Nucleic Acids

Question 1

What are the two types of nucleic acids?

Answer 1

• DNA (Deoxyribonucleic acid)
• RNA (Ribonucleic acid)

Both are important information-carrying molecules in living cells.

Question 2

What is the primary role of DNA in living cells?

Answer 2

Holds genetic information

DNA is essential for storing and transmitting genetic information.

Question 3

What is the primary role of RNA in living cells?

Answer 3

Transfers genetic information from DNA to ribosomes

RNA plays a crucial role in protein synthesis.

Question 4

What are the three components of a nucleotide?

Answer 4

• Pentose (five carbon sugar)
• Nitrogen-containing organic base (nitrogenous base)
• Phosphate group (phosphoric acid)

Nucleotides are the building blocks of nucleic acids.

Question 5

Who discovered the structure of DNA?

Answer 5

Watson and Crick

Their discovery revealed the double helix structure of DNA.

Question 6

What is the structure of DNA composed of?

Answer 6

• Two polynucleotide strands
• Hydrogen bonding
• Double helix

The double helix structure is crucial for DNA’s function.

Question 7

What sugar is found in DNA nucleotides?

Answer 7

Deoxyribose

This sugar differentiates DNA from RNA, which contains ribose.

Question 8

What are the four nitrogen-containing bases in DNA?

Answer 8

• Cytosine
• Thymine
• Adenine
• Guanine

These bases are essential for the genetic coding in DNA.

Question 9

What type of bond joins nucleotides within each strand of DNA?

Answer 9

Phosphodiester bonds

These bonds are formed during condensation reactions.

Question 10

What forms the backbone of the polynucleotide strands in DNA?

Answer 10

• Sugar
• Phosphate

The backbone provides structural support to the DNA molecule.

Question 11

What is the complementary base pairing in DNA?

Answer 11

• Adenine pairs with Thymine
• Guanine pairs with Cytosine

This pairing is crucial for DNA replication and function.

Question 12

What is a gene?

Answer 12

A section of a chromosome that codes for a sequence

Genes are the basic units of heredity.

Question 13

What is a homologous pair of chromosomes?

Answer 13

Chromosomes that have the same genes at the same location

Homologous chromosomes are important for genetic diversity.

Question 14

What is the structure of DNA in relation to histone proteins?

Answer 14

DNA is wrapped around histone proteins

This wrapping helps in the compaction and organization of DNA within the nucleus.

Question 15

What type of bonds join the bases in DNA?

Answer 15

Hydrogen bonds

Although individually weak, their large number maintains a stable structure.

Question 16

What structure is formed by the coiling of the DNA helix?

Answer 16

Super helix

This provides a compact store of genetic information.

Question 17

What are the backbones of DNA composed of?

Answer 17

Sugar-phosphate

These backbones support the structure of DNA.

Question 18

What is the relationship between the two DNA strands?

Answer 18

Anti-parallel

This orientation is crucial for replication and function.

Question 19

If DNA has 30% of organic bases which are adenine, what is the percentage of guanine present?

Answer 19

20%

This is based on the complementary base pairing rules (A-T, G-C).

Question 20

If DNA has 28% of organic bases which are thymine, what is the percentage of cytosine present?

Answer 20

22%

This follows the complementary base pairing rules.

Question 21

What are genes in the context of DNA?

Answer 21

Sections of DNA that contain coded information

They code for polypeptides that determine the nature and development of organisms.

Question 22

What essential ability does DNA have that is crucial for cell division?

Answer 22

Self-replicate

This ability is due to complementary base pairing.

Question 23

What can occur in DNA that provides genetic diversity?

Answer 23

Mutations

These alterations in the base sequence can lead to variation and are the basis for evolution.

Question 24

What type of DNA do prokaryotes have?

Answer 24

Circular

Unlike eukaryotes, which have linear DNA organized in chromosomes.

Question 25

What do genes code for that determines **inherited phenotype**?

Answer 25

Polypeptides ## Footnote These are the building blocks of proteins that influence traits.

Question 26

What is the **sugar-phosphate backbone** in DNA?

Answer 26

A structural component that supports the DNA molecule ## Footnote It forms the sides of the DNA ladder.

Question 27

What structural feature of DNA allows it to be a **helix**?

Answer 27

The arrangement of the sugar-phosphate backbone and base pairs ## Footnote This helical structure is crucial for DNA's stability.

Question 28

DNA is described as being **double stranded**. What does this mean?

Answer 28

It consists of two complementary strands that run in opposite directions ## Footnote This structure is essential for replication and stability.

Question 29

What does the term **large molecule** refer to in the context of DNA?

Answer 29

DNA is a macromolecule composed of many nucleotides ## Footnote This allows it to store a significant amount of genetic information.

Question 30

What role do **many hydrogen bonds** play in DNA?

Answer 30

They provide stability and strength to the DNA structure ## Footnote These bonds are crucial for holding the two strands together.

Question 31

What is the significance of the **sequence of bases** in DNA?

Answer 31

It codes for specific sequences of amino acids in proteins ## Footnote This sequence determines the genetic information carried by the DNA.

Question 32

What is meant by **complementary base-pairing** in DNA?

Answer 32

Adenine pairs with Thymine, and Guanine pairs with Cytosine ## Footnote This pairing is essential for accurate replication and transcription.

Question 33

How does the structure of DNA **protect the sequence of bases**?

Answer 33

The helical structure shields the bases from damage ## Footnote This protection is vital for maintaining genetic integrity.

Question 34

What is the function of each strand of DNA during **replication**?

Answer 34

Each strand serves as a template for the formation of a new complementary strand ## Footnote This ensures accurate duplication of genetic information.

Question 35

How does DNA's structure contribute to its **stability**?

Answer 35

The double helix and hydrogen bonds provide structural integrity ## Footnote This stability is crucial for the long-term storage of genetic information.

Question 36

What allows DNA to store a **large amount of information**?

Answer 36

The sequence of bases along the DNA strands ## Footnote This sequence encodes the genetic instructions for an organism.

Question 37

Why are **individual hydrogen bonds** described as weak in DNA?

Answer 37

They allow the helix to unzip easily for replication ## Footnote This property is essential for the process of DNA replication.

Question 38

What does DNA code for in terms of **polypeptides**?

Answer 38

Specific sequences of amino acids ## Footnote This coding is fundamental for protein synthesis.

Question 39

How does DNA enable **accurate replication** of information?

Answer 39

Through complementary base-pairing and the template mechanism ## Footnote This ensures that genetic information is faithfully copied.

Question 40

What is the structure of **RNA** compared to DNA?

Answer 40

RNA is a relatively short polynucleotide molecule ## Footnote It differs in several key structural aspects from DNA.

Question 41

What is the pentose sugar found in RNA?

Answer 41

Ribose ## Footnote This differs from the deoxyribose found in DNA.

Question 42

Which organic base in RNA replaces **Thymine** found in DNA?

Answer 42

Uracil ## Footnote The four bases in RNA are Adenine, Guanine, Cytosine, and Uracil.

Question 43

How do mRNA and tRNA differ from DNA in terms of structure?

Answer 43

They are single stranded ## Footnote This contrasts with the double-stranded structure of DNA.

Question 44

What is the **role of DNA replication**?

Answer 44

Growth and reproduction of organisms ## Footnote DNA replication occurs during the process of cell division.

Question 45

What enzyme breaks the hydrogen bonds during **DNA replication**?

Answer 45

DNA helicase ## Footnote This enzyme separates the two polynucleotide strands.

Question 46

In DNA replication, each strand acts as a **template** for the formation of what?

Answer 46

Two new complementary strands ## Footnote This process does not require an enzyme.

Question 47

What pairs with **Adenine** during DNA replication?

Answer 47

Thymine ## Footnote This is part of the specific complementary base pairing.

Question 48

What pairs with **Cytosine** during DNA replication?

Answer 48

Guanine ## Footnote This is part of the specific complementary base pairing.

Question 49

What type of bonds are formed between DNA nucleotides in new strands?

Answer 49

Phosphodiester bonds ## Footnote These bonds are formed in condensation reactions catalyzed by DNA polymerase.

Question 50

What is the term used to describe the replication process where each new DNA molecule contains one original strand?

Answer 50

Semi-conservative replication ## Footnote This means each new DNA molecule is identical to the original.

Question 51

Who demonstrated that DNA replication is **semi-conservative**?

Answer 51

Meselson and Stahl ## Footnote They conducted experiments using isotopes to show how DNA is replicated.

Question 52

What isotope was used to grow **E. coli** in the initial phase of the experiment?

Answer 52

15N ## Footnote The heavy isotope was used to ensure incorporation into the DNA.

Question 53

What was the normal isotope used after transferring the bacteria to a new medium?

Answer 53

14N ## Footnote This allowed observation of the transition in DNA weight after replication.

Question 54

What method was used to analyze the DNA after each division of the bacteria?

Answer 54

Centrifugation ## Footnote This technique separates DNA based on density, allowing differentiation between isotopes.

Question 55

Fill in the blank: DNA containing the heavy isotope **15N** is slightly ______ than DNA containing the normal isotope **14N**.

Answer 55

heavier ## Footnote This difference in weight is crucial for the centrifugation analysis.

Question 56

What was the purpose of allowing the **E. coli** to divide after being transferred to the medium with **14N**?

Answer 56

To observe the incorporation of the normal isotope into the DNA ## Footnote This step was essential to demonstrate the semi-conservative nature of replication.