KA3 - gene expression :) Flashcards
What does gene expression involve?
The transcription and translation of DNA sequences
Only a fraction of the?
genes are expressed
Transcription involves how many types of RNA?
Three.
- mRNA
- tRNA
- rRNA
Describe RNA
RNA is single stranded
composed of nucleotides
it contains a RIBOSE sugar, a phosphate and one of the 4 bases.
What are the bases in RNA?
URACIL, thymine, cytosine, guanine
What is uracil complimentary to?
ADENINE!
What is rRNA?
rRNA is ribosomal RNA and it joins with proteins to from the ribosome
Describe mRNA
- mRNA carries a copy of the DNA code from the nucleus to the ribosome
- mRNA is transcribed from DNA in the nucleus
- mRNA is translated into proteins by ribosomes in the cytoplasm
- Each triplet of bases is called a codon
- Each codon codes for an amino acid
Describe tRNA
- tRNA folds due to complimentary base pairing
- each tRNA molecule carries its specific amino acid to the ribosome
- each tRNA has an anticodon at one end and an attachment site for an amino acid on the other
What is the process of transcription?
- RNA polymerase moves along DNA unwinding the double helix and breaking the hydrogen bonds between bases
- RNA polymerase synthesises a primary transcript of mRNA from RNA nucleotides by complimentary base pairing
- Uracil is complimentary to Adenine!
What is the process of RNA splicing?
- RNA splicing forms the mature mRNA transcript
- Introns of the primary transcript are non-coding, so removed
- Exons are coding regions, so are joined together to form the mature transcript
- The order of the exons remain unchanged
What is the process of translation?
- tRNA is involved in the translation of mRNA into a polypeptide at the ribosome
- Translation begins at a start codon and ends at a stop codon
- Anticodons bond to codons by complimentary base pairing, translating the genetic code into a sequence of amino acids
- Peptide bonds join the amino acids together
- Each tRNA leaves the ribosome as the polypeptide is formed
What is alternative RNA splicing?
Different proteins can be made from one gene, as a result of alternative RNA splicing
Different mature transcripts are produced from the same primary transcript depending on which exons are retained
What are polypeptide chains?
Amino acids are linked by peptide bonds to form polypeptides
Polypeptide chains fold to form the 3D shape of a protein, held together by hydrogen bonds and other interactions between individual amino acids
What are phenotypes?
A phenotype is determined by the proteins produced as a result of gene expression.
Environmental factors also determine phenotype
