DNA Structure and Replication
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Questions and Answers

What type of sugar is found in deoxyribonucleotides?

  • Ribose
  • Deoxyribose (correct)
  • Fructose
  • Glucose

What is the orientation of the two strands in a DNA double helix?

  • Random
  • Antiparallel (correct)
  • Parallel
  • Perpendicular

Which nitrogenous base pairs with thymine in DNA?

  • Guanine
  • Cytosine
  • Adenine (correct)
  • Uracil

What marks the beginning of the DNA replication process?

<p>The origin of replication (ORI) (B)</p> Signup and view all the answers

What is the main role of helicase in DNA replication?

<p>To separate the two strands of DNA (D)</p> Signup and view all the answers

How are nucleotides connected in a DNA strand?

<p>By bonds between the phosphate group of one nucleotide and the sugar of another (A)</p> Signup and view all the answers

Why is primase necessary for DNA replication?

<p>It provides a starting point for DNA polymerase (D)</p> Signup and view all the answers

What characterizes semi-conservative replication?

<p>Each new DNA molecule contains one old strand and one new strand (D)</p> Signup and view all the answers

What is the function of Okazaki fragments?

<p>To assist in replicating the lagging strand (B)</p> Signup and view all the answers

In which direction can DNA polymerase build a new DNA strand?

<p>5’ to 3’ direction (C)</p> Signup and view all the answers

What role do SSB proteins play during DNA replication?

<p>They bind and stabilize separated DNA strands (A)</p> Signup and view all the answers

What is the role of Primase in DNA replication?

<p>It lays down a short RNA primer for DNA Polymerase 3 to attach to. (C)</p> Signup and view all the answers

Which statement about DNA Polymerase 3 is NOT true?

<p>It can only add nucleotides to the 5' end of the DNA strand. (A)</p> Signup and view all the answers

What happens during the replication of the lagging strand?

<p>It is done in short segments called Okazaki fragments. (C)</p> Signup and view all the answers

Which enzymes are involved in removing RNA primers after DNA replication?

<p>DNA Polymerase 1 (B)</p> Signup and view all the answers

What is the significance of the 5' to 3' directionality in DNA replication?

<p>It necessitates the use of Okazaki fragments on the lagging strand. (A)</p> Signup and view all the answers

Which nitrogen base pairs with Adenine in the DNA structure?

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

What is the primary function of Ligase in DNA replication?

<p>To seal gaps left between nucleotides after replication. (D)</p> Signup and view all the answers

Which scientists were pivotal in discovering the double helix structure of DNA?

<p>Watson, Crick, Wilkins, and Franklin (A)</p> Signup and view all the answers

What kind of structure does DNA have?

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

What is the sugar found in RNA?

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

Which base is found in RNA but not in DNA?

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

What is the main role of mRNA in protein synthesis?

<p>To communicate between DNA and ribosomes (A)</p> Signup and view all the answers

In which cellular structure does DNA typically remain in eukaryotic cells?

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

How many base pairs would there be from 8 DNA nucleotides?

<p>4 base pairs (A)</p> Signup and view all the answers

Which type of RNA is a major component of ribosomes?

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

What is the role of tRNA during protein synthesis?

<p>To decode mRNA (C)</p> Signup and view all the answers

Which of the following statements about nucleotides is true?

<p>They consist of a base, sugar, and phosphate. (A)</p> Signup and view all the answers

What hypothesis suggests that RNA preceded DNA in the evolution of life?

<p>RNA World hypothesis (D)</p> Signup and view all the answers

DNA polymerase 3 can initiate DNA replication without the need for a primer.

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

The two strands of DNA are parallel and have the same orientation.

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

Okazaki fragments are formed continuously on the leading strand during DNA replication.

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

DNA is a type of protein that carries genetic information in cells.

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

The sugar present in DNA is ribose.

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

In DNA, cytosine always pairs with guanine.

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

Adenine and thymine in DNA form two hydrogen bonds with each other.

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

Helicase is responsible for joining nucleotides together during DNA replication.

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

DNA ligase is responsible for breaking the hydrogen bonds between nitrogen bases during DNA replication.

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

Deoxyribonucleotides contain ribose as their sugar component.

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

RNA stands for ribonucleic acid and contains deoxyribose sugar.

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

In eukaryotic cells, both DNA and RNA can be found outside the nucleus.

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

The base uracil is found in DNA but not in RNA.

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

DNA is generally a double-stranded molecule, while RNA is mainly single-stranded.

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

MRNA's primary role is to transfer amino acids to ribosomes during protein synthesis.

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

The complementary base for adenine in RNA is thymine.

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

The RNA World hypothesis suggests that RNA came after DNA in the evolution of life.

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

Ribosomes are primarily made of RNA.

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

In DNA, the sugar component of the nucleotide is ribose.

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

The process of transcription involves creating a complementary RNA strand from DNA.

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

Flashcards

DNA's monomer

DNA is made of nucleotides.

Nucleotide structure

A nucleotide is a sugar, phosphate, and a base.

DNA's sugar

Deoxyribose is the sugar in DNA.

DNA's bases

Adenine, Thymine, Cytosine, and Guanine are the DNA bases.

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DNA double helix

Two DNA strands form a helix, with bases paired.

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Origin of Replication (ORI)

Specific DNA sequence where replication begins.

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DNA Polymerase 3's role

DNA polymerase 3 is the enzyme responsible for creating a new DNA strand, complementary to the template strand during replication.

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DNA Polymerase 3's primer need

DNA polymerase 3 requires a pre-existing RNA primer to start adding nucleotides. It can't begin replication on its own.

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Primase's function

Primase is the enzyme responsible for synthesizing the RNA primer that DNA polymerase 3 needs to begin replication.

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DNA Polymerase 1's role

DNA polymerase 1 removes the RNA primers used during replication and replaces them with DNA nucleotides.

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DNA Polymerase 3's 3' limitation

DNA polymerase 3 can only add nucleotides to the 3' end of a growing DNA strand. This limits the direction of replication.

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Leading vs. Lagging strands

The leading strand replicates continuously because it runs in the same direction as DNA polymerase 3's 5' to 3' activity. The lagging strand replicates discontinuously in short fragments (Okazaki fragments) because it runs opposite the direction of DNA polymerase 3's activity.

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Okazaki fragments' role

Okazaki fragments are short DNA segments synthesized on the lagging strand during replication. They are later joined together by ligase.

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Ligase's function

Ligase is the enzyme that joins Okazaki fragments together on the lagging strand, creating a continuous DNA strand.

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What does RNA stand for?

RNA stands for ribonucleic acid. It is a type of nucleic acid involved in protein synthesis.

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What are the three parts of a nucleotide?

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

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What is the difference between DNA and RNA sugar?

DNA contains deoxyribose sugar, while RNA contains ribose sugar.

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What are the bases in DNA?

DNA bases are Adenine, Thymine, Guanine, and Cytosine (A, T, G, C).

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What are the bases in RNA?

RNA bases are Adenine, Uracil, Guanine, and Cytosine (A, U, G, C).

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What does mRNA do?

Messenger RNA (mRNA) carries genetic information from DNA to ribosomes for protein synthesis.

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What does rRNA do?

Ribosomal RNA (rRNA) is a major component of ribosomes, which are responsible for protein synthesis.

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What does tRNA do?

Transfer RNA (tRNA) carries amino acids to ribosomes to match mRNA codons during protein synthesis.

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How many DNA bases are in 8 nucleotides?

Each nucleotide has one base, so 8 DNA nucleotides would have 8 bases.

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What is the complementary strand to A, T, T, G, A, C in DNA?

The complementary strand is T, A, A, C, T, G. Remember the base pairing rules: A with T, and C with G.

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DNA Replication Timing

DNA replication occurs before cell division (mitosis or meiosis) in a eukaryotic cell during interphase.

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Helicase

An enzyme that unwinds DNA by breaking hydrogen bonds between base pairs, separating the two strands.

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DNA Polymerase

An enzyme that builds a new DNA strand by adding nucleotides to the 3' end of the existing chain.

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Primase

An enzyme that creates short RNA primers, which allow DNA polymerase to start building new DNA strands.

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Leading Strand

The DNA strand that is synthesized continuously in the 5' to 3' direction, following the unwinding of DNA.

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Lagging Strand

The DNA strand that is synthesized discontinuously in short fragments (Okazaki fragments) in the 5' to 3' direction.

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DNA's Building Blocks

DNA is made up of smaller units called nucleotides, which are like the LEGO bricks that make up the whole molecule.

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Antiparallel Strands

The two DNA strands in the helix run in opposite directions, one going 5' to 3' and the other 3' to 5'.

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Base Pairing

Adenine (A) always pairs with Thymine (T), and Guanine (G) always pairs with Cytosine (C) in DNA.

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DNA Replication Start

Replication begins at a specific DNA sequence called the origin of replication (ORI), where the double helix unwinds.

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Okazaki Fragments

Short DNA segments synthesized on the lagging strand during replication, which are later joined together by ligase.

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Ligase's Role

The enzyme that joins Okazaki fragments together on the lagging strand, creating a continuous DNA strand.

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Primase's Role

The enzyme that creates short RNA primers which allow DNA polymerase to start building new DNA strands.

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What are nucleic acids made of?

Nucleic acids are made of monomers called nucleotides, which are the building blocks of DNA and RNA.

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What are the DNA bases?

DNA has four bases: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).

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What are the RNA bases?

RNA also has four bases: Adenine (A), Uracil (U), Guanine (G), and Cytosine (C).

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What is mRNA's job?

Messenger RNA (mRNA) carries the genetic information from DNA to ribosomes for protein synthesis.

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What is rRNA's job?

Ribosomal RNA (rRNA) is a major component of ribosomes, the machines that build proteins.

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What is tRNA's job?

Transfer RNA (tRNA) carries amino acids to ribosomes during protein synthesis. It matches each amino acid to its corresponding mRNA codon.

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What are the base pairing rules for DNA?

Adenine (A) always pairs with Thymine (T), and Guanine (G) always pairs with Cytosine (C).

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What is the process of transcription?

Transcription is the process of copying the genetic information from DNA to RNA.

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What is the complementary RNA sequence for A, T, T, G, A, C in DNA?

The complementary RNA sequence is U, A, A, C, U, G. Remember, RNA uses Uracil (U) instead of Thymine (T).

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Study Notes

DNA Structure and Replication

  • DNA, deoxyribonucleic acid, holds genetic information. It's a nucleic acid, one of two types (the other is RNA).
  • Nucleotides are the building blocks of nucleic acids. DNA nucleotides are deoxyribonucleotides; RNA nucleotides are ribonucleotides.
  • Nucleotides consist of a 5-carbon sugar (deoxyribose in DNA), a phosphate group, and a nitrogenous base.
  • The DNA bases are adenine (A), thymine (T), cytosine (C), and guanine (G).
  • DNA strands have a direction (5'-3').
  • DNA exists as a double helix, with sugar-phosphate backbones as the sides and complementary base pairs forming the rungs.
  • Base pairing: A with T, and C with G.
  • Antiparallel strands: The 5' end of one strand aligns with the 3' end of the other.

DNA Replication

  • Replication begins at the origin of replication (ORI).
  • Helicase unwinds the DNA double helix at the ORI.
  • Single-stranded binding proteins (SSBs) prevent the separated strands from re-pairing.
  • Topoisomerase prevents supercoiling of the DNA.
  • Primase adds RNA primers to provide a starting point for DNA polymerase.
  • DNA polymerase III builds new DNA strands in a 5' to 3' direction.
  • Leading strand is synthesized continuously.
  • Lagging strand is synthesized in Okazaki fragments.
  • DNA polymerase I removes RNA primers and fills in the gaps with DNA.
  • DNA ligase joins Okazaki fragments.
  • This process results in two identical DNA molecules from one original.
  • DNA polymerase proofreads for errors during replication. Semiconservative replication occurs, meaning each new DNA molecule has one original and one new strand.

RNA

  • RNA is a nucleic acid just as important as DNA, Hypothesised to predate DNA.
  • RNA is found in all living cells, in both the nucleus and cytoplasm/cytosol of eukaryotic and prokaryotic cells.
  • RNA is a single-stranded molecule.
  • The sugar in RNA is ribose (not deoxyribose).
  • RNA bases: adenine (A), uracil (U), guanine (G), and cytosine (C).
  • mRNA, rRNA, and tRNA are different types of RNA with specific roles in protein synthesis.

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Test your knowledge on the structure of DNA and the processes involved in its replication. This quiz covers essential concepts such as nucleotides, base pairing, and the mechanics of DNA replication. Enhance your understanding of genetic information and molecular biology.

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