In which stage of the first meiotic division, each chromosome undergoes longitudinal division to give rise to two sister chromatids ?
Zygotene
Diplotene
Diakinesis
Pachytene
In biotic community, which of the following can be called protective device ?
Mimicry
Symbiosis
Competition
Parasitism
Which of the following enzymes is used to join bits of DNA?
Ligase
Primase
Endonuclease
DNA polymerase
All eukaryotic genes contain two kinds of base sequences. Which of the following plays role in protein synthesis ?
Introns
Exons
Electrons
Both (a) and (b)
The direction of DNA replication is from :
amino acid end
3' end towards 5' end
5' end towards 3' end
amino terminus to carboxy terminus
In operon concept, regulator gene functions as:
repressor
regulator
inhibitor
initiator
A.
repressor
Operon is defined as a set of genes transcribed under the control of an operator gene. It is a segment of DNA containing adjacent genes including structural genes, an operator gene, and a regulatory gene. An operon is thus a functional unit of transcription and genetic regulation. In operon model, regulator gene directs the synthesis of proteins. It may be an active repressor or an inactive repressor.
Mirabilis jalapa is an example of
complete dominance
supplementary gene
incomplete dominance
complementary gene
Which of the following is dominant character according to Mendel ?
Dwarf plant and yellow fruit
Terminal fruit and wrinkled seed
White testa and yellow pericarp
Green coloured fruit and rounded seed
Lack of independent assortment of genes A and B in fruit fly Drosophila is due to :
repulsion
linkage
crossing-over
recombination
When two mutations are located in the same functional unit or in different functional units, then it is confirmed by :
test cross
back cross
reciprocal cross
complementation test