What is the effect of genetic drift on evolution? How does the founder effect work to cause change in allele
frequency? What will be an ideal response?
As we saw with the aftermath of the typhoon on Pingelap atoll, populations sometimes start
with a small number of individuals, or founders. Alleles carried by the founders, whether
they are advantageous or detrimental, become established in the new population. These
events take place simply by chance and are known as founder effects. Changes in allele
frequency that occur by chance from generation to generation in small populations are
examples of genetic drift. The impact of genetic drift is magnified in small populations. On
Pingelap, frequency of the mutant allele increased from 2.5% to 18–20% in just over 200
years.
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Two genes, A and B, are located 30 map units apart. The dihybrid shown in the attachment is mated to a tester aa bb. What proportion of the offspring is expected to be dominant for both traits?
A. 0% B. 15% C. 30% D. 35% E. 70%
How is the splicing of U2-dependent introns different from that of U12-dependent introns?
a. U12-dependent introns have no branch site. b. U2-dependent introns have longer consensus sequences at the splice sites. c. Most of the snRNPs in the spliceosomes are different. d. The SR proteins in the spliceosomes are different. e. U12-dependent introns are self-splicing.
What is the key concept addressed by the question?
What will be an ideal response?
Ascaris lumbricoides
A. larvae migrate to the pharynx, get swallowed, and return to intestines to mature. B. spreads to humans by ingestion of Ascaris eggs in food. C. is an intestinal roundworm. D. larvae penetrate into lymphatics and capillaries around intestines. E. All of the choices are correct.