Exam 4 - Genes & Genetic Disease

Question 1

What is genetic testing?

Answer 1

The sequence of human DNA to discover genetic differences, abnormalities, or mutations that may prove pathological in nature

Question 2

Conditions that genetic testing could prove beneficial

Answer 2

Carrier screening
Prenatal diagnosis of certain condition
Presymptomatic diagnosis
Testing for drug efficacy

Question 3

Carrier screening examples

Answer 3

Cystic fibrosis

Sickle cell

Question 4

What is prenatal diagnosis

Answer 4

Analysis of genetic make-up of fetus

Question 5

Examples of Presymptomatic diagnosis

Answer 5

Breast or colon cancer

Question 6

Testing for drug efficacy

Answer 6

HIV drug trials

Question 7

What is gene therapy?

Answer 7

The transplantation of normal genes into cells in place of missing of defective genes in order to correct genetic disorders

Question 8

Chromosomal aberrations

Answer 8

Polyploidy
Aneuploidy
Triploidy
Tetraploidy

Question 9

What is Down syndrome?

Answer 9

A type of aneuploidy that contains an extra copy of the 21st chromosome

Question 10

How often is Down syndrome seen?

Answer 10

1 in 800 births

Question 11

What increases the risk of having a Down syndrome child?

Answer 11

Increased maternal age

The risk rises dramatically after maternal age 35 and can be up to 5% greater in women older than 45

Question 12

Clinical manifestations of Down syndrome

Answer 12

IQ between 27 and 70
Low nasal bridge
Epicanthal folds
Protruding tongue
Flat, low set ears
Poor muscle tone
Short stature

Question 13

What defects affect survival rate of babies born with Down syndrome?

Answer 13

Congenital heart defects
Reduced ability to fight respiratory tract infections
Increased susceptibility to leukemia

Question 14

By 40 years of age, what happens to people with Down syndrome?

Answer 14

Symptoms that are nearly identical to Alzheimer’s

Question 15

Why do symptoms of Alzheimer’s show up in people with Down syndrome?

Answer 15

One of the genes that can cause Alzheimer disease is located on chromosome 21

Question 16

What is Turner syndrome classified as?

Answer 16

A sex chromosome aneuploidy

Question 17

Total chromosome count for Turner syndrome?

Answer 17

45 in each cell

Question 18

Who gets Turner syndrome?

Answer 18

Only females

Question 19

IQ of someone with Turner syndrome

Answer 19

Normal range

Question 20

Clinical manifestations of Turner syndrome

Answer 20

Usually sterile
Gonadal streaks rather than true ovaries
Short stature
Webbing of the neck (1/2 of cases)
Widely spaced nipples
Narrowing of aorta (coarctation 15-20% of cases)
Sparse body hair

Question 21

What is Klinefelter syndrome classified as?

Answer 21

A sex chromosome aneuploidy

Question 22

What do the chromosomes of someone with Klinefelter syndrome look like?

Answer 22

Have at least two X chromosomes, and a Y chromosome in each cell (47, XXY)
Because of the Y chromosome, these individuals are male

Question 23

Clinical manifestations of Klinefelter syndrome

Answer 23

Usually sterile
Develop female-like breast tissue (1/2 of cases)
Small testes
Sparse body hair
High-pitched voice
Tall stature
Mental impairment (moderate degree)

Question 24

A part of the chromosome is missing or deleted

Answer 24

Deletions

Question 25

What could happen if a fetus is developing with deletions?

Answer 25

There could be errors in development of fetus since some of the DNA instructions are missing

Question 26

A type of mutation that involves the production of one or more copies or duplicates of a gene, or region of a chromosome

Answer 26

Duplications

Question 27

Effect of duplications on a fetus

Answer 27

Less serious consequences

Question 28

The occurrence of two breaks on a chromosome, followed by the reinsertion of the missing fragment at the original location, but in inverted order

Answer 28

Inversions

Question 29

Results of inversions

Answer 29

No loss of genetic material

Individuals are said to be “balanced” and have no outward signs or symptoms

Question 30

Type of chromosomal abnormality in which a chromosome breaks and a portion of it reattaches to a different chromosome

Answer 30

Translocations

Question 31

Results of translocations

Answer 31

Normal appearance
Children of someone with translocations could have serious genetic issues
(3-5% of down syndrome cases)

Question 32

Chromosomal regions that are more prone to gaps or breaks (weak spot in the chromosome)

Answer 32

Fragile sites

Question 33

Results of fragile sites

Answer 33

Most fragile sites have no relationship to disease

Question 34

How common is Fragile X syndrome

Answer 34

1/4000 males
1/8000 females
(Relatively common)

Question 35

Why does Fragile X syndrome occur?

Answer 35

A particular fragile site on the long portion of the X chromosome has observable break in the DNA

Question 36

What is Fragile X syndrome associated with?

Answer 36

Substantial cognitive impairment

Question 37

What is fragile X the most common genetic cause of?

Answer 37

Intellectual disability (Down syndrome being number 1)

Question 38

Clinical manifestations of fragile X syndrome

Answer 38

Balance issues
Shaky hands
Numbness in hands and feet
Unstable mood
Memory loss
Cognitive impairment

Question 39

Define X-linked inheritance

Answer 39

• Conditions caused by genes located on the sex chromosomes

- Can be passed down from parent to child through genetic mutations on the X chromosome

Question 40

How does X-linked inheritance affect males vs females

Answer 40

Males more frequently affected by X-linked recessive diseases
Females are more frequently affected by X-linked dominant diseases

Question 41

Define sex-influenced traits

Answer 41

One that occurs in both males and females, this condition is more common in males

Question 42

Identify 3 sex-influenced traits

Answer 42

• Male pattern baldness
• breast cancer
• facial hair (soft vs coarse)