State the differences between: [4 MARKS]
(a) Chromosome and chromatid
(b) Centrosome and centromere
(c) Aster and spindle fibres
(d) Haploid and diploid

Each Part: 1 Mark

(a)
Chromosomes: They are fine thread-like structures present in the nucleus. They carry genes which are responsible to carry hereditary characters from parents to the offspring.
Chromatid: Each longitudinal half of a chromosomes is known as chromatid. A chromosome is composed of two delicate threads, the chromatids. These are joined together by centromere.
(b)
Centrosome: It is an organelle found in animal cells only. It occurs close to the nucleus and usually has two small granules called centrioles, which are embedded in a cytoplasmic body, called centrosome. It helps in cell division.
Centromere: Each chromosome appears constricted at one place. This place is called the centromere. The centromere attaches the chromosome with spindle fibres during cell division.
(c)
Aster: During prophase in mitosis, the centrosome splits into two. The two daughter centrioles move apart and each occupies one pole of the cell. Each centriole is surrounded by radiating rays, collectively called aster.
Spindle fibres: During prophase in mitosis, a number of fibres appear between the two daughter centrioles, which are called the spindle fibres.
(d)
Haploid: Haploid chromosomes are those which contain only one allele for a gene.
Diploid: It means two chromosomes, one from each parent.