DNA Structure and Function Quiz
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Questions and Answers

What is the primary function of helicase in DNA replication?

  • To transport RNA out of the nucleus
  • To unwind the DNA double helix (correct)
  • To synthesize new DNA strands
  • To repair damaged DNA

Which enzyme is responsible for linking Okazaki fragments during DNA replication?

  • Primase
  • DNA Polymerase
  • Helicase
  • DNA Ligase (correct)

What role does topoisomerase (gyrase) play during DNA replication?

  • It relieves tension in the DNA helix (correct)
  • It synthesizes the RNA primer
  • It unwinds the DNA strands
  • It covalently links DNA fragments

What is the function of endonuclease in DNA repair?

<p>To remove damaged DNA segments (C)</p> Signup and view all the answers

Which type of mutation introduces a stop codon?

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

What distinguishes exons from introns in a gene?

<p>Exons are retained, introns are discarded (A)</p> Signup and view all the answers

What is described as the worst type of mutation?

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

Which molecule primarily encodes genetic information in cells?

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

What is the purpose of the 5' G cap and the 3' poly-A tail in mRNA?

<p>To facilitate ribosome binding and transport (A)</p> Signup and view all the answers

Which of the following blots is used for transferring RNA?

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

What type of mutation is responsible for causing sickle cell disease?

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

What does Hardy-Weinberg equilibrium imply about a population?

<p>There are no mutations or migrations occurring. (C)</p> Signup and view all the answers

Which direction does transcription occur in DNA?

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

What is the most abundant type of RNA found in cells?

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

What term describes the heritable change in DNA?

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

What is the primary purpose of a restriction enzyme?

<p>To cut DNA (D)</p> Signup and view all the answers

What is the significance of DNA being double-stranded with antiparallel strands?

<p>It facilitates the replication process. (D)</p> Signup and view all the answers

What is the role of SSBPs during DNA replication?

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

How does telomerase function in cellular biology?

<p>It adds nucleotides to the ends of chromosomes. (B)</p> Signup and view all the answers

What types of proteins are vital for the formation of ribosomes?

<p>rRNA and ribosomal proteins (D)</p> Signup and view all the answers

What is the purpose of the promoter in the context of transcription?

<p>To specify where transcription begins. (B)</p> Signup and view all the answers

Which characteristic defines a missense mutation?

<p>It causes a single amino acid substitution. (B)</p> Signup and view all the answers

What is the function of ubiquitin in cellular processes?

<p>To tag proteins for degradation. (A)</p> Signup and view all the answers

What is the main outcome of gel electrophoresis?

<p>It separates nucleic acids by size. (D)</p> Signup and view all the answers

Which aspect is a distinguishing feature of introns compared to exons?

<p>Introns are non-coding and removed during RNA processing. (A)</p> Signup and view all the answers

What does DNA ligase specifically do during DNA replication?

<p>Links together Okazaki fragments. (B)</p> Signup and view all the answers

What type of selection is characterized by maintaining a constant environment without drastic changes?

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

What describes the process by which genetic changes occur randomly in a small population?

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

During what process are the primary transcripts of genes modified to become their mature form?

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

Which type of blot is specifically used for the detection of proteins?

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

What is the role of an enhancer in gene regulation?

<p>To interact with activators and inhibitors (D)</p> Signup and view all the answers

What is the main function of reverse transcriptase in viruses?

<p>To synthesize DNA from RNA (D)</p> Signup and view all the answers

What characteristic of an operator is significant in the regulation of gene expression?

<p>It is bound by a repressor to control gene accessibility (A)</p> Signup and view all the answers

How is DNA primarily separated into fragments after being cut by a restriction enzyme?

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

Which of the following mutations results in a change in the nucleotide sequence but does not result in a change in the protein's amino acid sequence?

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

What concept is best described as a change over time in lines of descent?

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

Flashcards

DNA Structure

A double-stranded helix, where strands run antiparallel, connected via hydrogen bonds between complementary bases (A-T, G-C). The bases are inside, and phosphates are outside the helix.

Helicase Function

Unwinds the DNA double helix during DNA replication.

DNA Polymerase Function

Builds new DNA strands by adding nucleotides in a 5' to 3' direction during replication.

Okazaki Fragments

Short DNA segments created on the lagging strand during DNA replication.

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Topoisomerase Function

Relieves tension in DNA during replication by cutting and rejoining the DNA strands.

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Promoter

A specific DNA sequence signaling where transcription begins.

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Gel Electrophoresis

Separates DNA, RNA, or proteins based on size using an electric field.

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Ubiquitin Function

Marks proteins for degradation by the proteasome, controlling protein levels.

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Nonsense mutation

A mutation that changes a codon to a stop codon, prematurely halting protein synthesis.

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Frameshift mutation

A mutation that shifts the reading frame of codons, drastically altering the amino acid sequence.

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Silent mutation

A mutation that changes a codon but doesn't alter the resulting amino acid.

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Southern Blot

A technique that identifies a specific DNA sequence.

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Hardy-Weinberg equilibrium

A theoretical state in which allele frequencies in a population remain constant from one generation to the next.

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Gene flow

The movement of genes between populations through migration and interbreeding.

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Stabilizing selection

A type of natural selection that favors average phenotypes and reduces variation.

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Reverse transcriptase

An enzyme that converts RNA into DNA.

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Single-Stranded Binding Proteins (SSBPs)

Bind to single-stranded DNA during replication to prevent the strands from re-annealing.

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DNA Ligase Function

Joins Okazaki fragments together on the lagging strand during DNA replication.

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Primase Function

Adds a short RNA primer to the starting point of DNA replication, allowing DNA Polymerase to begin.

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Telomerase Function

Replaces lost telomeres (ends of chromosomes) during replication, preventing DNA shortening.

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Plasmid Function

Small, circular DNA molecules found in bacteria. Can carry genes for antibiotic resistance or other traits.

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Ribosome Components

Ribosomes are made of ribosomal RNA (rRNA) and proteins. They are essential for protein synthesis.

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Western Blot

A technique used to identify specific protein sequences within a sample by separating protein molecules based on size, transferring them to a membrane, and then using antibodies to detect the target protein.

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Study Notes

DNA Structure and Function

  • DNA is a double-stranded helix.
  • Strands are antiparallel.
  • Held together by hydrogen bonds between complementary base pairs (A=T, G=C).
  • Bases are inside, phosphates are outside.
  • Uniform width (3 rings wide).

Enzyme Functions

  • Helicase: unwinds DNA.
  • DNA Polymerase: synthesizes DNA 5' to 3'.
  • SSBPs (single-stranded binding proteins): keep DNA single-stranded.
  • DNA Ligase: joins Okazaki fragments.
  • Topoisomerase (Gyrase): relieves stress during DNA replication.
  • Primase: adds a small piece of RNA (primer) to initiate DNA replication.
  • Endonuclease: cuts out damaged DNA segments.

Replication and Other Cellular Processes

  • Okazaki fragments: short DNA segments synthesized discontinuously on the lagging strand.
  • Plasmids: small, circular, double-stranded DNA molecules found in bacteria.
  • Ribosomes are made of rRNA (ribosomal RNA) and proteins.
  • mRNA (messenger RNA) codes for proteins.
  • Exons: expressed parts of genes, kept during translation.
  • Introns: intervening parts of genes, removed during translation.
  • Translation: initiation (small subunit, mRNA, initiator tRNA, large subunit), elongation (codon by codon), and termination (stop codon)
  • 5' cap and 3' poly-A tail: added to mRNA for stability and transport out of the nucleus.

Transcription and Regulation

  • Promoters: regions of DNA that signal where transcription begins.
  • RNA polymerase: binds to the promoter to initiate transcription.
  • Tightly packed DNA prevents transcription.

Mutations and Protein Structure

  • Missense mutation: changes a codon, resulting in a different amino acid.
  • Frameshift mutation: adds or subtracts a base, altering the reading frame.
  • Nonsense mutation: changes a codon into a stop codon, resulting in a truncated protein.
  • Silent mutation: changes a codon but does not alter the amino acid.

Gel Electrophoresis

  • Separates DNA, RNA, or proteins based on size using an electric field.

Ubiquitin

  • Tags proteins for degradation by the proteasome.

Other Concepts

  • Telomerase: maintains telomeres (chromosome ends).
  • Southern, Northern, and Western blots: techniques used to detect specific DNA, RNA, or proteins.
  • Hardy-Weinberg equilibrium: describes the conditions under which allele and genotype frequencies in a population remain constant.
  • Genetic drift: random change in allele frequencies in small populations (bottleneck & founder effect).
  • Sexual selection: advantageous mating traits give an advantage.
  • Temporal Isolation: species reproduce at different times or seasons.
  • Pre- and Postzygotic mechanisms: prevent or block the reproductive process between two organisms from different species.

Cellular Processes and Components

  • rRNA (ribosomal RNA): structural component of ribosomes.
  • r proteins: protein components of ribosomes.

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Description

Test your knowledge on the structure and function of DNA, including the roles of various enzymes in DNA replication. This quiz covers key concepts such as base pairing, the helix structure, and the enzymes involved in replication processes. Perfect for students studying molecular biology and genetics.

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