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20. Retroviruses are A) the causes of cholera and sickle cell disease B) the mos

ID: 254098 • Letter: 2

Question

20. Retroviruses are A) the causes of cholera and sickle cell disease B) the most primitive forms of life on earth C) able to carry out a form of sexual reproduction unknown in animals D) able to insert their genetic material into the genome of a host cel E) capable of infecting prokaryotic ells only 21. In the formula for determining a population's genotype frequencies, the pq in the term 2pq is necessary because: A) heterozygotes have two alleles B) the population is haploid C) heterozygotes can come about in three ways D) the population is doubling in number E) there are two types of homozygous genotypes 22. Which of the following is associated ONLY with prokaryotic cells ? A) nucleoid B) nucleolus C) nucleus D) nucleic acid E) cell wall 23. Which of the following is not a prezygotic isolating mechanism? A) prevention of fertilization B) death of hybrid fetuses C) temporal isolation D) individuals of two populations live in separate areas and do not encounter one another E) ALL OF THE ABOVE (A, B, C, and D) ARE EXAMPLES OF PREZYGOTIC ISOLATING MECHANISMS 24. Which of the following is an invertebrate with an open circulatory system? A) roundworm B) coral C) cow D) crab E) tapeworm

Explanation / Answer

20. Retroviruses are - D) able to insert their genetic material into the host's genome

In the formula of determining the population genotypes frequencies, the pq in the term 2pq is necessary because- A) heterozygotes have two alleles.

Associated only with prokaryotic cells- A) nucleoid

Not a prezygotic isolating mechanism- B) death of hybrid foetuses

Invertebrate with an open circulatory system- D) crab