Biology Chapter: Molecular Genetics
40 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the role of RNA polymerase during transcription?

  • To bond free RNA nucleotides to form the sugar-phosphate backbone. (correct)
  • To transport mRNA out of the nucleus.
  • To unwind the DNA double helix.
  • To splice introns from the mRNA molecule.

What must happen to the primary transcript before it becomes mature mRNA?

  • Introns must be spliced out. (correct)
  • Nucleotides must be removed from the ends.
  • It must be re-transcribed.
  • It must undergo translation.

Which of the following accurately describes a gene mutation?

  • It always results in a beneficial trait.
  • It occurs only during transcription.
  • It changes the sequence of base pairs in DNA. (correct)
  • It can only occur due to environmental factors.

What is the function of tRNA in translation?

<p>To attach amino acids and recognize codons on mRNA. (B)</p> Signup and view all the answers

During which step does the mRNA molecule exit the nucleus?

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

What type of bond links the deoxyribose sugars and phosphate groups in the DNA backbone?

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

What happens when a 'stop' codon is reached during translation?

<p>The amino acid chain is completed. (B)</p> Signup and view all the answers

Which direction does DNA polymerase synthesize a new strand?

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

Which characteristic of tRNA allows it to attach to specific amino acids?

<p>The presence of a triplet anticodon. (B)</p> Signup and view all the answers

What is an example of an insertion mutation?

<p>An extra nucleotide is added to the DNA sequence. (D)</p> Signup and view all the answers

What is the significance of the term 'semi-conservative' in DNA replication?

<p>It indicates that each daughter DNA contains one old and one new strand. (A)</p> Signup and view all the answers

What are the components that make up a nucleotide?

<p>A nitrogenous base, a pentose sugar, and a phosphate group (C)</p> Signup and view all the answers

Which nitrogenous bases are classified as purines?

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

Which nitrogenous base always pairs with adenine in DNA?

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

What role does DNA helicase play in DNA replication?

<p>It breaks hydrogen bonds between base pairs. (C)</p> Signup and view all the answers

How many hydrogen bonds are formed between adenine and thymine?

<p>2 hydrogen bonds (D)</p> Signup and view all the answers

What distinguishes DNA from RNA?

<p>DNA contains deoxyribose while RNA contains ribose. (B)</p> Signup and view all the answers

What are the two categories of nitrogenous bases in DNA?

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

Which statement accurately describes the antiparallel nature of DNA strands?

<p>One strand runs from 3' to 5', and the other 5' to 3'. (A)</p> Signup and view all the answers

Which of the following statements about DNA structure is true?

<p>DNA strands are antiparallel. (A)</p> Signup and view all the answers

What is the primary function of DNA ligase in the synthesis of the lagging strand?

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

What is the primary function of adenosine triphosphate (ATP) in cells?

<p>Providing energy for cellular processes (B)</p> Signup and view all the answers

What is the result of the condensation reaction catalyzed by DNA polymerase?

<p>Creation of the sugar-phosphate backbone (D)</p> Signup and view all the answers

What distinguishes RNA from DNA in terms of structure?

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

Which of the following best describes the components of ATP?

<p>Three phosphate groups, ribose sugar, and the base adenine (D)</p> Signup and view all the answers

What type of sugar is found in RNA nucleotides?

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

Why is the genetic code described as degenerate?

<p>Multiple codons can code for the same amino acid (C)</p> Signup and view all the answers

What role does messenger RNA (mRNA) play in protein synthesis?

<p>It acts as a template for polypeptide synthesis (A)</p> Signup and view all the answers

During the transcription process, where does this stage occur within the cell?

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

Which of the following statements about RNA structure is correct?

<p>RNA is made up of ribose sugars and nitrogenous bases linked by phosphodiester bonds (C)</p> Signup and view all the answers

What defines a gene in the context of DNA?

<p>A portion of DNA coding for a specific polypeptide (C)</p> Signup and view all the answers

What does the term 'triplet code' refer to in genetics?

<p>A three-nucleotide sequence that codes for amino acids (C)</p> Signup and view all the answers

What is the primary effect of an insertion mutation in DNA?

<p>It changes the original codon and affects subsequent codons. (C)</p> Signup and view all the answers

What distinguishes a substitution mutation from an insertion or deletion mutation?

<p>It only affects the amino acid in the triplet where it occurs. (C)</p> Signup and view all the answers

Which type of mutation is specifically known to create a premature stop codon?

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

What is a common outcome of a frameshift mutation caused by insertion or deletion?

<p>A completely different amino acid sequence is produced. (A)</p> Signup and view all the answers

Which of the following best describes a silent mutation?

<p>It does not change the resulting protein's amino acid sequence. (D)</p> Signup and view all the answers

What may be a consequence of a mutation that results in a significantly altered polypeptide?

<p>The protein may lose its ability to function. (C)</p> Signup and view all the answers

Which example represents a missense mutation?

<p>Changing one base that leads to a different amino acid. (A)</p> Signup and view all the answers

Which mutation is least likely to have an effect on the polypeptide's function?

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

Flashcards

What are nucleic acids made of?

Nucleic acids, like DNA and RNA, are long chains of smaller units called nucleotides.

What are the components of a nucleotide?

A nucleotide is composed of three parts: a nitrogen-containing base, a pentose sugar, and a phosphate group.

What nitrogenous bases are found in DNA and RNA?

Adenine (A), guanine (G), cytosine (C), and thymine (T) are the nitrogenous bases found in DNA. RNA uses uracil (U) instead of thymine.

What are purines and pyrimidines?

Adenine and guanine are purines, having a double-ring structure. Cytosine, thymine, and uracil are pyrimidines, having a single-ring structure.

Signup and view all the flashcards

What are the pentose sugars in DNA and RNA?

The pentose sugar in DNA is deoxyribose, while the pentose sugar in RNA is ribose.

Signup and view all the flashcards

How many strands do DNA and RNA have?

DNA is a double-stranded molecule, forming a double helix structure. RNA is single-stranded.

Signup and view all the flashcards

What is ATP and what is its structure?

ATP (adenosine triphosphate) is an energy-carrying molecule within cells. It is a nucleotide with adenine as the base and three phosphate groups.

Signup and view all the flashcards

What is a phosphorylated nucleotide?

ATP is a phosphorylated nucleotide, meaning a phosphate group has been added to a nucleotide.

Signup and view all the flashcards

Why is lagging strand synthesis discontinuous?

The synthesis of the lagging strand is discontinuous, meaning that it is synthesized in short, separate fragments called Okazaki fragments.

Signup and view all the flashcards

What does DNA ligase do during DNA replication?

DNA ligase acts as a 'glue' enzyme, joining the Okazaki fragments together to make a continuous complementary DNA strand.

Signup and view all the flashcards

What is the main difference between the sugars in DNA and RNA?

RNA contains the pentose sugar ribose, whereas DNA contains deoxyribose.

Signup and view all the flashcards

How is RNA different from DNA in terms of its structure?

RNA is single-stranded, while DNA is double-stranded.

Signup and view all the flashcards

What is the role of mRNA in protein synthesis?

Messenger RNA (mRNA) carries the genetic code from DNA in the nucleus to the ribosomes in the cytoplasm, where protein synthesis takes place.

Signup and view all the flashcards

What is a gene in terms of DNA?

A gene is a specific sequence of nucleotides within a DNA molecule that codes for a particular polypeptide.

Signup and view all the flashcards

How does the genetic code work?

The genetic code is a triplet code, meaning that each three-base codon codes for a specific amino acid.

Signup and view all the flashcards

Where does transcription occur, and what is its purpose?

The process of transcription occurs in the nucleus of the cell and involves the creation of a messenger RNA (mRNA) molecule from a DNA template.

Signup and view all the flashcards

Phosphodiester bonds

Covalent bonds that connect the sugar and phosphate groups in a DNA strand, forming the backbone.

Signup and view all the flashcards

Complementary base pairing

A specific base pairing rule in DNA where adenine (A) only bonds with thymine (T) and guanine (G) only bonds with cytosine (C).

Signup and view all the flashcards

DNA replication

The process where DNA copies itself before cell division, ensuring each new cell gets a full set of genetic information.

Signup and view all the flashcards

Semi-conservative replication

The method of DNA replication where each new DNA molecule contains one original strand from the parent DNA and one newly synthesized strand.

Signup and view all the flashcards

DNA helicase

An enzyme that breaks the hydrogen bonds between base pairs in DNA, unwinding the double helix to allow replication.

Signup and view all the flashcards

DNA polymerase

An enzyme that builds new DNA strands by adding nucleotides to the existing template strands during DNA replication.

Signup and view all the flashcards

5' to 3' direction

The direction in which DNA polymerase can only add nucleotides to a growing DNA strand, from the 5' end to the 3' end.

Signup and view all the flashcards

Replication fork

The site where DNA replication begins on a DNA molecule, where the double helix is opened up to allow access for the replication machinery.

Signup and view all the flashcards

Transcription

The process of copying the genetic information from DNA into a messenger RNA (mRNA) molecule.

Signup and view all the flashcards

Translation

The process of using mRNA to build a polypeptide (protein) chain.

Signup and view all the flashcards

Gene mutation

A change in the sequence of bases in a DNA molecule. It can lead to altered proteins.

Signup and view all the flashcards

Insertion mutation

A mutation where an extra nucleotide is inserted into the DNA sequence.

Signup and view all the flashcards

Exon

The coding portion of a gene that is used to make a protein.

Signup and view all the flashcards

Intron

The non-coding portion of a gene that is removed before protein synthesis.

Signup and view all the flashcards

Anticodon

The sequence of three bases on tRNA that complements a codon on mRNA during translation.

Signup and view all the flashcards

Codon

The sequence of three bases on mRNA that codes for a specific amino acid.

Signup and view all the flashcards

Deletion mutation

A mutation that occurs when a nucleotide (and therefore its base) is randomly deleted from the DNA sequence. It can change the reading frame and dramatically affect the produced polypeptide.

Signup and view all the flashcards

Substitution mutation

A mutation that occurs when a base in the DNA sequence is randomly swapped for a different base. It only affects the triplet where the mutation occurs.

Signup and view all the flashcards

Silent mutation

A substitution mutation that changes the amino acid sequence, but the final protein's structure and function remain the same.

Signup and view all the flashcards

Missense mutation

A substitution mutation that alters a single amino acid in the polypeptide chain. This can lead to significant changes in protein function.

Signup and view all the flashcards

Nonsense mutation

A substitution mutation that creates a premature stop codon, interrupting the polypeptide chain synthesis. This often results in a non-functional protein.

Signup and view all the flashcards

Frameshift mutation

The alteration of the reading frame in a DNA sequence due to the insertion or deletion of a nucleotide. This has a significant effect on the amino acid sequence.

Signup and view all the flashcards

Why are insertion/deletion mutations more severe than substitution mutations?

The insertion or deletion of one or two nucleotides in a DNA sequence causes a frameshift mutation, impacting the final polypeptide and protein function.

Signup and view all the flashcards

Study Notes

Nucleic Acids & Protein Synthesis

  • Nucleic acids, like DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are polynucleotides. Their monomers are nucleotides.
  • Nucleotides consist of three parts: a nitrogenous base, a pentose sugar, and a phosphate group.
  • Nitrogenous bases are categorized as purines (double ring structure - adenine and guanine) or pyrimidines (single ring structure - cytosine, thymine, and uracil).
  • DNA is double-stranded with deoxyribose sugar and bases A, T, C, G. DNA strands are antiparallel (5' to 3' and 3' to 5'). Hydrogen bonds link complementary base pairs (A-T, G-C).
  • RNA is single-stranded with ribose sugar and bases A, U, C, G.
  • Adenosine triphosphate (ATP) is a phosphorylated nucleotide, providing energy for cellular processes.
  • RNA nucleotides can have one, two, or three phosphate groups (AMP, ADP, ATP).

DNA Replication

  • DNA replication is semi-conservative, meaning each new DNA molecule consists of one original strand and one newly synthesized strand.
  • DNA helicase unwinds the DNA double helix, breaking hydrogen bonds between complementary base pairs.
  • DNA polymerase synthesizes new DNA strands using the original strands as templates. It can only build in the 5' to 3' direction. The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments (Okazaki fragments). DNA ligase joins the Okazaki fragments.

Protein Synthesis

  • Genes are sequences of nucleotides that code for polypeptides (proteins). DNA's nucleotide code is a triplet code (codons).
  • Transcription occurs in the nucleus. DNA unwinds. mRNA is synthesized using one DNA strand as a template. mRNA carries the genetic code from DNA to the ribosome.
  • Translation occurs in the cytoplasm. mRNA binds to ribosomes. tRNA molecules carry specific amino acids to the ribosome, matching codons on the mRNA to anticodons. Amino acids are linked to form a polypeptide chain (protein).
  • Translation proceeds until a stop codon on the mRNA is reached. This polypeptide chain is the final protein.

Gene Mutations

  • Gene mutations are changes in the DNA sequence, which can cause alterations in the resulting polypeptide and protein function.
  • Mutations occur when nucleotides are inserted, deleted or substituted.
  • Different types of mutations include insertion, deletion, and substitution.
  • Frameshift mutations (insertions or deletions) affect the reading frame and subsequently change the amino acid sequence downstream of the mutation, significantly altering the polypeptide.
  • Substitutions can be silent (no amino acid change), missense (different amino acid), or nonsense (premature stop codon).
  • Mutations can profoundly alter gene expression and protein function, sometimes leading to disease.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Nucleic Acids & Protein Synthesis PDF

Description

Test your knowledge on key concepts in molecular genetics, including transcription, translation, and DNA replication. This quiz covers the roles of RNA polymerase, tRNA function, and various types of mutations. Dive into the intricacies of genetic processes and enhance your understanding of molecular biology!

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser