genetic variation from chromosomes and single bases

Question 1

what parts make up a chromosome

Answer 1

telomere, short arm, centromere, long arm

Question 2

which arm on a chromosome does the most

Answer 2

long arm

Question 3

what is balanced rearrangement

Answer 3

a chromosome change where all the genetic material is present but maybe a part of a chromosome has stuck onto a different chromosome

Question 4

what is an unbalanced rearrangement

Answer 4

chromosome change where there is extra or missing chromosomal material. usually 1 - 3 copies of genome. bad news

Question 5

conventional clinical analysis

Answer 5

currently moving away from looking at chromosomes but understanding conventional cytogenetics is essential

Question 6

what is aneuploidy

Answer 6

whole extra or missing chromosome

Question 7

what is translocation

Answer 7

rearrangement of chromosomes

Question 8

what are insertion/deletion mutations

Answer 8

missing or duplicated material

Question 9

how does down syndrome come about

Answer 9

unbalanced rearrangement. 47xy + 21 (meaning chromosome 21 has attached to chromosome 47)

Question 10

what is a robertsonian translocation

Answer 10

they are chromosomal rearrangements that result from fusion of the long arms of two different chromosomes

Question 11

x chromosome aneuploidy

Answer 11

duplication of the x chromosome. better tolerated because of x inactivation in females

Question 12

what is reciprocal translocation

Answer 12

when bits of chromosomes swap to other parts. balanced. not important unless on important gene

Question 13

reproductive risks of reciprocal translocation

Answer 13

50% of conceptions will be normal or have the translocation. if big segments have been swapped the miscarriage can occur. small segments = dysmorphic delayed child

Question 14

how many base pairs for reciprocal translocations to have an effect

Answer 14

if smaller than 5 million base pairs then you cant see effect or see it on tests

Question 15

what is the FISH genetic test

Answer 15

fluorescence in situ hybridisation. its a test that looks for gene changes in cells. Makes them glow

Question 16

what does FISH test for

Answer 16

predominantly breast cancer cells. HER2

Question 17

what is the aCGH test

Answer 17

used to detect imbalances in genome. DNA based test that reflects underlying chromosomes. can detect imbalance of any size and polymorphisms

Question 18

what does the aCGH test make things look like

Answer 18

luminescent

Question 19

where do mutations come from

Answer 19

if one parent has a germ line mutation they can ass it on. if a parent is mosaic the child will be too

Question 20

what is mosaicism

Answer 20

occurs when a person has two or more genetically different sets of cells in their body. if abnormal outweigh normal then it can lead to disease. it can be chromosomal or point mutation in one gene

Question 21

somatic mosaicism

Answer 21

all cells suffer mutations as they divide, at meiosis and at mitosis

Question 22

how to chromosome changes promote cancer

Answer 22

they can activate oncogenes and delete tumour suppressor. eg HER2 can be amplified

Question 23

how do we analyse DNA: aCGH

Answer 23

for deletions/duplications

Question 24

how do we analyse DNA: PCR

Answer 24

polymerase chain reaction. allows us to select one small piece of the human genome and amplify it. to compare to normal genomes

Question 25

what percent of genome are exons

Answer 25

2-3%. the rest are non coding introns

Question 26

what do introns do

Answer 26

regulation of genes. spaces genes out. provides substrate to expand genome

Question 27

what is a germline mutation

Answer 27

any detectable variation within germ cells. the only mutations that can be passed on to offspring

Question 28

what is polymorphism

Answer 28

the presence of 2 or more variant forms of a specific DNA sequence that can occur among different people or populations