Transcript RNA and Transcription

 We
know that DNA is the genetic material
and its sequence of nucleotide bases
carry some sort of code. This code holds
instructions that tell a cell how to build
proteins, which in turn help to determine
an organism’s characteristics.
 But
how does a cell understand and read
this code to make proteins?
RNA
Chapter 13
What is RNA?
 Ribonucleic
acid
 Can be thought of as a disposable copy
of a piece of DNA
 What
is RNA’s job?
 To make proteins (Protein Synthesis)
Recall that…
 Segments
of genes in our DNA contain a
code for proteins that determine our traits
 DNA
is confined to the nucleus
 Protein
synthesis takes place in the
ribosomes
 Proteins
are made up of amino acids
Why RNA?
 RNA
can travel outside of the nucleus (via
the nuclear membrane’s pores) and carry
DNA’s code to the ribosomes
 Ribosomes
piece together amino acids
based on the RNA code to build the
proteins
 The
DNA stays safe inside the nucleus and
the RNA can travel to do the rest of the
work!
 DNA-
Contains the “master plan” with all
information needed to build a protein.
 RNA-
The “builder”, who works from a
blueprint, or disposable copy, of the
master plan.
 The
cell uses the DNA’s “master plan” to
prepare RNA “blueprints”.
Structure of RNA
 Single
stranded
 Ribose Sugar
 Phosphate group
 Adenine, Uracil, Cytosine, Guanine
Types of RNA
 Three
main types
 Messenger RNA (mRNA) – Carries DNA
code to ribosomes for translation.
 Ribosomal RNA (rRNA) – Ribosomes are
made of rRNA and protein.
 Transfer RNA (tRNA) – brings amino acids
to ribosomes for protein synthesis.
mRNA
-Carries
message to
ribosomes
- Made during
transcription
rRNA
- Structure of
ribosomes
tRNA
- Carries
amino acids to
ribosomes
Transcription (RNA
Synthesis)
 Segments
of DNA serve as templates to
produce complementary RNA molecules
 1.
RNA Polymerase binds to DNA at the
promoter site

Promotor: Region of DNA that shows
enzymes where to attach.
 2.
RNA polymerase separates DNA strands
by breaking hydrogen bonds
 3.
One strand of DNA is used as a
template to form a strand of RNA
 DNA’s
Adenine pairs with RNA’s Uracil
 DNA’s Thymine pairs with RNA’s Adenine
 Guanine and Cytosine pair normally
 4.
RNA polymerase eventually
reaches a terminator signaling it to
stop transcription
 5.
mRNA strand un-attaches, and
travels through nuclear
membrane’s pores to the ribosome
 The
ribosome will read this code
and make proteins from it- a
process known as translation (which
we will get to later on)
RNA strands are edited
before they’re translated
 Some
parts are removed and others are
expressed
 Introns- Portions cut out and discarded
 Exons- Expressed genes
 Why?
 Makes
it possible for a single gene to produce
many different forms of RNA
 Evolution- Small changes in sequences cause
dramatic effects on the cellular functioning of
genes
Transcription Video
 END
OF TRANSCRIPTION