Download RNA and Protein Synthesis

RNA
Transcription
The Structure of RNA
 RNA consists of a long chain of nucleotides
• It is made of a 5-carbon sugar (ribose),
phosphate group and nitrogen base
• RNA contains the four bases A, C, G, and U
(uracil)
Comparing DNA and RNA
There are four main differences between DNA and
RNA
 The sugar in RNA is ribose instead of
deoxyribose
 RNA is generally single-stranded
 RNA contains uracil instead of thymine
 There are three types of RNA and only 1 type of
DNA.
Types of RNA
 There are three main types of RNA
1.
Messenger RNA – (mRNA) carries
copies of instructions for the assembly of
amino acids into proteins from DNA to
the rest of the cell
2.
Ribosomal RNA – (rRNA) makes up the major part
of the ribosome
3.
Transfer RNA – (tRNA) transfers amino acids to
ribosomes during protein synthesis
RNA’s Functions
 RNA can have many functions, but
most RNA is involved in protein
synthesis
 The assembly of amino acids into
proteins is done by RNA
Transcription
 Transcription is the process where RNA
molecules are produced by copying a
sequence of DNA into a strand of RNA

 Transcription requires an enzyme called RNA
polymerase to bind to the DNA and separate the
strands
 One strand of DNA is used as a template to
assemble nucleotides into a strand of RNA
Transcription Steps
1.
RNA polymerase binds to the DNA in the promoter
regions and cause the DNA to unzip and unwind.
 Promoter regions have specific base sequences that tell
where transcription should begin. Start and Stop
2.
The enzyme directs the formation of H bonds
between the bases on DNA and the complementary
bases of RNA nucleotides.
 3.
RNA polymerase moves along the section of
DNA and forms the sugar-to phosphate bonds
between the RNA nucleotides.
 4. The polymerase reaches a sequence of bases on
DNA that signals transcription to stop.
 5. The RNA strand detaches from the DNA and goes
out into the cytoplasm.
 6. The DNA reforms its H bonds and coils into the
double helix.
 ALL THREE types of RNA are transcribed in this
manner.
Transcription
Needs to go to Ribosome for Translation
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA
polymerase
DNA
RNA
Translation
Beginning of Translation
 The code is read three letters at a time
 Each group of three letters is called a
codon
Beginning of Translation
 A codon is 3 consecutive nucleotides
that specify a single amino acid that is
to be added to the polypeptide
 tRNA is responsible for bringing the
amino acid and turning into a
polypeptide chain.
Steps of Translation
Step 1: mRNA is transcribed (copied) from DNA in the
nucleus and released into the cytoplasm
Step 2: mRNA attaches to a ribosome in the cytoplasm
as each codon of mRNA is read in the ribosome, tRNA
brings in the proper amino acid
the amino acids are turned into a polypeptide chain
(each tRNA carries only one amino acid)
each tRNA has 3 unpaired bases called anticodons
the bases are complementary to one mRNA codon
YOU WILL NEED TO MAKE A tRNA and cut out to
explain your last step.
Steps of Translation
Step 3: The ribosomes form peptide bonds between
the first and second amino acids
the ribosome simultaneously breaks the bond
between the tRNA and its amino acid causing the
tRNA to be released
Step 4: The polypeptide chain grows (elongation)
until a stop codon is reached
the polypeptide chain is released to complete its
protein conformation.
Codon and Anti-codon
Nucleus
Messenger RNA
Messenger RNA is transcribed in the nucleus.
Phenylalanine
tRNA
Lysine
mRNA
Transfer RNA
Methionine
The mRNA then enters the cytoplasm and
attaches to a ribosome. Translation begins at
AUG, the start codon. Each transfer RNA has
an anticodon whose bases are complementary
to a codon on the mRNA strand. The ribosome
positions the start codon to attract its
anticodon, which is part of the tRNA that binds
methionine. The ribosome also binds the next
codon and its anticodon.
Ribosome
Start codon
Reading The Genetic Code
Protein Synthesis
 Proteins are made by joining amino acids into long
chains called polypeptides
 Each polypeptide contains a different combination of
the 20 amino acids
 Each polypeptide contains a different combination of
the 20 amino acids
 Amino acids are biologically important organic
compounds. The key elements of an amino acid are
carbon, hydrogen, oxygen, and nitrogen.
Final ACT PROTEIN!!!!
 When the Ribosome reaches the stop codon, the last
polypeptide bond is formed and the protein chain is
released. The mRNA is then released from the
ribosome.
PRACTICE FROM BEGINNING
Everyone write in comp book
CHECK YOUR WORK
Transcription
mRNA Strand should look like this!!!
Translation
Final Process to make a protein