Bt cotton is a genetically modified organism. Taq DNA polymerase is obtained from Thermus aquaticus. Ti plasmid is from Agrobacterium tumefaciens, while pBR322 is an E. coli cloning vector.
Which of the following statements are true with reference to the sex determination in honeybees?
(A) An offspring formed from the union of a sperm and an egg develops as a female (queen or worker).
(B) An unfertilized egg develops as a male by parthenogenesis.
(C) A male has half the number of chromosomes than that of a female.
(D) Males produce sperms by meiosis.
(E) Honeybees have a haplodiploid sex-determination system.
Choose the correct answer from the options given below:
Male honeybees are haploid and produce sperms by mitosis, not meiosis. Therefore statement D is incorrect.
Since the origin and diversification of life on Earth, there have been five episodes of mass extinction of species.
How is the sixth, which is in progress, different from the previous episodes?
According to NCERT, the ongoing sixth mass extinction is primarily driven by human activities, with extinction rates estimated to be 100 to 1000 times higher than the natural background rate.
Which of the following statements are not true regarding restriction endonucleases?
(A) They are called molecular scissors. (B) These are the enzymes responsible for restricting the growth of bacteriophages in E. coli. (C) They cut the DNA only at the centre of the palindromic sites. (D) They remove nucleotides only from the ends of DNA fragments. (E) They recognise specific palindromic base-pair sequences.
Choose the correct answer from the options given below:
Restriction endonucleases are molecular scissors that recognize specific palindromic sequences. They do not always cut exactly at the centre of the recognition site, and they do not remove nucleotides from DNA ends; that is the function of exonucleases.