1.3 Gene Expression Flashcards
What is Gene expression?
The transcription and translation of DNA sequences
How much of the genes in a cell are expressed?
Only a fraction
What are the three types of RNA involved in in transcription and translation?
mRNA tRNA and rRNA
What is RNA?
A single stranded molecule composed of nucleotides containing ribose sugar, phosphate and the bases; cytosine, guanine, adenine and uracil
What is the role of mRNA?
Carries a copy of the DNA code from the nucleus to the ribosome.
What is mRNA?
transcribed from DNA in the nucleus and translated into proteins by ribosomes in the cytoplasm. Each triplet of bases on the mRNA molecule is called a codon and codes for a specific amino acid
What is the role of tRNA?
Folds due to complementary base pairing. Each tRNA molecule carries its specific amino acid to the ribosome
What is a ribosome made up of?
Ribosomal RNA (rRNA) and proteins
What is a tRNA molecule?
Has an anticodon (an exposed triplet of bases) at one end and attachment site for a specific amino acid at the other end
What is the role of RNA polymerase in transcription?
Transcription of DNA into primary mRNA transcripts
What does the RNA polymerase do?
Moves along DNA unwinding the double helix and breaking the hydrogen bonds between the bases. RNA polymerase synthesises a primary transcript of mRNA from RNA nucleotides by complementary base pairing
What is Uracil complementary to in RNA?
Adenine
What does RNA splicing form?
A mature mRNA transcript
What are the introns of the primary transcript?
Non-coding regions and they are removed
What are the exons of the primary transcript?
Coding regions and are joined together to form the mature transcript
What happens to the order of exons during splicing?
It is unchanged
What is mRNA translated into by tRNA?
A polypeptide (at a ribosome)
Where does translation begin and end
Begins at a start codon and ends at stop codon
How do anticodons and codons bond and what does this lead to?
Via complementary base pairing, this translates the genetic code into a sequence of amino acids
What joins the amino acids together?
Peptide bonds
What happens to the tRNA when the polypeptide is formed?
It leaves the ribosome
What happens as a result of alternative RNA splicing?
Different proteins can be expressed from one gene
How are different mature mRNA transcripts produced?
From the same primary transcript depending on which exons are retained
What links amino acids together?
Peptide bonds to form polypeptides.
What do polypeptide chains fold to form?
The three dimensional shape of a protein
What holds polypeptide chains together?
Hydrogen bonds
What determines a proteins function?
It’s large variety of shapes
How is a phenotype determined?
By the proteins produced as a result of gene expression, and environmental factors also influence phenotype
