Chromosomes

 TOPIC#14                 CHROMOSOMES 

CHROMOSOMES

        INTRODUCTION

             It is 4th basic part of nucleus.

              *During cell division a thin dark like structure chromatin appears made up of DNA and Protein and when that chromatin recoiled again and again form a structure called as Chromosome.

    DISCOVERY

          It is discovered during study of cell division first time seen by strusburger accordin to some book in 1815 and named as chromosome by waldhyer in 1888.

But according to some book the chromosome was first studied by walther fleming in 1882 in salamander larvae.

  STRUCTURE

        The chromosome was studied by compound microscope and it appear to be made up of arms and centromeres.

Centromere is the place on the chromosome where spindle fibers are attached during cell division .

Each chromosome consist of two identical chromatids held together at kinetochore means centromere.

NUMBERS OF CROMOSOMES IN SOME ORGANISMS:

                   MAN                       46(23 PAIRS)

                  CHIMPANZEE        48(24 PAIRS)

                  ONION                     16(8 PAIRS)

                  GARDEN PEA       14 (7 PAIRS)

                  FROG                     26(13 PAIRS)

                  DROSOPHILA     8(4 PAIRS)

                  POTATO                48(24 PAIRS)

                 PIGEON                80(40 PAIRS)

                 HONEY BEE       28 (14 PAIRS)

COMPOSITION OF CHROMOSOME:

            It is made up of DNA and PROTEINS.All the information of cell activities located on chromosomes in the form of genes(Part of DNA).

IMPORTANT POINTS:

The number of chromosomes in all individuals of same species remain constant generation after generation.

The full number of chromosomes in cell(somatic) called as diploid(2n).

The half number of chromosomes in cell(Germ) called as haploid(n).

IMPORTANT MCQS IN THIS TOPIC

1-The darkly stained body appears during cell division is called:

Answer:  CHROMOSOMES

2-The number of chromosomes in onion is:

Answer:  16(8 PAIRS)

3-The chromosomes is made up of:

Answer:  PROTEIN AND DNA

4-The number of chromosomes in pigeon:

Answer: 80(40 PAIRS)

5-The arms of chromosomes are called:

Answer:  CHROMATIDS

6-The chromosome appears during which stage;

Answer: DURING CELL DIVISION

7-The point where are chromatids attached are called:

Answer:  CENTROMERE

8-The centromere is also called as:

Answer:  PRIMARY CONSTRICTION

9-The germ cells have half chromomsomes called as:

Answer:  HAPLOID

10-The bacteria cell have_chromosome:

Answer:   1

11-The drosophila have_linkage groups:

Answer: 8 

IT IS SHORT NOTE ON CHROMOSOME WE WILL STUDY IT IN DETAIL IN CHAPTER INHERITANCE.

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