DNA, Genes, Protein Synthesis Flashcards
What is a gene?
A section of DNA that contains coded information for making polypeptides and RNA
Genetic code
The sequence of DNA triplets bases (or mRNA codons) that code for a specific amino acid.
Degenerate coding
When an amino acid is coded for by more than one triplet
Universal
All species have the same four bases, and each base sequence codes for the same amino acid in all species.
Non Overlapping
The first three bases are read as one codon and the next three are read as another, so each base is only part of one codon.
Exons
Sections of a gene: Coding sequences
Introns
Sections of a gene: Non coding sequences
Homologous pair
Two chromosomes that carry the same genes
Allele
An alternative form of a gene
Mutation
Changes in the base sequences that results in a different amino acid in chain causes diff. polypeptide which changes protein.
Genome
Complete set of genes in a cell
The function of Messenger RNA
Transfers DNA from nucleus to cytoplasm.
Structure of tRNA
Small molecule
Single-stranded chain folded into a clover leaf shape
Amino acid binding site, one end of the chain extends beyond the other so that the amino acid can easily attach to
Anticodon
sequence of three bases complementary to three bases on the codon
Transcription
Process of making pre-mRNA:
DNA helicase causes two strands of DNA to separate
The bases on one side of the DNA pair with its complementary base.
RNA polymerase moves along the strand and joins them together to form pre mRNA
RNA polymerase reaches stop codon and pre mRNA detaches.
Splicing
Formation of mRNA. Introns are removed from the pre-mRNA, exons are spliced together.
Prokaryotes
No splicing, mRNA produced straight from DNA as it contains no introns.
Translation
mRNA leaves nucleus through nucleus pore into cytoplasm.
At the ribosomes, anticodons on tRNA molecules complementary to codons on mRNA attach to codons and bring amino acids
Amino acids form peptide bonds, forming a polypeptide chain until stop codon.
Role of ATP in translation
ATP is hydrolysed into ADP and a phosphate which:
1) provides the energy for the amino acids to bind to the tRNA at the amino acid binding site.
2) provides the energy for the formation of peptide bonds between the amino acids.
Role of ribosomes in translation
- Attaches to mRNA and houses tRNA, allowing codon-anticodon complementary base pairing
- Allows peptide bonds to form between amino acids
