Gene expression Flashcards
What percentage of genes in a cell are expressed?
Only a fraction of the genes in a cell are expressed
What does gene expression involve?
The transcription, splicing and translation of DNA sequences
What is RNA and properties of RNA
RNA is single stranded and is composed of nucleotides containing ribose sugar, phosphate and bases: adenine, uracil, cytosine and guanine.
What bases pair in RNA?
Adenine pairs with Uracil and Cytosine pairs with Guanine
What are the three types of RNA?
mRNA, tRNA, rRNA
(Messenger RNA) (Transfer RNA) ( Ribosomal RNA)
What RNA’s are involved in transcription and translation
mRNA tRNA and rRNA
What is mRNA?
mRNA ( messenger RNA ) carries a complementary copy of the genetic code ( DNA ) from the nucleus to the ribosome.
mRNA is only complementary to ONE GENE in DNA
where is mRNA transcribed?
mRNA is transcribed in the nucleus and translated into proteins by ribosomes in the cytoplasm
where is mRNA translated?
mRNA is translated by ribosomes in the cytoplasm into proteins
where does RNA splicing occur?
RNA splicing occurs in the nucleus
what is a triplet of bases on mRNA called?
A codon
What is a triplet of bases on tRNA called?
An anticodon
What does the codon and anticodon code for?
A specific amino acid
how does tRNA fold?
tRNA folds due to complementary base pairing
What is the function of tRNA?
tRNA carries a specific amino acid to the ribosome for translation
Describe the structure of tRNA
tRNA has an attachment site for a specific amino acid at one end
tRNA has an anticodon ( exposed triplet of three complementary bases to mRNA codon ) at the other end
What forms the ribosome?
Ribosomal RNA ( rRNA ) and proteins
What is the function of rRNA?
To form the ribosomes along with proteins
What is stage 1 of transcription?
RNA polymerase moves along the DNA unwinding the double helix at a specific gene and breaking hydrogen bonds between bases.
What is stage 2 of transcription?
RNA polymerase synthesises a primary transcript of mRNA from RNA nucleotides by complementary base pairing to the DNA.
What occurs that causes a primary transcript to form a mature transcript?
RNA splicing
What occurs in RNA splicing?
Introns are removed and exons are retained and joined together to from a mature mRNA transcript
What are exons?
Exons are coding regions of DNA
What are introns?
Introns are non coding regions of DNA
Is the order of exons changed during splicing?
No, the order of exons is not changed.
How does translation begin and end!
Translation begins at a start codon and ends at a stop codon
What occurs in translation to produce a chain of amino acids?
Anticodons on tRNA bond to codons by complementary base pairing, translating the genetic code into a sequence of amino acids.
What joins amino acids together?
Peptide bonds join amino acids together.
What is formed when amino acids are bonded by peptide bonds?
A Polypeptide chain
What happens to tRNA as the polypeptide is formed?
tRNA leaves the ribosome to the cytoplasm to pick up another complementary amino acid for further translation.
What is alternative RNA splicing?
alternative RNA splicing is the process by which certain exons are retained or left out of the mature mRNA transcript to produce different proteins from one gene
What do polypeptides do?
Polypeptide chains fold to form the 3D shape of a protein
What are polypeptides held together by?
Hydrogen bonds and * other interactions between individuals amino acids *
What is phenotype determined by?
Phenotype is determined by proteins produced as a result of gene expression
What else influences phenotype?
Environmental factors.
