You identify a gene that controls fin size in zebrafish and after examining many fish you realize that in the population only two alleles exist for this gene. One allele is wild type leading to normal fins, and the other allele leads to small fins. Interestingly, only homozygous dominant individuals have a normal fin size, and all other individuals have small fins. What is the most likely explanation for the single-gene interaction of the fin alleles?
a. haplosufficient
b. complete dominance
c. codominant
d. haploinsufficient
e. recessive lethal alleles
You identify a gene that controls fin size in zebrafish and after examining many fish you realize that in the population only two alleles exist for this gene. One allele is wild type leading to normal fins, and the other allele leads to small fins. Interestingly, only homozygous dominant individuals have a normal fin size, and all other individuals have small fins. What is the most likely explanation for the single-gene interaction of the fin alleles?
a. haplosufficient
b. complete dominance
c. codominant
d. haploinsufficient
e. recessive lethal alleles
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Problem B: Prairie Dog Population Genetics
A relatively stable population of Black-footed Prairie Dogs (70,000 individuals) lives in a national park in
Saskatchewan, Canada. These creatures have various tones of brown fur, but may have brown or auburn tails.
Furthermore, tails may be of solid color (brown or auburn) or be tipped with white or black fur. Three alleles for
tail coloration exist in this population. These alleles include:
Allele | Trait | Notes on Phenotype and Relationship to other Alleles |
T | White Tip | Tail has white fur at tip. Completely dominant over t; codominant with T* |
t | Black tip | Tail has black fur at tip. Codominant with T*; recessive to T |
T* | Auburn tail | Background tail color is auburn when T* is present. Codominant with T or t |
The frequency of the (T) allele in this population is 0.28, and the frequency of the (t) is 0.4.
Answer each of the following. Show all of your work/calculations. Cite your rationale if appropriate.
1. List and describe all the possible genotypes and their respective phenotypes for this gene system in the
population.
2. Using the Hardy-Weinberg theorem, calculate the probable frequency of animals with the following
phenotypes in this population:
⢠White tipped tails
⢠Black tipped auburn tails
3. What is the expected combined frequency of individuals carrying the TT, TT* and Tt genotypes in this
population?
4. How many (number, not percentage) of the prairie dogs would you expect to have black tipped, auburn
tails? Explain.
5. In a different population of 10,000 prairie dogs (South Dakota, USA), only the T and t alleles are found. If
this group included only 400 animals with black tipped, brown tails, what is the probable number (not
frequency) of individuals that are homozygous dominant (TT) in this herd?
If an organismâs diploid chromosome number is 18, how many different possible combinations of homologous chromosomes lining up during meiosis exist for the eggs or sperm produced by that organism?
A. | 512 | |
B. | 9 | |
C. | 18 | |
D. | 128 | |
E. | 36 |
At the end of metaphase I, _______________ separate.
A. | sister chromatids | |
B. | germ cells | |
C. | homologous chromosomes | |
D. | haploid chromatids | |
E. | centrioles |
Mendel observed that dominant traits
A. | are seen in all of the F1 hybrid pea plants in his experiments. | |
B. | are expressed in all plants. | |
C. | were absent in the F1 generation of pea plants that he used in his experiments. | |
D. | were the only traits seen in the F2 generation of pea plants in his experiments. | |
E. | are only expressed in hybrids. |
Cytokinesis in plant cells differs from cytokinesis in animal cells because
A. | there is no difference. | |
B. | in plant cells, the cell plate must also divide into two parts. | |
C. | the contractile protein, actin, is important only in plant cells. | |
D. | plant cells have a rigid cell wall. | |
E. | a contractile ring forms only in plant cells. |
Sickle cell anemia is an example of what type of inheritance?
A. | complete dominance | |
B. | incomplete dominance | |
C. | codominance | |
D. | multiple alleles | |
E. | recessive dominance |
Which of the following statements is true:
A. | The dominant allele is masked in homozygous dominant individuals. | |
B. | With recessive genetic disorders, if both parents are carriers, the offspring will all be affected. | |
C. | In carriers, the recessive allele causes an intermediate phenotype. | |
D. | In recessive genetic disorders, the mother and/or father of an affected individual must also be affected. | |
E. | With dominant genetic disorders, the mother and/or father of an affected individual must also be affected. |
Skin cancers typically develop in the
A. | upper layers of the epidermis. | |
B. | lower layers of the dermis. | |
C. | subcutaneous layer. | |
D. | lower layers of the epidermis. | |
E. | upper layers of the dermis. |
Duchenne muscular dystrophy (MD) is inherited from an X-linked recessive allele. What is the probability that a son with Duchenne MD inherited this disease from his biological father?
A. | 1/2 | |
B. | 0 | |
C. | 1/16 | |
D. | 1/4 | |
E. | 1/8 |
The genetic makeup of a particular trait in an individual is its
A. | genotype. | |
B. | heterozygosity. | |
C. | phenotype. | |
D. | filial. | |
E. | dominance. |
What structure holds the sister chromatids to the spindle fibers?
A. | chromatin | |
B. | kinetochore | |
C. | MPF | |
D. | centromere | |
E. | cyclin |
If you view a cell in which the genetic material is beginning to be visible as separate bodies, and the nucleus has disappeared from view, you may surmise that the cells is in
A. | telophase. | |
B. | anaphase. | |
C. | interphase. | |
D. | metaphase. | |
E. | prophase. |
Gregor Mendel was successful in his analysis of the genetics of pea plants because
A. | he examined and analyzed both the F1 and F2 generations. | |
B. | he studied the parental plants to determine their differences. | |
C. | he decided to only look at his results in an objective manner. | |
D. | he studied a trait that had a strange inheritance pattern. | |
E. | pea plants have genetics different from other organisms. |
Tall corn plants (T) are dominant to dwarf plants (tt). Solid green leaves (G) are dominant to leaves with a white tip (gg). A cross between two corn plants yielded the following phenotypes: 51 tall plants with a white tip on their leaves; 43 dwarf plants with solid leaves; 48 dwarf plants with white tips on their leaves; 45 tall plants with solid leaves. What are the genotypes of the parents that produced these plants?
A. | None of the above | |
B. | TtGg x Ttgg | |
C. | ttGG x TTgg | |
D. | TtGg x TtGg | |
E. | TtGg x ttgg |
In humans, a gene that has been identified as causing a type of skin cancer is the
A. | superwoman echidna. | |
B. | mutant superman. | |
C. | sonic hedgehog. | |
D. | mutant mole rat. | |
E. | superhero aardvark. |
The segregation principle states that in sexually reproducing diploid organisms the two copies of each gene
A. | segregate from each other during meiosis. | |
B. | must always be the same allele. | |
C. | separate from each other during mitosis. | |
D. | will both wind up in either the sperm or egg. | |
E. | move together as a unit during meiosis. |
In what phases is the genetic material in the cell correctly referred to as chromatids?
A. | metaphase and telophase | |
B. | anaphase and metaphase | |
C. | interphase and telophase | |
D. | interphase and prophase | |
E. | metaphase and prophase |
Consider two traits for an organism, determined by two genes, each of which is governed by at least two alleles. In the case of a dihybrid individual, the gametes formed will be of either the parental type or the recombinant type. Recombinant type gametes are formed because of
A. | the principle of dihybrids. | |
B. | multiple alleles. | |
C. | heterozygosity. | |
D. | incomplete dominance. | |
E. | independent assortment. |
An allele is
A. | an alternate form of a gene. | |
B. | always recessive. | |
C. | the main factor determining a trait. | |
D. | always one of a pair. | |
E. | the dominant form of a gene. |
After the DNA is replicated, and it condenses in prophase, two identical rods of DNA are seen. These are
A. | spindle fibers. | |
B. | kinetochores. | |
C. | chromatids. | |
D. | chromatin. | |
E. | centromeres. |
Special cells found in the gonads that give rise to gametes upon division are called
A. | egg cells. | |
B. | somatic cells. | |
C. | germ cells. | |
D. | stem cells. | |
E. | basal cells. |