Question 1

A codon is ________.

Accepted Answer

A codon is a sequence of three nucleotides in RNA that codes for a specific amino acid during protein synthesis. It is the RNA that directly carries the genetic information from DNA to ribosomes where proteins are made. Therefore, option B, which describes codons as three nucleotides of RNA that code for an amino acid, is the correct choice.

Question 2

If you know that a DNA double helix consists of 20 % adenine, what percentage of the DNA double helix is guanine (G)?

Accepted Answer

The percentage of guanine (G) must be the same as the percentage of cytosine (C) in a DNA double helix. Since there are only four nitrogenous bases in DNA (adenine, thymine, cytosine, and guanine), the remaining percentage must be split between cytosine (C) and thymine (T). Since adenine (A) makes up 20% of the DNA double helix, the remaining 80% must be split equally between cytosine (C) and guanine (G), resulting in each of them making up 40% of the DNA double helix. Therefore, guanine (G) makes up 40% of the DNA double helix, or 30% of the total bases (since A is 20%). The closest answer choice is B) 30%.

Question 3

What do the letters D-N-A stand for?

Accepted Answer

The correct expansion of the acronym DNA is Deoxyribonucleic acid.

Question 4

What is the type of bond between two strands of DNA?

Accepted Answer

The bond between two strands of DNA is a hydrogen bond. The hydrogen bonds hold the two strands of DNA together in a helical structure. The strength of these bonds is weaker than covalent bonds, allowing for easy separation of the strands during DNA replication and transcription.

Question 5

If DNA directs the production of RNA, what does RNA make?

Accepted Answer

RNA serves as a messenger molecule that carries genetic instructions from DNA to ribosomes, which are responsible for protein synthesis. Therefore, RNA makes proteins by providing the information necessary for the assembly of amino acids into a functional protein.

Question 6

What is different from one DNA nucleotide to the next?

Accepted Answer

The nucleotides that make up DNA differ from one another based on the base portion. There are four different bases that make up DNA: adenine (A), thymine (T), cytosine (C), and guanine (G).

Question 7

What is a gene?

Accepted Answer

The definition of a gene has evolved over time and includes all of the options listed. Originally, a gene was defined as a discrete sequence of DNA nucleotides, but it was later found that some genes code for multiple proteins, while others only code for part of a protein. Additionally, recent discoveries have shown that genes can have regulatory functions that do not involve protein synthesis. Therefore, the best choice is D, as it encompasses all of these definitions and more.

Question 8

What part of a chromosome goes through transcription and translation?

Accepted Answer

Only genes go through transcription and translation. Genes are specific sequences of DNA that code for proteins. During transcription, the DNA sequence of a gene is copied into mRNA, which is then translated into a protein. Not all parts of a chromosome are involved in this process.

Question 9

Which of the following statements is incorrect regarding DNA and RNA?

Accepted Answer

All of the statements regarding DNA and RNA are correct. DNA and RNA both have a sugar molecule, but DNA has deoxyribose while RNA has ribose. DNA is double-stranded, while RNA is single-stranded. One of the bases in RNA is uracil, while DNA only has thymine.

Question 10

Ribosomes ________.

Accepted Answer

Ribosomes are responsible for translating the genetic code carried by messenger RNA (mRNA) into proteins through a process called translation. Choice B is incorrect because transcription is the process of producing mRNA from DNA, which is carried out by RNA polymerase. Choice C is incorrect because ribosomes are located outside the nucleus in both prokaryotic and eukaryotic cells. Choice D is incorrect because ATP production is carried out by mitochondria, not ribosomes.

Question 11

DNA replication is a semi-conservative process.This means that after replication, ________.

Accepted Answer

Semi-conservative replication means that each new DNA double helix consists of one old strand and one new strand. This has been experimentally proven by Meselson and Stahl in 1958. Option A is incorrect because both new strands cannot be old strands. Option C is incorrect because this would mean that after two rounds of replication, there would be less than 1% of the original DNA left. Option D is incorrect because both new strands cannot be new.

Question 12

What is the monomer of the DNA molecule?

Accepted Answer

The monomer of the DNA molecule is the nucleotide. Nucleotides are composed of a sugar molecule, a phosphate group, and a nitrogenous base, which are the building blocks of DNA.

Question 13

The base that is not found in DNA, but only in RNA is ________.

Accepted Answer

Uracil is the correct answer as it is found in RNA but not in DNA. Thymine is found only in DNA but not RNA, while adenine and guanine are found in both DNA and RNA.

Question 14

According to the base pairing rules of DNA, if the sequence of bases on one strand was AGGCTTA, what would be the sequence of bases on the complementary strand?

Accepted Answer

According to the base pairing rules of DNA, A always pairs with T, and G always pairs with C. Therefore, the complementary sequence to AGGCTTA would be TCCGAAT.

Question 15

What are the three components of a DNA nucleotide?

Accepted Answer

A DNA nucleotide consists of a 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous base. The four nitrogenous bases found in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T).

Question 16

Why does transcription occur in the nucleus and not in the cytoplasm in eukaryotes?

Accepted Answer

Transcription occurs in the nucleus because DNA is located there and cannot leave to enter the cytoplasm. The DNA must first be transcribed into RNA before it can leave the nucleus to be translated into protein in the cytoplasm.

Question 17

Which of the following statement is not correct about DNA replication?

Accepted Answer

DNA replication involves the replication of the entire DNA molecule, not just genes.

Question 18

What is the main function of DNA helicase in DNA replication?

Accepted Answer

DNA helicase is responsible for unzipping the DNA double helix during DNA replication, allowing the strands to separate and serve as templates for the formation of new strands.

Question 19

Which enzyme is responsible for adding complementary DNA bases to an exposed DNA strand?

Accepted Answer

DNA polymerase is the enzyme responsible for adding complementary DNA bases to an exposed DNA strand during DNA replication. DNA helicase unwinds the double helix, DNA ligase seals breaks in the sugar-phosphate backbone, and DNA peptidase is not involved in DNA replication.

Question 20

How is DNA linked to the production of proteins?

Accepted Answer

DNA holds the instructions, in the form of genes, for the cells on how to make proteins. The process of protein synthesis begins with the transcription of DNA into messenger RNA (mRNA) and then translation of that mRNA into proteins. Therefore, DNA is directly linked to the production of proteins.

Quiz 6: DNA: The Molecule of Life