Chapter 21 Study and Book Questions Flashcards
Define homozygous and heterozygous.
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.
What is the purpose of a pedigree?
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.
Explain why teratogens are difficult to identify.
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.
Explain why a woman carrying the gene for hemophilia can produce two hemophiliac sons when she is mated to a normal male
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.
Under what conditions does a female acquire an X-linked recessive disorder?
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.
Why are X-linked recessive disorders never passed from a father to a son?
The father passes his Y chromosome to a son, not the X chromosome carrying the defective gene
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?
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).
What is the probability that a parent carrying a dominant trait will pass that trait on to each child?
The probability that a parent carrying a dominant trait will pass that trait on is a 50% chance with each pregnancy
How can prenatal diagnosis demonstrate the sex of an unborn child?
Chromosome analysis indicates the components of pair 23, XX or XY. Ultrasound may show the penis.
Describe briefly amniocentesis and its purpose.
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.
- 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
Monosomy X can be identified by an abnormal karyotype.
Define congential defect/anomalies
congenital defects/ anomalies refer to disorders present at birth; they include genetic (inherited) as well as developmental disorders
Outline the etiology of chromosomal disorders
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
Define teratogenic agents
agents that cause damage during embryonic of fetal development ; often difficult to define
Differentiate between an inherited disorder and chromosomal disorder
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
Name and briefly describe single-gene disorders
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
Define monosomy
when one member of chromosome pair is lost during meiosis
Define trisomy
when there is an extra duplicated of one member of a chromosome pair; yielding 3 chromosome instead of two
Explain what is meant by mulfactorial disorder. Identifiy several examples
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
Explain how maternal substance abuse might cause developmental disorders, and identify the most critical time for embryonic development for such effects?
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
Explain how a congenital disorder might occur as a result of factors during labor and delivery
difficuluties encountered during or after birth that may temporarily deprive the newborn of O2 and cause brain damage (e.g. cerebral palsy)
What is a significant risk factor for chromosomal disorders
maternal age older than 35 years
Explain. thedifference betweent eh carrier of na infectious disease such as Hep B, and the carrier of a genetic disorder
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
In what type or types of inherited disorders is there a carrier state?
autosomal recessive and x-linked recessive disorders
monosomy x
turner syndrome
polysomy x
klinefelter syndrome
fragile x syndrome-
x-link dominant
cystic fibrosis
autosomal recessive
adult polycystic kidney disease
autosomal dominant
familial hypercholesterolemia
autosomal dominant disorder
duchenenne muscular dystrophy
x-linked recessive
sickle cell anemia
autosomal recessive
hemophilia A
x-linked recessive
klinefelter syndrom
chromosomal disorder
phenylketonuria
autosomal recessive
Huntingon disease
autosomal dominant
Tay-Sarchs disease
autosomal recessive
Schizophrenia
multifactorial disorder
Cleft lip and palate
multifactorial disorder
Turner syndrome
chromosomal disorder
What type of disorder is Down syndrome? How can it be diagnosed prenatally? What is the karyotype of an individual with Down Syndrome
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.
Outline the abnormalities or problems associated with Down syndrome
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
Describe the characteristic appearance of an individual with Down syndrome
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.
