Download RNA - Mayfield City Schools

RNA

A nucleic acid which acts as a messenger
between DNA and the ribosomes to carry
out the process of making proteins from
amino acids.

Structure is similar to DNA
http://www.genome.gov/P
ages/EducationKit/downlo
ad.html#3dvid
Short video clip introducing
translation.
RNA vs. DNA
1. Type of Sugar:
Sugar in RNA=Ribose
Sugar in DNA= Deoxyribose
2. Structure:
RNA=single strand of nucleotides
DNA= double helix (2 strands of
nucleotides)
3. Nitrogenous Bases:
RNA= Adenine-Uracil Cytosine-Guanine
DNA= Adenine-Thymine Cytosine-Guanine
4. Function
RNA

Consists of
nucleotides:
1. Sugar= ribose
2. Base
3. Phosphate

**only one strand**



G
C
U
A
Types of RNA

rRNA - Ribosomal RNA:
makes up the ribosomes: the
organelles that help make
proteins
tRNA - Transfer RNA:
Brings amino acids to
ribosomes during
translation (protein
synthesis).
mRNA - Messenger RNA:
Helps make proteins by
directing which proteins
are made.
Transcription Defined:
WHY is transcription
RNA synthesis= the
unzipping of the DNA
needed?
strands and synthesis of
DNA stays in the nucleus so
an RNA; by RNA
it needs a messenger like
polymerase(enzyme) and
RNA, to carry the genetic
using one of the DNA
information outside the
strands as a template.
nucleus.
Transcription and Translation
Learning Goal:
 Describe the process and purpose of
transcription and translation and how these
processes create a protein.

Transcription
First Step: RNA polymerase binds to a
promoter on the DNA. A promoter is a
sequence which RNA polymerase
recognizes and signals the starting point
of transcription.
 This first step is called Initiation : RNA
polymerase binds to a promoter


Elongation: RNA polymerase synthesizes
a new complimentary RNA strand. Base
pairing is done with DNA according to
the rules, except U pairs with A, instead
of T. U – uracil
Termination: Transcription continues
until the RNA polymerase reaches a
specific sequence of DNA, that signals
RNA polymerase to release both the DNA
molecule and the newly made singlestranded RNA molecule.

In eukaryotes: the most common
termination sequence is AATAAA.

In eukaryotes, the new RNA molecule is
actually called pre-m RNA. It contains
large segments of DNA that do not code
for any proteins.
 These non-coding segments of DNA are
called introns
 These introns are spliced out and the
remaining segments of RNA are cut and
pasted together. The segments of DNA
that code for proteins are called exons.

Transcription
Transcription=animated

 Codon:
3 nucleotide segment
of m RNA that codes for a
specific amino acid.

Translation:
(Protein Synthesis)=decoding of m-RNA into amino acids
to form proteins

Amino Acids
=subunits of Proteins
or polypeptides

Amino Acids:
20 different amino acids

M-RNA Strand

t-RNA:

Translation: the conversion of mRNA
code into a protein.

Occurs in the cytoplasm at ribosomes.
 Requires mRNA, ribosomes (rRNA &
proteins), tRNA, Amino Acids, and
energy.

tRNA structure: a strand of RNA ~80
nucleotides long with the 2 dimensional
shape of a cloverleaf. One end has an
anti-codon, which will bind to the codon
of the mRNA. The other end has the
amino acid, which corresponds to the
codon sequence.


1. Initiation: The ribosome, mRNA, and
the initiator tRNA with the first amino
acid come together. The initiator tRNA
binds to the start codon, which is AUG.
This occurs at the P-site.

. Elongation: An incoming tRNA
(carrying an amino acid) binds to the
correct codon at the A-site. Then a
peptide bond (a bond between amino
acids) is formed.

Termination: Elongation continues until
a stop codon is reached. They are UAA
UAG and UGA, A release factor protein
binds to the A-site and causes a chemical
reaction to free the polypeptide chain
from the ribosome.
Translation (animated)
*Process takes place on a ribosome

Formation of Polypeptide
Chain(Protein)=
Translation

Termination of Translation:
When the t-RNA anticodon reaches a stop codon
on m-RNA
