DNA As The Genetic Code Flashcards
What is a gene
A length of DNA that acts as a coding device for the synthesis of a particular polypeptide
What are the 4 main features of the genetic code
- Three base (triplet code)
- degenerate code
- non overlapping code
- universal code
What does the genetic code being degenerate mean
Most amino acids have more than one possible code
What does non overlapping code mean in terms of genetics
Each base in the sequence is read once
What is the significance of the genetic code being a triplet code
Three nucleotide bases codes for an amino acid
Why does DNA not act directly in protein synthesis
- Too long to move out of nucleus
- Retained in nucleus = better protected from the possibility of damaging changes
- Produces multiple copies of mRNA - many polypeptides synthesised simultaneously
What are the two stages of protein synthesis and give a brief description of each
- Transcription - DNA copied to mRNA
2. Translation - mRNA out of nucleus, into ribosome, direct synthesis of polypeptide
Describe the structure of mRNA
Single stranded Sugar phosphate backbone Base codes in sets of 3 Base of Uracil instead of T Shorter than DNA
Describe transcription
See notes
What are the two regions of pre-mRNA. Which one is the coding region?
Exons- coding region
Introns - non coding region
How is pre-mRNA converted into mRNA
Introns are cut out
Exons are spliced together
What are the three components of translation
mRNA
Ribosomes
Transfer RNA (tRNA)
Describe translation
See notes
What is a gene mutation
A spontaneous change in the DNA molecule
Often occurs as a result of a mistake when DNA is replicating
What are the two types of gene mutation? Give a brief description of each
Base substitution- base is replaced by another base
Base deletion- one base is omitted
