Exam1 06f by HC120211155058

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									Biol. 303    EXAM I 9/22/06                 Name___________________________________

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         This exam consists of 40 multiple choice questions worth 2.5 points each. On the
separate answer sheet, please fill-in the single best choice for each question. Please remember
to fill-in your student number on the answer sheet. Good luck!
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1.      Eukaryotic cells differ from prokaryotic cells in that

        1. prokaryotes do not have DNA.
        2. only eukaryotes have a true nucleus.
        3. only eukaryotic cells contain genetic material.
        4. eukaryotes are usually smaller than prokaryotes.


2.     A certain mammalian organism has a diploid number of chromosomes equal to 48. This
organism has one pair of sex chromosomes. How many autosomes does a gamete from this
organism contain?

        1. 48
        2. 46
        3. 24
        4. 23


Use the following information for questions 3 and 4:

     A diploid somatic cell from a rat has a total of 42 chromosomes.

3.      What is the total number of telomeres in a rat cell in G2?

        1. 42
        2. 84
        3. 126
        4. 168


4.      What is the total number of centromeres in a sperm cell from a rat?

        1. 21
        2. 40
        3. 42
        4. 84
5.     A place in the eukaryotic cell cycle at which a "decision" is made whether to proceed
through the cell cycle or to arrest cell cycle progression is generally known as

       1. S phase
       2. G1 phase
       3. a checkpoint
       4. mitosis


6.     Which step of mitosis leads to significant genetic variation?

      1. None. Mitosis normally produces identical cells.
      2. Telophase
      3. Prophase
      4. Metaphase


7.     An allele is

       1. a type of cell.
       2. a dominant trait.
       3. a form of a gene.
       4. an imaginary concept.


8.     In each one of Mendel's dihybrid crosses,

       1. codominance was not observed.
       2. the phenotypes in the F1 generation segregated in a 3:1 ratio.
       3. two distinct phenotypes were observed in the F1 generation.
       4. the genotypes in the F2 generation segregated in a 9:3:3:1 ratio.
9.       The figure below shows a chromosomal separation taking place. Little circles represent
centromeres. The letters stand for genes; capital and lowercase stand for different alleles. 2n in
this organism is 4. What process is shown?

       1. anaphase of mitosis
       2. telophase of meiosis I
       3. anaphase of meiosis I
       4. anaphase of meiosis II




                         A    B    C      d




                     A        b    C      d




10.    In a cross between two plants of the following genotypes: (AaBb x AaBb), which of the
following phenotypes should occur at the lowest frequency among the offspring?

       1. AB
       2. Ab
       3. aB
       4. ab


11.    Regarding the cross in question 10 above, the genotype AaBb should occur at what
frequency?

       1. 1/4
       2. 1/8
       3. 1/2
       4. 1/16
12.     A 9:3:3:1 ratio of phenotypes in the F2 generation of a dihybrid cross

       1. holds true only for genes on the same chromosome.
       2. indicates that the dihybrid cross is basically equivalent to two independent monohybrid
          crosses.
       3. is not indicative of independent assortment.
       4. indicates that an epistatic relationship exists between the two genes under
          investigation.


13.    Each of the following statements about meiosis is true EXCEPT

       1. the products of meiosis are haploid.
       2. most somatic cells do not enter into meiosis.
       3. during meiosis, crossing-over often occurs between non-homologous chromosomes.
       4. the complete process of meiosis requires two rounds of cell division.


14.    In a higher eukaryote, how many functional sperm will be produced from one meiosis in a
healthy male?

       1. one
       2. two
       3. three
       4. four


15.    Regarding bivalents,

       1. they form during metaphase II of meiosis.
       2. they each contain one sex chromosome.
       3. there are n of them produced in meiosis, where n = the haploid number of
          chromosomes.
       4. they each contain a total of two chromatids.


16.   What is the probability that, in an organism with a haploid number of 12, an egg will be
formed that contains all 12 chromosomes whose centromeres were derived from maternal
homologs?

       1. (1/12)2
       2. (1/10)12
       3. (1/2)12
       4. None of the above.
17.    In each of Mendel's monohybrid crosses of pea plants, the trait that disappeared in the F1
generation but reappeared in the F2 generation

        1. illustrated the principle of independent assortment.
        2. was a recessive trait.
        3. appeared in 3/4 of the plants in F2 generation.
        4. None of the above.


18.    The chi-square test involves statistical comparison between observed versus expected
values. One generally determines degrees of freedom as

        1. one less than the number of classes being compared.
        2. the number of categories being compared.
        3. one more than the number of classes being compared.
        4. the sum of the two categories.


19.     A tall, violet plant is crossed with a dwarf, white plant and all of the F1 offspring are tall,
violet. The F1 plants are selfed to produce the F2 generation. What fraction of the F2 generation
would you expect to be tall, white? (Assume independent assortment.)

        1. 1/4
        2. 9/16
        3. 3/16
        4. 1/16


20.     The principle of independent assortment

        1. explains the 3:1 ratio of phenotypes in the F2 generation of Mendel's dihybrid crosses.
        2. states that a dihybrid cross is essentially equivalent to a monohybrid cross.
        3. arises from the random alignment of different chromosomes at metaphase I of meiosis.
        4. none of the above.


21.    In the cross AaBbCcDd x AaBbCcDd, how many different phenotypes should appear
among the offspring? (Assume independent assortment, simple dominance/recessiveness for
each gene, and no epistasis or other gene interactions.)

        1. 8
        2. 27
        3. 4
        4. 16
Use the following pedigree for questions 22-26:


                I
                                   1          2                 3          4
                II
                           1              2       3         4                    5
                III
                                                   1
22.    Could the characteristic followed in the pedigree be caused by an autosomal dominant
disease? Why or why not?

       1. Yes, all individuals fit the autosomal dominant inheritance pattern.
       2. No, the offspring of I-1 and I-2 contradict an autosomal dominant inheritance.
       3. No, the offspring of I-3 and I-4 contradict an autosomal dominant inheritance.
       4. No, the offspring of II-3 and II-4 contradict an autosomal dominant inheritance.

23.     If the pedigree is for an autosomal recessive characteristic, which individuals are
definitely heterozygous?

       1. I-1, I-2, II-2, II-4 and II-5
       2. I-1, I-2, I-4, III-1
       3. I-1, I-2, II-4, II-5, III-1
       4. II-2, II-4, II-5, II-3

24.     Could the characteristics followed in the pedigree be caused by an X-linked recessive
allele?

       1. Yes, all individuals fit the X-linked recessive inheritance pattern.
       2. No, the offspring of I-1 and I-2 contradict an X-linked recessive inheritance.
       3. No, the offspring of I-3 and I-4 contradict an X-linked recessive inheritance.
       4. No, the offspring of II-3 and II-4 contradict an X-linked recessive inheritance.

25.    If the characteristic followed in the pedigree is autosomal recessive, what is III-1’s
genotype?

       1. either homozygous dominant or heterozygous
       2. definitely heterozygous
       3. definitely homozygous dominant
       4. there’s really no good way to tell

26.    If the characteristic in the pedigree X-linked recessive, what is III-1’s genotype?

       1. hemizygous for a dominant allele
       2. hemizygous for a recessive allele
       3. heterozygous
       4. can’t answer this question because the characteristic cannot be X-linked recessive.
27.   Red-green color blindness is X-linked recessive. A color-blind woman has a child with a
man having normal vision. Which phenotype is definitely NOT expected for the child?

       1. color-blind female
       2. color-blind male
       3. female with normal vision
       4. all of the above are possible phenotypes for the child.


28.     A woman and a man are both heterozygous for freckles (the dominant condition). If
 they have one child, what are the chances that it will not have freckles?

      1. 25%
      2. 50%
      3. It will depend on the sex of the child.
      4. 75%


29.    With in incomplete dominance, a likely phenotypic ratio resulting from a monohybrid
cross would be:

       1. 3:1
       2. 1:2:2:4
       3. 1:2:1
       4. 9:3:3:1


30.    A condition in which one gene influences the expression of another gene is called

       1. codominance.
       2. dominance.
       3. recessiveness.
       4. epistasis.


31.    Consider a gene with alleles "B" and "b". Suppose that the homozygous recessive
genotype bb is lethal during embryonic development. In a cross between two heterozygotes, Bb
x Bb, what percentage of the living offspring should be Bb?

       1. 1/2
       2. 1/3
       3. 1/4
       4. 2/3
32.   In a disputed parentage case, the child is blood type O while the mother is blood type B.
What blood type would exclude a male from being the father?

       1. O
       2. A
       3. B
       4. AB


33.    In “sex-influenced inheritance,”

       1.   a trait can be expressed in one sex only.
       2.   a given genotype produces a different phenotype in males versus females.
       3.   a given trait is on the X chromosome.
       4.   fathers never pass the trait to sons.


34.     When two genes fail to assort independently, the term normally applied is

       1.   Mendelian inheritance.
       2.   linkage.
       3.   incomplete dominance.
       4.   complementation.


35.    Which statement is true?

       1. two genes on the same chromosome can never assort independently from one another.
       2. two genes on different chromosomes will assort independently from one another.
       3. recombination will occur between a given pair of linked genes every time gametes are
       formed.
       4. two genes on the same chromosome will always appear to be genetically linked to one
       another in a dihybrid cross.


36.    If the percent recombination between A and B is 25%, the percent recombination between
B and C is 37%, and the percent recombination between A and C is 50%, then

       1. A is not linked to B.
       2. A and C are likely on the same chromosome.
       3. A and B assort independently.
       4. B and C are likely on different chromosomes.
37.     A female fruit fly heterozygous for three linked mutant alleles a,b,c, (genotype AaBbCc)
is crossed with a male fly that is homozygous recessive for all three mutant alleles. If the
phenotypes of the most common offspring are ABc and abC, and the least common offspring are
ABC and abc, then the order of the genes a b c on the chromosome is:

         1. a b c
         2. b a c
         3. b c a
         4. not enough information to tell.


38.      Assume that for the following genetic interval there is no interference.

           a                 b                        c



                20.0 cM           25.0 cM

Consider the following 3-factor (trihybrid) testcross: (abc/+++) X (abc/abc). What percent of
the offspring will be the products of a double crossover?

         1. 45%
         2. 10%
         3. 5%
         4. 2.5%


39.      Consider the following table of data from a synteny test using mouse/human hybrid cells
for assigning genes to human chromosomes.
------------------------------------------------------------------------------------
hybrid human chromosomes                     human gene product
cell:      present:                          present:

I         1 2 3 4 5 6                        A B
II        1      3 4       7 8 9             A B C
III       1 2              7 8               A
------------------------------------------------------------------------------------

      Based on the above data, the gene that produces product C is located on human
chromosome number:

         1. 1
         2. 2
         3. 9
         4. can't tell.
40.     Genes A, B, C, and D are on the same chromosome. Here is some data for the frequency
of crossing over between these four genes:

       Gene pair:           Percent recombination between the pair:

       A,B                    10
       B,C                    45
       C,D                     5
       A,C                    35
       A,D                    30

What is the order of the four genes on the chromosome?

       1. B A C D
       2. B A D C
       3. A B C D
       4. there's insufficient data to make this determination.




                                                  I’m sure I
                                                  got at least
                                                  a “B”
QUESTION NUMBER   CORRECT ANSWER


     1               2
     2               4
     3               4
     4               1
     5               3
     6               1
     7               3
     8               1
     9               4
    10               4
    11               1
    12               2
    13               3
    14               4
    15               3
    16               3
    17               2
    18               1
    19               3
    20               3
    21               4
    22               2
    23               3
    24               1
    25               2
    26               1
    27               1
    28               1
    29               3
    30               4
    31               4
    32               4
    33               2
    34               2
    35               2
    36               2
    37               3
    38               3
    39               3
    40               2

								
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