genetics

Question 1

how many chromosomes does a human have

Answer 1

23 pairs = 46. 1 pair sex linked

Question 2

what happens in mitosis (brief)

Answer 2

creates identical daughter cell

Question 3

what happens in meiosis

Answer 3

formation of gametes - crossing over and independent assortment

Question 4

describe RNA structure

Answer 4

single stranded, ribose backbone, uracil instead of thymine

Question 5

describe DNA structure

Answer 5

double stranded antiparallel, deoxyribose backbone, ATCG

Question 6

what determines protein production (4)

Answer 6

rate of transcription, rate of splicing, half-life of mRNA, rate of processing polypeptide

Question 7

what are polymorphisms

Answer 7

any variation in human genome with a frequency of less than 1%. doesn’t cause a disease but can predispose

Question 8

what are mutations

Answer 8

changes that cause a disorder

Question 9

briefly outline the cell cycle

Answer 9

G1–> S–>G2–> M

Question 10

where does DNA replication happen and therefore where mutations can occur

Answer 10

S phase

Question 11

what is a telomere in a chromosme

Answer 11

at either end that protects against damage

Question 12

describe the 3 components of a chromosome

Answer 12

centromere, short arm (p) and long arm (q)

Question 13

what is an acrocentric chromosome

Answer 13

very short short arm

Question 14

what is a metacentric chromosome

Answer 14

same length of arms

Question 15

what is a telocentric chromosome

Answer 15

centromere almost at terminal end. ie no X shape

Question 16

what is an aneuploidy and what are some types

Answer 16

abnormal number of chromosomes. monosomy = missing from a chromosome. trisomy = extra in a pair

Question 17

what is robertsonian translocation

Answer 17

two acrocentric chromosomes stuck end to end - short arms normlly lost

Question 18

what are reciprocal translocations

Answer 18

when chromosomes ‘swap’ genes

Question 19

what are types of sequence mutations

Answer 19

SNP’s (single nucleotide polymorphisms) or deletions/ insertions which can be more serious

Question 20

what does monosomy of sex chromosomes cause

Answer 20

turner’s syndrome

Question 21

what does trisomy of 18 cause

Answer 21

edward’s syndrome

Question 22

what does trisomy of 21 cause

Answer 22

down’s syndrome

Question 23

what does trisomy of 13 cause

Answer 23

patau syndrome

Question 24

why are X trisomy better dealt with

Answer 24

x inactivation

Question 25

what does the aCGH chromosome test detect

Answer 25

deletions and duplications - not balance rearrangements

Question 26

what dies FISH show

Answer 26

fluorescence that stains chromosomes, can be used to detects aneuploidy

Question 27

what doe PCR and NGS look at

Answer 27

very small sequence changes

Question 28

what is a balanced chromosomal arrangement

Answer 28

all genetic material there

Question 29

what is an unbalanced chromosomal arrangement

Answer 29

some missing or extra

Question 30

what is a mosaic individual

Answer 30

has some mutations but seems fine

Question 31

how can mutations occur

Answer 31

parent --> child, gametogenesis, during development, mitosis

Question 32

what is a missense mutation

Answer 32

base change causing amino acid change (

Question 33

what is a nonsense mutation

Answer 33

base change results in stop

Question 34

what does mendelian inheritance encompass

Answer 34

autosomal dominant, autosomal recessive, x linked, mitochondrial. inherited disorders

Question 35

what is the penetrance of a mutation

Answer 35

the likelihood of it causing a disease

Question 36

describe the difference between autsomonal dominant and recessive

Answer 36

dominant: only 1 faulty gene is required from 1 parent to cause disease (50%) chance. Recessive: 2 faulty genes requires (25%)

Question 37

when does x-linked occur

Answer 37

carried on X chromosome, Y is irrelevant. If mother has it and passes to boy he will be affected. If mother passes to girl 50% chance. This is due to X inactivation

Question 38

where does mitochondrial disease come from

Answer 38

mother --> child

Question 39

what does c. 9T>G. p.His3Gln mean

Answer 39

the 9th RNA base has changed from a T to a G. this has caused the 3rd amino acid to change from his to Gln

Question 40

what are non-mendelian disorders

Answer 40

mocaicism, imprinting and mitochondrial

Question 41

what is epigenetic variation and give an example

Answer 41

functional changes that occur not from DNA sequence eg methylation which inhibits DNA transcription

Question 42

what is imprinting

Answer 42

difference in gene expression depending what gene is inherited

Question 43

what do oncogenes do

Answer 43

promote cell division

Question 44

what do tumour suppressors do

Answer 44

inhibit cell division

Question 45

is cancer normally high penetrance or multifactorial

Answer 45

multifactorial

Question 46

what is the 2 hit hypothesis

Answer 46

one inherited copy of a gene and another zygotic acquired one

Question 47

when do mocaism mutations happen

Answer 47

post zygotic