Molecular Biology Quiz on DNA and RNA
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Questions and Answers

What is a primary distinguishing feature of RNA polymerase compared to DNA polymerase?

  • It only functions in the presence of free nucleotides.
  • It requires a primer to start synthesizing nucleotides.
  • It can initiate a new nucleotide chain without an existing end. (correct)
  • It synthesizes DNA rather than RNA.

Which DNA polymerase is primarily responsible for elongating the DNA strand during replication?

  • DNA polymerase V
  • DNA polymerase I
  • DNA polymerase III (correct)
  • DNA polymerase II

In which direction must DNA synthesis proceed?

  • 3’ to 5’ direction
  • 5’ to 3’ direction (correct)
  • 3’ to 3’ direction
  • 5’ to 5’ direction

What role does DNA polymerase I (DNAP I) play during DNA replication?

<p>It replaces the RNA primer with DNA. (C)</p> Signup and view all the answers

What happens to the last two phosphate groups during the addition of a nucleotide by DNA polymerase?

<p>They are hydrolyzed to form monophosphate. (A)</p> Signup and view all the answers

What conclusion did Avery, McCarty, and MacLeod reach regarding the transformation of bacteria?

<p>Only DNA from the S strain caused transformation. (D)</p> Signup and view all the answers

Which radioactive materials were used by Hershey and Chase to identify genetic material in viruses?

<p>Radioactive phosphorus and sulfur. (C)</p> Signup and view all the answers

What was demonstrated by centrifuging the mixtures in the Hershey-Chase experiment?

<p>Radioactive DNA was present in the bacterial pellet. (A)</p> Signup and view all the answers

What was the primary question driving the Hershey-Chase experiment?

<p>Which viral component reprograms the host cell? (D)</p> Signup and view all the answers

What method was used to determine if DNA was the heritable material?

<p>Analyzing the composition of the supernatant after centrifugation. (B)</p> Signup and view all the answers

What is the primary function of telomeres?

<p>To protect chromosomes from erosion (A)</p> Signup and view all the answers

What enzyme is responsible for adding telomeres to chromosomes?

<p>Telomerase (D)</p> Signup and view all the answers

How do prokaryotes avoid the problem of DNA shortening during replication?

<p>By employing circular DNA (C)</p> Signup and view all the answers

In which types of cells is telomerase activity typically found?

<p>Germ line cells (A)</p> Signup and view all the answers

What sequence is commonly repeated in human telomeres?

<p>TTAGGG (D)</p> Signup and view all the answers

At what approximate length do human telomeres generally lead to death from old age?

<p>5,000 bases (C)</p> Signup and view all the answers

What is the role of telomerase in germ line cells?

<p>Adding telomeres to chromosomes (D)</p> Signup and view all the answers

What happens to telomere length in humans from conception to adulthood?

<p>Decreases progressively (A)</p> Signup and view all the answers

What happens to somatic cells that lack telomerase?

<p>They age and have a finite lifespan (C)</p> Signup and view all the answers

Which of the following describes the process of reverse transcription in telomerase?

<p>Synthesis of DNA using RNA as a template (B)</p> Signup and view all the answers

What effect does aging have on the rate of telomere shortening?

<p>The rate initially decreases then may increase in advanced age (D)</p> Signup and view all the answers

What is the significance of the RNA component in human telomerase?

<p>It acts as a template for DNA synthesis (B)</p> Signup and view all the answers

What is the telomere length at birth in humans?

<p>10,000 bases (C)</p> Signup and view all the answers

What is a characteristic of telomeres in eukaryotic chromosomes?

<p>They consist of noncoding DNA (C)</p> Signup and view all the answers

What sequence does telomerase use to synthesize a complementary DNA strand?

<p>TTAGGG (C)</p> Signup and view all the answers

What may explain the finite lifespan of most cells?

<p>Loss of telomeres in cell division (C)</p> Signup and view all the answers

What role does telomerase play in germ line cells?

<p>It prevents the shortening of telomeres during DNA replication. (C)</p> Signup and view all the answers

Why might Dolly the sheep not have lived as long as typical newborns?

<p>Dolly's telomeres were the same length as the adult sheep from which she was cloned. (C)</p> Signup and view all the answers

What is a characteristic of cancer cells that requires them to have telomerase activity?

<p>They replicate infinitely without undergoing senescence. (A)</p> Signup and view all the answers

What is one reason why telomerase is not present in most somatic cells?

<p>It is unnecessary for the normal functioning of these cells. (C)</p> Signup and view all the answers

Which enzyme is primarily responsible for DNA replication in the cells mentioned?

<p>DNA polymerase III (D)</p> Signup and view all the answers

What did Friedrich Miescher discover in 1869?

<p>A substance he called nuclein, which is now known to be DNA. (C)</p> Signup and view all the answers

Why was there a debate over whether DNA or protein was the most important hereditary molecule in the early 20th century?

<p>Proteins were known to have clear functions and vast combinations. (B)</p> Signup and view all the answers

What is the primary function of telomerase in relation to DNA strands?

<p>To add nucleotide sequences to the ends of chromosomes. (A)</p> Signup and view all the answers

What does Phoebus Levene's Tetranucleotide hypothesis suggest about the sequence of bases in DNA?

<p>All bases are present in equal ratios. (B)</p> Signup and view all the answers

What was one of the key findings by Erwin Chargaff regarding base ratios in DNA?

<p>A = T and C = G. (A)</p> Signup and view all the answers

Which structural model was proposed by Linus Pauling regarding DNA?

<p>Triple helix structure with three intertwined strands. (C)</p> Signup and view all the answers

What technique did Rosalind Franklin & Maurice Wilkins use to determine the structure of DNA?

<p>X-ray diffraction. (D)</p> Signup and view all the answers

What error was identified in Linus Pauling's model of DNA?

<p>Phosphates were shown as negatively charged. (D)</p> Signup and view all the answers

How does X-ray crystallography help in determining the structure of molecules?

<p>By analyzing the diffraction pattern of bombarded X-rays. (B)</p> Signup and view all the answers

Who correctly determined that DNA is made up of chains of nucleotides?

<p>Phoebus Levene. (A)</p> Signup and view all the answers

What distinct feature was highlighted in Chargaff's observations of DNA?

<p>There is a specific ratio between purines and pyrimidines. (B)</p> Signup and view all the answers

Flashcards

RNA Polymerase vs. DNA Polymerase

RNA polymerase can begin a new chain with only a template, while DNA polymerase needs an existing chain's end (3' OH) to add nucleotides.

DNA Polymerase Action

DNA polymerase III (DNAP III) adds nucleotides in a 5' to 3' direction to an existing nucleotide chain, using the template strand as a guide.

DNA Polymerase I role

DNA polymerase I (DNAP I) replaces RNA primers with DNA during DNA replication.

DNA Replication Directionality

DNA synthesis always occurs in the 5' to 3' direction, meaning nucleotides can only be added to the 3' end of the chain.

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Antiparallel DNA Strands

The two DNA strands run in opposite directions (antiparallel) and cause complexities of DNA synthesis at the replication fork.

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Telomeres

Protective DNA sequences at the ends of eukaryotic chromosomes that prevent them from eroding during DNA replication.

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Telomere Shortening

The gradual decrease in the length of telomeres with each cell division.

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Eukaryotic Chromosomes

Chromosomes found in cells with a nucleus (like animal and plant cells)

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Telomere Function

Protect chromosomes from deterioration and to maintain chromosome integrity.

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Telomere Length and Aging

Telomere shortening as a potential mechanism driving processes associated with aging.

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Linear DNA

DNA that has two ends, unlike circular DNA.

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TTAGGG

Short, repeating DNA sequence found in human telomeres

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Circular DNA

DNA that is a closed loop, like a ring; found in prokaryotes (bacteria).

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Telomere

Protective caps at the ends of chromosomes that prevent them from being damaged or fused together.

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Telomerase

An enzyme that adds telomeres to chromosomes, maintaining their length.

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Telomerase's role

Maintains chromosome length by adding DNA sequences to the ends of chromosomes.

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Telomeres in germ line cells

Telomeres are added to germ line cells (cells that produce sex cells) before conception.

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Limiting lifespan (human cells)

Most somatic (non-sex) cells lose telomeres with divisions, limiting their lifespan.

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Telomerase in cancer cells

Cancer cells often have active telomerase, allowing them to divide indefinitely.

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Reverse transcriptase

Enzymatic activity within the telomerase to synthesise DNA from an RNA template.

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Ribonucleoprotein

A complex consisting of RNA and protein, which is the structure of telomerase.

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Avery, McCarty, MacLeod Experiment

Determined that DNA, not protein, is the genetic material by using purified DNA from S strain pneumonia bacteria, successfully transforming R strain bacteria into S strain bacteria.

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Hershey-Chase Experiment

Confirmed DNA as the genetic material by using bacteriophages (viruses that infect bacteria) with radioactive sulfur (labels protein) and phosphorus (labels DNA).

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Transforming Principle

The molecule responsible for genetic change in Griffith's experiment, later identified as DNA.

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Bacteriophage

A virus that infects bacteria; composed of DNA and protein, used in Hershey-Chase experiment.

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Radioactive Labeling

Technique used to identify components (e.g., DNA or protein) in the Hershey-Chase experiment.

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Telomere Function in Germ Line Cells

Germ line cells (sperm/egg) need telomerase to maintain telomere length for stable chromosome inheritance across generations.

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Telomerase Role in DNA Replication

Telomerase extends the 3' end of the template strand during DNA replication to prevent DNA loss.

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Telomere Shortening and Aging

Telomere shortening with cell division is linked to cellular aging, reduced cell division, and/or potential diseases.

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Telomere Length in Dolly

Dolly, the cloned sheep, had telomeres the length of the adult donor cell, not a newborn, influencing her shortened lifespan.

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Reason for Telomerase in Germ Line Cells

Maintaining telomere length in germ line cells avoids losing genetic information during cell division, crucial for passing traits down through generations.

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Cancer Telomere Length

Most cancer cells have active telomerase to maintain telomere length, allowing them to divide indefinitely and potentially leading to uncontrolled growth.

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Telomerase and Cancer Cell Formation

Adding telomerase to a normal cell alone will not make it cancerous, as other factors are required for carcinogenesis.

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Miescher's Nuclein Discovery

Miescher isolated nuclein, a substance later identified as DNA, from white blood cell nuclei.

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Protein coat (viral)

The protein shell that encloses a virus's genetic material (DNA or RNA).

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DNA structure

The arrangement of atoms within the DNA molecule; a double helix.

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Levene's tetranucleotide model

DNA contains a repeating of four bases (e.g. AGCTAGCTA) and the ratio of bases are the same.

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Chargaff's rule

The amounts of adenine (A) and thymine (T) bases are equal, and the amount of guanine (G) and cytosine (C) are equal.

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Pauling's triple helix model

Proposed a three-stranded DNA structure.

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X-ray diffraction

Technique to study the 3-dimensional structure of a molecule by analyzing how X-rays scatter from the molecule's atoms.

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DNA nucleotide components

A DNA nucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base.

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Chargaff's experiment

Determined the base ratios (A=T and C=G) in DNA from different organisms.

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