DNA Structure and Replication Quiz

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Questions and Answers

What is the consequence of a deletion in a gene's coding sequence that removes the start signal?

  • The gene may produce multiple copies of itself.
  • The gene may produce a non-functional protein. (correct)
  • The gene may produce an excess of functional proteins.
  • The gene may replicate faster.

Which type of chromosomal mutation involves the breaking of one chromosome and the rearrangement of the genetic material?

  • Deletion
  • Duplication
  • Inversion (correct)
  • Translocation

What is the result of chromosomal translocation?

  • A section of a chromosome is inverted.
  • A section of one chromosome is deleted.
  • A section of one chromosome becomes attached to a different chromosome. (correct)
  • A section of a chromosome replicates.

Which syndrome is associated with a deletion of a part of chromosome 5?

<p>Cri du Chat syndrome (B)</p> Signup and view all the answers

Which type of mutation involves a gene or region of a chromosome appearing two or more times in a row?

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

What is the primary structure of DNA as concluded by Rosalind Franklin?

<p>It has a helical structure with two strands. (C)</p> Signup and view all the answers

Which components of DNA are found on the outside of the helical structure?

<p>Sugar-phosphate backbones (D)</p> Signup and view all the answers

What distinguishes RNA from DNA?

<p>RNA includes uracil instead of thymine. (B)</p> Signup and view all the answers

What is the role of helicase in DNA replication?

<p>To cleave and unwind the DNA double helix. (B)</p> Signup and view all the answers

During DNA replication, what does the semi-conservative model imply?

<p>Each new DNA molecule contains one original strand and one new strand. (C)</p> Signup and view all the answers

What are the 'rungs' of the twisted ladder structure of DNA formed by?

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

Which nucleotide sequence represents the starting point of DNA replication?

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

What is the purpose of proofreading during DNA replication?

<p>To remove mismatched nucleotides. (C)</p> Signup and view all the answers

What direction does elongation occur in during DNA replication?

<p>5' to 3' (A)</p> Signup and view all the answers

Which enzyme is responsible for proofreading base pairing during DNA replication?

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

What term describes the segments of the lagging strand during DNA replication?

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

What type of mutation results from the deletion of one or more nucleotides that impacts the reading frame?

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

What is the role of DNA ligase during DNA replication?

<p>Connects Okazaki fragments (A)</p> Signup and view all the answers

Which strand is continuously replicated during DNA replication?

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

What is the primary function of transfer RNA (tRNA) during translation?

<p>Carries amino acids to the ribosome (A)</p> Signup and view all the answers

What codon initiates protein synthesis?

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

Which statement accurately describes a silent mutation?

<p>Has no effect on polypeptide production (D)</p> Signup and view all the answers

What is the first step in the process of protein synthesis?

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

Which nucleotide base is present in RNA but not in DNA?

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

What type of mutation could potentially cause a genetic disorder, such as sickle cell disease?

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

Which base pairs with Adenine (A) in RNA?

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

Which of the following correctly defines a point mutation?

<p>Substitution, insertion, or deletion of one or few nucleotides (A)</p> Signup and view all the answers

Flashcards

Replication

The process of copying DNA.

Gene

A functional sub-unit of DNA that directs the production of one or more polypeptides (protein molecules).

Genome

The total DNA in an organism's cells.

Chromosome

A length of DNA and associated protein; condensed form of genetic material.

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Helicase

The enzyme that binds to the DNA at the replication origin and unwinds the double helix.

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Semi-conservative Model

Each new molecule of DNA contains one strand of the original complementary DNA molecule and one new parent strand. Thus, each new DNA molecule conserves half of the original molecule.

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Replication Origin

The nucleotide sequence where DNA replication begins.

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Replication Bubble

The oval-shaped unwound area created during DNA replication, where two Y-shaped areas form at each end.

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Chromosomal Mutations

A change in the number or structure of chromosomes, affecting multiple genes and leading to various genetic disorders.

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Chromosomal Deletion

A section of a chromosome is deleted, leading to missing genetic information.

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Chromosome Duplication

A section of a chromosome appears two or more times in a row, duplicating the genes within that segment.

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Chromosome Inversion

A segment of a chromosome is flipped, essentially reversing the order of genes within that region.

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Translocation

A piece of one chromosome breaks off and attaches to a different chromosome.

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Replication Fork

The Y-shaped region where DNA replication begins.

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DNA Elongation

The process of adding new nucleotides to a growing DNA strand.

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DNA Polymerase

The enzyme responsible for adding new nucleotides to a growing DNA strand, proofreading, and removing RNA primers.

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RNA Primer

A short RNA sequence that acts as a starting point for DNA polymerase to begin adding nucleotides.

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Leading Strand

The strand of DNA that is synthesized continuously.

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Lagging Strand

The strand of DNA that is synthesized in short segments.

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Okazaki Fragments

Short segments of DNA synthesized on the lagging strand.

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DNA Ligase

The enzyme that joins Okazaki fragments together on the lagging strand.

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DNA Replication Termination

The process of completing new DNA strands and dismantling the replication machinery.

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Transcription

The process of copying genetic information from DNA to RNA.

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Messenger RNA (mRNA)

The molecule that carries genetic information from DNA to the ribosomes for protein synthesis.

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RNA Polymerase

The enzyme responsible for synthesizing RNA from DNA.

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Codon

A sequence of three bases in mRNA that codes for a specific amino acid.

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Transfer RNA (tRNA)

A type of RNA that carries a specific amino acid to the ribosome during translation.

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Study Notes

DNA Structure and Replication

  • DNA is a double helix, resembling a twisted ladder
  • Sugar-phosphate backbones form the "handrails"
  • Nitrogenous bases (A, T, G, C) form the "rungs"
  • Strands are antiparallel (5' to 3' and 3' to 5')
  • DNA is a thread-like molecule composed of two long strands of nucleotides
  • RNA is similar to DNA but contains ribose sugar, uracil instead of thymine, and is single-stranded
  • DNA replication follows a semi-conservative model; each new DNA molecule contains one original strand and one new strand.

Four Stages of DNA Replication

  • Initiation: Replication begins at a specific site (replication origin)
  • Elongation: New nucleotides are added to the 3' end of the existing strand.
  • Termination: Replication is completed
  • Proofreading: DNA polymerase corrects errors

Enzymes Involved in DNA Replication

  • Helicase: Unwinds the DNA double helix
  • DNA Polymerase: Adds nucleotides and proofreads
  • Primase: Creates RNA primers for nucleotide addition
  • DNA Ligase: Joins Okazaki fragments on the lagging strand

Leading and Lagging Strands

  • Leading strand: Synthesized continuously in the 5' to 3' direction
  • Lagging strand: Synthesized in short segments (Okazaki fragments) in the 5' to 3' direction.

Transcription and Translation

  • Transcription: DNA information is copied into mRNA
  • Translation: mRNA sequence is used to produce a polypeptide (protein)
  • Messenger RNA (mRNA): Carries genetic code from DNA to ribosomes
  • Transfer RNA (tRNA): Delivers amino acids to ribosomes during translation
  • Ribosomal RNA (rRNA): Forms part of ribosomes

Genetic Code and Mutations

  • Codons (3-base sequences) code for specific amino acids
  • Point mutations: Changes in single nucleotides
  • Silent mutations: No change in amino acid sequence
  • Missense mutations: Change to a different amino acid
  • Nonsense mutations: Premature stop codon, resulting in truncated protein
  • Frameshift mutations: Insertion or deletion altering the reading frame.

Protein Synthesis

  • Two main steps: transcription & translation
  • mRNA carries code to cytoplasm from DNA
  • tRNA brings amino acids, matching mRNA codons
  • Ribosome assembles polypeptide chain
  • Amino acid sequence determines protein structure and function.

Types of Mutations

  • Substitution, Insertion, Deletion of nucleotides
  • Frameshift mutations
  • Silent mutations : No effect on protein result
  • Mis-sense mutations: Alter amino acid sequence; could be harmful or neutral
  • Non-sense mutations; premature stop; harmfull
  • Chromosomal Mutations: Rearrangements involving multiple genes or chromosomes.
  • Duplication, Inversion, Deletion, Insertion, Translocation

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