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Protein Synthesis
Transcription and Translation
DNADNA
RNARNA
ProteinProtein
Scientists call this the:
Making Proteins
Where are the three
stages of the central
dogma in this
picture?
DNA
mRNA
tRNA
rRNA
protein
I’m DNAI’m
RNA.
How are we
different?
1. RNA is single stranded. DNA is double stranded.2. RNA and DNA has the same bases. But, RNA has
“U” for Uracil, instead of “T” or thymine.
4. The sugar in RNA is called “ribose” instead
of “deoxyribose” in DNA.
3. RNA’s base-pairing rule is A – U and C – G;
while DNA’s base-pairing rule is A – T and C - G
3 types of RNA
mRNA = DNA transcripttRNA = type of RNA that carries the amino acids to the
ribosome
rRNA = RNA that, combined with protein, makes up the
structural component of a ribosome
Making protein involves 2 steps
1. Transcription: creating
mRNA from DNA
2. Translation: creating
polypeptide (protein
polymer) from RNA
First, we’ll study transcription
transcription
DNA
mRNA
translation
polypeptide
ribosome
DNA Transcription
Making mRNA from DNA
To better understand
transcription, let’s first watch
an animation.
Steps for DNA transcription
1. DNA unzips at the gene of interest
2. RNA polymerase (enzyme) matches RNA nucleotide bases to the template strand of DNA, using A – U and C – G rule.
3. The mRNA strand is created and moves out of nucleus to the ribosome in the cytoplasm.
4. DNA zips back up.
Let’s practice being RNA polymerase by
playing CODON bingo!
DNA Translation
Making polypeptide (protein
polymer) from RNA
To better understand translation,
let’s first watch an animation.
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 mRNA1. Ribosomes attach to the “start” codon of
mRNA (AUG), signaling the start of translation
2. mRNA codons base-pairs with tRNA anticodons. The t-RNAs bring in the appropriate amino acids to be strung together.
3. Dehydration synthesis occurs between the amino acids, and they join, making a polypeptide (protein chain)
4. Ribosomes detach when they come across a “stop” codon (UAA, UAG, UGA). Protein synthesis is complete.
How do you
read an mRNA
table to figure
out the correct
sequence of
Amino Acids?
DNA template:
TAC GGC AAT ACT
mRNA:
AUG
Start – PRO – LEU - Stop
mRNA:
AUG CCG
mRNA:
AUG CCG UUA
mRNA:
AUG CCG UUA UGA
Start –Start – PRO –Start – PRO – LEU -
Amino Acid Sequence:
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?
Individual Activity:
Decoding from DNA
On your own, use a slightly different table
to decode the secrets of Foothill.
tttacccatagc
Translation: FTHS
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