Gene expression Flashcards
What is a genotype
Determined by the sequence of DNA bases in its genes
What is a phenotype
Determined by the proteins synthesised when genes are expressed
Describe RNA
Ribonucleic acid is single stranded and consists of phosphate, ribose sugar and a base. CYtosine, Guanine, Adenine or Uracil
Describe tRNA
Transfer RNA is folded due to complementary base pairs forming hydrogen bonds on the same strand. tRNA carries specific amino acids from the cytoplasm to the ribosome. it consists of an anticodon and an amino acid attachment site
Describe rRNA
rRNA and proteins form a ribosome
Describe mRNA
Messenger RNA carries a copy of DNA from the nucleus to the ribosome.
What is a codon
A triplet of of bases that code for an amino acid
Describe the two steps of transcription
RNA polymerase moves along the DNA, unwinding the double helix and breaking the hydrogen bonds. As it does this, it synthesises a primary transcript of mRNA.
Describe the two steps in Splicing
Exons in the primary mRNA transcript are retained and introns are removed. The exons are then joined together to form the mature mRNA transcript
Describe the 6 steps of Translation
- mRNA travels from the nucleus to the ribosome
- mRNA carries the genetic code in sets of 3 bases called codons
- Anticodons of tRNA, carrying its specific amino acid are joined to the complementary codons of mRNA
- tRNA disengages and returnes to the cytoplasm to collect another molecule of its specific amino acid.
- The amino acids are joined together by peptide bonds
- When the stop codon is reached, the ribosome disassociates and the chain of amino acids is released as a polypeptide
What is alternative RNA splicing
Different proteins can be expressed from the same primary mRNA transcript depending on which exons are retained.
