RNA, transcription and
translation
What I need to know:1. That phenotype is determined by proteins
that are produced as the result of gene
expression.
2. Structure and function of RNA (single
stranded, contains ribose sugar and a uracil
base replaces thymine)
3. The use of mRNA, rRNA and tRNA
What makes species different?
A cell’s genotype (genetic constitution) is
determined by the sequence of the DNA
bases in its genetic code.
A cell’s phenotype (physical and chemical
state) is determined by the proteins
that are synthesised when the genes
are expressed.
RNA
This second type of nucleic acid is called
ribonucleic acid. It has 3 main differences
in
comparison to DNA.
RNA
One
Number of
strands
Complementary Uracil
base pair of
adenine
Sugar present in Ribose
nucleotide
DNA
Two
Thymine
deoxyribose
5C
3C
Sequence of DNA bases
The chemical components of
DNA remains the same
throughout all species.
HOWEVER, it is the quantity
and order of the DNA bases
which are unique to
different species
Genetic Code
The information that DNA contains takes the
form of a code called the GENETIC CODE. The
DNA bases represents the language that the
code is written in.
There are only 4 bases but DNA codes for 20
different types of amino acids in proteins
ITS ALL ABOUT MAKING
PROTEINS!!!
Codon
Codons are the basic unit
for the genetic code
Bases are taken in groups
of 3 giving 64 (43)
different combinations.
Each amino acid is
coded for by one of
these 64 triplets of
bases
Proteins are made on the ribosome in the
cell
Where is the DNA located that holds the
code for making a protein?
• The information on DNA has to be
copied and transported out of the
nucleus and towards the ribosome.
• This involves the processes called
transcription and translation
RNA
mRNA (messenger RNA) is transcribed
(copied) from a section of DNA
tRNA (transfer RNA) meets with mRNA on
the ribosome and translates the DNA code
into a protein (translation). It carries the
amino acids
rRNA (ribosomal RNA) is the RNA
component of a ribosome which aids
protein synthesis
Now attempt the following questions
1) Draw an RNA nucleotide
2) State three differences found between DNA and
RNA
3) What does DNA code for?
4) How many different amino acids are there?
5) The DNA is read in sets. How many bases are
there in one set?
6) What is the function of mRNA?
Glossary
• CODON - a sequence of three nucleotides which together
form a unit of genetic code in a DNA or RNA molecule
• GENETIC CODE - the means by which DNA and RNA molecules
carry genetic information in living cells
• GENOTYPE – the alleles that an organism has for a particular
characteristic
• PHENOTYPE – the visible characteristics of an organism that
occur as a result of its genes
• TRANSCRIPTION - the process by which the information in a
strand of DNA is copied into a new molecule of messenger
RNA (mRNA)
• TRANSLATION - the process in which ribosomes create
proteins. In translation, messenger RNA (mRNA)—produced
by transcription from DNA—is decoded by a ribosome to
produce a specific amino acid chain, or polypeptide