14. The major components of a DNA molecular subunit are
a. a chromosome, deoxyribose, and double helix
b. a five-carbon sugar, phosphate group, and a nitrogen-containing base
c. adenine, guanine, cytosine, and thymine
d. all of the above
D
16. During DNA replication, all of the following steps occur EXCEPT
a. enzymes proofread new strands for errors and correct them
b. the double helix is unwound by DNA polymerases
c. base-pairing rules determine which nucleotide is added to new strands
d. each strand of a DNA double helix is copied, forming two identical double helixes
B?
17. When errors in nucleotide sequencing occur,
a. DNA polymerase replaces the incorrect nucleotide with the correct nucleotide
b. enzymes dissolve the incorrect nucleotide so DNA polymerase can add the correct one
c. purines replace pyrimidines in the DNA molecule
d. DNA polymerase proofreads for errors while another enzyme corrects it
A?
15. Which of the following is NOT true about DNA replication?
a. It must occur before a cell can divide
b. Two complementary strands are duplicated
c. the double strand unwinds and unzips while it's being duplicated
d. The process is catalyzed by enzymes called DNA mutagens
D?
Thanks
-MC
14. The correct answer is option b. In a DNA molecular subunit, the major components are a five-carbon sugar (deoxyribose), a phosphate group, and a nitrogen-containing base. These components are bonded together to form a nucleotide, which is the building block of DNA.
To arrive at this answer, you could have recognized that chromosomes are not part of a DNA molecular subunit (option a). Option c lists the nitrogen-containing bases, but it doesn't include the other components of the nucleotide. Therefore, option b is the correct answer.
16. The correct answer is option b. During DNA replication, the double helix is unwound by enzymes called DNA helicases, not DNA polymerases. DNA polymerases, on the other hand, are responsible for copying the strands and adding new nucleotides. This process leads to the formation of two identical double helixes.
To determine this answer, you could have recognized that the unwinding of the double helix is a different step from the copying process performed by DNA polymerases, making option b the correct answer.
17. The correct answer is option d. When errors in nucleotide sequencing occur, DNA polymerase proofreads for errors while another enzyme corrects them. This process ensures that any mistakenly incorporated nucleotides are replaced with the correct ones. This helps maintain the accuracy of the DNA sequence.
To arrive at this answer, you could have recognized that option a incorrectly states that DNA polymerase itself replaces the incorrect nucleotide. Options b and c suggest incorrect mechanisms that do not occur during error correction. Therefore, option d is the correct answer.
15. The correct answer is option d. The process of DNA replication is catalyzed by enzymes called DNA polymerases, not DNA mutagens. DNA mutagens are agents that can induce mutations in DNA, but they are not involved in the process of replication.
To determine this answer, you could have recognized that options a and b state true statements about DNA replication. Option c accurately describes the unwinding and unzipping of the double strand during replication. Therefore, the only incorrect statement is option d, making it the correct answer.