NDJ

Question 1

what % of karyotypically abnormal foetuses are due to wrong number of chromosomes?

Answer 1

90

Question 2

what is inheritence of the wrong number of chromosomes due to errors in?

Answer 2

meiotic chromosome segregation

Question 3

when are NDJ events more likely?

Answer 3

when fewer crossovers between homologous chromosomes and more likley is crossover closer to telomere

Question 4

what is the most common chromsomal abnormality that causes miscarriage?

Answer 4

polyploidy and of this triploidy

Question 5

most common trisomy at point of conception?

Answer 5

trisomy 16

Question 6

what is most common trisomy in live births?

Answer 6

downs, trisomy 21

Question 7

most common aneuploidy overall

Answer 7

45X turners

Question 8

why are sex aneuploids normally tolerated?

Answer 8

x chromsome can can be inactivated and Y contains few genes

Question 9

what are the technologies used for a rapid preliminary report on cell free foetal DNA?

Answer 9

FISH and QPCR

Question 10

what increases risk of mieotic NDJ?

Answer 10

age

Question 11

what happens in mitotic NDJ?

Answer 11

gametes fuse normally, but during early embryo development chromosome NDJ occurs during mitosis

Question 12

where are meosis errors more common?

Answer 12

in MI and in maternal gametes

Question 13

what measures length of chromosome and amount of crossovers?

Answer 13

centimorgans

Question 14

what does 1cM equal?

Answer 14

1% chance that 2 marks are separated due to a crossover

Question 15

in meisosis I NDJ what were the chromosomes compared to standard ones?

Answer 15

shorter with fewer crossovers

Question 16

in meiosis II NDJ what were the chromosomes?

Answer 16

longer with too many crossovers

Question 17

what does cohesin consist of?

Answer 17

smc1 and 3 hetrodimer. in mitosis scc1 closes the loop, in meiosis its rec8

Question 18

which bit of the chromosome in the cohesion the strongest?

Answer 18

the bit between the crossover and the telomere

Question 19

what is faithful disjunction dependent upon?

Answer 19

distal sister chromatin cohesion, relative to the centromere

Question 20

where are occytes arrested in foetal development?

Answer 20

prophase of meiosis I

Question 21

why are maternal NDJ more common?

Answer 21

the long phase of meiotic arrest may mean that the cohesion complexes are damaged slightly. if there are only a few crossovers, may all get damaged and NDJ more likley

Question 22

what is mocasism?

Answer 22

two or more cell populations with different genotypes within a single individual

Question 23

what can cause mosoacism?

Answer 23

mitotic NDJ resulting in trisomic and monosomic daughter cells

Question 24

what can confirm whether something is confined to the placenta?

Answer 24

amniotic fluid sample

Question 25

how can normal cells form from a MI NDJ event?

Answer 25

trisomic rescue

Question 26

what does maternal UPD of chromosome 16 cause?

Answer 26

growth restriction as a result of imprinted genes on chromosome

Question 27

what does the confinement of a trisomic cell line to the placenta depend upon?

Answer 27

when the rescue event occured in development

Question 28

what mechanisms can trisomic rescue occur by?

Answer 28

non-disjunction or anaphase lag