Chapter 21 Study and Book Questions

Question 1

Define homozygous and heterozygous.

Answer 1

Homozygous—the pair of alleles or genes at a site that determines a specific trait are identical.
Heterozygous—the pair of matching alleles for a trait that differs in expression.

Question 2

What is the purpose of a pedigree?

Answer 2

A pedigree chart can be used to trace a genetic trait back through previous generations by checking the occurrence of the disorder or characteristic in all family members. Such a chart may confirm the presence of an inherited condition in the family and indicate the type of inheritance.

Question 3

Explain why teratogens are difficult to identify.

Answer 3

The effects are not noted until data are collected at a much later time, and it may be difficult to identify one teratogen out of many possible factors to which any one person was exposed. Ethically, experiments cannot be performed to identify suspected teratogens; therefore, it requires collation of many incident reports over a long period of time to identify the source.

Question 4

Explain why a woman carrying the gene for hemophilia can produce two hemophiliac sons when she is mated to a normal male

Answer 4

The probability of passing on the gene for hemophilia is the same for each pregnancy, depending on the possible combinations of the genes derived from the parents, regardless of events in prior pregnancies.

Question 5

Under what conditions does a female acquire an X-linked recessive disorder?

Answer 5

Both parents must carry the defective gene for the female child to be affected. A female child may be a carrier if either parent passes on the defective gene.

Question 6

Why are X-linked recessive disorders never passed from a father to a son?

Answer 6

The father passes his Y chromosome to a son, not the X chromosome carrying the defective gene

Question 7

The pedigree for Queen Victoria of England, a carrier of hemophilia A, shows the transmission to some of her descendants, including members of many royal families in Europe, such as Russia and Spain, but not Germany. Hemophilia A does not affect anyone in the present British royal family. Can you explain why hemophilia A has disappeared from one family and appeared in others?

Answer 7

If an unaffected female child mates with an unaffected male, hemophilia A will not be carried forward. A female carrier child who mates with an unaffected male from a different family could produce affected children (see Figures 7-4 and 7-5).

Question 8

What is the probability that a parent carrying a dominant trait will pass that trait on to each child?

Answer 8

The probability that a parent carrying a dominant trait will pass that trait on is a 50% chance with each pregnancy

Question 9

How can prenatal diagnosis demonstrate the sex of an unborn child?

Answer 9

Chromosome analysis indicates the components of pair 23, XX or XY. Ultrasound may show the penis.

Question 10

Describe briefly amniocentesis and its purpose.

Answer 10

A needle is inserted through the abdominal wall into the uterus and amniotic sac, guided by ultrasound visualization and a small amount of amniotic fluid is withdrawn. The fluid is tested for marker enzymes or chemicals that are significant in certain diseases and the fetal cells in the fluid are cultivated for several weeks. As the cells proliferate, chromosomes may be extracted from a cell, a karyotype prepared to check for chromosome abnormalities in the fetus, and DNA testing may be done.

Question 11

11. Which of the following can be identified by an abnormal karyotype?
    a. Sickle cell disease
    b. Cystic fibrosis
    c. Monosomy X
    d. Tay-Sachs disease
    e. Huntington chorea

Answer 11

Monosomy X can be identified by an abnormal karyotype.

Question 12

Define congential defect/anomalies

Answer 12

congenital defects/ anomalies refer to disorders present at birth; they include genetic (inherited) as well as developmental disorders

Question 13

Outline the etiology of chromosomal disorders

Answer 13

errors in chromosomal duplication or reassembly during meiosis resulting abnormal placement of part of a chromosome (translocation) altered structure (deletion) or abnormal number of chromosomes

Question 14

Define teratogenic agents

Answer 14

agents that cause damage during embryonic of fetal development ; often difficult to define

Question 15

Differentiate between an inherited disorder and chromosomal disorder

Answer 15

inherited disroders are anh disorders resulting from abnormalities or damage to the genetic makeup, whereas chromosomal defects usually result from eeros during meiosis when the chromosomes are segregating when the DNA fragements are displaced or lost and therefor could involve many genes

Question 16

Name and briefly describe single-gene disorders

Answer 16

autosomal recessive disorders: both parents must pass on the defective gene to produce an affected child.
Autosomal dominant disorders an affected parent has 50% chance to pass the disorder to a child
X-linked dominant-dominant allele carried on the x-chromosomes-males and females can be affected
X-linked recessive disorders-alleles carried by the X chromosomes-manifested in heterozygous males-heterozygous females and carriers

Question 17

Define monosomy

Answer 17

when one member of chromosome pair is lost during meiosis

Question 18

Define trisomy

Answer 18

when there is an extra duplicated of one member of a chromosome pair; yielding 3 chromosome instead of two

Question 19

Explain what is meant by mulfactorial disorder. Identifiy several examples

Answer 19

when there is a combination of factors that is responsible for the congenital disorder that is polygenic-caused by multiple genes or inherited tendency that is
ex. anencephaly, cleft lip and palate, clubfood

Question 20

Explain how maternal substance abuse might cause developmental disorders, and identify the most critical time for embryonic development for such effects?

Answer 20

The most critical time for development is the first 2 months of gestation when organogensis occurs. Exposure to damaging substance may cause developlomental abnormality, premature birth, high risk fo r further illness in infant and increase risk for SID. the effect of exposure depend on te stage of development of the precise time of exposure

Question 21

Explain how a congenital disorder might occur as a result of factors during labor and delivery

Answer 21

difficuluties encountered during or after birth that may temporarily deprive the newborn of O2 and cause brain damage (e.g. cerebral palsy)

Question 22

What is a significant risk factor for chromosomal disorders

Answer 22

maternal age older than 35 years

Question 23

Explain. thedifference betweent eh carrier of na infectious disease such as Hep B, and the carrier of a genetic disorder

Answer 23

a carrier of an infectious disease is contagious and can pass infection to others. a carrier of genetic disorder is heterozygous for that particular disorder and usually does not have manifestation of the disorder; he may pass the faulty gene to his children

Question 24

In what type or types of inherited disorders is there a carrier state?

Answer 24

autosomal recessive and x-linked recessive disorders

Question 25

monosomy x

Answer 25

turner syndrome

Question 26

polysomy x

Answer 26

klinefelter syndrome

Question 27

fragile x syndrome-

Answer 27

x-link dominant

Question 28

cystic fibrosis

Answer 28

autosomal recessive

Question 29

adult polycystic kidney disease

Answer 29

autosomal dominant

Question 30

familial hypercholesterolemia

Answer 30

autosomal dominant disorder

Question 31

duchenenne muscular dystrophy

Answer 31

x-linked recessive

Question 32

sickle cell anemia

Answer 32

autosomal recessive

Question 33

hemophilia A

Answer 33

x-linked recessive

Question 34

klinefelter syndrom

Answer 34

chromosomal disorder

Question 35

phenylketonuria

Answer 35

autosomal recessive

Question 36

Huntingon disease

Answer 36

autosomal dominant

Question 37

Tay-Sarchs disease

Answer 37

autosomal recessive

Question 38

Schizophrenia

Answer 38

multifactorial disorder

Question 39

Cleft lip and palate

Answer 39

multifactorial disorder

Question 40

Turner syndrome

Answer 40

chromosomal disorder

Question 41

What type of disorder is Down syndrome? How can it be diagnosed prenatally? What is the karyotype of an individual with Down Syndrome

Answer 41

Down syndrome is a chromosomal disorder that is diagnosed prenatally through amniocentesis and karyotyping. The karyotype of an individual with Down Syndrome is trisomy 21.

Question 42

Outline the abnormalities or problems associated with Down syndrome

Answer 42

Down syndrome is trisomy 21 which results in nurmous defects in physical and mental development including hypotonic muscle, loss joints cervical instability , delayed developmental states, cognitive impairment, delayed sexual development. Miscellaneious other conditions. may be present, including visual, hearing and digestive problems, celiac disease; congenital heart disease, decreased resistance to infection and high risk for leukemia

Question 43

Describe the characteristic appearance of an individual with Down syndrome

Answer 43

individuals with down syndrome may have a small head and flat facial profiles, slanted eyes, brushfield spots in the irises and mouth that tends to hand open, a large protruding tongue and high arched palate and small hands with single palmar creases.