Module 6
FISH distinguishes chromosomes by using more than one fluorescent-tagged RNA strand, which will bind to complementary DNA sequences on a specific chromosome.
False
Geneticists study pedigrees in order to predict how traits determined by phenotype are inherited from one generation to the next.
False
Genotype can always be inferred from phenotype.
False
In humans, a mutation in the phenylalanine hydroxylase gene causes phenylketonuria (PKU), which is characterized by a wide variety of medical problems. This is an example of epistasis.
False
Males with Klinefelter syndrome lack a Barr Body.
False
Mendel's principle of independent assortment describes the separation of paired factors during the formation of gametes.
False
Nondisjunction of the XY pair during the first meiotic division can produce sperm with 2 X chromosomes and 2 Y chromosomes
False
The product rule is used to determine the probability that two parents with a Bb genotype will have a child who also has the Bb genotype.
False
The difference in traits observed in parents versus offspring
Genetic variation
Which of the following must be true for a female to have hemophilia?
Her mother is a carrier and her father has the disease.
The inheritance of traits from one generation to the next
Heredity
Tay-Sachs disease is a(n) ____ disease that results in blindness, intellectual disability, and death due to ____.
autosomal recessive; accumulation of lipids in brain cells
A couple in which the woman is homozygous dominant for clotting ability and the man has hemophilia A will produce:
carrier daughters and normal sons
The study of heredity
genetics
Scientists use the term ____________ to refer to the genetic makeup for that organism.
genotype
The genetic composition of an organism
genotype
abnormality in a blood clotting protein
hemophilia A
Refer to the accompanying figure. Based on the phenotypes of the third generation, the genotype of the father in the second generation must be:
heterozygous for albinism
The chromosome theory of inheritance, developed by Sutton and Boveri, provided an explanation for Mendel's principle of segregation by proposing that
homologous chromosomes segregate during meiosis.
A cross of two medium height hybrid plants produces offspring that are dwarf, medium, and tall in a ratio of 1:2:1. This is an example of
incomplete dominance.
defect in amino acid metabolism
phenylketonuria
A gene that controls seed coat color in peas also determines the susceptibility of these peas to a particular disease. This situation is referred to as
pleiotropy
Preimplantation genetic diagnosis is done:
on cells of an in vitro fertilized embryo
A couple who does not have cystic fibrosis but are both heterozygous has already had three girls with cystic fibrosis, and are hoping to have a healthy child for their fourth. What are the chances that the fourth child will be a healthy male?
3/8
Dominant traits remove recessive traits when both are present in the same individual.
False
The height of pea plants from a cross between parent plants heterozygous for height, in which tall is dominant, would be
3 tall: 1 short.
Two Martians fall in love and marry. One Martian is homozygous for red eyes and the other is heterozygous. The recessive eye color is purple. What is the probability that they will have a child with purple eyes (assuming Martians have similar genetics to humans)?
0
What are the predicted phenotypes of the male children from the union of a woman who is heterozygous for hemophilia and a man who has normal blood clotting characteristics? (Use the Punnett square to verify your answer.)
1 hemophilia:1 healthy
If a couple is planning on having two children, what is the probability that both will be male?
1/4
What is the probability that two lizards heterozygous for stripes on their tails (Ss) will produce homozygous offspring with no stripes (ss)?
1/4
What are the predicted phenotypes of the children from a union of a woman who is heterozygous for hemophilia and a man who is normal? (Use the Punnett square to verify your answer.)
25 % hemophilia: 75% normal
In a two-point test cross, 36 of the offspring were recombinant types. The remaining 64 offspring were parental types. How many map units separate the two loci?
36
The normal human karyotype contains ____ total chromosomes, consisting of ____ autosomes and ____ sex chromosomes.
46; 22; 2
An organism with the genotype of AaXx can produce gametes containing ____ if the two genes are unlinked.
AX, Ax, aX, or ax
Alternative gene variants
Allele
Which of the following represents the possible genotype(s) resulting from a cross between one homozygous (BB) individual and one heterozygous (Bb) individual?
BB and Bb
Which of the following represents the possible genotype(s) resulting from a cross between a heterozygous individual (Bb) and one that is homozygous (bb)?
Bb and bb
Heterozygous individuals express both homozygous phenotypes.
Codominance
Which statement accurately characterizes an ethical consideration surrounding human genetics?
Consanguineous matings are prohibited by half of U.S. states due to the increased risk of autosomal recessive alleles.
A mating between individuals with different alleles at two loci is known as?
Dihybrid cross
Which of the following statements about dosage compensation is false?
Dosage compensation is a mechanism that makes equivalent the two doses in the male and the single dose in the female.
What explains the viability of individuals with aneuploidies for the sex chromosomes?
Dosage compensation, by which one X chromosome per cell is inactivated.
The presence of certain alleles at one locus can prevent or mask the expression of alleles at a different locus.
Epistasis
Which describes the interaction between genes such that the presence of certain alleles in one locus affects the expression of certain alleles in the other locus?
Epistasis
Which of the following does NOT describe Mendel's research and proposed Model of Inheritance?
Factors may be expressed, hidden in a given generation or lost.
A test cross is performed to determine phenotype.
False
Heterozygous individuals have a phenotype that is intermediate between the parental phenotypes.
Incomplete dominance
Which of the following refers to the expression of an intermediate phenotype in heterozygous individuals?
Incomplete dominance
Why has the dominant mutant allele for Huntington's disease been able to persist in human populations despite its devastating effects?
Its symptoms do not typically show until after the individual has had children.
The expression of a trait in an organism
Phenotype
One defective enzyme may affect the function of many cells.
Pleiotropy
Offspring exhibit continuous variation in phenotypes.
Polygenic inheritance
____ refers to multiple independent pairs of genes having similar and additive effects on the same characteristic.
Polygenic inheritance
The sex of most mammals, birds, and insects is determined by
Sex Chromosomes
absence of an enzyme to break down normal membrane lipid
Tay-Sachs disease
A heterozygous fruit fly with normal wings and a gray body (VvBb) is crossed with homozygous flies with vestigial wings and black bodies (vvbb). Out of 800 total F1 progeny, 296 are normal gray, 328 are vestigial black, 99 are normal black, and 77 are vestigial gray. What is the best explanation for this result?
The loci for wing length and body color are on the same chromosome.
Why are most infants with phenylketonuria usually healthy at birth?
The mother breaks down phenylalanine for both herself and her fetus.
Blood types A, B, AB, and O are controlled by how many alleles representing a single locus?
Three
According to data from the ENCODE project, approximately 80% of the human genome is associated with biological function.
True
If a cell has two X chromosomes, XIST will become active in one of them, producing a special type of regulatory RNA molecule known as long noncoding RNA..
True
In fragile X syndrome, the fragile X gene contains a nucleotide triplet that repeats 200 to 1000 times.
True
Polyploidy may arise from the failure of chromosomes to separate during cell division or by the fertilization of an egg by more than one sperm.
True
The science of comparative genomics to study human gene function is possible because much of the human genome is conserved among other closely related species.
True
The zygote and early embryonic cells of female mammals have how many X chromosomes?
Two
The cells of female mammals, including humans, contain two __________.
X chromosomes
Hemophilia A is an example of a(n) _____ disease and is characterized by a lack of blood-clotting factor ____.
X-linked; VIII
A karyotype reveals that an individual is XYY. Based on your knowledge of human genetics, you correctly conclude that this individual has ____, and is a phenotypically _____.
XXY karyotype; fertile male
Aneuploidies describe:
a condition in which an extra chromosome is present or one is absent
In individuals with cystic fibrosis:
abnormal mucous secretions occur throughout the body systems.
Alternative forms of a gene are called ___________.
alleles
Mendel's principle of segregation states that
alleles separate from each other before forming gametes.
Nondisjunction during mitosis leads to:
an individual with a clone of abnormal cells
Colchicine is a drug that:
arrests cells in mitotic metaphase
defect in the protein that regulates chloride transport across cell membranes
cystic fibrosis
Cri du chat syndrome arises from:
deletion of part of chromosome 5
A heterozygous fruit fly with normal wings and a gray body (VvBb) is crossed with homozygous flies with vestigial wings and black bodies (vvbb). This type of cross is known as a
dihybrid cross.
Genetic screening can be used to identify:
diseases caused by single gene mutations
A gene that affects, prevents, or masks the expression of a gene at another locus is a(n) ____ gene.
epistatic
A fragile site:
is associated with cancerous cells
The physical location of a gene on a chromosome is called
its locus.
Color blindness is more common in males than in females because
males only need to inherit the recessive maternal color blindness allele to be color blind.
Polyploidy:
may be the result of more than one sperm fertilizing an egg
Autosomal aneuploidies arise by:
meiotic nondisjunction
The range of phenotypic possibilities that can develop from a certain dog genotype under different environmental conditions is called the
norm of reaction.
Huntington's disease is caused by a:
nucleotide triplet repeat
Human genetics can be most effectively studied using:
population studies of large extended families
Gene therapy involves:
replacing a mutant allele in certain body cells with a normal allele
Fragile X syndrome:
results in learning, attention, and hyperactivity disabilities in males
Comparing the human and mouse genomes has revealed that the mouse and human:
share most genes
hemoglobin molecules stick to each other
sickle cell anemia
All calico cats are female because
the calico phenotype is caused by random X chromosome inactivation.
The probability that two genes will be separated by crossing-over is related to
the distance between the two genes on the chromosome.
In genomic imprinting:
the expression of a gene in the progeny depends upon which parent the gene is inherited from.
Maternal PKU can result in serious effects in fetuses. This problem occurs because:
the mother is homozygous recessive for PKU and cannot metabolize phenylalanine
Down syndrome is characterized by:
the presence of 47 chromosomes per somatic cell
The selective advantage linked to the high frequency of the cystic fibrosis allele in Caucasians is:
the prevention of excessive water loss associated with certain types of diarrhea
What was revealed with the completion of the Human Genome Project?
the sequence of the entire human genome
A ____ is best used to demonstrate the linkage of two genes.
two-point test cross