Gene Expression Flashcards
What is the first step of protein synthesis?
Transcription
What enzyme is responsible for RNA synthesis during transcription?
RNA polymerase
Where does translation occur in a cell?
Ribosome
What is the function of transfer RNA (tRNA) during translation?
Carries its specific amino acid to the ribosome
What is the role of messenger RNA (mRNA) in protein synthesis?
Carries a copy of the DNA Code from the nucleus to the ribosome. produced by the process of transcription.
What are the three types of RNA involved in protein synthesis?
mRNA, tRNA, rRNA
What is the function of ribosomal RNA (rRNA) during translation?
Forms the ribosome’s structure
What is the role of the stop codon in translation?
Signals the end of protein synthesis
What is the process called when mRNA is decoded to produce a protein?
Translation
What is an intron
Non- coding sequence of DNA
What is a primary transcript
Molecule made when DNA Is transcribed. Contains both the introns and exons
Ribosome
Site of protein synthesis- composed of rRNA and protein
RNA (4)
- Ribonucleic acid.
- single stranded
-contains ribose sugar instead of deoxyribose - The base uracil replaces thymine
RNA Splicing
Joining of exons following the removal of introns from a primary transcript
Are all genes expressed
Only a fraction of the genes in a cell are expressed
triplet of bases on mRNA molecule
Is called a codon and codes for a specific amino acid
tRNA (3)
-Transfer RNA. Has an anticodon (triplet of three bases) on one end
-An attachment site for a specific amino acid on the other end
-It carries its specific amino acid to the ribosome.
Two main stages of protein synthesis
Transcription
Translation
Genotype
Determined by an organisms DNA sequence
Phenotype
The physical result of the genotype + environment
E.g blue eyes
Alternative RNA splicing
One gene can produce many different proteins as a result of alternative RNA splicing.
Different mature mRNA transcripts are produced from the same primary transcript depending on which exons are retained.
Transcription process
- RNA polymerase enzyme moves along the DNA unwinding the double helix and breaking the hydrogen bonds between the bases
- RNA polymerase synthesises a primary transcript of mRNA using free RNA nucleotides by complementary base pairing. Uracil in RNA is complementary to adenine
- RNA splicing forms a mature transcript of mRNA from the primary transcript. This is where the introns which are the non coding regions are removed and the exons which are the coding regions are joined together to create the mature mRNA transcript.
- The order of the exons remain unchanged during splicing and the mature transcript is ready to leave the nucleus and travel to the ribosome
Translation process
- The mature mRNA transcript travels through the cytoplasm and attaches to the ribosome
- tRNA molecules travel to the ribosome
- a start codon signals the beginning of translation
- The anti codons bond to the codons by complementary base pairing. Translating the genetic code into a sequence of amino acids
- Peptide bonds form between the amino acids to form the polypeptide chain
- Used tRNA molecules exit the ribosome as the polypeptide chain is formed
- a stop codon signals the end of translation
Protein structure (3)
-Amino acids are linked by peptide bonds to form polypeptide chains.
-Polypeptide chains fold to form 3D Shapes of protein. Held together by hydrogen bonds and other interactions between individual amino acids.
- proteins have a wide variety of shapes which determines their functions
