DNA, genes, protein synthesis Flashcards
What is a gene?
Section of DNA with a specific base sequence that codes for a specific protein
Define genome
The complete set of genes in each cell of an organism
Define proteome
The full range of proteins produced by the genome in that organism
What are the 4 main features of the genetic code?
Read in triplets
Non-overlapping
Universal
Degenerate
Define transcription
Copying a gene into a short strand of mRNA, which is able to leave the nucleus
Define translation
Using the mRNA as a template to make a polypeptide chain
What does splicing remove?
Non coding introns from pre-mRNA
Summarise the process of translation
- mRNA attaches to ribosome
- tRNA transport specific amino acids to the ribosome by binding their anticodons with the mRNA codons - starting at start codon
- Peptide bonds form between adjacent amino acids
- Ribosome moves along one codon, releasing the first tRNA, which will pick up another amino acid
- Process continues until stop codon
What is a gene mutation?
Any change to the quantity of bases or base sequence in the DNA
What are the two main types of gene mutation?
Point mutations
Frame shifts
What is a point mutation?
A mutation only affecting one nucleotide/base
What is a base substitution?
A nucleotide is replaced with another nucleotide with a different base
What are the 3 possible outcomes of base substitution?
- New triplet codes for different amino acid —> effect depends on role of that AA —> polypeptide may change shape affecting function
- New triplet codes for same AA —> no effect
- New triplet codes for stop codon
What is base deletion/addition ?
A nucleotide is lost or added from DNA sequence
What is the consequence of base deletion?
Causes frame shift left - all subsequent triplets are affected
What are the 2 forms of chromosome mutation?
Polyploidy — changes in whole sets of chromosomes
Non-disjunction — when an organism has one extra or fewer chromosome
