OCR A Level Biology 6.1 Cellular Control
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Questions and Answers

What is the result of a nonsense mutation?

  • The mutation alters the genetic code without affecting protein synthesis.
  • The mutation creates a premature stop codon. (correct)
  • The mutation results in a longer polypeptide chain than expected.
  • The mutation leads to an enzyme with enhanced activity.

Which type of mutation can result in a significant alteration to a polypeptide's shape?

  • Substitution mutation
  • Neutral mutation
  • Beneficial mutation (correct)
  • Frame shift mutation

Which of the following is NOT a result of harmful mutations?

  • Change in active site shape leading to loss of substrate binding.
  • Altered characteristics that improve an organism's function. (correct)
  • Incompletely formed polypeptides affecting protein function.
  • Decreased strength in structural proteins.

What effect can a beneficial mutation have on an organism?

<p>It can result in altered characteristics advantageous for survival. (B)</p> Signup and view all the answers

How can gene mutations be classified based on their effects?

<p>Into beneficial, harmful, and neutral mutations. (C)</p> Signup and view all the answers

What effect do transcription factors have on gene expression?

<p>They can either promote or inhibit transcription. (A)</p> Signup and view all the answers

What is the estimated percentage of human genes that code for transcription factors?

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

How do transcription factors allow organisms to respond to their environment?

<p>By binding to specific regions of DNA. (C)</p> Signup and view all the answers

What is the role of oestrogen in gene control in mammals?

<p>It is involved in controlling the oestrus cycle and sperm production. (B)</p> Signup and view all the answers

Where do some transcription factors bind to regulate gene expression?

<p>To the promoter region of the gene. (D)</p> Signup and view all the answers

What can happen when there is an increase in transcription factors binding to a gene's promoter?

<p>Transcription may be increased. (B)</p> Signup and view all the answers

Which of the following statements about transcription factors is true?

<p>They can have varying effects on gene expression. (A)</p> Signup and view all the answers

What occurs when a repressor protein binds to the operator region?

<p>Transcription of structural genes is prevented. (C)</p> Signup and view all the answers

What is the first action oestrogen takes after diffusing through the plasma membrane?

<p>It binds to the oestrogen receptor. (C)</p> Signup and view all the answers

What role does oestrogen play in gene transcription?

<p>It causes a change in receptor shape, facilitating transcription. (C)</p> Signup and view all the answers

Which statement accurately describes the oestrogen receptor?

<p>It is a transcription factor that binds to specific DNA sequences. (C)</p> Signup and view all the answers

What effect does gibberellin have on the amylase gene during seed germination?

<p>It stimulates the synthesis of the enzyme amylase. (A)</p> Signup and view all the answers

Which component is essential for the synthesis of amylase in the presence of gibberellin?

<p>Repressor protein DELLA. (D)</p> Signup and view all the answers

How does gibberellin influence the presence of mRNA for amylase in germinating seeds?

<p>It increases the amount of amylase mRNA present. (D)</p> Signup and view all the answers

What is the primary role of the transcription factor PIF in gibberellin's action?

<p>To initiate transcription of the amylase gene. (C)</p> Signup and view all the answers

What change occurs in the receptor when oestrogen binds to it?

<p>It undergoes a conformational change. (C)</p> Signup and view all the answers

What was the primary advantage of high melanin production in early humans living in Africa?

<p>Enhanced protection from UV radiation (C)</p> Signup and view all the answers

Why did certain mutations that decreased melanin production provide a selective advantage in cooler temperate climates?

<p>They allowed for better absorption of vitamin D. (B)</p> Signup and view all the answers

What term is used to describe mutations that lead to harmful effects in an organism?

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

Which health problems can arise from a deficiency in vitamin D?

<p>Rickets and increased cancer risk (A)</p> Signup and view all the answers

How did human populations adapt to varying levels of sunlight in terms of melanin production?

<p>Diverse variations of melanin production based on region (B)</p> Signup and view all the answers

What role does DELLA protein play in the regulation of amylase gene transcription?

<p>It prevents the transcription factor from binding to the promoter of the amylase gene. (A)</p> Signup and view all the answers

What is the result of gibberellin binding to its receptor?

<p>It causes the breakdown of DELLA protein. (C)</p> Signup and view all the answers

What happens after the breakdown of DELLA protein?

<p>Transcription of the amylase gene is initiated. (C)</p> Signup and view all the answers

Why is RNA analysis important in understanding gene expression?

<p>It allows matching RNA to specific genes to identify which genes are expressed. (A)</p> Signup and view all the answers

What is a likely consequence of the amylase gene being transcribed?

<p>The production of amylase enzyme. (D)</p> Signup and view all the answers

What function does the transcription factor PIF serve in the process?

<p>It binds to the promoter for the amylase gene. (D)</p> Signup and view all the answers

Which of the following statements is true regarding gibberellin and DELLA protein?

<p>Gibberellin promotes the degradation of DELLA protein. (C)</p> Signup and view all the answers

What is the primary effect of transcription on gene expression?

<p>It produces RNA from DNA. (C)</p> Signup and view all the answers

What is an insertion mutation?

<p>A mutation where a nucleotide is added into the DNA sequence (D)</p> Signup and view all the answers

How does an insertion mutation affect the DNA sequence?

<p>It can create a new triplet and alter subsequent triplets (C)</p> Signup and view all the answers

Which of the following statements is true regarding mutations in non-coding sections of DNA?

<p>They have no effect on the amino acid sequence (D)</p> Signup and view all the answers

What is a frameshift mutation?

<p>A mutation that alters the reading frame of the DNA sequence (B)</p> Signup and view all the answers

Which of the following best describes the relationship between DNA sequences and amino acids?

<p>Three nucleotides together form a coding unit for one amino acid (D)</p> Signup and view all the answers

Flashcards

Insertion Mutation

A type of mutation where one or more nucleotides are added into the DNA sequence.

Frameshift Mutation

A mutation that changes the reading frame of the DNA sequence, often drastically altering the amino acid sequence of the protein.

Deletion Mutation

A mutation where one or more nucleotides are removed from the DNA sequence.

Substitution Mutation

A mutation where one nucleotide is swapped for another in the DNA sequence.

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Silent Mutations

Many mutations occur in the non-coding regions of DNA, having no impact on the amino acid sequence.

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Nonsense mutation

A mutation that introduces a premature stop codon in the DNA sequence, leading to an incomplete polypeptide chain.

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Beneficial mutation

A change in the DNA sequence that alters the protein's function, potentially leading to beneficial effects for the organism.

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Neutral mutation

A change in the DNA sequence that has no noticeable effect on the organism's phenotype.

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Harmful mutation

A change in the DNA sequence that leads to a harmful effect on the organism's phenotype.

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Active site

The specific region of an enzyme where the substrate binds.

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Melanin

The pigment responsible for skin, hair, and eye color, offering protection from harmful UV radiation.

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Inheritance

The process by which an organism's characteristics are passed down to its offspring, influencing their traits.

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Fitness

The ability of an organism to survive and reproduce in its environment.

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Transcription factors

Proteins that bind to specific regions of DNA to regulate gene expression.

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Transcription

The process of copying genetic information from DNA to RNA.

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Promoter region

The region of DNA where transcription factors bind to regulate gene expression.

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Transcription rate

The rate at which a gene is transcribed into RNA.

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Effector molecule

A regulatory molecule that binds to a transcription factor, influencing its ability to bind to DNA and regulate gene expression.

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Operator region

The region of DNA where the repressor protein binds to prevent transcription.

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Repressor protein

A protein that binds to the operator region and prevents the transcription of a gene.

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Oestrogen

A hormone involved in controlling the oestrus cycle and sperm production in mammals.

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DELLA protein

A protein that binds to the transcription factor, preventing it from binding to the promoter of the amylase gene and starting transcription.

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PIF

A transcription factor that binds to the promoter of the amylase gene, initiating the transcription of amylase.

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Gibberellin

A plant hormone that triggers the breakdown of DELLA protein, allowing the transcription factor to bind to the promoter of the amylase gene.

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Promoter of the Amylase gene

A specific region of the DNA molecule to which the transcription factor binds. This binding triggers the transcription of the amylase gene.

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Amylase

The enzyme responsible for breaking down starch into simpler sugars.

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RNA analysis

The analysis of RNA present in a cell to identify which genes are being expressed.

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Genome

The complete set of genetic information in an organism.

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How does oestrogen regulate gene expression?

Oestrogen is a lipid-soluble hormone that can pass through the plasma membrane of cells and bind to oestrogen receptors located in the nucleus. These receptors are transcription factors, meaning they can control gene expression by binding to promoter regions and influencing the transcription of specific genes.

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What is the mechanism of oestrogen's action on gene transcription?

Once oestrogen binds to its receptor, it triggers a conformational change in the receptor protein. This change causes the receptor to detach from a protein complex it was previously associated with and bind to the promoter region of a target gene.

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What is the role of gibberellin in plant development?

Gibberellin is a plant hormone that plays a crucial role in seed germination. It stimulates the synthesis of the enzyme amylase by affecting the transcription of the amylase gene.

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How does gibberellin regulate amylase synthesis?

The DELLA protein is a repressor protein that inhibits amylase synthesis. When gibberellin is present, it triggers the breakdown of DELLA protein, removing the inhibition and allowing the transcription factor PIF to activate the amylase gene.

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What are transcription factors and how do they work?

Transcription factors are proteins that bind to specific DNA sequences called promoters, which regulate the transcription of genes. They play a crucial role in gene expression by controlling the initiation of transcription.

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What is the promoter region of a gene?

The promoter region is a specific DNA sequence located upstream of a gene. It provides a binding site for transcription factors, which can regulate the rate at which the gene is transcribed.

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Why is amylase important for seed germination?

The enzyme amylase is responsible for breaking down starch into simpler sugars, which can be used as an energy source during seed germination. Gibberellin's regulation of amylase gene transcription is essential for this process.

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How does gibberellin affect mRNA levels?

Messenger RNA (mRNA) is a type of RNA molecule that carries genetic information from DNA to ribosomes, where proteins are synthesized. When gibberellin stimulates amylase gene transcription, there is an increase in the amount of amylase mRNA produced, leading to increased amylase synthesis.

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Study Notes

OCR A Level Biology 6.1 Cellular Control

  • Gene mutations are changes in the DNA base pair sequence, potentially altering polypeptides.
  • Mutations can be spontaneous or induced by mutagens like radiation or chemicals.
  • Insertion mutations add nucleotides, causing a frameshift.
  • Deletion mutations remove nucleotides, also causing a frameshift.
  • Substitution mutations replace one nucleotide with another, potentially changing a single amino acid.
  • Silent mutations do not alter the amino acid sequence.
  • Beneficial mutations can lead to advantageous traits.
  • Harmful mutations may cause diseases.
  • Neutral mutations have no noticeable effect.
  • Gene expression is regulated by mechanisms controlling the rate of gene transcription.
  • These mechanisms include: transcriptional, post-transcriptional, and post-translational.
  • Regulatory genes control the expression of structural genes (which make proteins).
  • The lac operon in prokaryotes is an example of transcriptional gene control, which regulates the breakdown of lactose in bacteria.
  • Structural genes (lacZ, lacY, lacA) code for enzymes involved in lactose metabolism.
  • The regulatory gene (lacI) codes for a repressor protein that interacts with the operator.
  • When lactose is present, it binds to the repressor, preventing it from blocking transcription.
  • When lactose is absent, the repressor binds to the operator, and transcription does not occur.
  • Transcription factors are proteins that bind to specific DNA regions to regulate gene expression.
  • They can increase or decrease the rate of transcription.
  • Oestrogen is a lipid-soluble hormone that can diffuse across cell membranes and regulate gene expression by influencing transcription factors.
  • Gibberellin is a plant hormone that stimulates seed germination by manipulating the transcription factor DELLA.
  • Mitosis is cell division for growth, replacement, and repair.
  • Apoptosis is programmed cell death, crucial for development and removing damaged cells.
  • Genes controlling cell division and apoptosis include proto-oncogenes and tumour suppressor genes.
  • Cell cycle checkpoints ensure DNA integrity, and cyclins and cyclin-dependent kinases regulate cell cycle progression.
  • External and internal stimuli can influence gene expression and apoptosis.

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OCR A Level Biology Cellular Control PDF

Description

This quiz covers Gene mutations and cellular control mechanisms as outlined in the OCR A Level Biology syllabus. Understand types of mutations, their effects, and the regulation of gene expression. Perfect for students preparing for their A Level examinations.

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