PCB3063 Exam 1Quizes and answers
Autosomal Dominant
-Appear in every generation
-Males & females equally affected
-All affected individuals have an affected parent
-Most affected individuals are heterozygotes
Autosomal Recessive
-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
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
e. That the two stages of meiosis are independent of one another
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
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
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
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
b. in mitotic anaphase
,c. in meiotic anaphase I
d. in meiotic anaphase II
e. in both meiotic anaphase I and anaphase II
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
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
-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.
-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
-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
-no transmission from M
-maternal inheritance
-potential for the disease to affect both sons and daughters of affected F
Homozygote
An individual with 2 identical alleles for a gene
Heterozygote
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
d. phenotypes
e. alleles
a. genes
If the green pea pod allele (G) is dominant to the yellow allele (g), a cross between
two heterozygous plants would be expected to produce _____.
a. all green
b. 1/4 green and 3/4 yellow
c. 1/2 green and 1/2 yellow
d. 3/4 green and 1/4 yellow
e. all yellow
c. 3/4 green and 1/4 yellow
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