Gene Expression Flashcards
Chromosomes contain
a complete set with every gene needed to make every protein that the organism will ever need to make
however in a particular cell, only a small fraction of genes are ever expressed
Gene expression
Process by which specific genes are activated to produce a required protein
Gene expression process
Made up from transcription and translation
Involves RNA
mRNA
Moves from nucleus to ribosome
linear molecule
every 3 bases is described as a codon (codes for amino acid)
RIBOSOME
where proteins are synthesised in cytoplasm
How many natural amino acids
20
Protein Functions
Enzymes
Hormones
Other structures within body, such as collagen
RNA
JOINED TO FORM SINGLE STRAND
nucleotides joined by strong covalent bond
has sugar ribose (not deoxy)
Thyamine is replaced by Uracil
tRNA
cloverleaf-shaped molecule
made up from single stand RNA which folds due to base pairing to form unusual shape
Has triplet anti-codon site and an attachment for specific amino acid
rRNA
rRNA and proteins form ribosome
ribosome is site of protein synthesis
exons
Coding regions of gene
Introns
Non-coding regions
Process of removing introns
RNA splicing
RNA splicing
Produce primary transcript
Then remove introns and join remaining exons
This forms MATURE transcript of mRNA
Alternative RNA Splicing
Benefit of RNA splicing is that one gene can produce many different proteins as a result of segments are treated as introns and exons
Transcription
RNA polymerase moves along DNA unwinding strand
Hydrogen bonds break between pairs, which allows unzipping of helix
RNA polymerase breaks bonds, synthesises a primary transcript of mRNA using RNA nucleotides - these form hydrogen bonds with exposed DNA strand by complementary base pairing
primary transcript of mRNA is processed to produce mature transcript of mRNA
mature mRNA now ready to leave nucleus to go to ribosome
Translation
mRNA molecule leaves through cytoplasm and attaches to ribosome
tRNA molecule transport specific amino acid to ribosome
each mRNA codon codes for specific amino acid
First codon is start codon - beginning of translation
Anti-codons and codons match up and dorm complementary base pairs
peptide bond forms between adjacent amino acids to form polypeptide bond
using tRNA molecules exit ribosome and collect another specific amino acid
last codon is stop codon which signals end of translation
What causes polypeptide chains to fold into repeating pattern
hydrogen bonds
