Download RNA and Protein Synthesis

RNA AND PROTEIN
SYNTHESIS
The Plan…

How does DNA control cell activities if it can’t leave
the nucleus?
 It


sends a messenger! - messenger RNA (mRNA for short)
Remember, DNA contains the code for making
proteins.
DNA can’t leave the nucleus, so RNA has to help out
and actually make the proteins on the ribosomes.

Ribonucleic Acid


Ribonucleic acid (RNA)
What makes up a nucleotide?
- molecule that controls
the production of
proteins for cells.
A strand of RNA is made
of repeating units
(monomers) called
nucleotides (like DNA)
RNA vs. DNA
Three differences between
RNA and DNA:
 Single-stranded
 Ribose
instead of
Deoxyribose
 Uracil instead of Thymine

Checkpoint: RNA vs. DNA
DNA
Double strand
 Deoxyribose
 Contains Thymine
 Stays in nucleus

RNA
Single Strand
 Ribose
 Contains Uracil
 Leaves nucleus


Types of RNA

Messenger RNA (mRNA)
 single,
uncoiled strand
 serves as pattern for assembly of amino acids

Transfer RNA (tRNA)
 carries
amino acids to the
ribosome
 single stranded

Ribosomal RNA (rRNA)
 globular
form
 makes up the structure of the ribosome



Transcription
Process of making mRNA from a
single–strand of DNA.
The nitrogen bases in RNA always
bond to their complement on the
DNA strand


ADENINE binds to URACIL
GUANINE binds to CYTOSINE

Steps in Transcription
1.
2.
3.
The enzyme RNA polymerase “unzips” the
complementary strands of DNA into two single
strands.
RNA nucleotides bond to a single strand of DNA
The finished mRNA is released and the two DNA
strands “re-zip”
Steps in Transcription
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA
polymerase
DNA
RNA
Transcription animation

mRNA Processing
AUGGGCAUUAGCCUA

Enzymes remove (cut out)
introns because they interrupt
the coding sequence
• INTRONS INTERRUPT … INTRONS OUT !!!
• Exons are left behind to be “expressed” (translated) as needed
proteins
Again...
unit of transcription in a DNA strand
exon
intron
exon
transcription
mRNA
snipped
out
intron
into pre-
snipped
out
mature mRNA transcript
exon

Checkpoint!

Transcribe the DNA strand into RNA:
TAC TCG TCC ATA GGC ATC
AUG AGC UGG UAU CCG UAG

Protein Synthesis


Bases in mRNA code for
the amino acids which
will make a functioning
protein.
A group of three
sequential bases on an
mRNA strand is a
CODON.
Lab – Part 1



Read the introduction
and highlight 5
important facts
Transcribe the two DNA
sequences.
Complete the Codon
activity

The Genetic Code


There are a possible 64 CODONS that code for 20
AMINO ACIDS and a START/STOP SIGNAL.
The genetic code is universal among all organisms.
The Genetic Code
mRNA strand – G C A A C G U U G C U A C U G
Amino Acids – Alanine - Threonine - Leucine Leucine - Leucine -

Steps in Translation

1.
2.
Process of using RNA to assemble amino acids into
proteins.
mRNA moves out of the nucleus and attaches to
ribosome.
tRNA transports amino acids to the ribosome.
Steps in Translation

Steps in Translation
3.
4.
5.
The anticodon on tRNA bonds to the
complementary codon on mRNA.
Amino acids form peptide bonds and form a
strand – a polypeptide.
The stop codon on mRNA ends the process and the
new protein is released.
Steps in Translation
Translation animation
Your Turn!
Be A Ribosome …
Translate your codons
into amino acids:
AUGCAUAGCCUA
Met
Protein Synthesis Video
His
Ser
Leu
Lab – Part 2

Now it’s your turn to be RNA!
Concept Mapping for RNA

Translation --------------------------Anti-codon

Peptide bond ----------------------Amino Acids

Uracil --------------------------------RNA

Challenge: mRNA -----tRNA ------rRNA