Unit 1.3 - Gene Expression Flashcards
What does gene expression involve?
The transcription and translation of DNA sequences
What is the phenotype determined by?
The proteins produced as a result of gene expression
What can result from alternative RNA splicing?
Different proteins can be expressed from one Gene.
Only a fraction of genes in a cell are what?
Expressed
What are the characteristics of RNA?
It’s single-stranded, it contains the base uracil instead of thymine, and it contains the sugar ribose instead of deoxyribose
What are the complimentary base pairs in RNA?
Guanine + Cytosine
Uracil + Adenine
Describe translation?
Translation begins at a start codon and ends at a stop codon
Anti codons bond to codons by complementary base pairing, translating the genetic code into a sequence of amino acids
Peptide bonds join the amino acids together
Each tRNA then leaves the ribosome as the polypeptide is formed.
What does mRNA do?
Messenger RNA carries a copy of the genetic code on DNA to the nucleus to the ribosome
Why does tRNA fold?
Due to complementary base pairing
What does tRNA carry?
A specific amino acid to the ribosome
What are ribosomes composed of?
Ribosomal RNA and proteins
What are the regions of the primary transcript called?
Coding regions - exons
Non - coding regions - Introns
What does the production of mature mRNA by RNA splicing involve?
It involves the removal of introns and the joining together of exons.
This forms the mature transcript. The order of exons is unchanged during splicing.
What does RNA splicing form?
A mature mRNA transcript
What’s the role of RNA polymerase in transcription?
- RNA polymerase 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 translates mRNA into a polypeptide and where does it occur?
tRNA translates mRNA into polypeptide and it occurs at the ribosome
How can different mature mRNA transcript be produced from the same primary transcript?
It depends on which exons are retained.
What determines a proteins function?
It’s shape
What can also influence phenotype?
Environmental factors
What happens to mRNA?
- mRNA is transcribed from DNA in the nucleus
- It’s 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 does a tRNA molecule have?
An anticodon at one end and an attachment site for a specific amino acid at the other end
Describe the three dimensional structure of proteins?
- Amino acids are linked by peptide bonds to form polypeptides
- Polypeptide chains fold to form the three dimensional shape of a protein held together by hydrogen bonds and other interactions between individual amino acids.
