Chapter 14 Quiz Flashcards
DNA nucleotides contain ___. (Mark all that apply)
Group of answer choices
ribose sugar
a phosphate group
nitrogen containing bases
uracil
The correct answers are:
A phosphate group
Nitrogen-containing bases
Explanation:
Ribose sugar: DNA contains deoxyribose sugar, not ribose. Ribose is found in RNA.
A phosphate group: Every nucleotide in DNA contains a phosphate group.
Nitrogen-containing bases: DNA nucleotides contain four nitrogenous bases—adenine (A), thymine (T), guanine (G), and cytosine (C).
Uracil: Uracil is found in RNA, not DNA, where it replaces th
Which of the following bases are purines? (Mark all that apply)
Group of answer choices
adenine
guanine
cytosine
thymine
The correct answers are:
Adenine
Guanine
Explanation:
Purines: Adenine (A) and Guanine (G) are purines, which have a double-ring structure.
Pyrimidines: Cytosine (C) and Thymine (T) are pyrimidines, characterized by a single-ring structure. (In RNA, uracil replaces thymine as a pyrimidine.)
Which of the following is correct about base pairs?
Group of answer choices
guanine always pairs with cytosine
purines always bond to other purines
pyrimidines are only found in RNA
uracil is one of the bases found in DNA
The correct answer is:
Guanine always pairs with cytosine
Explanation:
Guanine always pairs with cytosine: True. In DNA, guanine (G) forms three hydrogen bonds with cytosine (C).
Purines always bond to other purines: False. Purines (adenine and guanine) always pair with pyrimidines (thymine or cytosine in DNA) to maintain the DNA structure.
Pyrimidines are only found in RNA: False. Pyrimidines (cytosine and thymine) are found in DNA, while cytosine and uracil are found in RNA.
Uracil is one of the bases found in DNA: False. Uracil is found only in RNA, where it replaces thymine.
Regarding their structure, cytosine and thymine have a ___ ring.
Group of answer choices
single
double
triple
The correct answer is:
Single
Explanation:
Cytosine and thymine are pyrimidines, which are characterized by a single-ring structure. In contrast, purines (adenine and guanine) have a double-ring
Replication of DNA requires which of the following? (Mark all that apply)
Group of answer choices
unwinding
complementary base pairing
joining of Okasaki fragments
joining of amino acids
The correct answers are:
- Unwinding
- Complementary base pairing
- Joining of Okazaki fragments
Explanation:
1. Unwinding: The DNA double helix must unwind to allow access for enzymes to replicate the strands. This process involves enzymes like helicase.
- Complementary base pairing: New nucleotides are added based on the original strand’s sequence following the rules of base pairing (A with T, G with C).
- Joining of Okazaki fragments: On the lagging strand, DNA is synthesized in short segments called Okazaki fragments, which are joined by DNA ligase.
- Joining of amino acids: This is part of protein synthesis (translation), not DNA replication.
The process of copying a DNA molecule to make another DNA molecule is known as ___.
Group of answer choices
replication
transcription
translation
hydrolysis
The correct answer is:
- Replication
Explanation:
- Replication: This is the process of copying a DNA molecule to produce an identical DNA molecule. It ensures that each daughter cell receives a complete set of DNA during cell division.
- Transcription: This involves copying a DNA sequence into an RNA molecule.
- Translation: This is the process of converting mRNA into a protein.
- Hydrolysis: This is a chemical reaction where water is used to break bonds, not involved in DNA copying.
The unwinding of DNA occurs due to ___.
Group of answer choices
helicase
polymerase
ligase
primase
The correct answer is:
- Helicase
Explanation:
- Helicase: This enzyme is responsible for unwinding the DNA double helix by breaking the hydrogen bonds between the complementary bases, creating two single strands for replication.
- Polymerase: DNA polymerase synthesizes new DNA strands by adding complementary nucleotides to the template strand.
- Ligase: DNA ligase seals the gaps between Okazaki fragments on the lagging strand.
- Primase: This enzyme synthesizes RNA primers, which provide a starting point for DNA polymerase during replication.
During DNA replication, new complementary nucleotides are positioned and joined by ___.
Group of answer choices
polymerase
helicase
ligase
primase
The correct answer is:
- Polymerase
Explanation:
- Polymerase: DNA polymerase is the enzyme responsible for adding new complementary nucleotides to the template strand and forming phosphodiester bonds, effectively joining the nucleotides to create a new DNA strand.
- Helicase: Unwinds the DNA double helix to make the strands accessible.
- Ligase: Joins Okazaki fragments on the lagging strand by sealing the sugar-phosphate backbone.
- Primase: Synthesizes RNA primers to initiate DNA synthesis.
The ___ strand of DNA is synthesized continuously during DNA replication.
Group of answer choices
leading
lagging
parental
RNA
The correct answer is:
Leading
Explanation:
Leading strand: This strand is synthesized continuously in the 5’ to 3’ direction, moving toward the replication fork. DNA polymerase can add nucleotides without interruption.
Lagging strand: This strand is synthesized discontinuously in short segments called Okazaki fragments because it moves away from the replication fork.
Parental strand: Refers to the original DNA strands that serve as templates for replication.
RNA: RNA is not a strand of DNA; it is involved in transcription, not replication.
The 3’ end of each Okazaki fragment is joined to the 5’ end of the next fragment by ___.
Group of answer choices
ligase
helicase
polymerase
primase
The correct answer is:
Ligase
Explanation:
Ligase: DNA ligase seals the gaps between Okazaki fragments on the lagging strand by forming phosphodiester bonds between the 3’ end of one fragment and the 5’ end of the next.
Helicase: Unwinds the DNA helix.
Polymerase: DNA polymerase adds nucleotides but cannot join Okazaki fragments.
Primase: Synthesizes RNA primers needed to initiate DNA synthesis on the lagging strand.
Genes code for ___.
Group of answer choices
proteins
DNA
lipids
carbohydrates
The correct answer is:
Proteins
Explanation:
Genes code for proteins: Genes are segments of DNA that contain the instructions for synthesizing proteins through the processes of transcription and translation.
DNA: Genes themselves are composed of DNA, but they do not code for DNA.
Lipids: While some genes may regulate lipid metabolism, they do not code directly for lipids.
Carbohydrates: Similar to lipids, some genes may be involved in carbohydrate metabolism, but they do not directly code for carbohydrates.
Electrophoresis separates molecules according to their ___.
Group of answer choices
size
shape
location
texture
The correct answer is:
- Size
Explanation:
- Size: Electrophoresis separates molecules (such as DNA, RNA, or proteins) primarily based on their size. Smaller molecules move faster through the gel matrix, allowing for separation from larger molecules.
- Shape: While shape can influence movement, size is the primary factor in separation during electrophoresis.
- Location: This does not relate to the separation process in electrophoresis.
- Texture: This is not a relevant factor in electrophoresis.
Which of the following is confined to the nucleus in eukaryotes?
Group of answer choices
DNA
RNA
proteins
ribosomes
The correct answer is:
- DNA
Explanation:
- DNA: In eukaryotic cells, DNA is confined to the nucleus, where it is organized into chromosomes.
- RNA: While transcription occurs in the nucleus, RNA can also be found in the cytoplasm after it is synthesized.
- Proteins: Proteins are synthesized in the cytoplasm (on ribosomes) and can be found throughout the cell.
- Ribosomes: Ribosomes are found in the cytoplasm and on the rough endoplasmic reticulum, not confined to the nucleus.
