expansion

Question 8

penetrance

Answer 8

frequency with which a trait is manifested by individuals carrying the gene eg cystic fibrosis high penetrance, haemochromatosis low penetrance

Question 9

genomic imprinting

Answer 9

genes expressed from only one chromosome. parent of origin dependent. can be caused by deletion, point mutations and uniparental disomy

Question 10

epigenetic modifications

Answer 10

heritable changes in gene function not explained by changes in DNA sequences. change in structure which stops it being available for translation

Question 11

uniparental disomy

Answer 11

two copies of one parents chromosomes (UPD)

Question 12

how are mitochondrial mutations passed on

Answer 12

nuclear inheritance

Question 13

how can chromatin be made more accessible

Answer 13

histones can be enzymatically modified and can be displaced by chromatin remodelling complexes (both processes are reversible)

Question 14

polysome

Answer 14

several ribosomes translating mRNA at one time

Question 15

ways of detecting DNA mutations

Answer 15

PCR, gel electrophoresis, ARMS, restriction endonucleases, DNA sequencing

Question 16

types of numerical abnormalities

Answer 16

trisomy (Down syndrome), monosomy (turners syndrome)

Question 17

types of structural abnormalities

Answer 17

deletions, insertions, inversions, translocations

Question 18

robertsonian translocation

Answer 18

when the long arms of two acrocentric chromosomes fuse at the centromere and the two short arms are lost.

Question 19

acrocentric

Answer 19

chromosome with centromere near one end so that one chromosomal arm is short and one is long

Question 20

types of genetic mutations

Answer 20

non coding. coding- silent, missense, nonsense, frameshift

Question 21

what is inherited mutation

Answer 21

mutation passed on from parents.

Question 22

what is de novo mutation

Answer 22

an alteration in a gene that is present for the first time in one family member as a result of a mutation in a germ cell of one of the parents or the fertilised egg itself. common in dominant disorders, uncommon in recessive

Question 23

hardy Weinberg equilibrium

Answer 23

allele frequency remains constant generation to generation. psqrd +2pq + qsqrd =1

Question 24

factors that influence hardy Weinberg equilibrium

Answer 24

selective pressures, population size, mating randomness, gene flow, founder effect, natural selection

Question 25

clinical applications fo HWE

Answer 25

useful for calculating risk in genetic counselling ad planning population based carrier screening programmes eg Orkney

Question 26

heterozygote advantages eg

Answer 26

cystic fibrosis gives resistance to cholera, sickle cell anaemia gives resistance to malaria

Question 27

genetic drift

Answer 27

random fluctuation of one allele transmitted to high proportion of offspring by chance

Question 28

founder effect

Answer 28

the reduction in genetic variation that results when a small subset of a large population is used to establish a new colony