Chapter 24 Gen

Question 1

Loss-of-function mutation

Question 2

Gain-of-function mutation

Answer 2

Mutation changes protein so it gains a new function

Question 3

Dominant Negative Mutation

Answer 3

Mutant gene product acts antagonistically to the wild-type gene product

Question 4

Haploinsufficiency

Answer 4

Heterozygote has 50% of the functional protein

Question 5

Thousands of human diseases have a _______ basis

Answer 5

genetic

Question 6

When an individual exhibits a disease, the disorder is____

Answer 6

more likely to occur in genetic relatives than in the general population

Question 7

True or False: Identical twins share the disease more often than fraternal twins

Answer 7

true

Question 8

DIfferent populations tend to have_____

Answer 8

different frequencies of the disease

Question 9

The disease tends to develop at the ______

Answer 9

age of onset

Question 10

The human disorder resembles a genetic disorder_______

Answer 10

that has a genetic basis in another mammal

Question 11

Correlation is observed between a disease and a ______

Answer 11

mutant human gene or a chromosomal alteration

Question 12

Inheritance patterns of human diseases may be determined via

Answer 12

pedigree analysis

Question 13

Types of Inheritance of Human Diseases and Traits

Answer 13

Autosomal recessive
Autosomal Dominant
X-linked Recessive
X-Linked Dominant
Y-Linked

Question 14

Autosomal Recessive Inheritance

Answer 14

1. Frequently, an affected offspring will have two unaffected
   parents
2. When two unaffected heterozygotes have children, the
   percentage of affected children is (on average) 25%
3. Two affected individuals will have 100% affected children
4. The trait occurs with the same frequency in both sexes

Question 15

Examples of Autosomal Recessive Disorders

Answer 15

• Albinism- tyrosinase
• Cystic Fibrosis- CFTR, a chloride transporter
• Phenylketonuria (PKU)- phenylalanine hydroxylase
• Sickle cell disease- b globin

Question 16

Autosomal Recessive Disorders

Answer 16

Disorders that involve defective enzymes typically have an
autosomal recessive mode of inheritance
* The heterozygote carrier has 50% of the functional
enzyme
* This is sufficient for a healthy (unaffected) phenotype
Hundreds of genetic diseases are inherited this way
* In many cases, the mutant genes responsible have been
identified and characterized\

Question 17

Autosomal Dominant Inheritance

Answer 17

1. An affected offspring usually has one or both affected
   parents
   * Can be altered by reduced penetrance
2. An affected individual with only one affected parent is
   expected to produce (on average) 50% affected offspring
3. Two affected, heterozygous individuals will have (on
   average) 25% unaffected offspring
4. The trait occurs with the same frequency in both sexes
5. For most dominant disease-causing alleles, the
   homozygote is more severely affected with the disorder

Question 18

Mechanisms of Autosomal Dominant Disorders

Answer 18

Haploinsufficiency
Gain-of-function mutations
Dominant Negative Mutation

Question 19

Examples of Autosomal Dominant Disorders

Answer 19

• Aniridia
• Achondroplasia
• Marfan syndrome
• Familial hypercholesterolemia

Question 20

X-Linked Recessive

Answer 20

1. Males are much more likely to exhibit the trait
2. The mothers of affected males often have brothers or
   fathers who are affected with the same trait
3. The daughters of affected males will produce (on
   average) 50% affected sons

Question 21

Examples of X-linked recessive

Answer 21

Duchenne muscular dystrophy
* Hemophilia A
* Hemophilia B
* Androgen insensitivity syndrome

Question 22

X-Linked Dominant Inheritance

Answer 22

Characteristics of such disorders are:
* Males are often more severely affected
* Females may be less affected due to wild-type copy on the
other X chromosome
* Females are more likely to exhibit the trait when it is lethal
to males
* Affected mothers have a 50% chance of passing the trait
to daughters

Question 23

Examples of X-Linked Inheritance

Answer 23

• Vitamin D-resistant rickets
• Rett syndrome
• Aicardi syndrome
• Incontinentia pigmenti

Question 24

Y-Linked Traits

Answer 24

All sons show the trait if father has it
* No daughters will show the trait

Question 25

Examples of Y-Linked Traits

Answer 25

Hypertrichosis

Question 26

Huntington’s DIsease

Answer 26

-Autosomal Dominant
-Major symptom of this disease is the degeneration of certain types of neurons-leads to personality changes, dementia, and early death (age of onset-middle age)
-Mutation in a gene that encodes for protein named huntingtin

Question 27

Albinism Mechanism

Answer 27

Loss-of-function

Question 28

PKU Mechanism

Question 29

CF Mechanism

Question 30

Tay-Sach’s DIsease Mechanism

Question 31

WHy do X-linked recessive disorders affect males

Answer 31

Because the mother having both X has to give the disorder to the son who only has one X

Question 32

Why does red-green color blindless affect males?

Answer 32

Because it is X-linked recessive, meaning that if the mom has the carrier for it she will pass it down to her son and he will have it

Question 33

Why are males termed hemizygous?

Answer 33

Males only have a single copy of X-linked genes

Question 34

Locus heterogeneity

Answer 34

phenomenon that a disease can be caused by mutations in two or more different genes

Question 35

Everything about PKU

Question 36

Screening for PKU in newborns and preventing the development of PKU

Question 37

Genetic Testing

Answer 37

use of tests to discover if an individual carries a genetic abnormality

Question 38

genetic screening

Answer 38

population-wide genetic testing

Question 39

Amniocentesis

Answer 39

Fetal cells are obtained from the amniotic fluid

Question 40

Chorionic Villus Sampling

Answer 40

Fetal cells are obtained from the chorion (fetal part of the placenta)

Question 41

Pre-implantation Genetic Diagnosis

Answer 41

Tests are done to check for problems for patients who do IVF

Question 42

Prions

Answer 42

Proteinaceous infectious particles

Question 43

Mechanisms of prion diseases

Answer 43

PrPSc proteins act as a
catalyst to convert normal
proteins to the abnormal
conformation

PrPSc proteins form
aggregates in brain and
nervous system

The PrPSc proteins can
spread by excretion into
bloodstream