Genetic Information Experiments: Avery to RNA

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Questions and Answers

What did Griffith suggest was necessary for capsule synthesis in his transformation experiments?

A compound involved in muscle development

Protein molecules

Deoxyribose nucleic acid (correct)

Living bacterial cells

What did the experiments by Avery, MacLeod, and McCarty reveal about DNA?

It is only found in animal cells.

It is less important than proteins in heredity.

It can be synthesized from RNA.

It serves as the primary carrier of genetic information. (correct)

In the Hershey and Chase experiment, what isotopes were used to label DNA and proteins?

H2 and O18

P32 and S35 (correct)

N14 and C12

C14 and N15

What conclusion was drawn from the Hershey and Chase experiment regarding phage DNA?

It entered the bacteria and directed new phage production. Signup and view all the answers

Which statement accurately describes the role of RNA in certain viruses?

Purified RNA can induce symptoms of infection in certain plants. Signup and view all the answers

What did Hershey and Chase use as evidence to support that DNA, not proteins, was the genetic material?

Only P32 labeled DNA entered the bacteria. Signup and view all the answers

What constitutes the central part of some viruses as opposed to others?

Either RNA or DNA Signup and view all the answers

What characteristic reveals the function of RNA from the tobacco mosaic virus?

It induces specific lesions when introduced to host plants. Signup and view all the answers

What is the primary structural feature of DNA as proposed by Watson and Crick?

Double helix Signup and view all the answers

In the DNA structure, what does it mean for the two chains to be antiparallel?

The chains run in opposite directions Signup and view all the answers

Which nitrogenous base pairs with adenine (A) in DNA?

Thymine (T) Signup and view all the answers

What is the spacing between the nitrogenous bases in the DNA structure?

0.34 nm Signup and view all the answers

What sugar is present in RNA as opposed to DNA?

Ribose Signup and view all the answers

Which types of RNA are directly involved in protein synthesis?

rRNA and tRNA Signup and view all the answers

Which of the following RNA molecules serves as a structural component of the ribosome?

rRNA Signup and view all the answers

What role do small nuclear RNAs (snRNAs) play in mRNA processing?

Splicing Signup and view all the answers

What is the primary electrical charge of nucleic acids due to?

Phosphate groups Signup and view all the answers

At what wavelength do nucleic acids absorb UV light most effectively?

260 nm Signup and view all the answers

Which pairing of nucleobases is more stable due to additional hydrogen bonding?

G=C Signup and view all the answers

What is required for in vitro DNA synthesis according to Kornberg's experiments?

DNA polymerase I and dNTPs Signup and view all the answers

In which direction does DNA synthesis occur during replication?

5‘ to 3’ Signup and view all the answers

What happens to DNA strands during denaturation?

Their hydrogen bonds are broken Signup and view all the answers

What does the renaturation process allow for after DNA denaturation?

Re-association of complementary strands Signup and view all the answers

What provides the energy for the nucleotides to be added to the growing DNA strand during replication?

Release of inorganic pyrophosphate Signup and view all the answers

What characterizes semi-conservative replication?

Each replicated DNA molecule consists of one parental strand and one new strand. Signup and view all the answers

What was the main finding of the Meselson-Stahl experiment regarding DNA replication?

DNA replication is semi-conservative. Signup and view all the answers

What happens to the density of newly synthesized DNA when E. coli is transferred from a medium with 15N to one with 14N?

After one generation, an intermediate density band appears. Signup and view all the answers

How many origins of replication are found in E. coli?

One, located at oriC. Signup and view all the answers

In prokaryotic DNA replication, what initiates DNA duplication?

A replication protein binding to oriC. Signup and view all the answers

During which stage of DNA replication do its two strands separate?

At the origin of replication. Signup and view all the answers

Which characteristic is true of the replication process in bacteria?

Replication is bidirectional. Signup and view all the answers

In conservative replication, what happens to the original DNA strands?

They remain unaltered and separate from newly synthesized strands. Signup and view all the answers

What role does single-stranded binding protein play in DNA replication?

It stabilizes single-stranded DNA. Signup and view all the answers

What is the primary function of topoisomerase during DNA replication?

To correct supercoiling of DNA strands. Signup and view all the answers

How does DNA pol I contribute to DNA replication?

It replaces RNA primers with DNA. Signup and view all the answers

What is the main responsibility of DNA pol III during DNA replication?

To proofread newly synthesized DNA. Signup and view all the answers

What is the role of primase in DNA replication?

To synthesize a single RNA primer. Signup and view all the answers

Which of the following statements is false regarding DNA pol II?

It participates in DNA replication. Signup and view all the answers

What is the purpose of exonuclease activity in DNA polymerases?

To remove incorrect nucleotides. Signup and view all the answers

Which enzyme is responsible for linking Okazaki fragments?

DNA ligase Signup and view all the answers

Study Notes

Griffith's Transformation Experiments

Griffith proposed that a transforming principle, later identified as DNA, was necessary for capsule synthesis in bacteria.
He observed that heat-killed virulent bacteria could transfer their virulence to live non-virulent bacteria.

Avery, MacLeod, and McCarty's Experiments

They identified DNA as the transforming principle.
They demonstrated that DNA, not protein, was responsible for transferring genetic information.

Hershey and Chase Experiment

They used radioactive isotopes to label DNA (³²P) and proteins (³⁵S) in bacteriophages.
They determined that DNA, not protein, entered the bacterial cells during phage infection.

Hershey and Chase Conclusion

Phage DNA, not protein, contains the genetic information required for the production of new phages.

Role of RNA in Certain Viruses

Some viruses use RNA instead of DNA as their genetic material.
These viruses can directly use their RNA to produce proteins, bypassing the need for DNA.

Evidence Used by Hershey and Chase

The ³²P labeled DNA was found inside the bacterial cells, while the ³⁵S labeled protein remained outside.

Central Part of Viruses

Some viruses contain a central core of DNA, while others contain RNA.

Tobacco Mosaic Virus

The RNA of the tobacco mosaic virus acts as the genetic material.
Its function is revealed by its ability to direct the synthesis of viral proteins.

DNA Structure

Watson and Crick proposed the double helix structure of DNA.
It consists of two antiparallel strands of nucleotides linked by hydrogen bonds.

Antiparallel Chains

The two chains of DNA run in opposite directions (5' to 3' and 3' to 5').
This arrangement allows for proper base pairing.

Base Pairing

Adenine (A) pairs with thymine (T) via two hydrogen bonds.
Guanine (G) pairs with cytosine (C) via three hydrogen bonds.

Spacing Between Bases

The nitrogenous bases in DNA are spaced 0.34 nm apart.

RNA Sugar

RNA contains ribose sugar, while DNA contains deoxyribose sugar.

RNA Involved in Protein Synthesis

Messenger RNA (mRNA) carries genetic information from DNA to ribosomes.
Transfer RNA (tRNA) delivers amino acids to the ribosomes for protein synthesis.
Ribosomal RNA (rRNA) combines with proteins to form ribosomes.

Role of snRNAs

They participate in the processing of mRNA, including splicing and capping.

Electrical Charge of Nucleic Acids

Nucleic acids have a negative charge due to the phosphate groups in their backbone.

UV Light Absorption

Nucleic acids absorb UV light most effectively at 260 nm.

Stable Base Pairing

Guanine (G) and Cytosine (C) pairing is more stable due to three hydrogen bonds.

In Vitro DNA Synthesis

Kornberg's experiments revealed the requirements for in vitro DNA synthesis:
DNA polymerase, a template DNA strand, deoxynucleoside triphosphates (dNTPs), and magnesium ions (Mg²⁺).

Direction of DNA Synthesis

DNA synthesis occurs in the 5' to 3' direction.
New nucleotides are added to the 3' end of the growing strand.

Denaturation

During denaturation, the hydrogen bonds between DNA strands break.
The double helix separates into two single strands.

Renaturation

Renaturation allows for the reassociation of complementary DNA strands after denaturation.

Energy for DNA Synthesis

The energy for nucleotide addition comes from the hydrolysis of the high-energy phosphate bonds in dNTPs.

Semi-Conservative Replication

Each new DNA molecule contains one original strand and one newly synthesized strand.

Meselson-Stahl Experiment

It confirmed the semi-conservative mode of DNA replication.
They showed that after one round of replication, DNA molecules have an intermediate density.

Density of Newly Synthesized DNA

When E.coli is transferred from a medium with ¹⁵N to one with ¹⁴N, the density of newly synthesized DNA decreases.

E. coli Origins of Replication

E.coli has one origin of replication (oriC).

Initiation of Prokaryotic DNA Duplication

The origin of replication (oriC) is recognized by specific proteins that initiate DNA duplication.

Strand Separation

The two strands of DNA separate during the initiation stage of replication.

Bacterial Replication

Bacterial DNA replication is bidirectional, meaning it proceeds in both directions from the origin of replication.

Conservative Replication

In conservative replication, the original DNA strands remain together, and two completely new strands are synthesized.

Single-Stranded Binding Protein

It binds to single-stranded DNA during replication, preventing them from re-annealing.

Topoisomerase

It relieves the tension ahead of the replication fork by cutting and rejoining DNA strands.

DNA Pol I

It removes RNA primers and replaces them with DNA nucleotides.
It also has a 3' to 5' exonuclease activity for proofreading.

DNA Pol III

It is the primary enzyme responsible for synthesizing new DNA strands.
It has a 5' to 3' polymerase activity and a 3' to 5' exonuclease activity.

Primase

It synthesizes short RNA primers that provide a starting point for DNA polymerase.

DNA Pol II

It is involved in DNA repair, not replication.

Exonuclease Activity

Exonuclease activity in DNA polymerases allows for the removal of incorrectly incorporated nucleotides.

Linking Okazaki Fragments

DNA ligase joins the Okazaki fragments together on the lagging strand.

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Description

Explore key experiments that established DNA and RNA as carriers of genetic information. This quiz covers the Avery, MacLeod, and McCarty experiment as well as the Hershey and Chase experiment, alongside the role of RNA in viral genetics. Test your understanding of these foundational concepts in molecular biology.