Genetics And Plant Breeding - Study Mode
[#651] Choose the wrong one.
Correct Answer
(D) The cdc mutants are temperature insensitive
(G) Generally dicots have a lower number of chromosomes than monocots
(I) Lipid biosynthesis occurs in peroxisome
Explanation
Solution: From the given statements about cdc gene and cell cycle, the last statement that cdc mutants are temperature insensitive is wrong while all other are correct. Genes that code for proteins that regulate the CELL DIVISION CYCLE. These genes form a regulatory network that culminates in the onset of MITOSIS by activating the p34cdc2 protein. Cdc genes are temperature sensitive. A total of 59 new temperature-sensitive cdc mutants are described which grow normally at 25°C but become blocked at DNA replication or mitosis when incubated at 36°C.
[#652] The plasmalemma and the tonoplast in an osmotic system function as
Correct Answer
(C) Semipermeable membrane
Explanation
Solution: The plasmalemma and the tonoplast in an osmotic system function as Semipermeable membranes. Plasmalemma is selectively permeable because substances do not cross it indiscriminately. The main function of a semipermeable membrane in cells is to separate the cell from the environment while allowing for the controlled transport of molecules in and out of the cell. Tonoplast is a single membrane that bounds the vacuoles and separates them from the cytoplasm. The vacuoles release their contents into the cytoplasm, diluting the cytoplasm and restoring the osmotic balance across the cell membrane.
[#653] Most of the mutations are
Correct Answer
(B) Harmful
Explanation
Solution: Most of the mutations are harmful. Mutational effects can be beneficial, harmful, or neutral, depending on their context or location. Most non-neutral mutations are deleterious. In general, the more base pairs that are affected by a mutation, the larger the effect of the mutation, and the larger the mutation's probability of being deleterious.
[#654] Which of the following is antitranspirant?
Correct Answer
(C) Both A and B
Explanation
Solution: Phenyl Mercuric Acetate (PMA) and Abscisic Acid (ABA) are antitranspirant. Antitranspirants are compounds applied to the leaves of plants to reduce transpiration. Fungicides like phenyl mercuric acetate (PMA) and herbicides like atrazine in low concentrations serve as antitranspirants by inducing stomatal closing. Abscisic acid will cause the flow of K+ ions from the guard cells and end in the closure of the stomata. Therefore, this is also categorize as antitranspirant.
[#655] If the DNA of a species has the mole fraction of G + C = 0.48, the mole fraction of A will be
Correct Answer
(A) 0.26
Explanation
Solution: If the DNA of a species has the mole fraction of G + C = 0.48, the mole fraction of A will be 0.26.