Chapter 5

Question 1

pros of genetic analysis in humans

Answer 1

good understanding of the system
good records exist
vested interest in inheritance of human disease

Question 2

cons of genetic analysis in humans

Answer 2

long generation time
inability to test crosses
small numbers of offspring

Question 3

autosomal dominant traits

Answer 3

appear equally in males and females
unaffected persons do not transmit the trait
affected persons have at least one affected parent

Question 4

autosomal recessive traits

Answer 4

appear equally in males and females
tend to skip generations
more likely to appear among progeny of related parents

Question 5

x linked recessive traits

Answer 5

appear more often in males than females and are not passed from father to son

Question 6

x linked dominant traits

Answer 6

do not skip generations 
affected males pass the trait to all of their daughters and none of their sons
affected females (if heterozygous) pass the trait on to about half of their sons and half of their daughters

Question 7

y linked traits

Answer 7

appear only in males

all male offspring of an affected male are affected

Question 8

monozygotic twins

Answer 8

identical gene sets

Question 9

dizygotic twins

Answer 9

share 50% of genes

Question 10

concordance

Answer 10

the percentage of twin pairs who share a specific trait

Question 11

ultrasonography

Answer 11

used to detect some genetic disorders in a fetus and to locate the fetus during amniocenteses and chorionic villus sampling

Question 12

amniocentesis

Answer 12

a sterile needle is inserted through the abdominal wall into the amniotic sac where a small amount of fluid is drawn. this fluid contains fetal cells which are separated and cultured

Question 13

chorionic villus sampling

Answer 13

can be performed early in pregnancy
a catheter is inserted through the vagina and cervix and into the uterus. it is placed into contact with the chorion, the outer layer of the placenta. suction removes a small piece of chorion and its cells are used directly for genetic test, no culturing required

Question 14

maternal blood testing

Answer 14

provides information about the fetus based on components found circulating in the mother

Question 15

fetal cell sorting

Answer 15

allows isolation of the few fetal cells that end up in maternal blood. the cells are propogated and analyzed

Question 16

preimplantation genetic diagnosis

Answer 16

sometimes used to test for genetic disorders of fetuses fertilized in vitro before implantation in the uterus

Question 17

newborn screening

Answer 17

genetic analysis of blood from newborns is commonly done to identify treatable recessive traits

Question 18

heterozygote screening

Answer 18

useful for identifying carriers of recessive disorders

Question 19

presymptomatic testing

Answer 19

individuals at risk for autosomal dominant traits that are expressed later in life may benefit from knowledge so that early surveillance and detection can be employed