AGR 3303 - Genetics 2 Oct 2000

University of Florida - Fort Lauderdale

Exam #1: PARTICULATE GENETICS

Multiple choice (75 pts.)

Please read these carefully. One and only one response (a, b, c, d, or e) completely and correctly answers the question, or completes the statement. Circle the appropriate response and turn in this exam. Make sure your circle is unambiguous. Take time to relax. (Suggestion: put the problem into gene symbols, if that helps you to visualize the problem and its solution.)

1. Compare these two of Mendel's postulates: segregation vs. independent assortment.
1. Segregation involves longitudinal division while independent assortment involves reductional division.
2. Mendel observed the chromosomal basis for segregation, but could not see the basis for independent assortment.
3. Both segregation and independent assortment involve unit factors in the cells
4. Both segregation and independent assortment require two or more genes.
5. Either segregation or independent assortment result in a 9:3:3:1 phenotypic ratio.
2. A single gene has three alleles. In a diploid organism, how many possible genotypes are there involving this gene?
1. 3
2. 4
3. 6
4. 8
5. 9
3. Two genes each have two alleles. In a diploid organism, how many possible genotypes are there?
1. 3
2. 4
3. 6
4. 8
5. 9
4. Two genes each have two alleles, one dominant and the other recessive. In a diploid organism, what is the maximum possible number of phenotypes?
1. 3
2. 4
3. 6
4. 8
5. 9
5. Green colorblindness in humans is a sex-linked recessive trait. In a family, the daughter has normal vision, whereas the son is colorblind. One can realistically surmise:
1. the mother was heterozygous for colorblindness
2. the father was heterozygous for colorblindness
3. the father was homozygous for color blindness
4. the mother most probably was colorblind
5. the father most probably was colorblind
6. The idea of unit factors of inheritances was not obvious because:
1. the religious view of fixity of species would not allow it
2. early plant breeders were not systematic in their recordkeeping
3. "The Origin of Species" by Darwin had not yet been published
4. DNA had not been discovered
5. early plant breeders did not make as many hybrids as Mendel
7. Which human blood phenotypes are always associated with phenotypically homogeneous (all the same) offspring?
1. Mother A mates with father O
2. Mother A mates with father B
3. Mother AB mates with father O
4. Mother O mates with father O
5. Mother A mates with father A
8. A dominant lethal allele can exist in a population:
1. only if the gene is expressed after sexual maturity
2. only if it is recessive
3. only if it is heterozygous
4. only if it is on a sex chromosome
5. only if it expresses an enzyme
9. The Russian Lysenko proposed the cold treatment of potatoes to make the next crop of potatoes, and those that followed, more resistant to winter. This is an example of:
1. the idea that inherited traits can be acquired by environmental influences
2. evolution by the survival of species occurs
3. that Mendel's postulates can be extended to new situations
4. a mutation
5. something that happens readily in polyploids
10. A family of four genetically related siblings has phenotypes A, B, O, and AB, therefore:
1. the parents could be A and B phenotypes
2. the parents could be A and O phenotypes
3. they may be related on their mom's side, but there must be at least two daddies
4. the parents could be AB and AB phenotypes
5. not sure about their dads, but the siblings must have different mamas
11. An alien geneticist escaping from Planet X brought to earth two pure-breeding breeds of frogs. One characteristically croaked "rib-it rib-it" and the other croaked "knee-deep knee-deep." Continuing his research on Planet Earth, the geneticist discovered that when the Rib-it breed was crossed with the Knee-deep breed, all the tadpoles grew up saying "bud-weis-er." Realizing the market potential, a large brewery company intermated the Bud-weis-er frogs and discovered that they were not true-breeding, as they segregated in the ratio of 1:1:2 for Rib-it, Knee-deep, and Bud-weis-er. The results are consistent with the hypothesis:
1. the gene for croak sound has three alleles, with dominance for Bud-weis-er over Rib-it and Knee-deep
2. there are two alleles of the croak sound gene and they are related by codominance
3. the croak sound gene is linked to the X-chromosome
4. there must be complete dominance of Rib-it over Knee-deep
5. croaking sound is controlled by two tightly linked genes that never cross over.
6. there is not such thing as a croak sound genes, the whole thing is based on ventriloquy
12. An inheritance study evaluates deviations from the null hypothesis of Mendel's 3:1 ratio, comparing the observed to the expected distribution of progeny. The result is P = 0.50, therefore:
1. accept the null hypothesis
2. reject the null hypothesis
3. there must be independent assortment
4. there must be epistasis
5. there must be two genes involved
13. Thalassemia is an inherited anemia controlled by a single allele. Homozygous persons have Thalassemia major, which is almost always fatal in childhood. Heterozygous persons have Thalassemia minor, and are mildly affected. An infant has Thalassemia major. What is the likelihood that a subsequent child of the same parents will have either Thalassemia major or Thalassemia minor?
1. 0%
2. 25%
3. 50%
4. 75%
5. 100%
14. An autosomal gene is one located on a chromosome other than a sex chromosome, therefore:
1. it is sex-linked
2. it is X-linked
3. it shows Mendelian patterns of segregation
4. it does not show Mendelian patterns
5. It only expresses in the male
   
15. Mendel's fourth postulate was independent assortment, which is observed:
1. when two genes are tightly linked on the same chromosome
2. with monohybrids
3. when two genes are distantly linked or on different chromosomes
4. only in peas
5. during mitosis
16. One of the features of polyploids in plants is that:
1. they have higher fertility and seed set than regular diploids
2. their chromosomes pair and disjoin neatly
3. deleterious dominant alleles are exposed
4. they do not survive
5. they have extra whole sets of chromosomes
17. What is true about the two divisions of meiosis?
1. both involve reductional division
2. both involve equational or longitudinal division
3. the amount of DNA is the same in the daughter cells as in the sporocyte
4. the first division results in two daughter cells
5. the second division results in a reduction of the chromosome number
18. Bread wheat arose under human cultivation through a process of
1. interspecific hybridization
2. acquired inheritance
3. spontaneous generation
4. pangenesis
5. epigenesis
19. In the chi-square test the P refers to:
1. the chance that results could have been caused by a true null hypothesis
2. the chance that the results could have been caused by a false null hypothesis
3. the chance that the results could have been caused by a true alternative hypothesis
4. the null hypothesis should be accepted
5. the chance that the alternative hypothesis is correct.
20. Calico ("tortoise-shell") cats are always female because:
1. the maternal X chromosome is always heterochromatized into a Barr body
2. she always receives her X chromosomes from her mother, which may also be calico
3. either the maternal or paternal X chromosome is inactivated so all cells throughout the calico cat have the same inactivated chromosome
4. either the maternal or paternal X chromosome is randomly inactivated at an early stage of development
5. codominance
21. Coat color of horses can be cremello (almost white), palomino (golden coat with lighter mane and tail), or chestnut (brown). Among these phenotypes, palomino never breed true. Cremello and chestnut always breed true when they are mated with other horses of the same coat color. What is the simplest explanation for these relationships?
1. multiple alleles
2. epistasis
3. codominance
4. inactivation of the X-chromosome
5. Lyon hypothesis
22. Coat color of mice is determined by interacting loci: bb gives albino, A_B_ gives agouti (an alternating light and dark combination), and aaB_ gives black. What are the phenotypic frequencies of the offspring from the dihybrid (a cross between two double heterozygotes, that is, a cross between two AaBb)?
1. 15 agouti :1 albino
2. 9 agouti : 3 black : 4 albino
3. 9 agouti : 4 black : 3 albino
4. 12 agouti : 3 black : 1 albino
5. 3 black : 1 albino
23. Down syndrome is a human genetic condition involving:
1. a point mutation
2. polyploidy
3. polygenic inheritance
4. an extra autosome
5. XYY
24. Of the four main genetic capabilities, the one explained by the Central Dogma is:
1. mutation
2. storage
3. pangenesis
4. replication
5. expression
25. In the Punnett's square, the way it is used in Klug and Cummings, the rows and columns represent:
1. the distribution of the phenotypes
2. heterozygotes
3. homologous sets of chromosomes
4. possible gametic genotypes
5. sex chromosomes

Please write your answers in the white region below and number each.

36. What are some ways that a sex-linked gene differs in inheritance from an autosomal gene?
37. Tifway bermudagrass (T-419) has 27 chromosomes because it is an artificial interspecific hybrid between an 18-chromosome female parent and a 36-chromosome male parent. What kind of plant does that make Tifway, and what kind of fertility characteristic would you expect?
38. What is an enzyme and what does it do? Assuming that a gene has the genetic code for a particular enzyme, explain how alleles of that gene often show complete dominance and complete recessiveness.
39. Describe the alternation of generations starting with haploid gametes. What are the main events? What happens to the chromosome number?
40. The book used an example of pink snapdragons to illustrate incomplete or partial dominance. Make up gene symbols and whatever else you need (e.g., arrows, tables) to show the results of a monohybrid cross, and the resulting phenotypic ratio.
41. How can continuous or quantitative gene effects be obtained from unit factors of inheritance?
42. Illustrate and name the major components of the cell, making sure to include those that are important in genetics.