Avichal's Blog : Biology

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Wednesday 13 July 2016

Q.1 A parenchymatous cells having thirty units of DNA, undergoes repeated mitotic division. Assess and explain the DNA units present in the cell(cells) during:- · Prophase · Anaphase · Early telophase · Late telophase · Interphase

ANSWER -

Prophase – It is largest stage of mitosis after interphase, at the time of prophase chromosomes in the beginning appears as five heteropycnotic threads and nucleus look like a ball of wool. The no. of DNA is 60 at this time.

Anaphase – It is the shortest of the mitotic phase, anaphase, occurs when the mutual attachment between two sister chromatids cases at that point the centromere of each chromatid on the metaphase plate separates from its sister centromere and the product of this division, which may now called daughter chromosomes move towards opposite pole of the spindle – total units as DNA = 60. Daugther units towards opposite pole -30-30.

Early telophase – 60 in cell (total) 30-30 towards opposite poles.

Late telophase – 30 in daughter nuclei, 60 in cell because at this time, cell having to daughter nuclei.

Interphase – Having 60 units of DNA due to duplication in S-phase of cell cycle.

Tuesday 12 July 2016

Q – How the discovery of electron microscope has helped in better understanding the ultrastructure of the cell?

Ans-

In microbiology there is very major role of electron microscope now a days to analyze micro organisms.

Antony van leeuwenhoek discovered simple microscope to observe small micro-organisms.by the help of simple microscope he successfully discovered bacteria, rbc,sperm cells.

Another scientist Robert hooke made compound microscope .

If we talk back past centuries the light microscope was the most important instrument for studying micro organism. However even the very best microscope have 0.2 µm resolution limit those days it was very difficult to seen those days it was very difficult to seen virus under light microscope because viruses are too small but prokaryotes con be observed because they are usually only 1 and 2 µm in diameter just their general shape and major morphological features are visible.

Q- Why mendal’s law of inheritance could get due to recognition after four decades from the time of their publication? Discuss briefly. Also discuss how the unpublished part of the result of mendal experiments delayed the discovery of linkage between genes?

Ans – Gregor Mendel a little known Central European monk, was only whose ideas had been Published in 1866 but largely went unrecognized until 1900 Which was long after his death.

His ideas published Experiment in plant hybridization in pro of the natural society (1866) Brunn. However for 34 years, his paper remained unknown, here three main reasons –

1. Those days Biologists were much attracted towards Darwin's theory of evolution, and concentrated on the study of life. Histories of various plants animals

2. Scientists never imagined the mathematics had any Connections with biology and so mendel’s statistical approach was beyond their comprehension.

3. Later some time mendel's work was rediscovered simultaneously in 1900 by Devries (Holland), Correns (Germany) and Tschermak (Austria). Since they were working on experimental breeding the significance of their discovery become apparent at once to them.

Mendel considered that a single gene is responsible for the traits, it is now known that several genes are involves in the production of same traits although a single gene substitution can influence the basic biochemical reactions and thus responsible for alternative end products, for a particular traits there may be two or more than two gene.

Mendel law of dominance as a fundamental inherent properly of the allele is no longer tenable to all cases mendel studied character were in each of even pairs there were only two alternative pairs there forms of each character, means only two allele were present in each character but later work showed for a character these can be several phenotypes.

Therefore the concept of alternative allelomorphs had to be modified by concept of multiple allelism. Exception of this phenomenon were discovered by Bateson Punnet (1905), due to linkage and crossing over.