Download 12.3 RNA and Protein Synthesis

12.3 RNA and Protein Synthesis
1. The Structure of RNA
• single stranded
• working copy of one
gene
– disposable
2. The Structure of RNA
• one gene from DNA can
produce many strands
of RNA
• instead of thymine (T),
uracil (U)
3. Differences between RNA and DNA
• DNA is double stranded, RNA is single
stranded
• DNA contains deoxyribose sugar, RNA contains
ribose sugar
• DNA has thymine; RNA has uracil
4. Types of RNA
• three types
– messenger RNA (mRNA)
– ribosomal RNA (rRNA)
– transfer RNA (tRNA)
5. Types of RNA
• Messenger RNA
– Also known as mRNA
– Carry instructions for making amino acids into proteins
– Messenger from DNA to the rest of the cell
6. Types of RNA
• Ribosomal RNA
– Also known as rRNA
– Make up part of the ribosome (protein making organelle)
7. Types of RNA
• Transfer RNA
– Also known as tRNA
– Transfers each amino acid to the ribosome
– mRNA tells tRNA where to take the amino acid
8. Transcription
• copying part of
the DNA into RNA
9. Transcription
• requires enzyme RNA
polymerase
• RNA polymerase binds to
DNA and separates the
strands
– Similar to DNA replication
10. Transcription
• RNA polymerase uses
one strand of DNA as
a template to make
RNA
• Begins transcription
at promoters
– Promoter sequences on
the DNA shows RNA
polymerase where to
start making RNA
• Makes tRNA, mRNA
and rRNA
11. RNA Editing
• DNA in eukaryotes
contain introns and
exons
– Introns do not code for
proteins
– Exons code for proteins
• Expressed
12. RNA Editing
• RNA will copy both
introns and exons from
the DNA
– Introns need to be cut
out to make a working
piece of RNA
• Remaining pieces of
exons will be spliced
together to form the
final mRNA sequence
13. The Genetic Code
• Genetic code, or language of mRNA
instructions, is read three letters at a time
14. The Genetic Code
• Each three letter sequence, or “word”, codes
for one amino acid
• these three letter words are known as codons
• Codons are found on the mRNA
• The protein is determined by the order of
each amino acid in the sequence
15. The Genetic Code
• There are 64 possible
codons
• One codon, AUG, is known
as the “start” codon for
protein synthesis
• There are also two possible
sequences that are called
“stop” codons
– Show where polypeptide
(protein) ends
– UGA, UAA, UAG
16. Translation
• Making a protein from a
strand of mRNA
• before translation
occurs, mRNA is
transcribed from DNA
17. Steps of Translation
1. mRNA attaches to a
ribosome
– Each codon moves
through the
ribosome
– Codons are “read”
by the ribosome
18. Steps of Translation
2. As mRNA moves through the ribosome,
tRNA brings the correct amino acid to the
ribosome
tRNA carries the amino acid matching
the codon on the mRNA sequence
19. More about tRNA
• each tRNA carries only
one type of amino acid
– each tRNA has three
unpaired bases known
as an anticodon
– the anticodon sequence
is determined by the
amino acid it carries and
is complimentary to the
codon (on the mRNA)
20. Translation Continues…
3. Ribosome forms a
peptide bond between
the amino acids
(forming a protein)
21. Translation
4. The tRNA from the first
amino acid is then
released from the
ribosome
5. Ribosome then moves
to the next codon and a
new tRNA comes in
22. Translation Continues!
6. Polypeptide chain
grows until the
ribosome reaches a
“stop” codon
23. Translation Complete!
7. Once a stop codon is
reached, the ribosome
releases it’s polypeptide
chain and the mRNA
14. Label each Lettered Object
15. The Roles of RNA and DNA
• DNA is like the master plan of the cell
• If DNA is damaged, the whole cell could die
• RNA is like copies of this master plan that can
be taken all around the cell to be made into
product or proteins
• If RNA is damaged, it’s okay, more can be
made
16. Genes and Proteins
• genes code for proteins which are what carry
out expression of these genes
• proteins code for enzymes which cause certain
reactions to take place
– these reactions are what cause traits!