Transcript DNA & PROTEIN SYNTHESIS

RNA & PROTEIN
SYNTHESIS
Chapter 12
Section 3
Pages 300-306
I.
RNA
A. What Is It?
1. RIBO-NUCLEIC ACID
- The “Middle-Man” between DNA
(nucleus) & the ribosomes (cytoplasm).
2. Structure
a. Ribose (Sugar)
b. Single-stranded, not double.
c. Thymine is replaced by URACIL.
- Adenine binds with Uracil.
d. RNA can be found inside and outside
of the nucleus (DNA is always inside!)
II.
What Codes For A Protein?
A. The genetic code allows for almost
an infinite amount of different
proteins.
B. Every 3 bases of DNA (or mRNA) is
referred to as a CODON.
- Each codon codes for 1 amino acid.
Example:
GCA codes for the amino
acid Alanine.
C. Proteins are made outside the nucleus.
Why?
That is where they are needed the most!
III. Types of RNA
1. mRNA (Messenger RNA)
a. A copy of the information
found in DNA.
b. Carries instructions to the
ribosomes on how to make a
specific protein.
2.
rRNA (Ribosomal RNA)
- make up ribosomes, which
direct the synthesis of a protein.
3. tRNA (Transfer RNA)
- carries amino acids to the
ribosomes where they are
connected to form proteins.
IV. STEPS IN PROTEIN SYNTHESIS
STEP 1: Transcription
A. The process whereby mRNA is made
from DNA.
- Very similar to DNA Replication.
- Occurs inside the Nucleus.
1. An enzyme (RNA Polymerase) binds to
an area of DNA called a Promoter.
- Where Transcription will start.
2. RNA Polymerase unwinds & separates
the DNA strand.
- One half will be used as a template to
make mRNA.
3. Complimentary “RNA” nucleotides
match up with each DNA base.
4. A single strand of mRNA continues to
grow until a “STOP” codon is reached.
Transcription in the nucleus
Transcription Animation
• http://www.biostudio.com/d_%20Transcript
ion.htm
STEP 2: Translation
A. The process of converting the info.
in mRNA into a protein.
- Occurs within the cytoplasm on a
ribosome.
1. mRNA leaves the nucleus and binds to a
ribosome, it will bind at AUG, which is
the start codon for the amino acid
methionine.
2. The ribosome moves along the mRNA
and reads every three bases (codon).
3.
tRNA (compliment of mRNA) picks up
specific amino acids from the cytoplasm
and attaches to the mRNA strand.
4.
The “anticodon” of tRNA temporarily
attaches to its complimentary codon on
mRNA and adds its amino acid.
•
5.
Amino acids are bonded with peptide bonds
forming a polypeptide
This process continues until a “STOP”
codon is reached.
* When complete, a single protein has
been produced.
Translation
Translation fill in
Translation Animation
• http://highered.mcgrawhill.com/olc/dl/120077/micro06.swf
Mutations
Pages 307-308
Ch. 12-4 Mutations
• Mutation – a change in a DNA sequence
that affects genetic information
• Two types:
• 1. Gene mutation
• 2. Chromosomal
mutation
1. Types of Mutations
A. Point Mutations
- A change in a single base pair.
Example:
Mrs. Cowley is cool!
ATG TCA AAT CGA
Mrs. Cowley is _______?
ATG TCA AAT GGA
B.
Frameshift Mutations
- A mutation which causes an entire shift in
the genetic message.
Examples:
Deletion:
ATG ACG GCA TTG TCT GGA
ATG AGG CAT TGT CTG GA_
ATG ACG GCA TTG TCT GGA
Insertion: ATG ACT GGC ATT GTC TGG A
- The entire protein sequence has been changed!
Gene Mutations
C. Chromosomal Mutations
- Affects large sections of DNA rather
than smaller sections.
- Portions of a chromosome (s) can be
added, deleted or reversed.
Example:
Down Syndrome (Trisomy 21)
- Child has 47, instead of 46
chromosomes.
* What are some characteristics of
someone with Trisomy 21?
Deletion
Duplication
Inversion
Translocation