BSC 2011-Midterm I EXAM KEY B

1.When you cross a homozygous dominant (i.e., AA) individual with a homozygous recessive (i.e., aa) individual, and then cross the resulting F1 generation, the F2 generation has a ratio of 1:2:1 for its ____________ and a ratio of 3:1 for its __________.
a. phenotype; genotype
*b. genotype; phenotype
c. homologous chromosomes; sister chromatids
d. color; leaves

2. Why do you use an individual expressing a recessive trait (e.g., white flowers in Mendel's experiments with peas) for a test-cross?
a. Because you like the recessive trait
*b. Because the genotype of the recessive trait is known
c. Because you did not have any other individuals available for the test-cross
d. Because you know the genotype of the individual expressing the dominant trait

3. You are investigating the inheritance of a single character (e.g., flower color) in a plant. You want to determine the genotype of a plant possessing the dominant trait (e.g., purple flowers). This plant of unknown genotype is crossed with another plant, which is homozygous recessive (e.g., white flowers). The resulting offspring from the cross show a 1:1 phenotype ratio of purple and white flowers. What is the genotype of the plant with purple flowers used in the cross?
a. homozygous for the dominant allele
b. homozygous for the recessive allele
*c. heterozygous
d. none of the above

4. If you do a monohybrid cross between two heterozygous individuals (i.e., Aa x Aa) where the dominant trait is purple flowers and the recessive trait is white flowers, the phenotypic ratio would be 3:1. What percentage of the purple flowers are heterozygotes?
*a. 66%
b. 50%
c. 33%
d. none are heterozygotes

5. Penetrance is:
a. the frequency that the dominant or homozygous recessive gene is expressed phenotypically
b. the degree to which a phenotype is expressed among individuals
c. a categorical character
d. a continuous character
*e. Letters a & c are correct

6. Polygenic inheritance differs from pleiotropy by:
a. Polygenic inheritance deals with multiple genes affecting a single trait
b. Polygenic inheritance deals with one gene affecting multiple phenotypes
c. Polygenic inheritance and pleiotropy are the same
d. Polygenic inheritance gives rise to quantitative characters that vary along a continuum or a gradient.
*e. both a & d are correct

7. Why is there generally no selection against disorders that manifest themselves during late stages of peoples' lives?
*a. Because people usually do not know they have a disorder until they have already reproduced, therefore, the disorder is passed along to future generations
b. Because selection does not occur on disorders
c. Because individuals like to pass along disorders to future generations
d. Because people with late acting disorders do not reproduce

8. Mapping genes on chromosomes is based on the assumption:
a. that the probability of crossing over or a recombination event is not proportional to the distance between genes
b. Genes that are closer together have a greater chance of crossing over occurring between them
c. There is no correlation between the probability of crossing over and the distance between genes
*d. The probability of crossing over is proportional to the distance between genes

9. What precondition(s) must be met in order for selection to result?
*a. a trait that has heritable variation with fitness consequences
b. a trait that has fitness consequences
c. a trait that is not passed to the next generation
d. a trait that is heritable
e. a trait that has individual variation

10. Binary fission is
a. common among eukaryotic cells
*b. used by bacteria for reproduction
c. easy for large, complicated cells
d. not used for cell reproduction

11. Mitosis
a. occurs in gametes
*b. occurs in somatic cells
c. reduces the number of chromosomes in a cell
d. produces 4 different haploid cells

12. How is genetic variation generated as a result of meiosis?
a. through recombination
b. through random fertilization
c. through independent assortment of chromosomes
*d. all of these

13. Sister chromatids differ from homologous chromosomes by:
a. sister chromatids are exact copies of a particular chromosome
b. homologs are not identical copies of a particular chromosome
c. homologs are exact copies of one particular chromosome
d. sister chromatids are not identical copies of a particular chromosome
*e. a & b are correct

14. During anaphase I in meiosis
a. sister chromatids separate
b. chromosomes line up along the metaphase plate
*c. homologous chromosomes separate
d. recombination takes place

15. In a monohybrid cross, how does one determine if a particular allele is recessive or dominant?
*a. By the ratio of the phenotypes expressed
b. By the sex ratio of the offspring
c. The phenotypes are labeled recessive or dominant
d. You can not tell whether or not an allele is recessive or dominant


16. Gene duplications:
*a. can result in gene families
b. are always deleterious
c. are always beneficial
d. can result in inversions

17. Compared to meiosis, mitosis
a. is more complex
b. results in more variation
*c. results in less variation
d. results in haploid cells

18. If gene B is more likely than random to be inherited with gene A, then they are:
a. on different chromosomes
*b. linked
c. independently assorting
d, randomly fertilizing

19. Epistasis:
*a. results when alleles at one locus mask the effect one at another locus
b. when dominant alleles mask recessive ones at the same locus
c. is the same as incomplete dominance
d. is when a single gene has more than one effect

20. A disease, in addition to causing kidney problems, leads to slower growth of people who carry the gene. This is an example of:
a. bad luck
*b. pleiotropy
c. epistasis
d. environmental effects

21. Meiosis of a cell with 10 chromosomes (when diploid) produces
*a. 4 cells with 5 chromosomes each
b. 1 cell with 10 chromosomes
c. 2 cells with 10 chromosomes each
d. 4 cells with 10 chromosomes each

22. The mass of an alien's offspring is controlled by 3 pairs of alleles. The heaviest alien newborn genotype is AABBCC, while the lightest possible is aabbcc.The lightest mass is 10 g and the heaviest is 16 g, thus each allele represented by a capital letter contributes 1 g to mass of the offspring. What is the lightest offspring possible from a cross of AaBBCc xAaBbCc and how likely is it to occur?
*a. 11 g, 1/32
b. 10 g, 1/64
c. 11 g, 1/64
d. 12 g, 1/32

23. A phenotypically normal couple have a child that expresses 2 autosomal recessive traits. How likely are they to have a second child that is phenotypically normal?
a.1/4
b.1/16
c. 3/4
*d.9/16
e.1/8

24. If color blindness (an x-linked recessive) is found in 10% of males, how likely is it to be found in females?
a.10%
*b.1%
c.0.1%
d.0%
e.5%

25.Trisomy is typically results from
a. sex linkage
*b. non-disjunction
c. a polygenic trait
d. linkage
e. polyploidy


26. In humans, fathers can pass Y-linked alleles to their
*a. sons
b. daughters
c. mothers
d. none of the above

27. In this example, a gene that codes for eye color is located on the X sex chromosome; the w+ allele phenotypically expresses red eyes and w allele phenotypically expresses white eyes. A heterozygous female for this gene (w+w: red-eyes) is crossed with a hemizygous male (w+: red-eyes). The expected F1 phenotypic ratio (red eyes to white eyes) is __________. In addition, of the offspring in the F1 generation, all females have red eyes and the males have a _________ phenotypic ratio of red eyes to white eyes.
a. 1:1; 3:1
*b. 3:1; 1:1
c. 1:1; 1:1
d. 3:1; 3:1

28. The sequence ABCDEFG mutating to ACBDEFG is an example of:
a. Translocation
b. Deletion
*c. Inversion
d. Duplication

29. Extranuclear genes are found in
*a. mitochondria
b. prokaryotes
c. microtubules
d. Golgi bodies
e. centromeres

30. Heterocatalytic refers to ________________ and autocatalytic refers to ___________
*a. protein transcription and translation; replication of DNA
b. having two different copies of alleles; having the same two copies of alleles
c. having the same two copies of alleles; having two different copies of alleles;
d. having an enzyme acting on another enzyme; having an enzyme acting on itself

31. DNA reproduces according to the ____________ model
a. conservative
b. dispersive
c. automotive
*d. semi-conservative
e. heterocatalytic

32. During replication, new DNA is synthesized in the ___________ direction
a. 3' to 5'
b. 5' to 3'
c. both 3' to 5' and 5' to 3'
d. 3' to 6'

33. Genes were originally thought to be proteins because:
a. organisms are complex therefore their instructions must be complex
*b. nucleic acids were too complex to be understood
c. it is possible to generate complex instructions from a simple code
d. only proteins were found in the nucleus

34. Which of the following are most similar to one another?
a. translocations
b. homologues
*c. complementary strands of DNA
d. sister chromatids

35. A woman has patches of skin with and without sweat glands all over her body. Which of following explanations is most likely?
a. Y-activation
b. multiple somatic mutations
*c. X-inactivation
d. non-disjunction
e. aneuploidy