DNA: The Molecule of Life Quiz

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Questions and Answers

What is the primary function of DNA in living organisms?

To act as a shield against environmental toxins

To facilitate energy production

To provide structural support to cells

To store genetic instructions for cell activities (correct)

What component is NOT part of a nucleotide in DNA?

Phosphate group

Amino acid (correct)

Nitrogenous base

5-carbon sugar

How do the strands of DNA differ from each other?

One strand contains only ribose sugar

One strand is composed entirely of adenine and thymine

One strand runs in the opposite direction at the 5' and 3' ends (correct)

One strand has a different length than the other

What are the four nitrogenous bases found in DNA?

Thymine, Adenine, Guanine, Cytosine Signup and view all the answers

What is the significance of DNA's double-stranded structure?

It enables replication and repair processes Signup and view all the answers

What is the backbone of a DNA molecule made up of?

Phosphate groups and 5-carbon sugars Signup and view all the answers

How many chromosomes are typically found in each human cell?

46 Signup and view all the answers

What is a polymer in the context of DNA?

A chain of repeating nucleotide units Signup and view all the answers

Which nitrogenous bases form three hydrogen bonds?

Guanine and Cytosine Signup and view all the answers

What is the role of RNA primase in DNA replication?

To create the RNA primer for DNA polymerase Signup and view all the answers

What is the significance of the replication fork during DNA replication?

It indicates where the leading and lagging strands are separated Signup and view all the answers

How does DNA polymerase correct mistakes during replication?

By removing mismatched nucleotides from the end of the strand Signup and view all the answers

Which scientist was responsible for confirming the helical structure of DNA?

Rosalind Franklin Signup and view all the answers

What is the primary reason Rosalind Franklin did not receive full recognition for her contributions to the discovery of DNA?

She shared her findings with others Signup and view all the answers

What are Okazaki fragments?

Discontinuous segments of the lagging strand Signup and view all the answers

How many base pairs does human chromosome 1 contain?

247 million Signup and view all the answers

What substance did Friedrich Miescher first isolate that would later be termed DNA?

Nuclein Signup and view all the answers

What makes the lagging strand more complex to replicate than the leading strand?

It replicates in the opposite direction Signup and view all the answers

Study Notes

DNA: The Molecule of Life

DNA is the most complex and important molecule in existence.
Its structure wasn't understood until about 60 years ago.
DNA is incredibly diverse; if all the DNA from a single cell were stretched out, it would be longer than the individual.
The human body contains trillions of cells.
If all the DNA from all the human body cells were connected, it would reach the sun 600 times.
DNA stores genetic instructions, programming cellular activities.
It's a 6-billion-letter code assembling the components that make individuals unique.
This code holds the same principles for all living things.
Each cell contains 46 chromosomes, each holding a large DNA molecule.
Chromosomes are packaged with proteins in the cell nucleus.
DNA is an acid found in the nucleus.
RNA is another nucleic acid, discussed later.
Nucleic acids are the fourth major class of biological molecules after carbohydrates, lipids, and proteins.

DNA Structure

DNA is a polymer, consisting of repeating nucleotides.
Nucleotides have three components: a 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous base.
Four nitrogenous bases define the genetic code: Thymine (T), Adenine (A), Guanine (G), and Cytosine (C).
DNA exists as a double-stranded molecule, resembling a twisted ladder.
Sugar and phosphate groups form the ladder's sides.
These sides run in opposite directions (5' and 3' ends).
Bases connect the two strands via weak hydrogen bonds.
Adenine pairs with Thymine (A-T), and Guanine pairs with Cytosine (G-C).
(G-C) base pairs form three hydrogen bonds, stronger than the two hydrogen bonds of (A-T) pairs.
The base sequence determines individual traits.
For example, the sequence TTCAGTCG on chromosome 1 (247 million base pairs) differs from AGGTCCATG.
Chromosome 1, if printed, would be a 200,000-page book.

DNA Replication

Cells constantly divide, requiring complete DNA copies.
This process, replication, produces 10,000 copies of the DNA "book" within hours.
Every cell in an organism has identical DNA copies from the original copy.
During a lifetime, DNA replicates itself trillions of times, using each original DNA strand as a template to build a new complementary strand.
Helicases unwind the DNA double helix, breaking hydrogen bonds.
Replication begins at the replication fork, with leading and lagging strands.
Separated strands serve as templates for new strands.
DNA polymerase adds nucleotides to the leading strand continuously, complementing the sequence.
A primer is needed for DNA polymerase to initiate DNA synthesis.
RNA primase adds a short RNA primer for DNA polymerase to attach and begin building the new strand.
DNA polymerase adds nucleotides only to the 3' end of the strand.
Lagging strand replication is more complex, involving short Okazaki fragments.
RNA primase creates multiple RNA primers for the lagging strand.
DNA polymerase fills in the gaps corresponding to each primer.
DNA ligase joins Okazaki fragments into a complete lagging strand.
Replication errors are rare (approximately 1 in 10 billion nucleotides).
DNA polymerase can often correct errors by removing mismatched nucleotide pairs.

DNA Discovery

Friedrich Miescher discovered DNA in 1869 by studying white blood cells from bandages.
He purified a substance, called nuclein, later renamed DNA.
Rosalind Franklin, using X-ray diffraction, likely first confirmed DNA's helical structure.
She also identified the sugar-phosphate backbone on the outside of the DNA helix.
Franklin's contributions were not fully recognized, partly due to her willingness to share knowledge, providing insights to Watson and Crick, and her untimely death.
Her X-ray images were used by Watson and Crick without her knowledge.
Watson and Crick were awarded a Nobel Prize in 1962, a prize not awarded posthumously, thus excluding Franklin.

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Description

Test your knowledge about DNA, the essential molecule that stores genetic information. This quiz covers its structure, complexity, and the role it plays in living organisms. Discover fascinating facts about DNA and its importance in biology.