Transcript Protein Synthesis

Protein Synthesis
Beth Walker
Importance of Proteins & DNA
A.
B.
C.
DNA carries the instructions for making
all proteins.
A portion of a DNA strand with
instructions for making a protein is called
a gene
Proteins are made up of many building
blocks or monomers called amino acids.
Importance of Proteins & DNA
D. Proteins perform the following important
functions:
– Enzymes, which speed up chemical
reaction sin the body.
– Keratin, which makes up our hair
and nails.
– Collagen, which makes up our skin.
– Hemoglobin, which transports O2 in
our body
E. There are 20 different amino acids, such as
valine, lysine, and leucine, which are put in
various arrangements to make proteins
Transcription: making mRNA from
DNA
How Does Transcription Occur?
1.
Starts with replication
2.
Location: nucleus and cytoplasm
3.
DNA is once again split apart by an
enzyme
4.
Free-floating mRNA nucleotides
attach to the exposed DNA strand.
REMEMBER THERE IS NO THYMINE IN
mRNA!!!!!
Transcription
How Does Transcription Occur?
5. mRNA separates from DNA and we now
have a single-strand of messenger RNA.
6. Three nucleotides on an mRNA strand
are called a codon. By looking at a codon
chart, we can determine the amino acid
that mRNA strand will put together.
Codon Chart
Using the Chart
• PRACTICE USING THE CODON
CHART……look up the amino acid for
each codon listed below.
UUG  leucine
UAC  tyrosine
ACG  theorine
AAA  lysine
Using the Codon Chart
•
***Notice that there are start and stop
codons that will tell where to begin and
where to end the protein.
7. The start codon is AUG, so the first amino
acid in a protein will always be methionine
8. The stop codons are UAA, UGA, and
UAG. The last amino acid in a protein will
always be coded by a “stop” codon.
How Does Translation Occur?
How does Translation Occur?
1. The amino acids coded for by the codons
are linked together to make a protein.
2. Location: ribosome
3. mRNA travels out of the nucleus to a
ribosome.
4. The ribosome looks for the “start” codon.
Translation
How Does Translation Occur?
5. All codons after that will attach to the
ribosome.
6. In the cytoplasm, tRNA, a clover-leaf shaped
RNA, will attach to free floating amino acids
and form anticodons (made up of tRNA).
7. Amino acids come from proteins that we eat
and they are broken down during digestion.
8. tRNA pairs with mRNA and brings the correct
amino acid with it to the ribosome.
9. Peptide bonds are formed between the amino
acids, and voila, a protein is formed.
Transcribe & Translate a Gene Here
Transcription & Translation –
Practice Problem
DNA: GCGTATTACGGGGTGCCATATACTGGT
mRNA:
tRNA:
Protien: