Robinson Lectures

Question 1

Smallest human chromosome

Answer 1

Chromosome 21

Question 2

What is unique about mouse chromosomes?

Answer 2

All acrocentric

Question 3

What is unique about Rhea Americana chromosomes?

Answer 3

Many microsomes

Question 4

Down syndrome genotype

Answer 4

47, +21

Question 5

Klinefelter syndrome genotype

Answer 5

47, XXY

Question 6

Edwards syndrome phenotype

Answer 6

47, +18

Question 7

Patau syndrome genotype

Answer 7

47, +13

Question 8

Incidence of trisomy 21 at conception and birth

Answer 8

C: 1/200
B: 1/800

Question 9

Incidence of trisomy 18 at conception and birth

Answer 9

C: 1/500
B: 1/5000

Question 10

Incidence of Klinefelter syndrome at conception and birth

Answer 10

C: 1/500
B: 1/1000

Question 11

Incidence of trisomy 13 at conception and birth

Answer 11

C: 1/500
B: 1/10,000-20,000

Question 12

Incidence of triploidy at conception and birth

Answer 12

C:1/100
B: 1/60,000

Question 13

Turner syndrome genotype

Answer 13

45, X

Question 14

Incidence of Turner syndrome at conception and birth

Answer 14

C: 1/100
B: 1/10,000

Question 15

Why are sex chromosome abnormalities better tolerated than autosomal chromosome abnormalities?

Answer 15

1. Not many genes carried on the Y chromosome

2. X-chromosome inactivation

Question 16

Which trisomies are rare in clinical pregnancies?

Answer 16

1, 11, 19

Question 17

Which monosomies are rare in clinical pregnancies?

Answer 17

All

Question 18

Which trisomies are commonly found in miscarriages?

Answer 18

All (incl. 47, XXX and 47, XXY)

Question 19

Which monosomies are commonly found in miscarriages?

Answer 19

45, X

Question 20

Which trisomies can survive to term?

Answer 20

13, 18, 21
47, XXY
47, XYY
47, XXX

Question 21

Which monosomies can survive to term?

Answer 21

45, X (rarely)

Question 22

Which polyploidy can survive to term?

Answer 22

Triploidy, rarely

Question 23

What is the leading cause of miscarriages?

Answer 23

Chromosome abnormalities

Question 24

What is the combined incidence of trisomy at birth?

Answer 24

1/300

Question 25

Are females with Turner syndrome fertile?

Answer 25

No, streaked ovaries

Question 26

Are 47, XXX females fertile?

Answer 26

Yes

Question 27

Are Klinefelter (47, XXY) males fertile?

Answer 27

No

Question 28

Are 47, XYY males fertile?

Answer 28

Yes

Question 29

Which chromosomes can be involved in Robertsonian translocations?

Answer 29

Acrocentric chromosomes (13, 14, 15, 21, and 22)

Question 30

DiGeorge syndrome genotype

Answer 30

Deletion in chromosome 22

Question 31

Main disadvantage of targeted cytogenetic approaches

Answer 31

Need a probe specific to the sequence you are testing

Question 32

Main disadvantages of array-based cytogenetic approaches

Answer 32

Expensive Detect meaningless changes Cannot detect balanced or structural changes

Question 33

Which chromosomal abnormality was found to be a main cause of chronic myelogenous leukaemia?

Answer 33

Translocation between chromosome 22 and chromosome 9

Question 34

William’s syndrome genotype

Answer 34

Recurrent deletion in chromosome 7

Question 35

DiGeorge syndrome genotype

Answer 35

Recurrent deletion on chromosome 22

Question 36

What gene is missing in Williams syndrome?

Answer 36

Elastin gene

Question 37

Which cytogenetic technique can be used to detect deletions?

Answer 37

FISH

Question 38

Which cytogenetic technique can be used to detect duplications?

Answer 38

FISH (use in interphase cells)

Question 39

Which cytogenetic technique can detect complex rearrangements?

Answer 39

M-FISH or SKY

Question 40

Muntjac chromosomes are unique because

Answer 40

Closely related species have very different numbers of chromosomes

Question 41

aCGH vs SNP array

Answer 41

aCGH: requires control DNA; cannot detect polyploidy or balanced translocations SNP array: doesn’t require control DNA; can detect polyploidy, parental origin, or loss of heterozygosity

Question 42

CMA vs G-banding

Answer 42

CMA: can detect smaller changes; don’t need to culture blood; can use DNA samples that were preserved; can have ambiguous/false positives; more expensive G-banding: can’t detect as small changes; need to culture blood (takes more time); cheaper

Question 43

Size of microscopic structural variants

Answer 43

>3MB (visible with G-banding)

Question 44

Size of submicroscopic structural variants

Answer 44

50 bp - 3 MB

Question 45

Which regions of the genome contain lots of CNVs?

Answer 45

Pericentromeric and subtelomeric regions

Question 46

Which genes are least affected by CNVs and why?

Answer 46

Genes associated with diseases (select for a certain copy number)

Question 47

How do CNVs differ in individuals with a disease compared to healthy controls?

Answer 47

Individuals with disease have on average larger CNVs

Question 48

How does one know if a CNV is pathogenic?

Answer 48

More likely pathogenic: De novo, larger size (>1MB), includes a gene that is affected by dosage, rare, similar cases in database Less likely pathogenic: Inherited from an unaffected patient, small size, few genes disrupted, common in the population (including healthy individuals)

Question 49

What percentage of developmental delay do de novo CNVs account for?

Answer 49

14%

Question 50

Where do most errors to trisomy occur?

Answer 50

Maternal M1

Question 51

Where is meiosis arrested in females?

Answer 51

Diplotene of prophase 1

Question 52

What are 3 possible causes of meiosis errors?

Answer 52

Failure of recombination or SC formation; failure of cohesin at sister chromatids or chiasmata; failure of spindle

Question 53

How common are lethal chromosome abnormalities in humans at conception?

Answer 53

1/5

Question 54

What aspects of chromosomes are conserved across species?

Answer 54

Centromere, telomere

Question 55

Robertsonian translocation frequency in population

Answer 55

1/800

Question 56

Genotype of chimpanzee

Answer 56

2n = 48

Question 57

What is the function of cot-1 DNA in M-FISH/SKY?

Answer 57

Blocks out repetitive regions in the genome so you don’t get cross-hybridization for repeats on different chromosomes

Question 58

What is the genotype of Sewyer syndrome?

Answer 58

46, XY with no SRY region