Genetic Diseases

Question 1

Alleles

Answer 1

Different DNA sequences for the same gene.

Question 2

Homozygote

Answer 2

An individual with matching alleles at the same locus on both chromosomes.

Question 3

Heterozygote

Answer 3

When the paired alleles have different alleles at the same locus.

Question 4

Dominant alleles

Answer 4

Need only to be present in one copy to be expressed in heterozygotes. A= dominant allele

Question 5

Recessive alleles

Answer 5

Need to be present in two copies to be expressed. a= recessive alleles

Question 6

What are the characteristics of autosomal dominant inheritance?

Answer 6

Half of children with one affected patent are affected by the disease. No skipped generations

Question 7

What are the characteristics of autosomal recessive inheritance?

Answer 7

Skipped generations are common. Cluster among siblings. 25% of the children with two patents who are carriers for the gene mutation are affected with the disease.

Question 8

What are examples of autosomal dominant inheritance?

Answer 8

Huntington’s disease. Marfan syndrome. Achondroplasia.

Question 9

Mating of related individuals can increase risk of autosomal recessive disease, is called:

Answer 9

Consanguinity.

Question 10

What diseases are examples of autosomal reccesive inheritance?

Answer 10

Cystic fibrosis. Sickle cell anemia.

Question 11

What diseases are examples of X-linked recessive inheritance?

Answer 11

Hemophilia. Duchenne muscular dystrophy.

Question 12

Characteristics of x-linked recessive inheritance.

Answer 12

Males are much more commonly affected. Skipped generations are common. No transmission from father to son.

Question 13

What process occurs that causes trisomy 21?

Answer 13

Chromosomal nondisjunction.

Question 14

A male patient presents with Hemophilia A and has a wife with no trace of the disease. What would the pedigree of the male patient look like?

Answer 14

X’Y

Question 15

Autosomal aneuploidy

Answer 15

An abnormal number of chromosomes.

Question 16

Type of chromosomal disorder that is always lethal.

Answer 16

Monosomies

Question 17

Non-sex chromosome

Answer 17

Autosome

Question 18

Individual’s complete set of chromosomes.

Answer 18

Karyotype

Question 19

Observable traits that are determined by genetic make-up.

Answer 19

Phenotype

Question 20

What does it mean when we say that one allele is dominant over another allele of the same gene?

Answer 20

It is expressed even in the presence of the other allele.

Question 21

True or false. Some genetic changes affect only one gene, but other kinds of genetic changes can impact the presence or absence of thousands of genes.

Answer 21

True

Question 22

Aa———Aa This diagram shows…. AA Aa aA aa

Answer 22

A pedigree for two heterozygous parents. The chances of producing an affected homozygous child.

Question 23

True or false.
Individuals who are XX can express an X-linked recessive disease.

Answer 23

True

Question 24

How can individuals who have 2 X chromosomes (XX) express an X-linked recessive disease?

Answer 24

They must inherit the defective allele from their mother and father.

Question 25

Achondroplasia is caused by an _________ gene mutation.

Answer 25

Autosomal dominant

Question 26

In addition to developmental delays and intellectual disabilities, common characteristics associated with Down syndrome include:

Answer 26

Congenital heart defects.
Premature aging.
Increased risk for leukemia.

Question 27

What is the greatest factor for chromosomal nondisjunction?

Answer 27

Maternal age, on women older than 35.

Question 28

What are characteristics features of Achondroplasia?

Answer 28

Abnormal skeletal development: short arms and legs, distinct head.

Question 29

What are characteristic features of Marfan syndrome?

Answer 29

Elastic collagen: long limbs and aneurysms.

Question 30

What are the characteristic feature for Cystic fibrosis?

Answer 30

Causes cells to create thick mucus. Mucous plugs obstruct the respiratory tract, pancreatic duct, and other organs.

Question 31

What are the characteristic feature of Sickle cell anemia?

Answer 31

Causes changes in the hemoglobin triggered by hypoxic conditions, temperature changes, and other factors.

Question 32

What are the characteristic feature of Hemophilia A?

Answer 32

Bleeding disorder caused by a clotting factor deficiency. Causes prolonged nose bleeds.

Question 33

What are the characteristic feature for Duchenne muscular dystrophy?

Answer 33

Mutation on the protein dystrophin causes loss of muscle tissue starting around age 4.

Question 34

A couple have three offspring, one child with an autosomal dominant disease trait and two who are unaffected. The father is affected by the autosomal dominant disease, but the mother does not have the disease gene. What is the recurrence risk of this autosomal dominant disease for their next child?

Answer 34

50%

Question 35

A couple have three offspring, one child with an autosomal recessive disease and two who are unaffected. Both parents are carriers for the disease gene. What is the recurrence risk of this autosomal recessive disease for their next child?

Answer 35

25%

Question 36

What is an accurate characteristic of an autosomal recessive disease?

Answer 36

The disease tends to cluster in siblings

In the absence of a spontaneous mutation, autosomal recessive diseases occur when two individuals who are carriers for the disease gene mate and produce offspring. Every time this course has another child, the risk of expressing the disease is 25%. Therefore if these parents have multiple children, there may be multiple siblings affected.

Question 37

Cystic fibrosis is caused by an ______ gene mutation.

Answer 37

autosomal recessive

Cystic fibrosis is the most prevalent autosomal recessive disorder. See p. 3 in the Genetic Diseases Lecture Notes.

Question 38

A family has three children with cystic fibrosis. Which option best describes how the second and third children developed this condition?

Answer 38

Both parents, who are carriers of the mutated gene, each passed one mutated gene to the child.

Question 39

Males express disease more frequently than females with X-linked recessive gene mutations.

Answer 39

True

The only way a female can develop a X-linked recessive gene is if her mother is a carrier (X’X) and her father has the disease (X’Y). In this case, the risk of this occurring is 25%. In the majority of cases a female carrier will mate with an unaffected male. In this case the chances of producing a male with the disease is 25% and the risk of producing a female with the disease is 0%. On average 50% of the females will be carriers and 25% will be unaffected.

Question 40

A boy with Duchenne muscular dystrophy likely inherited the disease gene from his mother.

Answer 40

True

Duchenne muscular dystrophy is an X-linked recessive disease, and therefore the boy must have inherited the mutation form his mother.

Question 41

Which are the characteristics of X-linked recessive diseases?

Answer 41

Females are carriers for the X-linked gene mutation
No male-male transmission of the disease
Skipped generations are common

Question 42

A couple is undergoing genetic counseling. After their appointment with the genetic counselor, they ask the clinic nurse, ‘What is karyotyping’? The nurses’ best response is:

Answer 42

“Karyotyping will provide information about the gender of the baby and the number and structure of the chromosomes.”

Karyotyping provides genetic information such as gender and chromosome structure.

Question 43

The vast majority of conceptions with chromosomal mutations survive to birth because they are generally not that serious.

Answer 43

False

Chromosomal mutations occur in ~ 1 out of 12 conceptions, however the majority of these fetuses do not survive to term because the resulting complications cause severe developmental problems.

Question 44

The most common cause of Down syndrome is:

Answer 44

maternal chromosomal nondisjunction.

Down syndrome is a trisomy that occurs when the 21st chromosomes fail to separate during the first stage of cell division in the female ovum (meiosis I). The result is three chromosomes in one ovum and none in the other. When the ovum with two copies of chromosome 21 encounter the sperm, the resulting offspring is potentially a gamete with three copies of chromosome 21 (two from the mother and one from the father) or a gamete with one copy of chromosome 21 (zero from the mother and one from the father).

Question 45

In addition to developmental delays and intellectual disabilities, common characteristics associated with Down syndrome include:

Answer 45

Increased risk for leukemia
Premature aging
Congenital heart defects

Question 46

A father and mother are carriers of phenylketonuria (PKU), an autosomal recessive disease that causes an inborn error in metabolism resulting in intellectual disability, seizure disorder and other problems. Their 2-year-old daughter has PKU. The couple tells the nurse that they are planning to have a second baby. Because their daughter has PKU, they are sure that their next baby won’t be affected. What response by the nurse is most accurate?

Answer 46

You are both carriers, so each baby has a 25% chance of being affected.

The chance is one in four that each child produced by this couple will be affected by PKU disorder. This couple still has an increased likelihood of having a child with PKU. Having one child already with PKU does not guarantee that they will not have another. No correlation exists between gender and inheritance of the disorder because PKU is an autosomal recessive disorder.

Question 47

The unlicensed assistive personnel (UAP) asks the primary nurse, “How does someone get hemophilia A?” Which statement would be the nurse’s best
response?

Answer 47

“The mother carries the gene mutation and passes it on to the son.”

Question 48

A maternal-newborn nurse caring for a mother who just delivered a baby born with Down syndrome. What would be the priority body system to assess immediately after birth?

Answer 48

Cardiovascular system.

Up to 47% of infants born with Trisomy 21 or Down Syndrome have a congenital heart defect (see Chapter 27 in text), therefore it is imperative that the health care team conduct a thorough cardiovascular assessment immediately after birth in order to identify life threatening cardiac conditions.