6.1.1. Cellular Control

What is a gene?

A length of DNA that codes for a protein

What is a genome?

The complete set of genes in an organism

What is gene expression?

Process by which information in a gene is used to produce a protein

What are the two stages of protein synthesis?

Transcription and translation

What is transcription?

Process of copying DNA into mRNA in the nucleus

What enzyme is involved in transcription?

RNA polymerase

What happens during transcription?

DNA unwinds → complementary RNA nucleotides pair → mRNA formed

What is mRNA?

Messenger RNA that carries genetic information from DNA to ribosomes

What is translation?

Process of assembling amino acids into a protein at ribosomes

What is a codon?

Triplet of bases on mRNA coding for an amino acid

What is tRNA?

Transfer RNA that carries amino acids to ribosomes

What is an anticodon?

Triplet of bases on tRNA complementary to mRNA codon

What happens during translation?

mRNA binds ribosome → tRNA brings amino acids → peptide bonds form → protein produced

What is a polypeptide?

Chain of amino acids forming a protein

What is the genetic code?

Set of rules by which base triplets code for amino acids

What are the features of the genetic code?

Universal, non-overlapping, degenerate

What does degenerate mean?

Multiple codons code for the same amino acid

What is a mutation?

A change in DNA base sequence

What are types of mutation?

Substitution, insertion, deletion

What is a substitution mutation?

One base replaced by another

What is an insertion mutation?

Extra base added

What is a deletion mutation?

Base removed

What is a frameshift mutation?

Insertion/deletion shifts reading frame of codons

What is a silent mutation?

No change to amino acid sequence

What is a missense mutation?

Different amino acid produced

What is a nonsense mutation?

Stop codon formed → protein shortened

What is epigenetics?

Changes in gene expression without altering DNA sequence

What is DNA methylation?

Addition of methyl groups to DNA → reduces transcription

What is histone modification?

Changes to histone proteins affecting gene expression

What is a transcription factor?

Protein that controls gene expression by binding to DNA

What are oncogenes?

Mutated genes that cause uncontrolled cell division

What are tumour suppressor genes?

Genes that regulate cell division and repair DNA

What happens when tumour suppressor genes fail?

Uncontrolled cell division

What is cancer?

Disease caused by uncontrolled cell division

What are carcinogens?

Substances that increase risk of mutations

What are examples of carcinogens?

Tobacco smoke, radiation, UV light

What is the cell cycle?

Series of stages a cell goes through to divide

What are the stages of the cell cycle?

Interphase, mitosis, cytokinesis

What happens in interphase?

DNA replication and cell growth

What happens in mitosis?

Nucleus divides → identical nuclei formed

What happens in cytokinesis?

Cytoplasm divides → two daughter cells formed

Why is mitosis important?

Growth, repair, asexual reproduction

What is apoptosis?

Programmed cell death

Why is apoptosis important?

Removes damaged or unnecessary cells

What happens if apoptosis fails?

Cells continue dividing → cancer may develop

What is the role of cyclins?

Proteins that regulate progression through cell cycle

What is the role of checkpoints in the cell cycle?

Ensure conditions are correct before progression

What is differentiation?

Process by which cells become specialised

What is a stem cell?

Undifferentiated cell that can divide and differentiate

What types of stem cells are there?

Embryonic, adult, induced pluripotent stem cells