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35 Cards in this Set

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abortion
Expulsion of a pre-term embryo or fetus from the uterus.
allele
One of two or more molecular forms of a gene that arise by mutation and specify slightly different versions of the same trait.
aneuploidy
In cells, too many or too few chromosomes relative to the parental number.
autosome
Any chromosome of a type that is the same in males and females of a species
crossing over
At prophase I of meiosis, the reciprocal exchange of segments between two nonsister chromatids of a pair of homologous chromosomes; results in novel combinations of alleles.
deletion
Loss of a chromosome segment. Also, a mutation involving the loss of one or more bases of a DNA molecule.
disease
Illness caused by an infectious, dietary, or environmental factor.
duplication
DNA sequence repeated several to many hundreds or thousands of times.
fetus
Stage of animal development; in humans, the start of the ninth week to birth.
gene
Unit of information for a heritable trait in DNA, passed from parents to offspring.
gene locus
A gene’s chromosomal location.
genetic disorder
Heritable defect in one’s genetic material; causes mild to severe medical problems.
in vitro fertilization
IVF. Combining sperm and eggs outside the body, as in a petri dish.
inversion
Mutation in which a section of chromosome becomes oriented in reverse.
linkage group
All genes on a chromosome.
nondisjunction
Failure of sister chromatids or homologous chromosomes to separate during meiosis or mitosis. Daughter cells end up with too many or too few chromosomes.
pedigree
Chart of genetic connections.
polyploidy
Having three or more of each chromosome type characteristic of a species.
sex chromosomes
Chromosomes that, in certain combinations, determine a new individual’s sex.
syndrome
A set of symptoms that characterize an abnormality or a disorder.
testosterone
Male sex hormone produced in testes; functions in sperm formation and development of secondary sexual traits.
translocation
Of cells, a repositioning of a stretch of DNA to a new chromosomal location with no molecular loss. Of vascular plants, distribution of organic compounds through phloem.
y-linked gene
Gene on a Y chromosome.
Crossing over during meiosis results in combinations of alleles not present in the parental cell. True or False?
True
A human sperm carrying a Y chromosome fertilizes an egg. Assuming the egg is normal, what sex will the offspring be?

a. female
b. either, depending on the temperature at fertilization
c. not enough information
d. male
correct answer: d
The probability that a crossover will disrupt the linkage between two genes is proportional to:

a. the number of alleles for the genes.

b. the distance between the genes.

c. none of the choices.

d. the time of _expression of the genes.
correct: b
The human X chromosome:
a. is much larger than the Y chromosome.
b. carries the master gene for male sex determination.
c. carries about 330 genes.
d. is an autosome.
correct answer: A
Genes that are closely linked:

a. are rarely separated by crossing over.
b. have never been found in humans or other mammals.
c. are on nonhomologous chromosomes.
d. usually govern the same trait.
correct answer A
6 What standardized symbols are used to represent males and females on a pedigree?

a. a star for males and a square for females
b. a square for females and a circle for males
c. a square for males and a circle for females
d. a question mark for both males and females
Correct C
Huntington disease is governed by autosomal dominant inheritance. What is the likelihood that a person who has one heterozygous affected parent and one normal parent will develop the disease?
a. 50%
b. 0% (impossible)
c. 75%
d. 100% (certain)
Galactosemia is governed by autosomal recessive inheritance. What is the likelihood that a person who has one affected parent and one homozygous normal parent has the disorder?

a. 0% (impossible)
b. 75%
c. 100% (certain)
d. 50%
answer: A
If a man has hemophilia (an X-linked recessive trait) and his wife is homozygous for the normal allele,

a. all sons will have hemophilia.
b. all daughters will have hemophilia.
c. all daughters will be carriers.
d. all offspring will have hemophilia.
answer: C
Cri-du-chat syndrome is a genetic disorder caused by:

a. trisomy of chromosome 17.
b. a deletion from chromosome 5.
c. an inversion on chromosome 12.
d. a translocation between chromosomes 9 and 22.
answer: b
Down syndrome:

a. occurs only in males.
b. is also known as trisomy 21.
c. affects only the central nervous system.
d. results from a deletion.
answer: B
A gene's most common form is called the:

a. wild-type allele.
b. mutant allele.
c. dominant allele.
d. homozygous form.
answer: a