Question 1

As B-DNA is gradually heated,the absorbance at 260 nm

Accepted Answer

A) increases. 
B) decreases. 
C) stays the same. 
D) is half way between that of poly (AT and poly (G
C) . 
A) increases. 
B) decreases. 
C) stays the same. 
D) is half way between that of poly (AT and poly (G
C) . A

Question 2

The 30 nm fibers of a chromosome are attached to a(n)________ scaffold that holds the fibers in large loops.

Accepted Answer

A) RNA-protein 
B) glycoprotein 
C) actin filament 
D) histone 
A) RNA-protein 
B) glycoprotein 
C) actin filament 
D) histone A

Question 3

Which enzyme would be least useful for recombination experiments that introduce new fragments of DNA into an existing DNA molecule?

Accepted Answer

A) EcoRI G↓AATTC. 
B) SmaI CCC↓GGG. 
C) XhoI C↓TCGAG. 
D) All are equally useful. 
A) EcoRI G↓AATTC. 
B) SmaI CCC↓GGG. 
C) XhoI C↓TCGAG. 
D) All are equally useful. B

Question 4

Stem-loop structures in RNA resemble the ________ form of double-helical DNA.

Accepted Answer

A) A 
B) B 
C) Z 
D) supercoiled circular 
A) A 
B) B 
C) Z 
D) supercoiled circular

Question 5

What is the function of DNA topoisomerases?

Accepted Answer

A) Cleaving nucleotides from the ends of DNA. 
B) Adding or removing supercoils. 
C) Methylation of the nitrogenous bases. 
D) Packaging of DNA into nucleosomes. 
A) Cleaving nucleotides from the ends of DNA. 
B) Adding or removing supercoils. 
C) Methylation of the nitrogenous bases. 
D) Packaging of DNA into nucleosomes.

Question 6

Which type of RNA is the most abundant in living cells (by percent)?

Accepted Answer

A) Ribosomal. 
B) Messenger. 
C) Small. 
D) Transfer. 
A) Ribosomal. 
B) Messenger. 
C) Small. 
D) Transfer.

Question 7

All five histones are rich in ________ amino acid residues whose positive charges allow binding to the sugar-phosphate backbone of DNA.

Accepted Answer

A) lysine and alanine 
B) lysine and arginine 
C) leucine and alanine 
D) leucine and arginine 
A) lysine and alanine 
B) lysine and arginine 
C) leucine and alanine 
D) leucine and arginine

Question 8

Deoxyribonucleosides and ribonucleotides contain two hydroxyl groups that can be phosphorylated.

Accepted Answer

A) True 
 B)False

Question 9

The abbreviation pppT indicates

Accepted Answer

A) TMP. 
B) TDP. 
C) TTP. 
D) 3,5' TP. 
E) None of the above. 
A) TMP. 
B) TDP. 
C) TTP. 
D) 3,5' TP. 
E) None of the above.

Question 10

Which best describes the structure of a nucleosome core particle?

Accepted Answer

A) A histone octamer with DNA threaded through its center. 
B) About 50 bp of DNA associated with one histone H1 molecule. 
C) One nucleosome plus one histone H1 and linker DNA. 
D) A histone octamer wrapped approximately two times around with DNA. 
A) A histone octamer with DNA threaded through its center. 
B) About 50 bp of DNA associated with one histone H1 molecule. 
C) One nucleosome plus one histone H1 and linker DNA. 
D) A histone octamer wrapped approximately two times around with DNA.

Question 11

Histone ________ is not part of the histone octamer,but binds to linker DNA and is responsible for higher-order chromatin structure.

Accepted Answer

A) H1 
B) H2 
C) H3 
D) H4 
E) None of the above 
A) H1 
B) H2 
C) H3 
D) H4 
E) None of the above

Question 12

"Five prime to three prime" description of a DNA strand refers to

Accepted Answer

A) the phosphorylated 5' carbon at one end,the 3' at the other end. 
B) the location of the hydroxyl groups. 
C) the phosphodiester backbone of DNA. 
D) the phosphorylated 5' carbon on one sugar and the 3' carbon on the next sugar. 
A) the phosphorylated 5' carbon at one end,the 3' at the other end. 
B) the location of the hydroxyl groups. 
C) the phosphodiester backbone of DNA. 
D) the phosphorylated 5' carbon on one sugar and the 3' carbon on the next sugar.

Question 13

Changes in the topology and three-dimensional shape of B-DNA can result from

Accepted Answer

A) incubation with proteases. 
B) supercoiling. 
C) isomerization. 
D) hydration. 
A) incubation with proteases. 
B) supercoiling. 
C) isomerization. 
D) hydration.

Question 14

When stretched,strands of poly (dT)give no resistance until it is in the fully extended form because it is wound in a tight helical form.

Accepted Answer

A) True 
 B)False

Question 15

For DNA,a plot of the change in absorbance versus temperature would be ________,which indicates ________.

Accepted Answer

A) hyperbolic;a simple equilibrium between the native conformation and denatured DNA 
B) linear;the breaking of bonds between the base pairs is an independent process 
C) variable in shape (hyperbolic,linear or sigmoidal);the dependence of the denaturing process on the sequence of the DNA 
D) sigmoidal;cooperativity where disruptions in the base stacking at one position destabilizes the stacking in neighboring base pairs 
A) hyperbolic;a simple equilibrium between the native conformation and denatured DNA 
B) linear;the breaking of bonds between the base pairs is an independent process 
C) variable in shape (hyperbolic,linear or sigmoidal);the dependence of the denaturing process on the sequence of the DNA 
D) sigmoidal;cooperativity where disruptions in the base stacking at one position destabilizes the stacking in neighboring base pairs

Question 16

Topoisomerases cut one or both coiled DNA strands,wind the ends by rotation,and then rejoin the cut ends.

Accepted Answer

A) True 
 B)False

Question 17

Which recognition sequence is not a palindrome? (DNA sequences are shown in the standard 5'→3' direction)

Accepted Answer

A) GGGCCC. 
B) TCTAGA. 
C) AAGCTT. 
D) Both B and C. 
E) None of the above.All of the sequences shown are palindromes. 
A) GGGCCC. 
B) TCTAGA. 
C) AAGCTT. 
D) Both B and C. 
E) None of the above.All of the sequences shown are palindromes.

Question 18

Absorption of single-stranded DNA at 260 nm is less than that of double-stranded DNA.

Accepted Answer

A) True 
 B)False

Question 19

Which statement is not true about histones?

Accepted Answer

A) They are positively charged at biological pH. 
B) They only occur in eukaryotes. 
C) Most species that have histones contain five different types. 
D) There is wide variation in the amino acid sequences of histones among species. 
A) They are positively charged at biological pH. 
B) They only occur in eukaryotes. 
C) Most species that have histones contain five different types. 
D) There is wide variation in the amino acid sequences of histones among species.

Question 20

How might mitochondrial DNA be distinguished from eukaryotic nuclear DNA?

Accepted Answer

A) Mitochondrial DNA is in the Z conformation,nuclear DNA is in the B conformation. 
B) Mitochondrial DNA is methylated,nuclear DNA is not. 
C) Nuclear DNA is linear,mitochondrial DNA are circular. 
D) They cannot be distinguished and must be clearly separate during purifcation. 
A) Mitochondrial DNA is in the Z conformation,nuclear DNA is in the B conformation. 
B) Mitochondrial DNA is methylated,nuclear DNA is not. 
C) Nuclear DNA is linear,mitochondrial DNA are circular. 
D) They cannot be distinguished and must be clearly separate during purifcation.

Exam 19: Nucleic Acids

As B-DNA is gradually heated,the absorbance at 260 nm

The 30 nm fibers of a chromosome are attached to a(n)________ scaffold that holds the fibers in large loops.

Which enzyme would be least useful for recombination experiments that introduce new fragments of DNA into an existing DNA molecule?

Stem-loop structures in RNA resemble the ________ form of double-helical DNA.

What is the function of DNA topoisomerases?

Which type of RNA is the most abundant in living cells (by percent)?

All five histones are rich in ________ amino acid residues whose positive charges allow binding to the sugar-phosphate backbone of DNA.

Deoxyribonucleosides and ribonucleotides contain two hydroxyl groups that can be phosphorylated.

The abbreviation pppT indicates

Which best describes the structure of a nucleosome core particle?

Histone ________ is not part of the histone octamer,but binds to linker DNA and is responsible for higher-order chromatin structure.

"Five prime to three prime" description of a DNA strand refers to

Changes in the topology and three-dimensional shape of B-DNA can result from

When stretched,strands of poly (dT)give no resistance until it is in the fully extended form because it is wound in a tight helical form.

For DNA,a plot of the change in absorbance versus temperature would be ________,which indicates ________.

Topoisomerases cut one or both coiled DNA strands,wind the ends by rotation,and then rejoin the cut ends.

Which recognition sequence is not a palindrome? (DNA sequences are shown in the standard 5'→3' direction)

Absorption of single-stranded DNA at 260 nm is less than that of double-stranded DNA.

Which statement is not true about histones?

How might mitochondrial DNA be distinguished from eukaryotic nuclear DNA?

Introduction to Biochemistry

Water

Amino Acids and the Primary Structures of Proteins

Proteins: Three-Dimensional Structure and Function

Properties of Enzymes

Mechanisms of Enzymes

Coenzymes and Vitamins

Carbohydrates

Lipids and Membranes

Introduction to Metabolism

Glycolysis

Gluconeogenesis, the Pentose Phosphate Pathway, and Glycogen Metabolism

The Citric Acid Cycle

Electron Transport and Atp Synthesis

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

DNA Replication, repair, and Recombination

Transcription and RNA Processing

Protein Synthesis

Filters

For DNA,a plot of the change in absorbance versus temperature would be ,which indicates .