Chapter 17 Nucleotides and Nucleic Acids (Questions)

What is the function of topoisomerase? A. Relieving strain in the DNA ahead of the replication fork. B. Elongating new DNA at a replication fork by adding nucleotides to the existing chain. C. Adding methyl groups to bases of DNA. D. Unwinding of the double helix. E. Stabilizing single-stranded DNA at the replication fork.

A. Relieving strain in the DNA ahead of the replication fork.

The nucleotides in DNA and RNA have a __________________ linkage between the anomeric center of the sugar and a particular nitrogen atom of the nitrogenous base.

B-N- glycosidic

DNA is coiled around ___________, proteins whose positive charge facilitates the packing of the negatively charged DNA into nucleosomes, which coil further to form the fibrous X-shape structure of chromosomes.

Histones

Translation occurs at?

Ribosomes

What are the three types of RNA?

mRNA, tRNA, rRNA

What are the three stop codons? What is the function of a stop codon?

1. UGA 2. UAA 3. UAG. A stop codon signifies the end of an amino acid.

What do nucleotides contain?

A monosaccharide, a nitrogenous base, and a monophosphate ester linkage at the 5'-hydroxyl group of the monosaccharide.

A nucleotide contains what?

A nitrogenous base, which is derived from either pyrimidine or purine. RNA and DNA both contain adenine (A), guanine (G), and cytosine (C). DNA also contains thymine (T), where as RNA also contains uracil (U).

What is a gene?

A sequence of nucleotides on DNA that codes for a particular protein.

The complete sequence of nucleotides in DNA of an organism, it's genome, is distributed among its chromosomes. The human genome has _________ base pairs distributed across ______ chromosomes.

A. 1 million; 20 B. 3 billion; 46 C. 2 billion; 32 D. 3 billion; 16

Indicate the complementary sequence of nucleotides that would appear on the adjacent DNA strand from the 3' to the 5' end. A. 5' AGTCCG 3' and B. 5' CCTTGA 3'

A. 3' TCAAGGC 5' and B. 3' GGAACT 5'

DNA polymerase catalyze the synthesis of a polynucleotide in the ______________ direction. Therefore, one strand is synthesized continuously (the leading strand) while the other is synthesized in fragments (the lagging strand). A. 5'->3' B. 3'->5'

A. 5'->3'

DNA polymerase would be best described as A. Fast and accurate B. Slow and inconsistent C. Steady and consistent

A. Fast and accurate

Synthesized continuously A. Leading strand B. Lagging strand C. Both

A. Leading strand

Synthesized in the same direction as the movement of the replication fork A. Leading strand B. Lagging strand C. Both

A. Leading strand

What part of the DNA double helix has the following properties? A. Is hydrophobic B. Stabilizes the helix by base stacking C. Is hydrophilic and interacts with the surrounding aqueous environment D. Stabilizes the helix by hydrogen bonding

A. The nitrogenous bases B. The nitrogenous bases C. The sugar-phosphate backbone D. The base pairs C-G and A-T

How is a nucleoside named?

According to the identity of the nitrogenous base with a change in the ending of the name of the nitrogenous base.

Every three non-overlapping nucleotides on an mRNA, a codon, specifies one _____________ during translation.

Amino acid

In double-stranded DNA, a nitrogenous base on one strand hydrogen bonds to a complementary nitrogenous base on the other strand across from it. The base pairings in DNA are? A. A-G; C-T B. A-T; G-C C. A-C; G-T

B. A-T; G-C

The two strands of a DNA double helix are arranged _____________: one strand has its 5' end opposite the 3' end of the other strand. A. Parallel B. Antiparallel

B. Antiparallel

Why is the lagging strand synthesized in fragments during DNA replication?

Because the two strands of DNA are antiparallel and DNA polymerase can build nucleotides only in the 5' -> 3' direction. So, the lagging strand begins at the replication fork and works outward from the replication fork while the replication fork moves in the opposite direction, exposing more of the parent strand. Thus, the next fragment is built from the new site of the replication fork to the start of the previous fragment.

An Okazaki fragment has which of the following arrangements? A. Primase, polymerase, ligase B. 3' RNA nucleotides, DNA nucleotides 5' C. 5' RNA nucleotides, DNA nucleotides 3' D. DNA polymerase I, DNA polymerase III

C. 5' RNA nucleotides, DNA nucleotides 3'

DNA polymerase is the enzyme involved in forming this polynucleotide A. Leading strand B. Lagging strand C. Both

C. Both

Requires DNA ligase to join fragments A. Leading strand B. Lagging strand C. Both

C. Both

Synthesized in the 5' -> 3' direction A. Lagging strand B. Leading strand C. Both

C. Both

Which enzyme catalyzes the elongation of a DNA strand in the 5' to 3' direction? A. Primase B. DNA ligase C. DNA polymerase III D. Topoisomerase E. Helicase

C. DNA polymerase III

There are ______ different nucleotides from which to build DNA or RNA. A. Three B. Five C. Four D. Eight

C. Four

The leading and lagging strand differ in that A. The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction. B The leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end. C. The lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together. D. The leading strand is synthesized at twice the rate of the lagging strand.

C. The lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together.

What does transfer RNA (tRNA) do?

Carries an amino acid to the ribosome, according to the codon specified by mRNA, by base pairing to its complementary anticodon at one end of the tRNA.

What are ribosomes?

Composed of rRNA and proteins, and located in the cytosol. A ribosome reads an mRNA in the 5'->3' direction, one codon (three nucleotides) at a time.

The monosaccharide component of a nucleotide is _______________ in RNA and ________________ in DNA.

D-ribose; 2'-deoxy-D-ribose

At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork: 3' C C T A G G C (T) G C A A T C C 5' An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence? A. 5' G C C T A G G 3' B. 3' G C C T A G G 5' C. 5' A C G T T A G G 3' D. 5' A C G U U A G G 3' E. 5' G C C U A G G 3'

D. 5' A C G U U A G G 3'

Amino acids have have more than one codons, usually differing in the ___________ nucleotide of the codon. A. Second B. Fourth C. Seventh D. Third

D. Third

Genetic information flows from ________ to ________ in the nucleus of the cell during transcription. Then, at ribosomes in the cytosol, translation of mRNA into proteins occur.

DNA; mRNA

Is a histone protein positively charged or negatively charged? Explain how the charge on a histone facilities the formation of nucleosides.

Histone proteins are positively charged. The positive charge on histones is attracted to the negative charge on DNA, making it easier to coil DNA upon itself and form the compact structure of a nucleosome. Remember opposite charges attract and like charges repel.

What type of interaction hold the two strands of DNA together? What is the advantage of this type of interaction over covalent bonding?

Hydrogen bonding and base stacking. The advantage of noncovalent interactions is that it allows the two strands of DNA to be separated when the strands need to be read, such as during DNA replication and transcription.

What is the role of RNA polymerase II in transcription?

Is the enzyme in human cells that catalyze the synthesis of mRNA from nucleotides that are complementary to the template strand of DNA. RNA polymerase II assembles nucleotides from the 5' to the 3' end of the polynucleotide (the 3' to the 5' end of the DNA template strand).

Describe the process of transcription.

Is the process in which a gene, a segment of the template strand of DNA, is used as a template for synthesizing a single strand of mRNA with a complementary sequence of nucleotides.

What is a genome?

It is the entire DNA sequence for an organism.

In which direction does DNA polymerase always assemble a polynucleotide?

It's always synthesized in the 5' -> 3' direction

What characteristic of the x-ray image of DNA suggests it has a helical structure?

It's symmetry

What is the genetic code?

It's the list of all 64 codons and their corresponding amino acids, including stop and start codons.

What role does DNA ligase play in DNA replication?

Joins adjacent lagging strand fragments to create the lagging strand.

What role does DNA polymerase play in DNA replication?

Joins nucleotides to the growing polynucleotide in the 5' to 3' direction, by forming monophosphate diester linkages. It also proofreads for errors in the nucleotide sequence of the daughter strands.

A nucleoside contains a _________ and a ___________.

Monosaccharide; nitrogenous base

The nucleic acids DNA and RNA are polynucleotides constructed from a sequence of many ______________

Nucleotides

Transcription occurs in the ________ of the cell, where the template strand of a gene is copied as a complementary single-stranded mRNA transcript.

Nucleus

Where in the cell does transcription occur: the nucleus or they cystosol?

Occurs in the nucleus of the cell

What's the error rate of DNA polymerase?

One in a billion nucleotides after proofreading

Transcription is catalyzed in human cells by __________________and occurs from the 5' to the 3' end in the mRNA transcript.

RNA polymerase II

What does "gene expression" mean?

Refers to the transcription and translation of a gene to produce a particular protein. It usually occurs when a particular protein is required by the cell.

What are the two common types of genetic mutations?

Substitution mutations and frameshift mutations

Are the two strands of a DNA double helix parallel or antiparallel? What does this mean?

The two strands of DNA are antiparallel, which mean the 5' end of one strand is opposite the 3' end of the other strand.

How many base pairs are there in the human genome?

There are 3 billion base pairs in the human genome.

The major form of DNA is composed of what?

Two polynucleotides strands twisted around each other in a right handed double helix.

DNA replication begins with?

Unwinding DNA and exposing each parent strand, which serves as he template for a complementary daughter strand. Each new double-stranded DNA contains one strand from the original double helix and one new daughter strand.

What role does helicase play in DNA replication?

Unwinds the DNA double helix at the replication fork, exposing new sections of the two parent strands.

What type of RNA is a component of ribosomes? What other type of biomolecule makes up a ribosome?

rRNA. Proteins