Genetic Engineering Multiple Choice Questions on “Markers”.
1. One of the commonly used markers is the URA3 gene. It encodes for ______ biosynthesis.
a) adenine
b) uracil
c) guanine
d) cytosine
Answer: b
Explanation: URA3 gene is a commonly used selectable marker. It encodes an enzyme for uracil biosynthesis. The enzyme encoded is orotidine-5’-phosphate decarboxylase.
2. CAN1 gene encodes a permease that causes uptake of _________ analogue.
a) toxic guanidine
b) toxic arginine
c) non-toxic guanidine
d) non-toxic arginine
Answer: b
Explanation: CAN1 gene encodes a permease that causes uptake of toxic arginine analogue. It causes consequent cell death.
3. Loss of SUP4 abolishes canavanine uptake, it is arginine analogue.
a) True
b) False
Answer: a
Explanation: Loss of SUP4 abolishes canavanine uptake. It is an arginine analogue. It causes canavanine resistance and cells can be readily selected.
4. Phosphoribosyl amino-imidazole carboxylase is a component of _______ biosynthesis pathway.
a) pyrimidine
b) purine
c) both purine and pyrimidine
d) only adenine
Answer: b
Explanation: Phosphoribosyl amino-imidazole carboxylase is a component of the purine biosynthesis pathway. The mutation for this enzyme is used in the selection of SUP4 gene.
5. Cells that have lost SUP4 gene acquire _____ pigment and are visibly distinguishable from others.
a) red
b) blue
c) green
d) pink
Answer: a
Explanation: Cells that have lost SUP4 gene acquire red colour and this makes them visibly distinguishable from others. This is the basis for selection.
6. Cells mutant in _____ gene can be selected by using 5-fluoro orotic acid, which is turned into ____ products by wild type protein.
a) SUP4, toxic
b) SUP4, non-toxic
c) URA3, toxic
d) URA3, non-toxic
Answer: c
Explanation: Cells mutant in URA3 gene can be selected by using 5-fluoro orotic acid, which is turned into toxic products by wild type protein. URA3 gene is responsible for uracil biosynthesis.
7. The replicating plasmid vectors in yeast can be divided broadly into how many categories?
a) 1
b) 2
c) 3
d) 4
Answer: b
Explanation: The replicating plasmid vectors in yeast can be broadly divided into two main categories. These are yeast centromeric plasmid and yeast episomal plasmid vectors.
8. Yeast centromeric plasmid (YCp50) contains ampicillin and tetracycline resistant gene.
a) True
b) False
Answer: a
Explanation: Yeast centromeric plasmid contains ampicillin and tetracycline resistance gene along with an origin of replication.
9. CEN4 in YCp50 is an example of _______
a) tetracycline resistant gene
b) ampicillin resistant gene
c) chromosomal centromeric sequence
d) autonomously replicating sequence
Answer: c
Explanation: CEN4 in YCp50is an example of chromosomal centromeric sequence. It allows partitioning of the plasmid in the same way as endogenous chromosomes are partitioned.
10. Yeast episomal plasmids have the following feature?
a) They contain ARS and CEL both
b) They contain ARS but not CEL
c) They contain CEL but not ARS
d) CEL is necessarily present but ARS may or may not be present
Answer: b
Explanation: Yeast episomal plasmids are those plasmids which contain ARS sequence but CEL may not be present necessarily.
11. Cis-acting REP 3 sequence is present in Yeast episomal plasmids. Choose the statement which holds true for it?
a) It is present along with chromosomal centromeric sequence
b) It is the site of action of proteins that help in partitioning
c) It gives less stability to that of YCs
d) The copy number is low than that of YCs