Fill in the blanks

(a) DNA replicates in the …………… phase of the cell cycle.

(b) Mitosis occurs in our …………… cells.

(c) Meiosis occurs only in …………… cells.

(d) Modern humans have 46 chromosomes. Their sperms and eggs will have …………… chromosomes each.

(e) During the pairing of chromosomes in meiosis, the …………… chromosomes come to lie side by side.

(f) The two non-sister chromatids of a paired chromosome are attached to each other at …………… during the process of crossing over.

Name these:

(a) Two main constituents of Chromatin

(b) Two kinds of Nucleic acids

(c) Three components of a Nucleotide

(d) Four Nitrogenous bases

(e) Two kinds of Nitrogenous bases

(f) Two components of Nucleosome

(g) Two kinds of Cell division

(h) Four main phases of Karyokinesis

(i) Two steps of the process Mitosis

(j) Two kinds of haploid cells of human body

Correct the following statements for mistakes, if any.

(a) The four nitrogenous bases in the DNA are Guanine, Thiamine, Adrenaline and Cytosine.

(b) Genes are specific sequences of bases on a chromosome.

(c) A nucleotide is composed of a sulphate, a sugar (pentose) and a nitrogenous base.

(d) Nucleosomes are groups of cysteine molecules surrounded by DNA strands.

(e) If there are 46 chromosomes in a cell, there will be 23 chromatin fibres inside the nucleus during interphase.

Define the following terms:

(a) Chromosome

(b) Gene

(c) Cell division

(d) Chromatid

(e) Aster