Cellular Control

What Cellular Control covers

Cellular control opens Module 6, examined on Biological Diversity. It covers the three kinds of gene mutation and their effects, the lac operon as a model of gene regulation, transcription factors and splicing, the homeobox and Hox genes that lay out a body plan, apoptosis, and how mutation leads to cancer.

The 6 subtopics

Each one has its own page.

• Gene mutations and their effectsSubstitution, insertion and deletion, missense and nonsense mutations, why a frameshift is so damaging, and when a mutation is neutral, harmful or beneficial.Open →
• The lac operonThe lacZ, lacY and lacA genes, the promoter, the operator and the regulatory gene, and what changes at the operon when lactose is present.Open →
• Transcription factors and post-transcriptional controlTranscription factors as activators and repressors, introns, exons and splicing, alternative splicing, and post-translational control through cyclic AMP.Open →
• Homeobox and Hox genesWhat the homeobox encodes and why it is so highly conserved across species, and how Hox genes are arranged and what their mutation can produce.Open →
• Mitosis and apoptosisWhy both are needed during development, and the shrinking, chromatin condensation, DNA breakdown and apoptotic bodies of programmed cell death.Open →
• Oncogenes, tumour suppressor genes and cancerThe normal role of proto-oncogenes and tumour suppressor genes in the cell cycle, and what happens to that control when either one is mutated.Open →

What you need to know

Answer each one before you reveal it.

Take Cellular Control further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Insertion mutation vs Deletion mutation

  Insertion mutation: addition of one or more nucleotides to a DNA sequence. Deletion mutation: removal of one or more nucleotides from a DNA sequence.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What is a substitution mutation?

   Model answer

   The replacement of one or more nucleotides with different nucleotides in a DNA sequence.

2. 2

   Define an insertion mutation.

   Model answer

   The addition of one or more nucleotides into a DNA sequence.

3. 3

   What is a deletion mutation?

   Model answer

   The removal of one or more nucleotides from a DNA sequence.

4. 4

   Why might a single nucleotide substitution have no effect on the protein produced?

   Model answer

   It may result in a silent mutation if the new codon still codes for the same amino acid due to the degeneracy of the genetic code.

5. 5

   What is a missense mutation and how does it arise?

   Model answer

   A missense mutation occurs when a substitution causes a different amino acid to be incorporated into the polypeptide, potentially altering protein structure and function.

6. 6

   How does a nonsense mutation affect translation?

   Model answer

   A substitution creates a premature stop codon, causing early termination of translation and producing a truncated, usually non-functional protein.

What is inside Levo

Six ways to work the same material.

Cellular Control revision questions

What does Cellular Control cover in OCR A-Level Biology?

6 subtopics: gene mutations and their effects, the lac operon, transcription factors and post-transcriptional control, homeobox and hox genes, mitosis and apoptosis and oncogenes, tumour suppressor genes and cancer. Each one has its own page with questions and model answers.

How is Cellular Control organised?

By the OCR H420 specification, subtopic by subtopic, so it matches the order you are taught it in.