Question 1

What chemical force must be overcome in order to separate the two DNA strands during replication?

Accepted Answer

The hydrogen bonds between the base pairs must be overcome in order to separate the two DNA strands during replication. Hydrogen bonds are relatively weak chemical interactions, which allows for the separation and unwinding of the DNA double helix during replication.

Question 2

For a DNA strand that contains the sequence AGT in the 5' to 3' direction,what nucleotides are found on the other DNA strand in the 5' to 3' direction?

Accepted Answer

A

Question 3

If an organism's DNA contains 20% adenine nucleotides,what percentage of its DNA is composed of thymine nucleotides?

Accepted Answer

According to Chargaff's rules, in DNA, the amount of adenine (A) is equal to the amount of thymine (T). Therefore, if there is 20% adenine, there must also be 20% thymine.

Question 4

Which of the following enzymes is needed to seal breaks in the sugar-phosphate backbone during replication?

Accepted Answer

DNA ligase is the enzyme responsible for sealing breaks in the sugar-phosphate backbone during DNA replication. The other enzymes listed (DNA polymerase, RNA polymerase, and helicase) have different functions in the replication process. RNA ligase is not a recognized enzyme.

Question 5

The central dogma of molecular biology states that the information contained within genes flows in which direction?

Accepted Answer

The central dogma of molecular biology states that the information contained within genes flows in the direction from DNA to mRNA to protein. This means that DNA serves as a template for the synthesis of mRNA, which in turn acts as a template for the synthesis of protein. This process is also known as gene expression. The other choices are not consistent with the central dogma of molecular biology.

Question 6

tRNAs carrying the correct amino acid recognize the proper codons on the mRNA because

Accepted Answer

tRNAs recognize mRNA codons through complementary base pairing between the tRNA's anticodon and the mRNA codon. This allows for the correct amino acid to be added to the growing polypeptide chain. Additionally, tRNAs are charged with the correct amino acid through the action of aminoacyl-tRNA synthetases, which ensure that the correct amino acid is added to the tRNA before it enters the ribosome.

Question 7

Which of the following is an incorrect match?

Accepted Answer

Transcription is the process of synthesizing an RNA molecule from a DNA template. During transcription, the DNA sequence is read and the RNA molecule is built by complementary base pairing. There are three types of RNA molecules that can be produced during transcription: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). The main function of tRNA is to transport amino acids to the ribosome for protein synthesis, whereas mRNA carries the genetic information from DNA to the ribosome for protein synthesis. Therefore, transcription does not result in the formation of tRNA molecules.

Question 8

If an organism's DNA contains 20% adenine nucleotides,what percentage of its DNA is composed of guanine nucleotides?

Accepted Answer

DNA is composed of four nucleotide bases: adenine (A), thymine (T), guanine (G), and cytosine (C). These bases pair up in a specific way: A pairs with T, and G pairs with C. Because of this pairing, the percentage of adenine in DNA must equal the percentage of thymine, and the percentage of guanine must equal the percentage of cytosine.
If the DNA contains 20% adenine, then it must also contain 20% thymine. The remaining 60% must be composed of guanine and cytosine. Since these two bases pair up together, they must each make up half of the remaining 60%, or 30% each. Therefore, the percentage of guanine in the DNA is 30%.

Question 9

DNA replication is called semiconservative because

Accepted Answer

Semiconservative replication means that each of the resulting DNA molecules has one original (old) strand and one newly synthesized strand. This has been experimentally demonstrated by the famous Meselson-Stahl experiment in 1958. Therefore, option B is the correct answer. Option A is incorrect because both strands of the resulting DNA molecules are new, and option C is incorrect because both strands are not new. Option D is incorrect because nucleotides are incorporated into the replicated DNA molecules, and option E is incorrect because both strands have the same sequence of nucleotides as the original DNA molecule.

Question 10

mRNA must be processed in the cytoplasm before being used in protein synthesis.

Accepted Answer

The processing of mRNA in a eukaryote occurs within the nucleus. Then, the mRNA leaves the nucleus and enters the cytoplasm, where it is translated into a protein.

Question 11

During the elongation cycle of translation,the A site on a ribosome functions in

Accepted Answer

During elongation, the A site on the ribosome functions in receiving a new tRNA with the correct amino acid. This tRNA then forms a base pair with the mRNA codon in the A site, allowing for the addition of the correct amino acid to the growing polypeptide chain.

Question 12

For a DNA strand composed of the sequence AGT in the 5' to 3' direction,the free phosphate is on the ____ nucleotide and the free hydroxyl is on the ____ nucleotide.

Accepted Answer

The free phosphate group is always attached to the 5' carbon of the first nucleotide in the sequence, which is adenine (A) in this case. The free hydroxyl group is found on the 3' carbon of the last nucleotide in the sequence, which is thymine (T) here.

Question 13

This figure represents

Accepted Answer

The answer of This figure represents 
...

Question 14

The genetic code in bacteria is different than the genetic code in animals and plants.

Accepted Answer

The genetic code is almost universal, and suggests that all life on Earth originated from a single ancestral life form.

Question 15

For a DNA strand that is two nucleotides long,how many different sequences are possible?

Accepted Answer

The answer of For a DNA strand that is two...

Question 16

The x-ray diffraction pattern of DNA discovered by Rosalind Franklin showed that DNA

Accepted Answer

The x-ray diffraction pattern of DNA discovered by Rosalind Franklin showed that DNA is both helical and has a repeated pattern. The helical structure is referred to as a double helix, while the repeated pattern is due to the regularly spaced base pairs within the DNA molecule.

Question 17

The three steps that are required for DNA replication are

Accepted Answer

The three steps required for DNA replication are unwinding (separating the two strands of DNA), complementary base pairing (matching up nucleotides with their complementary bases), and joining (connecting nucleotides to form a new strand of DNA). Option A lists these three steps in the correct order. The other options either list incorrect steps or list the steps in an incorrect order.

Question 18

A defect in DNA ligase would most likely cause

Accepted Answer

DNA ligase is responsible for sealing nicks in the sugar-phosphate backbone of DNA, so a defect would result in gaps remaining after replication.

Question 19

According to Chargaff's rules,___ always pairs with ____,and _____ always pairs with _____.

Accepted Answer

Chargaff's rules state that A (adenine) always pairs with T (thymine) and G (guanine) always pairs with C (cytosine) in DNA. Thus, choice B is the only option that correctly pairs A with T and G with C.

Question 20

If an organism's DNA contains 17% adenine nucleotides and 33% guanine nucleotides,what percentage of its DNA is composed of cytosine nucleotides?

Accepted Answer

The answer of If an organism's DNA contains 17% adenine...

Quiz 11: DNA Biology