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PCB3063 Exam 1 With complete solutions
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PCB3063 Exam 1 With complete solutions
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PCB3063 Exam 1 With completesolutions
Autosomal Dominant ANS✔✔ -Appear in every generation
-Males & females equally affected
-All affected individuals have an affected parent
-Most affected individuals are heterozygotes
Autosomal Recessive ANS✔✔ -Skips generations
-Males & females equally affected
-All affected individuals are homozygous recessive
-Unaffected parents of affected offspring are obligate heterozygotes
-Occurs more often in consanguineous matings
law of independent assortment ANS✔✔ the law that states that genes separate independently of one
another in meiosis
What is independent assortment?
a. That in diploids, two alleles exist on independent chromosomes
b. That the two homologous chromosomes separate and become independent of each other during
meiosis
c. That the two alleles for a single gene can be crossed over during prophase 1 independently of one
another
d. That nonhomologous chromosomes move independently of one another in meiosis
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,e. That the two stages of meiosis are independent of one another ANS✔✔ d. That nonhomologous
chromosomes move independently of one another in meiosis
As seen in the figure, how one homologous pair separates does not influence how a different
homologous pair separates. For unlinked genes, this leads to variations in alleles in the gametes.
What is the probability that two parents who are heterozygous for the recessive trait of albinism will
have two albino offspring?
a. 1/2
b. 1/4
c. 1/8
d. 1/16
e. 1/32 ANS✔✔ d. 1/16
For each birth, the probability that the couple will have a homozygous recessive child is 1/4. Using the
product law, the probability of having two such offspring is 1/4 x 1/4 = 1/16.
Law of Segregation ANS✔✔ Mendel's law that states that the pairs of homologous chromosomes
separate in meiosis so that only one chromosome from each pair is present in each gamete
Law of Dominance ANS✔✔ In many traits one allele is dominant over the other allele. The "weaker
(recessive" allele is only expressed when it is paired with another recessive allele
Mendel's third postulate is "During the formation of gametes, the paired unit factors separate, or
segregate, randomly so that each gamete receives one or the other with equal likelihood." When does
this segregation occur?
a. in G1
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,b. in mitotic anaphase
c. in meiotic anaphase I
d. in meiotic anaphase II
e. in both meiotic anaphase I and anaphase II ANS✔✔ c. in meiotic anaphase I
The alleles separate ("segregate") from one another when the homologs are separated. The two
homologs migrate to opposite poles at anaphase I.
How many different types of gametes can be formed by the genotype AaBbCc?
a. 3
b. 4
c. 8
d. 16
e. 32 ANS✔✔ c. 8
First, you must determine the number of different heterozygous gene pairs (n) involved. Once n is
determined, 2n is the number of different gametes that can be formed. Here, there are three
heterozygous genes, so the correct formula is 2^3 = 8.
The possible gametes are as follows.
P genotype: AaBbCc
Gametes: ABC, ABc, AbC, Abc, aBC, aBc, abC, abc
X-linked dominant ANS✔✔ -disorders caused by mutations in genes on the X chromosome,
-In females (who have two X chromosomes), a mutation in one of the two copies of the gene in each cell
is sufficient to cause the disorder.
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, -In males (who have only one X chromosome), a mutation in the only copy of the gene in each cell
causes the disorder.
-males experience more severe symptoms of the disorder than females
-No male to male transmission
X-linked recessive ANS✔✔ -disorders caused by mutations in genes on the X chromosome.
-In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to
cause the condition.
-In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene
to cause the disorder.
-affect males more frequently
-no male-to-male transmission
Mitochondrial inheritance ANS✔✔ -no transmission from M
-maternal inheritance
-potential for the disease to affect both sons and daughters of affected F
Homozygote ANS✔✔ An individual with 2 identical alleles for a gene
Heterozygote ANS✔✔ An individual with 2 different alleles for a gene
Mendel's first postulate is "Genetic characters are controlled by unit factors existing in pairs in an
individual." What is a modern term for "unit factors?"
a. genes
b. chromosomes
c. D N A
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