WEEK2: THE GENETIC CODE Flashcards
Define genetic code.
The genetic code is the set of rules used by living cells to translate information encoded within genetic material (DNA or RNA sequences of nucleotide triplets, or codons) into proteins.
Describe the flow of genetic material.
1.DNA replication
2.DNA transcription
3.DNA translation
What is DNA replication?
When does it happen?
Why does it happen?
*Copying of genetic material.
*Prior to cell division
*To ensure the new daughter cells have a complete copy of the cellular DNA.
What is transcription?
Transcription is the first step in gene expression. It involves copying a gene’s DNA sequence to make an RNA molecule.
Name the structure generated by transcription that carry information for protein synthesis.
mRNA.
State the 3 major classes of RNA and their function.
mRNA- Serves as a template code
tRNA- Serves as an adapter molecule.
rRNA- Holds translational components in correct position, catalyzes the reaction.
Name the enzyme that carries out transcription.
RNA Polymerase.
Transcription of a gene takes place in three stages: initiation, elongation, and termination.
Describe TRANSCRIPTION PROCESS.
1.Initiation.
*RNA polymerase binds to a sequence of DNA called the promoter, found near the beginning of a gene.
*Once bound, RNA polymerase separates the DNA strands, providing the single-stranded template needed for transcription.
2.Elongation
*One strand of DNA, the template strand, acts as a template for RNA polymerase.
- As it “reads” this template one base at a time, the polymerase builds an RNA molecule out of complementary nucleotides, making a chain that grows from 5’ to 3’.
- The RNA transcript carries the same information as the non-template (coding) strand of DNA, but it contains the base uracil (U) instead of thymine (T).
3.Termination
*Sequences called terminators signal that the RNA transcript is complete.
*Once they are transcribed, they cause the transcript to be released from the RNA polymerase.
State the 3 features of the genetic code.
SPECIFICITY: A codon always code for the same amino acid.
UNIVERSALITY: The same codon is used in all living organisms.
DEGENERACY: One amino acid may have more than codon.
State the start CODON.
AUG-Methionine
State the stop codons.
What are they also called.
UAA, UAG, UGA
Termination or nonsense codons
What is a codon?
What is it used for?
A sequence of three nucleotides which form a genetic code in a DNA or RNA for a specific amino acid.
To specify and code for all the 20 amino acids.
Name the 4 bases of an RNA.
Adenosine
Cytosine
Guanine
Uracil
Why IS THE GENETIC CODE CONSIDERED comma less mean?
In genetics, comma less means that there is no signal to indicate the end of one codon and the beginning of the next.
The arrangement of the codons is without a gap.
