Genetic Engineering Multiple Choice Questions on”Generation of Transgenic Organisms”.
1. If the embryo is at one-cell stage then it is found in ____________
a) ovary
b) oviduct
c) uterus
d) either ovary or uterus
Answer: b
Explanation: When embryo is at one-cell stage it is found in oviduct. This is important for the generation of whole organisms that are transgenic. Isolation of one-cell embryo is done and then it is micro-injected into the pro-nucleus.
2. Embryonic stem cells are also used for generation of transgenic organisms. They are obtained from _______ of a developing ________
a) trophoectoderm, gastrula
b) trophoectoderm, blastula
c) inner cell mass, blastula
d) inner cell mass, gastrula
Answer: c
Explanation: Embryonic stem cells are also used for generation of transgenic organisms. They are obtained from the inner cell mass of a developing blastula. A developing blastula composes of inner cell mass and it is surrounded by trophoectoderm.
3. Embryonic stem cells (ES) are isolated and are injected again into the blastocoel of a developing embryo. The embryo which develops is entirely made up of these cells only.
a) True
b) False
Answer: b
Explanation: ES cells are isolated and are injected into the blastocoel of the developing embryo. But the embryo is not composed wholly of ES cells and thus it is said to be chimeric.
4. ES cells are used in order to ensure that insertion is done at the required chromosomal location and it is called as ____________
a) gene targeting
b) knocking out
c) knocking in
d) gene disruption
Answer: a
Explanation: ES cells are used in order to ensure that insertion is done at the required chromosomal location and the process is termed as gene targeting. In some cases, it is not necessary to ensure that integration is taking place at a normal chromosomal location.
5. If a gene is inactivated by gene targeting then it is called as ____________
a) knock-in gene
b) knock-out gene
c) gene disruption
d) insertional inactivation
Answer: b
Explanation: If a gene is inactivated by gene targeting then it is called a knock-out gene. If a gene is replaced by some other gene then it is called as knocking in.
6. Integration events may be insertional involving _____ crossover or replacement involving _____ crossovers.
a) single, single
b) double, double
c) double, single
d) single, double
Answer: d
Explanation: Integration can be done by either insertion or replacement. Insertion is carried out by using single crossover and replacement is carried out by double crossover.
7. It is necessary to analyze the genome of transgenic cells to confirm that the site of integration is correct. This is carried out by southern blotting.
a) True
b) False
Answer: a
Explanation: It is necessary to analyze the genome of transgenic cells to confirm that the site of integration is correct and it is carried out by southern blotting. DNA from cultures derived from individual transformed cells is used for screening.
8. The gene targeting approach produces individuals which are ______ for inactivation of the gene.
a) homozygous
b) heterozygous
c) either only homozygous or only heterozygous
d) both heterozygous and homozygous