Download Making Proteins

DNA
Making Proteins
This image
summarizes the
processes of
transcription and
translation.
What are the three
stages in this process
(central dogma) and
where are they in this
picture?
mRNA
rRNA
protein
tRNA
RNA
• RNA (Ribonucleic Acid)
– Contains Ribose as the sugar in its sugarphosphate backbone
• RNA has Uracil rather than Thymine as a
base
– Base pairs: A – U C – G
• 3 types of RNA
– messenger (mRNA)
– transfer (tRNA)
– ribosomal (rRNA)
Transcription
in Prokaryotes
• DNA is transcribed into
mRNA
Translation
in Prokaryotes
• mRNA serves as the
instructional material to
make proteins
Transcription
in Eukaryotes
• DNA is transcribed into
pre-mRNA
RNA Processing
in Eukaryotes
• Non-coding regions of
the mRNA, called
introns, are removed
from the pre-mRNA.
Translation
in Eukaryotes
• The mRNA with only
the coding region (the
exons) leaves the
nucleus.
• Translation from
mRNA to protein
occurs in the
cytoplasm.
Steps of DNA Transcription
Making mRNA from DNA
1. Helicase unzips DNA at the gene of interest
2. RNA polymerase matches RNA nucleotide
bases to DNA, using one side as a template.
3. The mRNA strand is created. It now
compliments the original DNA strand (G-C
and A-U).
4. Ligase helps the strand of DNA to close
again.
5. mRNA strand moves out of nucleus to
ribosomes, DNA zips up.
Key Players in Translation
rRNA = RNA that makes up a ribosome
tRNA = RNA that transfers specific amino acids
mRNA = RNA transcribed from DNA
Codon = 3 nucleotides in a row on a strand of
mRNA that code for an amino acid
Anticodon = 3 nucleotides in tRNA that base pair
with the codon
Amino Acids = monomers of proteins
(20 in humans)
Steps to Translation
Making proteins from mRNA
1. Ribosomes attach to the “start” codon of
mRNA (AUG), signaling the beginning of the
protein chain
2. mRNA codons are matched to corresponding
tRNA anticodons and appropriate amino acids
are strung together.
3. Dehydration synthesis occurs between the
amino acids, and they join, making a protein
chain with peptide bonds in between
4. Ribosomes detach when they come across a
“stop” codon (UAA, UAG, UGA). Protein
synthesis is complete.
Why do you
think RNA
uses the
“triplet
code”?
Do the math on
your own or
with a
neighbor.
CODON BINGO
• Fill in the Bingo Card (on page 45) with the
20 different amino acids.
– Use your table on page 44 to help
– Watch out for repeated amino acids!
• Wait for your teacher to begin calling out
DNA letters to begin playing
Translation
Activity
• You and your
classmates need to
discover the
hidden protein in
your bag.
• Follow the
instructions in the
bag to unlock the
mystery protein.
What if a single base is changed?
What if a single base is changed?
What if a single base is changed?