Question

a) Its time to refresh your memory on the different types of DNA mutations. Define the following:
• point mutation, substitution, transversion, transition, point deletion, point insertion, frameshift mutation
b) Define “gene regulation” and describe why this is an important process for all cells?
c) Define operon and describe the major components that exist in an operon. Why are operons most
common in prokaryotes but not in eukaryotes?
d) Differentiate between “inducible operon” and “repressible operon”.

Answer 1

point mutation- it is the mutation affecting one single nucleotide base of a nucleic acid by means of addition, deletion or substitution.

Substitution- it is a mutation that exchanges one base for another

Transversion- It is a specific kind of point mutation in DNA, in which a single purine is substituted for a pyrimidine or vice versa.

Transition- It is a base-pair-substitution point mutation that substitutes a purine for the other purine or a pyrimidine for the other pyrimidine, so that the purine/pyrimidine axis of the DNA molecule is maintained

Point deletion- Point mutation by the deletion of a nucleotide during replication

Point Insertion- Point mutation b addition of an extra base pair to a sequence of bases

Frameshift Mutation- a mutation caused by the addition or deletion of a base pair or base pairs in the DNA of a gene resulting in the translation of the genetic code in an unnatural reading frame from the position of the mutation to the end of the gene.

b) Gene regulation includes the mechanisms that act to induce or repress the expression of a gene. It is important to regulate the differentiation and proper development and functioning and also to respond to an kind of changes.

c) operon- it is a unit made up of linked genes which regulate other genes responsible for protein synthesis.

components of operon - made up of 3 basic DNA components:

• Promoter – a nucleotide sequence that enables a gene to be transcribed
• Operator – a segment of DNA to which a repressor binds
• Structural genes – the genes that are co-regulated by the operon.

When an operon is transcribed, all of the genes on the operon are on the same mRNA. Operons occur in prokaryotes, but not eukaryotes. In eukaryotes, each gene is made on individual mRNAs and each gene has its own promoter

d) inducible operon-i) it is a specific small molecule that binds to a bacterial regulatory protein and changes its shape so that it cannot bind to an operator, thus switching an operon on ii) if lactose absent, the repressor is active, and blocks RNA polymerase from binding to operator iii) if lactose present, repressor is inactive and RNA polymerase binds to operator

repressible operon- i) it is the protein that inhibits gene transcription ii) this protein binds to the DNA in or near the promoter.
iii) when bound to operator there is no production of tryptophan iv) if too much tryptophan present, bounds to repressible operon, which then binds to operator