Transcript Nucleic Acids and Protein Synthesis

Nucleic Acids and Protein
Synthesis
CENTRAL DOGMA
• DNA  RNA  Protein  Trait
DNA TO PROTEINS
• DNA is the blueprint for
life – it contains your
genetic information
• The order of the bases
in a segment of DNA
(Gene) codes for a
particular protein; these
proteins then determine
your traits
• How do you get from a
4-letter code to an
entire organism?
A GENE IS A SEGMENT OF DNA THAT
CODES FOR A PROTEIN. NOT ALL DNA
CODES FOR PROTEINS.
DNA TO RNA: TRANSCRIPTION
• In the first step of protein synthesis, the code of DNA
is transcribed onto a molecule of RNA – this step of
the process is known as Transcription
• DNA is too big and too sensitive to leave the
nucleus. However, proteins are made in the
ribosomes, so the information in DNA must be
transferred.
• It will be transferred to a molecule of RNA
• RNA is also used because it allows the genetic
information to move from the nucleus (safe) to the
cytoplasm (dangerous)
RNA
• RNA = Ribonucleic acid
• It is still a nucleic acid – therefore it is
made up of nucleotides (3 components:
sugar, phosphate group and nitrogen
bases)
• It uses ribose as its sugar
• Instead of using thymine, it uses uracil
(A, U, G, C)
• It is a single strand only
Types of RNA - mRNA
• Messenger RNA (mRNA): single uncoiled chain that carries the
genetic information from the nucleus to the cytosol
Types of RNA - tRNA
 Transfer RNA (tRNA): single chain in the formation of a
hairpin shape, each piece is bound to a specific amino
acid
Types of RNA - rRNA
 Ribosomal RNA (rRNA): most abundant form, wraps
around ribosomal proteins to make up the ribosomes
where proteins are made
Transcription
• Process by which genetic information is copied (transcribed)
from DNA to RNA
• RNA polymerase initiates transcription by binding to a specific
area of DNA called promoters
• What do you think a promoter is?
• A promoter starts, or promoters the beginning of transcription
• Where the polymerase binds, the DNA strands separate and a
template is created upon which RNA is created
Transcription (continued)
• RNA polymerase attaches to the first nucleotide and adds on
complementary bases using uracil instead of thymine
• Continues until the polymerase reaches the termination signal
• What do you think a termination signal does?
• Termination signal causes the polymerase to release the DNA and RNA
Protein Synthesis
• When mRNA is produced it will be used in protein synthesis or
the production of proteins
• Proteins consist of polypeptides which consist of amino acids
• There are 20 possible amino acids
Translation: Protein Assembly
• This process takes the information that was transcribed into mRNA and translates it into
a protein
• It begins when a piece of mRNA attaches to a ribosome
• mRNA is “read” by the ribosome. It is read in segments of 3 letters called codons
• Each codon codes for a specific amino acid. That amino acid is brought by a piece of tRNA
which “transfers” amino acids.
• tRNA is also read in segments of 3 letters called anticodons. The anticodon is
complementary to the codon found on mRNA ( i.e. if the codon is AUG the anticodon is
UAC)
• Eventually a stop codon is reached. They do not code for amino acids. They tell the
ribosome to stop adding amino acids.
• Many ribosomes may work at once on one piece of mRNA
Genetic Code
• Correlation between
nucleotides and amino
acids
• Codon: 3 mRNA
nucleotides; codes for a
specific amino acid
• One codons codes to
start (AUG – amino
acid Methionine) and 3
codons can stop (UAA,
UAG, UGA – no amino
acids)
• If you had a codon
AAG, what amino acid
would you have?
• lysine