1.
Which of the following is NOT a base found on a DNA molecule?
Correct Answer
A. Alanine
Explanation
Alanine is not a base found on a DNA molecule. DNA molecules are made up of four bases: adenine, thymine, guanine, and cytosine. Alanine, on the other hand, is an amino acid that is not part of the DNA structure. It is one of the building blocks of proteins and is not directly involved in DNA replication or coding.
2.
The sugar molecule found in DNA is:
Correct Answer
D. Deoxyribose
Explanation
Deoxyribose is the correct answer because it is the sugar molecule found in DNA. DNA, or deoxyribonucleic acid, is composed of nucleotides which consist of a phosphate group, a nitrogenous base, and a sugar molecule. In DNA, the sugar molecule is deoxyribose, while in RNA (ribonucleic acid), the sugar molecule is ribose. Sucrose, glucose, and fructose are all types of sugars, but they are not the sugar molecules found in DNA.
3.
A nucleotide consists of which 3 molecules?
Correct Answer
A. Sugar, pHospate, Base
Explanation
A nucleotide consists of three molecules: sugar, phosphate, and base. The sugar molecule is a pentose sugar, usually either ribose or deoxyribose. The phosphate molecule is a phosphoric acid group, which forms the backbone of the nucleotide chain. The base molecule is a nitrogenous base, which can be adenine (A), thymine (T), cytosine (C), guanine (G) in DNA, or adenine (A), uracil (U), cytosine (C), guanine (G) in RNA. These three molecules together make up the structure of a nucleotide, the building block of nucleic acids like DNA and RNA.
4.
DNA has _______ strand(s) and RNA has ________ strand(s)
Correct Answer
C. 2, 1
Explanation
DNA has two strands, while RNA has one strand. This is because DNA is a double-stranded molecule, consisting of two complementary strands that are held together by hydrogen bonds. RNA, on the other hand, is a single-stranded molecule. The difference in the number of strands between DNA and RNA is a fundamental distinction between these two types of nucleic acids.
5.
In a DNA molecule, adenine always bonds to ____________.
Correct Answer
B. Thymine
Explanation
In a DNA molecule, adenine always bonds to thymine. This is known as complementary base pairing, where adenine forms two hydrogen bonds with thymine. This pairing is essential for DNA replication and the accurate transmission of genetic information. Adenine does not bond with uracil, guanine, cytosine, or itself in DNA. Uracil is found in RNA instead of thymine.
6.
DNA Naturally assumes a ___________________ shape.
Correct Answer
D. Double helix
Explanation
DNA naturally assumes a double helix shape due to its structure. DNA is made up of two strands of nucleotides that are connected by hydrogen bonds. These two strands twist around each other in a spiral shape, forming a double helix. This structure is important because it allows for the replication and transmission of genetic information. The double helix shape also provides stability and protection for the genetic material within the DNA molecule.
7.
DNA has 2 functions. To store and use the codes for building______________, and to copy itself for making______________.
Correct Answer
D. Proteins, New cells
Explanation
DNA has two main functions. One is to store and use the codes for building proteins, which are essential for the structure and function of cells. The other function is to copy itself for making new cells, ensuring the transmission of genetic information to the next generation.
8.
During DNA replication, what enzyme is responsible for "unzipping" the DNA molecule?
Correct Answer
A. DNA helicase
Explanation
DNA helicase is responsible for "unzipping" the DNA molecule during DNA replication. This enzyme unwinds and separates the double-stranded DNA by breaking the hydrogen bonds between the base pairs. This process creates two separate strands that serve as templates for the synthesis of new DNA strands during replication. DNA helicase plays a crucial role in DNA replication by facilitating the unwinding of the DNA molecule and allowing the replication machinery to access the individual strands for copying.
9.
What type of bond holds the bases together in the middle of a DNA molecule?
Correct Answer
A. Hydrogen
Explanation
Hydrogen bonds hold the bases together in the middle of a DNA molecule. These bonds form between the nitrogenous bases of the DNA strands, specifically between adenine and thymine, and between guanine and cytosine. Hydrogen bonds are relatively weak compared to covalent bonds, but they play a crucial role in stabilizing the DNA structure and allowing for the separation and replication of DNA strands during cell division.
10.
Which of the following is NOT a type of RNA?
Correct Answer
B. CRNA
Explanation
cRNA is not a type of RNA because it does not exist in biological systems. The correct types of RNA are rRNA (ribosomal RNA), mRNA (messenger RNA), and tRNA (transfer RNA). rRNA plays a crucial role in protein synthesis, mRNA carries genetic information from DNA to the ribosomes, and tRNA helps in the actual assembly of amino acids into proteins. However, cRNA is not a recognized type of RNA and is not involved in any biological processes.