Unit 1 (K3) - Gene expression Flashcards
What is RNA (ribonucleic acid) composed of?
Nucleotides containing ribose sugar, a phosphate and 1 of 4 bases.
What are the 4 bases found on RNA?
Cytosine, Guanine, Adenine, and Uracil.
What is Uracil complimentary to on RNA?
Adenine
Is RNA single-stranded or double-stranded?
Single-stranded
What is essential for mRNA synthesis?
RNA polymerase, ATP
What does mRNA do?
mRNa carries copy of the genetic code from the nucleus to the ribosome.
What are the triplets of bases called on mRNA?
Codons
What do codons do?
Code for a specific amino acid.
What does rRNA (Ribosomal RNA) do?
Carries a specific amino acid to the ribosome from the cytoplasm.
What is the structure of rRNA?
rRNA is folded due to complimentary bases on the same single strand, forming hydrogen bonds. rRNA has anticodons and a specific amino acid attachment site.
What are the exposed triplet of bases on rRNA called?
Anticodons.
What do codons on mRNA bind to?
Anticodons on tRNA.
What is the first stage of gene expression called?
Transcription
What is the second stage of gene expression called?
Translation
Explain the process of Transcription
- RNA polymerase unwinds the double helix breaking the hydrogen bonds between the bases.
- RNA polymerase synthesises a primary transcript of mRNA.
- It adds free RNA nucleotides to the forming strand by complimentary base pairing.
- RNA splicing forms a mature mRNA transcript.
- Mature mRNA transcript travels from the nucleus into the cytoplasm where it becomes translated into a sequence of amino acids.
Explain the process of Splicing
This is when introns (non-coding regions) of the primary transcript is removed. the exons (coding regions) are spliced together to form the mature mRNA transcript.
What is Alternative RNA Splicing?
This is where different proteins can be expressed from one gene.
What is the process of Alternative RNA Splicing?
This is where different mRNA transcripts are produced from the same primary transcript depending on which exons are retained.
Explain the process of Translation in brief steps
- Mature mRNA travels from nucleus to the ribosome in the cytoplasm.
- mRNA carries genetic code in the form of sets of 3 bases called codons.
- Anticodons on tRNA carrying a specific amino acid are matched to complimentary codons on mRNA.
- tRNA returns to the cytoplasm to collect another specific amino acid.
- The amino acids are joined together in a chain by peptide bonds.
- This forms a polypeptide chain.
What is a stop and start codon on mRNA?
Start codons act as a starting point for translation and when the stop codon is reached the ribosome disassociates and the polypeptide chain is released.
