Biochem 8.2 Untitled Quiz

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Questions and Answers

What is the primary structure that forms the backbone of nucleic acids?

Fatty acid chains

Sugars linked to phosphates (correct)

Steroid rings

Amino acid sequences

What role do histone proteins play in relation to DNA?

They negatively charge DNA strands

They neutralize and store negatively charged DNA (correct)

They help synthesize RNA

They facilitate nucleotide modifications

Which enzyme is responsible for synthesizing RNA?

RNA polymerase (correct)

DNA polymerase

Reverse transcriptase

RNA ligase

What is the first nucleotide in a growing nucleic acid strand incorporated into the chain?

The nucleotide at the 5' end Signup and view all the answers

What mechanism is employed by some DNA polymerases to correct nucleotide errors?

3'-5' exonuclease activity Signup and view all the answers

What is the consequence of deamination in nitrogenous bases?

It removes the nitrogenous base from the sugar Signup and view all the answers

What type of bond do exonucleases hydrolyze to remove nucleotides?

Phosphodiester bonds at the ends Signup and view all the answers

Which occurs when a nucleic acid grows?

The 3' end attacks the 5' end of the next nucleotide Signup and view all the answers

What role do pi interactions play in the structure of DNA?

They stabilize the specific DNA conformation. Signup and view all the answers

Which of the following is true about RNA's structure during transcription?

RNA temporarily pairs with the DNA template strand. Signup and view all the answers

What characterizes the helical structure formed by RNA folding on itself?

It involves hydrogen bonding between complementary bases. Signup and view all the answers

Which of the following accurately describes the representation of tRNA structures?

2D structures depict complementary base pairing clearly. Signup and view all the answers

What do Chargaff’s rules specify regarding the composition of DNA?

The number of guanine bases equals the number of cytosine bases. Signup and view all the answers

Which statement is true regarding RNA's biological functions?

RNA can fold into complex three-dimensional shapes. Signup and view all the answers

How are the phosphodiester bonds represented in RNA structures?

As solid lines between adjacent nucleotides. Signup and view all the answers

In which conformation do bases in a DNA double helix primarily reside?

Stacked almost on top of each other. Signup and view all the answers

What is the pairing rule for purines and pyrimidines in DNA?

Every purine is paired with a pyrimidine. Signup and view all the answers

Chargaff's rules apply to which type of nucleic acid structure?

Double-stranded DNA only. Signup and view all the answers

If a double-stranded DNA molecule contains 200 base pairs and 97 guanine bases, how many thymine bases are present?

103 Signup and view all the answers

Which statement is true regarding base pairing within RNA?

Guanine pairs with uracil in RNA. Signup and view all the answers

What environmental condition can disrupt the stability of nucleic acid secondary structures?

Extreme pH levels. Signup and view all the answers

In a DNA-RNA complex, how do the bases pair when adenine is present?

Adenine pairs with uracil in RNA. Signup and view all the answers

What is the optimal pH for DNA annealing?

Near 7.4. Signup and view all the answers

What occurs during wobble pairing in tRNA?

Some bases pair differently than expected. Signup and view all the answers

What type of bond is formed during nucleotide polymerization?

Phosphodiester bond Signup and view all the answers

Which group of the nucleotide reacts with the phosphate group of another nucleotide?

3' hydroxyl group Signup and view all the answers

Which of the following correctly describes nucleoside triphosphate (NTP) in nucleotide polymerization?

NTPs serve as the building blocks for nucleic acid synthesis. Signup and view all the answers

What is released during the condensation reaction in nucleotide polymerization?

Pyrophosphate Signup and view all the answers

What is the sequence of a nucleic acid traditionally written from?

5' end to 3' end Signup and view all the answers

How is a dinucleotide formed?

By linking two nucleotides via a phosphodiester bond Signup and view all the answers

What term is used to describe nucleic acids that contain a few nucleotides?

Oligonucleotides Signup and view all the answers

What is the significance of the carbon numbering system in nucleotides?

It is essential for understanding the structure of nucleic acids. Signup and view all the answers

What is the function of DNA ligase in nucleotide repair?

To provide the energy needed to repair the nick Signup and view all the answers

What is the primary structure of a nucleic acid composed of?

The arrangement of nucleotides Signup and view all the answers

Which base pairing occurs in DNA?

Adenine pairs with Thymine Signup and view all the answers

What structural feature contributes to the stability of the DNA double helix?

Hydrogen bonding between complementary bases Signup and view all the answers

What is meant by the term 'antiparallel orientation' of DNA strands?

One strand runs 5' to 3' while the other runs 3' to 5' Signup and view all the answers

What role does the hydrophobic effect play in the structure of DNA?

It helps stabilize the double helix structure Signup and view all the answers

What occurs if there is a single mismatch in base pairing during DNA annealing?

It can significantly reduce the favorability of annealing Signup and view all the answers

Which of the following accurately describes complementary bases in DNA?

Each base pair consists of one purine and one pyrimidine Signup and view all the answers

How does a change in pH affect the functional groups in bases?

It can lead to protonation or deprotonation of functional groups. Signup and view all the answers

What role do histones play in eukaryotic DNA structure?

They interact with negatively charged phosphate groups to stabilize DNA. Signup and view all the answers

Which factor has the greatest impact on the melting temperature (Tm) of a double helix?

The length of the helix and its GC content. Signup and view all the answers

What occurs to the strands of a double helix when subjected to higher temperatures?

The strands denature and come apart. Signup and view all the answers

What is the significance of GC content in a double helix?

Higher GC content results in a higher melting temperature due to more hydrogen bonds. Signup and view all the answers

What is the melting temperature (Tm) in the context of DNA?

The temperature at which 50% of the double helices denature. Signup and view all the answers

How do salts influence DNA stability?

They stabilize the phosphate groups through cation interaction. Signup and view all the answers

In the context of PCR, what is manipulated to optimize the melting temperature?

The GC content and salt conditions. Signup and view all the answers

Study Notes

Nucleic Acid Formation

Nucleic acids are polymers formed from nucleotides
DNA and RNA are two types of nucleic acids
Nucleotides are composed of a sugar, a phosphate group, and a nitrogenous base
The carbons in the sugar component are numbered using a prime symbol (')
Nucleic acids form when the 3' hydroxyl group of one nucleotide reacts with the 5' phosphate group of another
This forms a phosphodiester bond, linking the nucleotides
The reaction is a condensation reaction, where pyrophosphate (PP) is released instead of water
The 5' end of a nucleic acid has a free phosphate group
The 3' end has a free hydroxyl group
Nucleic acid sequences are written in the 5' to 3' direction

Base Pairing and Secondary Structure

The sequence of nucleotides is the primary structure of a nucleic acid
Nucleic acids can form secondary structures, such as the double helix in DNA
In DNA, two strands twist around each other forming a double helix structure
The strands are anti-parallel, meaning the 3' end of one strand aligns with the 5' end of the other
Hydrogen bonds between complementary bases (A-T and G-C) hold the two strands together
This gives complementary bases
Base pairing in nucleic acids follows Chargaff's rules:
- The number of adenine bases equals the number of thymine bases
- The number of guanine bases equals the number of cytosine bases
- The sum of purines equals the sum of pyrimidines
These rules only apply to double-stranded nucleic acids

Double Helix Stability

Nucleic acid secondary structure can be disrupted by environmental factors (pH, salt, temperature)
Optimal pH for DNA annealing is near 7.4
Higher temperatures cause the hydrogen bonds holding the helix together to break, causing denaturation
Melting temperature (Tm) is the temperature at which 50% of the double helices in a solution denature
Higher GC content results in a higher melting temperature (Tm)
The melting curve's sigmoidal shape indicates cooperative denaturation, where separation of portions of the helix becomes easier as more portions separate

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