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Flashcards in Genetics III - Final Deck (81):
1

Down's Syndrome is Trisomy____.

21

2

_____% Down's Syndrome involves Trisomy 21

95%

3

Of the 95% of Down's Syndrome that involve Trisomy 21, ____ % involve ______,____

and _____% involve ______,_____

90% maternal meiosis, MI

10% paternal meiosis, MII

4

What rearrangement occurs in the Acrocentric Chromosomes?

Robertsonian Translocation

5

What are the 5 Acrocentric chromosomes?

13, 14, 15, 21, 22

6

Robertsonian translocations involve ______ hooked together.

Acrocentrics

7

T/F
Balanced Robersonian translocations involve the long arms of 2 acrocentric chromosomes.

(13,14,15,21,22)

True

8

A balanced Robertsonian translocation between chromos 14 and 21 will yield how many total chromosomes?

45

9

If a woman is carrying a balanced Robertsonian translocation between chromos 14 and 21, how many of her gametes will be viable?

50%

10

A woman and her brother are carriers of a balanced Robertsonian translocation (14 and 21) - which has the highest risk to have a child with Down's Syndrome?

Female

***always higher with female

11

A woman with a balanced Robertsonian translocation between 14 and 21 has a Down's baby - how many chromosomes does the baby have?

How many copies of 21?

46 (NOT 47)

3 copies 21

12

Most Down's Syndrome pts have ____ chromosomes

If mother has a translocation of 14 and 21, the Down's person will have ____ chromosomes

47

46

13

What could explain a man having a baby with Prader-Willi and his sister having a child with Angleman?

Balanced Translocation involving chromo 15

14

What is the Karyotype of Turner syndrome?

45, X

15

How many 45, X (Turner's) are spontaneously aborted?

99%

16

What is the only viable monosomy in humans?

(only viable hemizygous condition)

Turner Syndrome

17

How many Barr bodies would you see in Turner's Syndrome?

0

18

T/F
A Barr body is an inactivated X chromosome in a female and enables Lyonization

True

19

45, X:

Turner's

20

45, XX t(14;21)

phenotypically normal

21

46, XX

46, XY

normal

22

46, XX, t(14,21), +21

Down's

23

47, XXY

Klinefelters

24

What is the worst Robinsonian translocation?

21 for 21

(fusion of chromosome 21)

25

Where does the nondisjunction that creates 47 XYY occur?

**NOT Klinefelters (47 XXY)

Male Meiosis II

26

Nondisjuction in Male Meiosis I will result in:

Nondisjuction in Male Meiosis II will result in:

**sex chromosomes

Kleinfelters (XXY)

XYY (or XXX)

27

7 reasons to have a Karyotype?

Ambiguous genitalia (growth, development)

Dysmorphic features

Stillbirth/neonatal death

Fertility problems

Family history

Neoplasia

Pregnancy in advanced maternal age

28

When is genetic testing for minors usually ok?

Conditions manifesting before 18

29

Mechanism of Type I Osteogenesis Imperfecta W/O Dentinogenesis imperfecta:

Haploinsufficiency

30

Mechanism of Type I Osteogenesis Imperfecta With Dentinogenesis Imperfecta:

Dominant Negative

31

T/F
Type I Osteogenesis Imperfecta With DI (as opposed to without DI) are more likely to have fractures at birth

True

32

What resource is to be used for a patient that needs genetic testing?

Genetic Testing Registry

33

A son has a trait more commonly affecting females - what is the recurrence risk?

(2 things)

More than if female was affected

Greater if you have a daughter

34

How many chromosomes in Triploidy?

69

35

What is the most common mechanism that produces Triploidy (69 chromos)?

2 sperm fertilize ovum

36

What is the Prognosis for Triploidy (60 chromos)?

Babies born but don't live long

37

How many chromosomes in Tetraploidy?

92

38

What is the Karyotype in tetraploidy?

92, XXXX

or

92, XXYY

39

What is the usual mechanism that creates Tetraploidy?

Failure early division/cleavage in zygote

40

What is the Prognosis for Tetraploidy (92 chromos)?

Embryos can form - no babies viable

41

How does Tetraploidy compare to Triploidy?

(incidence)

3x Less common

42

How does Triploidy compare to Tetraploidy in terms of incidence?

3x More common

43

A phenotype produced by exposure to an environmental agent...

(this can look like a genetic disorder)

Phenocopy

44

When multiple genes contribute to a phenotype...

(diabetes)

Polygenic

***each has small contribution

45

When both Genes and the Environment can contribute to a phenotype...

Multifactorial

46

What are 3 factors that contribute to the recurrence risk of a multifactorial trait like clefting?

Number affected individuals in Family

Severity

If individual is of sex Least affected, recurrent risk higher

47

What is the one major way genetic testing is different from other types of tests?

Implications for Family Members

48

Whole Exome sequencing focuses on...

Exons

49

What bill prevents genetic discrimination?

*in terms of job attainment and Health insurance

GINA

Genetic Info Nondiscrimination Act

50

T/F
Robertsonian translocations are between metacentric chromos

False

*acrocentric

51

T/F
Balanced translocation carriers are at risk to have unbalanced offspring

True

*often how identified

52

T/F
A 14,21 Robertsonian translocation will have 1/2 unviable gametes

True

53

T/F
The normal X will be turn on in a woman with translocation between autosome and X chromosome.

False

***apparently bad chromo will take over

54

What is the most likely way a female expressed X-linked recessive disorder?

What is the least likely?

Skewed X inactivation

Mutation pseudoautosomal region Y (females don't have Y)

55

T/F
Skewed X expression, Uniparental disomy, Turner's, Consanguinity, and Balanced translocation from Autosome to X can all uncover X-linked recessive in Females

True

56

Most common mechanism in PWS and AS?

Deletion

57

RR if UPD is mechanism of PWS or AS?

less than 1/1000

58

RR if inherited methylation defect is mechanism for PWS or AS?

50%

59

Prader-Wili Syndrome, which results from either father's 15 deletion or Uniparental Disomy from mother, is also...

Contiguous gene syndrome

60

PWS results from absence of ____ contribution of chromo 15.

AS results from absence of _____ contribution of chromo 15.

Father's

Mother's

61

Angelman Syndrome can result from a mutation is _______.

Single gene

62

What test provides the highest detection rate for PWS and AS?

What test detects deletions?

Methylation

FISH

63

If deletion is the mechanism for PWS or AS, what is the recurrence risk?

less than 1/1000

64

Compulsive eating and developmental delay are seen in what Syndrome?

Prader-Willi

65

Seizures, Ataxia, and an inability to talk are seen in what Syndrome?

Angelman

66

If PWS and AS are seen in the same family, what is the most likely mechanism?

Translocation

67

T/F
PWS and AS are the best examples of Imprinting in humans

True

68

Triploid have how many chromosomes?

Any viable?

Mechanism?

69

Die as newborn

2 sperm, 1 ovum

69

Tetraploid fetuses have how many chromosomes?

Viability?

Mechanism?

92

No live births

Early cleavage failure

70

p.Gly180Arg:

p.Gly180*

p.Gly180Gly

p.Gly180Serfs*4

Missense

Nonsense

Silent

Frameshift

71

T/F
Whole exome sequencing detects mutations in coding exons

True

72

Human disorder = Male Calico Cat

Klinefelter's

73

Different Clinical phenotypes caused by mutations in the Same Gene is...

Clinical Heterogenicity

74

T/F
Mito DNA links a woman to all her children and her daughter's descendants

True

75

Fragile X:

Huntington's:

Freidreich ataxia:

Myotonic dystrophy

5' UTR

1st Exon

Intron

3' UTR

76

What is the only Autosomal Recessive disorder currently known to be caused by a Trinucleotide repeat?

Freidreich Ataxia

77

If a disorder has 1000's of repeats it does not occur in the _______.

If a disorder has hundreds of thousands of repeats, it can be detected with _______

Coding region

Southern Blot

78

T/F
Minors are only tested for disorders occurring in childhood

True

79

What major disorder is due to a missense mutation - one AA for another?

Sickle Cell Anemia

80

Would a pt with know sickle cell go through chromosome analysis?

No.

Cause knows - no need

81

Different mutations, same locus, similar phenotype:

Different phenotypes, mutations in same gene:

Different mutations, different gene (locus), similar phenotype:

Different expressions of mutant allele:

Allelic heterogeneity

Clinical heterogeneity

Locus heterogeneity

Variable expressivity

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