Sollars - Patterns of Inheritance I / II

Question 1

Index Case

Answer 1

Clinically affected family member through whom attention is first drawn

Question 2

Penetrance

Answer 2

Probability gene will have any phenotypic expression at all

Question 3

Expressivity

Answer 3

Severity of expression of the phenotype

Question 4

Pleiotropy

Answer 4

When an allele of a gene produces several phenotypic effects

Question 5

Autosomal Dominant

Answer 5

1. Multiple Generations
2. Males/Females Equal
3. Male to Male
4. 50/50 shot for offspring of affected

Homozygous = lethal

Question 6

Polycytic Kidney Disease

(ADPKD)

vs

(ARPKD)

Answer 6

ADPKD - Renal cyst disease; 1:500 Late Onset, Autosomal Dominant

ARPKD - Renal cyst disease; Early Onset, Autosomal Recessive

Question 7

What are most inborn errors of metabolism? (enzymes, proteins, etc)

Answer 7

Autosomal Recessive

Question 8

Autosomal Recessive

Answer 8

1. Males/Females Equal
2. Both parents must be carriers
3. Recurrence risk = 25% for offspring
4. Some Ethnic groups are hit harder
5. Consanguinity can play a role

Question 9

Tay Sachs

Answer 9

Autosomal Recessive

Ethnic prevalence in Ashkenazi Jews

Cherry red spot retina

Question 10

Phenylketonuria

Answer 10

Autosomal Recessive

Mental retardation, fair skin, preventable w/early diet intervention

Caucasians

Question 11

Consanguinity

Answer 11

Genetic relationship w/one common ancestor (inbreeding)

Question 12

Avg Genes Shared for:

Parents/Siblings/Children

Grandparents/Aunts/Uncles/Nieces/Nephews/Grandchildren

First Cousins

First Cousins, Once Removed

Answer 12

50

25

12. 5
13. 25

Question 13

At what level of consanguinity does the risk = normal population risk?

Answer 13

Fourth; ~6.25%

Question 14

Isonymous Marriage

Answer 14

Same surname, but doesn’t always = consanguinity; e.g. Smith is a common name

Question 15

X Linked Recessive

Answer 15

1. Much higher in males
2. All daughters of infected males will be carriers (they only have one X to give)
3. Sons of carrier females 50/50 chance
4. Never father to son (they give a Y, not X)

Question 16

Hemophilia A

Answer 16

X linked recessive

1:5000 males

*** Exception would be Turner female

Question 17

Duchenne Muscular Dystophy (DMD)

Answer 17

X Linked Recessive

1:3000 males; 1:2500 females carrier

Defect in HUGE gene (Xp21)

Question 18

X Linked Dominant

Answer 18

1. Twice as many females as males (2x X chroms)
2. Affected females (heterozygote); 50/50 offspring transmission
3. All daughters, no sons of affected males, rules out autosomal inheritance

Question 19

Rett Syndrome

Answer 19

X Linked Dominant

Mental retardation in females; usually lethan in males

Question 20

Vitamin D Resistant Rickets

Answer 20

X Linked Dominant

Xp22.2-p22.1

Question 21

Mitochondrial Inheritance

Answer 21

1. Maternal origin
2. All offspring of affected female at risk
3. All daughts of affected/carrier female at risk of transmitting

Heteroplasmy of mitochondria key to varying phenotypes

Question 22

Leber’s Hereditary Optic Neuropathy (LHON)

Answer 22

Mitochondrial

Rapid bilateral death of optic nerve in young adults; more severe in males; rare

Question 23

Kearns-Sayre Syndrome (KSS)

Answer 23

Mitochondrial

Pigmentary degeneration of retina and cardiomyopathy

Question 24

MERRF (ragged red fiber)

Answer 24

Mitochondrial

Question 25

Y-Linked (Holandic) Inheritance

Answer 25

Only males affected

Only father to son

Question 26

Pseudoautosomal Inheritance

Answer 26

Pertains to set of genes carried by both X/Y chromosomes; involved with sex reversal

Question 27

Chromosome Translocation Inheritance Pattern

Answer 27

1. Individuals w/balanced translocations can pass on multiple possibilites of gametes
2. Miscarriages
3. Infertility
4. Unusual/dysmorphic features
5. Child/stillbirth w/malformations

Question 28

Additivity Principle

Answer 28

OR

P(1) + P(2)

Question 29

Indpendence Principle (Multiplication)

Answer 29

AND

P(1,2) = P(1)*P(2)

Question 30

Hardy Weinberg Equilibrium Rules

Answer 30

1. No mutations
2. No migration
3. Random mating
4. No genetic drift
5. No selection