Lecture 3

Question 1

True or False: Two different genotypes may have the same phenotype

Answer 1

True (e.g dominant homozygote and heterozygote for CF have same “normal” phenotype - AA vs. Aa)

Question 2

___ risk: no affected child yet born
___ risk: have one or more affect kids

Answer 2

Occurrence Risk
Recurrence Risk

Question 3

What is an example in which the same genotype may productive different phenotypes in different environments?

Answer 3

PKU
- If diet that is low in phenylalanine is initiated within 1 month of birth, individual with genotype does not have phenotype of intellectual disability

Question 4

True or False: First degree relatives are those related at the parent offspring or sibling level while Second degree relatives are removed by one additional generation step (e.g grandparents, grandkids)

Answer 4

True

Question 5

___-degree relatives include first cousins and great grandchildren

Answer 5

Third-degree

Question 6

An arrow usually denotes the ___ or first individual diagnosed in the pedigree or the person from whom the pedigree is drawn

Answer 6

proband

Question 7

Mutations in __ gene results in PKU, which is a disease in which person is unable to metabolized phenylalanine

Answer 7

PAH

Question 8

True or False: Environment can include genetic environment, as well as external environment

Answer 8

True

Question 9

What are four features of autosomal dominance?

Answer 9

1) Vertical transmission
2) No skipped generations
3) Equal proportion of females and males
4) Father to son transmission possible

Question 10

Postaxial polydactylyl is an example of an ____ ___ trait
A. Autosomal recessive
B. Autosomal dominant
C. X-linked

Answer 10

B. Autosomal dominant

Question 11

True or False: In autosomal dominant traits, males and females are affected with equal frequency and male to male transmission of trait can occur

Answer 11

True

Question 12

True or False: In autosomal dominant traits, unaffected individuals have affected offspring

Answer 12

False - in autosomal dominant traits, unaffected individuals do NOT have affected offspring

Question 13

True or False: In autosomal dominant inheritance, the heterozygous state is MORE severe than the homozygous state

Answer 13

False - heterozygous state is LESS severe than homozygous

Question 14

What type of mutations are common in autosomal dominant traits?

Answer 14

Spontaneous mutations

Question 15

First degree relatives (parents and kids or parents and sibling) share ___% of DNA

Second degree relatives (grandkids and grandparents) share __% of DNA

Third degree relatives (first cousins) share __% of DNA

Answer 15

50%
25%
12.5%

Question 16

What’s the difference between a first cousin once removed and a second cousin?

Answer 16

First cousin once removed
- First cousin of your parent
- Child of first cousin

Second cousin:
- Children of first cousins are second cousins to each other

Question 17

True or False: Children of second cousins are third cousins to each other

Answer 17

True

Question 18

When inheritance of a single gene results in a phenotype, this is known as ____ inheritance

Answer 18

Mendelian

Question 19

True or False: Most affected individuals are heterozygous and have one affected heterozygous (Aa) parent and one unaffected homozygous (aa) parent

Answer 19

True

Question 20

Which four disorders are inherited as autosomal dominant traits? Which genes are associated?

Answer 20

1) Huntington’s Disease - HTT gene
2) Marfan Syndrome - FBN1 gene
3) Neurofibromatosis Type 1 - NF1 gene
4) Retinoblastoma - Rb gene

Question 21

On average, ___ of the offspring of affect individuals are affected
A. 1/4
B. 1/2
C. 100%

Answer 21

1/2

Question 22

True or False: In autosomal dominant traits, genetically unaffected persons do not have affected offspring

Answer 22

True

Question 23

True or False: In autosomal dominant traits, the trait rarely shows variation in expression

Answer 23

False - in autosomal dominant traits, the trait FREQUENTLY shows variation in expression

Question 24

In autosomal dominant traits, basic defects tend to involve _____ _____

Answer 24

structural protein

Question 25

What are two diseases in which homozygous state is more severe?

Answer 25

1) Factor V Leiden Mutation 2) Prothrombin Mutation * inherited thombophilia

Question 26

Who is at a greater risk for a DVT? A. Heterozygote with Factor V Leiden mutation B. Homozygous with Factor V Leiden mutation

Answer 26

B. Homozygous with Factor V Leiden mutation

Question 27

Mutation in the ___ gene can lead to Factor V Leiden mutation, which follows a autosomal dominant inheritance and is more severe in homozygotes A. CY11B2 B. F5 C. F2

Answer 27

B. F5

Question 28

True or False: A G20210A mutation in the F2 gene can give rise to Factor V Leiden mutation

Answer 28

False - A G20210A mutation in the F2 gene can give rise to the Prothrombin mutation

Question 29

True or False: Factor V Leiden mutation is more severe in homozygotes while Prothrombin mutation is more severe in heterozygotes

Answer 29

False - both Factor V Leiden and Prothrombin mutation are MORE severe in homozygotes

Question 30

True or False: For both Factor V Leiden mutation and Prothrombin mutation, there is hormonal influence on disease expression

Answer 30

True

Question 31

True or False: In sex-linked disorders, one sex may be more apt to express disease phenotype

Answer 31

True

Question 32

True or False: Male and females are not equally likely to inherit BRCA mutations. However, males are still very likely to develop breast cancer.

Answer 32

False - male and females ARE equally likely to inherit BRCA mutations and males are UNLIKELY to develop breast cancer

Question 33

Who can pass the mutant BRCA allele to daughter, who then develop breast cancer at a young age? A. Unaffected father B. Unaffected mother C. Affected mother D. Affected father

Answer 33

A. Unaffected father

Question 34

True or False: A person can appear to have no family history of breast cancer if the allele has been passed from male to male in previous generations

Answer 34

True

Question 35

What are four features of autosomal recessive inheritance?

Answer 35

1) Horizontal transmission 2) Skipped generations 3) Equal proportions of female and males 4) Father to son transmission possible

Question 36

True or False: Persons affected with autosomal recessive diseases ALWAYS have two carrier (heterozygous) parents

Answer 36

False - Persons affected with autosomal recessive diseases ALMOST ALWAYS have two carrier (heterozygous) parents

Question 37

True or False: BRCA1 and BRCA2 genetic mutations are examples of a sex-limited disorder

Answer 37

True

Question 38

Tyrosine-negative albinism is an example of which type of inheritance? A. Autosomal Dominant B. Sex-limited C. Sex-linked D. Autosomal Recessive

Answer 38

D. Autosomal Recessive

Question 39

Provide 6 examples of autosomal recessive disorders: (hint: Gun Shot Wound, THC)

Answer 39

G - Gaucher Disease (N370S) S - Sickle Cell (HbB) W - Wilson's Disease (ATP7B) Tay Sachs (HEXA) Hereditary Hemochromatosis (HFE) CF (CFTR)

Question 40

True or False: Almost all persons with hereditary hemochromatosis have two carrier parents

Answer 40

True - since hereditary hemochromatosis is a autosomal recessive condition

Question 41

True or False: A person with an autosomal recessive disorder may have two of the SAME mutant alleles or two DIFFERENT mutant alleles (compound heterozygote)

Answer 41

True

Question 42

True or False: Many people with hemochromatosis have two different mutations in HFE

Answer 42

False - many people with CF have two DIFFERENT mutations in CFTR

Question 43

Many people with this autosomal recessive disorder are compound heterozygotes: A. Wilson Disease B. Sickle Cell Disease C. CF D. Tay Sachs Disease E. Gaucher Disease F. Hereditary Hemochromatosis

Answer 43

F. Hereditary Hemochromatosis

Question 44

____, an iron storage disorder, is both autosomal recessive and sex limited A. Wilson Disease B. Sickle Cell Disease C. CF D. Tay Sachs Disease E. Gaucher Disease F. Hereditary Hemochromatosis

Answer 44

F. Hereditary Hemochromatosis

Question 45

Why does iron not build up in women with hemochromatosis to the same degree as men?

Answer 45

Menses

Question 46

True or False: Women with hemochromatosis present at older ages than men

Answer 46

True

Question 47

What is the prevalence of affect children in autosomal recessive inheritance? A. 100% B. 75% C. 50% D. 25%

Answer 47

D. 25%

Question 48

True or False: In autosomal recessive inheritance, disease phenotype is not seen in every generation and males and females are affected with equal frequency

Answer 48

True

Question 49

A high prevalence of a rare autosomal recessive disease suggests _____, which is mating of closely related individuals (usually first cousins)

Answer 49

consanguinity