Transcript Chapter 3 Section 4 Protein Synthesis

DNA to Proteins
3-4
• The sequence of nitrogen bases found in
the DNA are responsible for determining
what type of protein will be created by the
cell.
• Proteins are small molecules that basically
control our bodies.
What is RNA
• RNA is similar to DNA with a couple of
changes:
– RNA is single stranded
– Instead of using the nitrogen base thymine
RNA uses uracil.
Types of RNA
• mRNA – messenger RNA carries the
coded message found in the DNA out into
the cytoplasm of the cell where the
proteins will be made
• tRNA – transfer RNA carries amino acids,
which are the building blocks of proteins,
to the be used to build the protein
Types of RNA
• rRNA – a small strand of RNA that makes
up part of a ribosome.
Gene to Protein
Steps to Protein Creation
• Transcription – making a strand of mRNA
from a segment of DNA and then the
mRNA leaves the nucleus of travels to the
cytoplasm of the cell
• Translation – uses the strand of mRNA
as a template to piece together amino
acids to form the protein
Transcription
• Transcription – the DNA strand is
unzipped to allow a strand of mRNA to be
created from its exposed nitrogen bases
• The new strand of mRNA are made by
matching new nitrogen bases with the
exposed nitrogen bases from the unzipped
strand of DNA.
• Once the mRNA is made and processed in
the nucleus, it will leave the nucleus
through small openings in the nuclear
membrane called pores.
• Once in the cytoplasm, the process of
translation will begin.
What are proteins made of?
• Proteins are made of smaller building blocks
called amino acids.
• The amino acids are pieced together to form a
very long chain that then folds over to create a
very specific shaped structure we call a protein.
• Each type or protein has a specific job based on
its shape.
The mRNA consists of the nitrogen bases
A,U,C,G arranged in a specific order.
• Proteins consist of chains of the 20 amino
acids arranged in a specific order.
• So what is the link between the two?
Codons
• A codon is a sequence of three
nucleotides in a row which code for a
certain amino acid.
• Each codon codes for one or more amino
acids.
• Start Codon – tells where the translation
will begin , it will always be AUG
• Stop Codon – one of three specific
codons indicating where translation will
stop; UAA, UAG, UGA
Translation
• Once the mRNA has left the nucleus, the
process of translation is ready to begin.
• In translation, amino acids are arranged in
order according to the sequence of codons
located on the mRNA.
• This sequence of amino acids will
determine the shape of the final protein.
tRNA
• This is the molecule that will carry a specific
amino acid to the ribosome to be attached to the
chain of amino acids called a polypeptide chain
(pre-protein).
• The tRNA is similar in structure to mRNA in that
it has nitrogen bases.
• Anticodon – a series of three nitrogen bases at
one end of the tRNA used to match with the
mRNA codons
Ribosomes
• Ribosome play an important role in
translation.
• They are the location where the mRNA
and tRNA come together to join the amino
acids to from the protein.