Download PROTEIN SYNTHESIS

PROTEIN SYNTHESIS
NAME _______________________
DATE ____________ BLOCK _____

Traits are due to genes and genes make proteins. The sequence of bases on
a strand of DNA (CGA-TTC-GCT-AAT-ATC) represents a gene that
determines a particular trait through a protein.

Scientists discovered that groups of three bases (called a _____________)
code for a specific amino acid.

Because the DNA is inside the nucleus and the ____________________
(organelle that makes proteins) is in the cytoplasm, the directions for
making the protein must be sent from the nucleus to the cytoplasm. This is
done with a molecule called mRNA (messenger RNA).

There are 2 differences between DNA and RNA.
RNA is a single strand of nucleotides.
RNA does not have thymine (T) as a base, instead uracil (U) replaces
thymine.

Enzymes cut open the section of DNA bearing the gene.

Copier enzymes go along the open strand and make a mRNA that
complements the open strand of DNA.
CGA-TTC-GCT-AAT-ATC
mRNA = GCU-_ _ _-_ _ _-_ _ _-_ _ _
for example: DNA =

mRNA travels to the ribosome in the cytoplasm.
The ribosome “reads” each codon. Each codon tells the ribosome (look at the
genetic code chart) which amino acid is needed. A tRNA (transfer RNA)
molecule brings that amino acid to the ribosome.
o GCU codes for alanine
o AAG codes for
o CGA codes for
o UUA codes for
o UAG codes for
The ribosome connects the amino acids into a protein. This protein is responsible
for the appearance of a trait.

*PLEASE NOTE: glutamate and glutamic acid are the same amino acid!
Now you will make your own protein!
1. Select a section of DNA from your table.
DNA strand # _____
a. The leading strand (top strand) codes for a protein.
2. Act like an enzyme and zip open (cut open) your DNA segment and tape
the leading strand in the boxes below (throw away the lagging strand).
DNA
mRNA
3. Act as a copier enzyme and in the boxes below your leading strand, write out the
mRNA that complements your DNA protein coding segment.
4. The mRNA leaves the nucleus and goes to the ribosome carrying the instructions
to make a protein. Using the genetic code, act as the ribosome reading the mRNA
codons to learn what amino acids are needed to make your protein. Fill in chart
below.
mRNA codon
Amino acid
5. Acting as the tRNA, bring the correct amino acids to the ribosome so you can
build your protein below.