Transcription and translation are the two main processes by which genes are expressed into proteins. During transcription, DNA is copied into messenger RNA (mRNA) by RNA polymerase. In eukaryotes, mRNA undergoes processing after transcription where introns are removed and exons are joined together. Translation occurs where the mRNA is read by ribosomes to produce a polypeptide chain based on the mRNA sequence. There are three steps to translation - initiation, elongation, and termination. Gene expression is regulated at transcriptional and post-transcriptional levels through promoter regions, epigenetic modifications, and alternative splicing of mRNA.

1. IB Biology Chapter 2 Notes: Transcription & Translation AHL (7.2 & 7.3) NAME:
Word Definition
Polysome Many ribosomes translating the same mRNA at the same time
Nucleoside
triphosphates
Nucleotides with three phosphates. They break off to provide energy for reactions
Introns Portions of mRNA that are removed and not used for translation
Exons Portions of mRNA that are used for translation
Splicing The process of removing introns
Promoter Portion of DNA in front of gene that RNA poly attaches to
Release factor Protein that attaches to ribosome at stop codon
Initiation Start of translation or transcription
Elongation When the ribosome moves to read the next mRNA codon and add another amino
acid to the growing polypeptide
Termination The end of transcription or translation
tRNA activating
enzyme
An enzyme that attaches the correct amino acid to a tRNA molecule
A-Site The site on the ribosome where new tRNAs enter
P-Site The middle site on the ribosome
E-Site The site on the ribosome from which tRNAs leave after dropping off an amino acid

2. 7.2.7 Describe the promoter
as an example of non-coding
DNA with a function.
7.2.1 Gene expression is
regulated by proteins that
bind to specific base
sequences in DNA.
7.2.2 The environment of a
cell and of an organism has
an impact on gene
expression.
7.2.3 Nucleosomes help to
regulate transcription in
eukaryotes.
7.2.8 Analyze changes in
DNA methylation patterns.
7.2.4 Transcription occurs in
a 5’ to 3’ direction.
7.2.5 Eukaryotic cells
modify mRNA after
transcription.
List functions of non-coding DNA sequences:
What is a ‘Promoter?’
Enhancers:
Silencers:
Promoter-proximal elements:
What is the role of the environment in gene expression?
Example of Siamese cats:
How do nucleosomes regulate transcription?
What is the effect of direct methylation of DNA?
Describe what steps occur in eukaryotes to modify pre-mRNA to mature mRNA before Translation:

3. 7.2.6 Splicing of mRNA
increases the number of
different proteins an
organism can produce.
7.3.12 Use molecular
visualization software to
analyze the structure of
eukaryotic ribosomes and a
tRNA molecule.
7.3.11 tRNA-activating
enzymes illustrate enzyme-
substrate specificity and the
role of phosphorylation.
7.3.1 Initiation of translation
involves assembly of the
components that carry out
the process.
How can ‘alternative splicing’ lead to greater variety in proteins produced in Translation?
Ribosome tRNA
Drawing of
structure
Description
of structure
Describe how tRNA-activating enzymes work:
How do these enzymes illustrate enzyme-substrate specificity?
Outline the steps ofInitiation:

4. 7.3.2 Synthesis of the
polypeptide involves a
repeated cycle of events.
7.3.3 Disassembly of the
components follows
termination of translation.
7.3.4 Free ribosomes
synthesize proteins for use
primarily within the cell.
7.3.5 Bound ribosomes
synthesize proteins primarily
for secretion or for use in
lysosomes.
7.3.6 Translation can occur
immediately after
transcription in prokaryotes
due to the absence of a
nuclear membrane.
7.3.13 Identify polysomes in
an electron micrograph.
Outline the steps ofElongation:
Outline the steps ofTermination:
Explain why translation can occur immediately after transcription in prokaryotes,but not eukaryotes:
What are polysomes?