DNA Structure & Function Quiz
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Questions and Answers

What are the components of a nucleotide?

  • Phosphate group, ribose sugar, nitrogen base
  • Deoxyribose sugar, amino acid, nitrogen base
  • Phosphate group, deoxyribose sugar, glucose
  • Phosphate group, deoxyribose sugar, nitrogen base (correct)

DNA is a single-stranded molecule.

False (B)

What are the four kinds of nitrogen bases found in DNA?

Thymine (T), Cytosine (C), Adenine (A), Guanine (G)

DNA's structure includes a double-helix formed by ______ base pairing.

<p>complementary</p> Signup and view all the answers

Match the nitrogen bases with their corresponding pairs:

<p>Thymine = Adenine Cytosine = Guanine Adenine = Thymine Guanine = Cytosine</p> Signup and view all the answers

How many hydrogen bonds form between thymine and adenine?

<p>2 (B)</p> Signup and view all the answers

The DNA strands run parallel to each other.

<p>False (B)</p> Signup and view all the answers

What is the charge of histones that help package DNA?

<p>Positive</p> Signup and view all the answers

DNA is made of long chains of ______.

<p>nucleotides</p> Signup and view all the answers

How many base pairs make up one turn of the DNA helix?

<p>10 (D)</p> Signup and view all the answers

What is the primary flow of genetic information as described by the Central Dogma of Biology?

<p>DNA to RNA to Protein (B)</p> Signup and view all the answers

The lagging strand in DNA replication is synthesized continuously.

<p>False (B)</p> Signup and view all the answers

How many cells are estimated to be in the human body?

<p>50 trillion</p> Signup and view all the answers

The _____ binds to DNA and relieves torsional stress during DNA replication.

<p>topoisomerase</p> Signup and view all the answers

What is the role of DNA helicases in DNA replication?

<p>To unwind the double helix (C)</p> Signup and view all the answers

Each replication bubble formed during DNA replication contains a single replication fork.

<p>False (B)</p> Signup and view all the answers

What enzyme is responsible for adding nucleotides during DNA replication?

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

The synthesis of a new DNA strand occurs in the _____ direction.

<p>5’ to 3’</p> Signup and view all the answers

Match the following terms with their roles in DNA replication:

<p>DNA polymerase I = Replaces RNA primer with DNA nucleotides RNA primase = Synthesizes RNA primers DNA ligase = Joins Okazaki fragments DNA helicase = Unwinds the DNA double helix</p> Signup and view all the answers

What does a eukaryotic chromosome contain in terms of replication origins?

<p>Thousands of replication origins (B)</p> Signup and view all the answers

Flashcards

What is DNA?

A nucleic acid that carries genetic information in the form of a code made up of four nucleotide bases.

What is a nucleotide?

The building blocks of DNA, each composed of a phosphate group, a deoxyribose sugar, and a nitrogenous base.

What are the four bases in DNA?

The four nitrogenous bases in DNA: adenine (A), guanine (G), cytosine (C), and thymine (T).

What is the difference between purines and pyrimidines?

Adenine and guanine have a double-ring structure, while cytosine and thymine have a single-ring structure.

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What does it mean that DNA strands are antiparallel?

DNA has two strands that run in opposite directions, with one strand's 5' end aligned with the other strand's 3' end.

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What is complementary base pairing?

The two strands of DNA are held together by hydrogen bonds between specific base pairs: adenine always pairs with thymine (A-T), and guanine always pairs with cytosine (G-C).

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What is a double helix?

The helical structure of DNA, with one complete turn every 10 base pairs.

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What is the charge of DNA?

The phosphate groups in DNA's backbone are negatively charged, making DNA a negatively charged molecule.

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What are histones?

Proteins that help package and organize DNA within the nucleus of a cell.

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How long is the DNA in a human cell?

DNA is a remarkably long molecule, and if you unraveled all the DNA in your body, it could stretch to the sun and back many times.

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DNA replication

The process of copying a DNA molecule to create an identical copy

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Origin of replication

A specific sequence of DNA where replication begins

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Replication bubble

A structure formed during DNA replication, containing two replication forks moving in opposite directions

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RNA primer

A short RNA sequence that acts as a primer for DNA polymerase to start replication

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DNA polymerase III

The enzyme that adds nucleotides to the 3' end of a growing DNA strand, synthesizing a new strand in the 5' to 3' direction

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DNA polymerase I

The enzyme that degrades the RNA primer and replaces it with DNA nucleotides

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Leading strand synthesis

The process of synthesizing a new DNA strand continuously, following the movement of the replication fork

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Lagging strand synthesis

The process of synthesizing a new DNA strand discontinuously, forming short fragments that are later joined together

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Okazaki fragment

A short DNA fragment synthesized on the lagging strand during DNA replication

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DNA ligase

The enzyme that joins Okazaki fragments together to form a continuous DNA strand

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Study Notes

DNA Structure & Function

  • DNA is a nucleic acid, specifically deoxyribonucleic acid
  • Composed of long chains (polymers) of nucleotides
  • Each nucleotide consists of a phosphate group, a deoxyribose sugar group, and a nitrogen-containing base
  • DNA has four types of bases: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G)
  • A and G are purines; C and T are pyrimidines
  • DNA is a double-stranded helix (like a spiral staircase)
  • The two strands are antiparallel, running in opposite directions (5' to 3' and 3' to 5')
  • Bases pair up: A with T (2 hydrogen bonds); C with G (3 hydrogen bonds)
  • One turn of the DNA helix occurs every 10 base pairs
  • Negatively charged phosphate groups face outward
  • Complementary base pairing (Watson-Crick model) is essential for DNA replication and function

DNA Replication

  • Replication begins at specific sites called origins of replication
  • A replication bubble forms, with two replication forks extending outwards
  • Eukaryotic chromosomes have multiple origins of replication; prokaryotic chromosomes typically have only one
  • DNA replication is semi-conservative, meaning each new DNA molecule consists of one original (parental) strand and one newly synthesized strand
  • DNA polymerase III is the primary enzyme responsible for adding nucleotides to the growing DNA strand in a 5' to 3' direction
  • RNA primase adds a short RNA primer to initiate DNA synthesis
  • DNA polymerase I removes the RNA primer and replaces it with DNA nucleotides
  • DNA ligase joins the fragments of the lagging strand (Okazaki fragments)
  • Important proteins for replication include: DNA helicases, single-stranded DNA binding proteins, RNA primase, DNA polymerase I & III, and DNA ligase

Proteins for DNA Replication

  • DNA helicases unwind the DNA double helix
  • Single-strand binding proteins prevent the separated strands from reannealing
  • RNA primase synthesizes short RNA primers
  • DNA polymerase III extends the new DNA strand from the primer
  • DNA polymerase I replaces RNA primers with DNA
  • DNA ligase seals the gaps between Okazaki fragments

Central Dogma of Biology

  • Describes the flow of genetic information from DNA to RNA to proteins
  • DNA replicates to pass on genetic information
  • Transcription converts DNA to RNA within the nucleus
  • Translation converts RNA to protein in the cytoplasm

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Description

Test your knowledge on the structure and function of DNA. This quiz covers the components of DNA, including its nucleotides, double-helix configuration, and base pairing rules. Dive into the specifics of DNA replication and understand the foundational concepts in molecular biology.

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