Lecture 2

Question 1

What is the term for too many or too few chromosomes?

Answer 1

aneuploidy

most common

Question 2

What are the 3 trisomy compatible with life?

Answer 2

Trisome 21, 18, 13

Question 3

What is the main risk factor associated with Trisomy 21?

Answer 3

increased maternal age >30 years

Question 4

What is the most common genetic cause of mental retardation?

Answer 4

Trisomy 21

Question 5

33% of patients with Trisomy 21 also have associated disease of this organ.

Answer 5

congenital heart disease

Question 6

Trisome 21 are at an 15-fold increased risk of what cancer?

Answer 6

leukemia

and premature dementia

Question 7

95% of down syndrome chromosome abnormalities is caused by what?

Answer 7

Trisomy 21

Question 8

The majority of trisomy 21 is caused by what type of disjunction?

Answer 8

non-disjunction in maternal meiosis 1

Question 9

What are the 5 acrocentric chromosomes?

Answer 9

13, 14, 15, 21, 22

Question 10

What is Robertsonian translocation?

Answer 10

translocation of 2 acrocentric chromosomes

Question 11

Mosaicism occurs in _____

Answer 11

mitosis

Question 12

Down syndrome is primarily diagnosed when?

Answer 12

prenatally

Question 13

What are the 3 prenatal screening tests for Down syndrome?

Answer 13

• non-invasive prenatal testing (NIPT)
• first trimester risk assessment (FTRA)
• quad/penta screening

Question 14

What are the 3 components of the first trimester risk assessment (FTRA)?

Answer 14

• HCG
• plasma protein type A
• ultrasound

Question 15

What are the 5 components of the quad/penta screening?

Answer 15

• AFP
• B-HCG
• inhibin-A
• Estriol
• h-HCG

Question 16

If any of the prenatal screening tests for Down come back positive what diagnostic tests could you perform next?

Answer 16

• Amniocentesis

- Chorionic Villus Sampling (CVS)

Question 17

Which of the Down prenatal diagnostic tests can be done between 15-20 weeks?

Answer 17

amniocentesis

Question 18

Which of the Down prenatal diagnostic tests can be done between 10-12 weeks?

Answer 18

Chorionic Villus Sampling (CVS)

Question 19

Which of the trisomies results in HYPERtonia?

Answer 19

Trisomy 18

Question 20

What is the cause of velocardiofacial syndrome?

Answer 20

small deletion of chromosome 22 Q arm at position 11.2

Question 21

Why does Turner Syndrome result in a less severe phenotype?

Answer 21

• because only one X chromosome is active in any given cell anyway

Question 22

A short, webbed neck, short stature and amenorrhea is consistent with this aneuploidy.

Answer 22

Turner Syndrome

Question 23

What are the heart defects associated with Turner Syndrome? (3)

Answer 23

• aortic valve stenosis
• coarctation of the aorta
• bicuspid aortic valve

Question 24

Klinefelter syndrome primarily affects what gender?

Answer 24

males

more Xs the worse the phenotype

Question 25

Infertility, small testes, and gynecomastia is consistent with this aneuploidy.

Answer 25

Klinefelter syndrome

Question 26

What is the cause of sex reversal disorders?

Answer 26

abnormal allosome crossing over occuring at the SRY gene

Question 27

Single gene disorders is especially important in what population?

Answer 27

pediatrics

Question 28

If you express the gene when the individual is heterozygous for the allele this means it is a ________ gene.

Answer 28

dominant

Question 29

ABO blood group is what time of dominance?

Answer 29

co-dominant

Question 30

If an individual has to be homozygous to express an allele this means it is a ________ gene.

Answer 30

recessive

Question 31

What distinguishes X-linked disorders?

Answer 31

lack of male-male transmission

Question 32

In X-linked _______ diseases, carrier females (heterozygous) consistently have a disease phenotype.

Answer 32

dominant *X-linked recessive do not express the disorder phenotype*

Question 33

This is the probability that a gene will have any phenotypic expression.

Answer 33

penetrance

Question 34

This is the severity of expression of a phenotype among individuals with a given genotype.

Answer 34

expressivity