Humanoids on the newly explored planet Brin (in a hypothetical galaxy in ~50 years from the present) have a gene structure similar to our own, but many very different plants and animals.
One species of a small birdlike animal has an extremely variable tail length, which is a highly polymorphic trait. Geneticists have come to realize that there are eight separate genes for tail length per haploid genome, with each gene having two alleles. One allele for each gene (a, b, and so on) increases the length by 1 cm, whereas the other allele (a2, b2, and so on) increases it by 0.5 cm. One bird was analyzed and found to have the following genotype:
a1a1b2b2c1c2d1d2e2e2f1f2g1g1h1h2What is the length of its tail?
A) 6 cm
B) 8 cm
C) 12 cm
D) 24 cm
E) 36 cm
Answer: C
One species of green plant, with frondlike leaves, a spine-coated stem, and purple cup-shaped flowers, is found to be self-pollinating. Which of the following is true of this species?
A) The species must be haploid.
B) Its reproduction is asexual.C) All members of the species have the same genotype.
D) Some of the seeds would have true-breeding traits.
E) All of its dominant traits are most frequent.
Answer: D
If the environmental parameters, such as temperature, humidity, atmosphere, sunlight, and so on, are mostly Earthlike, which of the following do you expect of its types of leaves, stems, and flowers?
A) The genes for them would have originated on Earth.
B) Genes for these traits would have a common ancestor with those from Earth.C) Such plants could be safely eaten by humans.
D) Genotypes for these traits would be identical to Earth plants with the same traits.
E) Phenotypes would be selected for or against by these environmental factors.
Answer: E
Marfan syndrome in humans is caused by an abnormality of the connective tissue protein fibrillin. Patients are usually very tall and thin, with long spindly fingers, curvature of the spine, sometimes weakened arterial walls, and sometimes ocular problems, such as lens dislocation. Which of the following would you conclude about Marfan syndrome from this information?
A) It is recessive.
B) It is dominant.C) It has a late age of onset (> 60).
D) It is pleiotropic.
E) It is epistatic.
Answer: D
Learn More :
Biology
- What is a syndrome?
- At which phase(s) is it preferable to obtain chromosomes to prepare a karyotype?
- In 1956 Tijo and Levan first successfully counted human chromosomes. What is the reason it took so many years to do so?
- A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition?
- Down syndrome has a frequency in the U.S. population of ~1/700 live births. In which of the following groups would you expect this frequency to be significantly higher?
- What is the source of the extra chromosome 21 in an individual with Down syndrome?
- An inversion in a human chromosome often results in no demonstrable phenotypic effect in the individual. What else may occur?
- Abnormal chromosomes are frequently found in malignant tumors. Errors such as translocations may place a gene in close proximity to different control regions. Which of the following might then occur to make the cancer worse?
- A phenotypically normal prospective couple seeks genetic counseling because the man knows that he has a translocation of a portion of his chromosome 4 that has been exchanged with a portion of his chromosome 12. Although he is normal because his translocation is balanced, he and his wife want to know the probability that his sperm will be abnormal. What is your prognosis regarding his sperm?
- Of the following human aneuploidies, which is the one that generally has the most severe impact on the health of the individual?
- In humans, male-pattern baldness is controlled by an autosomal gene that occurs in two allelic forms. Allele Hn determines nonbaldness, and allele Hb determines pattern baldness. In males, because of the presence of testosterone, allele Hb is dominant over Hn. If a man and woman both with genotype HnHb have a son, what is the chance that he will eventually be bald?
- A nonreciprocal crossover causes which of the following products?
- One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is this alteration called?
- If nondisjunction occurs in meiosis II during gametogenesis, what will be the result at the completion of meiosis?
- Which of the following two genes are closest on a genetic map of Drosophila?
- Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons?
- Why does recombination between linked genes continue to occur?
- Recombination between linked genes comes about for what reason?
- The centimorgan (cM) is a unit named in honor of Thomas Hunt Morgan. To what is it equal?
- Three genes at three loci are being mapped in a particular species. Each has two phenotypes, one of which is markedly different from the wild type. The unusual allele of the first gene is inherited with either of the others about 50% of the time. However, the unusual alleles of the other two genes are inherited together 14.4% of the time. Which of the following describes what is happening?
- What is the reason that linked genes are inherited together?
- What does a frequency of recombination of 50% indicate?
- How would one explain a testcross involving F1 dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced?
- Which of the following statements is true of linkage?
- Women (and all female mammals) have one active X chromosome per cell instead of two. What causes this?
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