Comparison between tract and nerve

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  Comparison between tract and nerve Nerve Nerve contain bundle of axons (nerve fibers) in the peripheral nervous system (PNS) that transmits signals between the central nervous system (CNS) and other parts of the body. It is the most important part of peripheral nervous system Location: Peripheral nervous system. Structure: Made of axons, connective tissue layers (endoneurium: axon is surrounded by it , perineurium: bundle of axons are surrounded by it, epineurium: whole nerve trunk is surrounded by it), and blood vessels. It gets myelination by Schwann cell   Function: Carries sensory signals to the CNS (afferent) from peripheral part of body or motor signals carry from from the CNS (efferent) to target organs like skeletal muscle, cardiac muscle, smooth muscle or glands Example: Sciatic nerve, median nerve, except optic nerve (though optic nerve is technically part of CNS in develop...
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Difference between nondisjunction in mitosis , meiosis I and meiosis II

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Difference between nondisjunction in mitosis , meiosis I and meiosis II


nondisjunction in mitosis

nondisjunction in meiosis I

nondisjunction in meiosis II
During cell division, each chromosome is composed of two identical sister chromatids. During the anaphase stage of mitosis , these sister chromatids normally separate, and one chromatid goes into each daughter cell.
However, when nondisjunction occurs, the chromatids do not separate.
The result is that one cell receives both chromatids, while the other cell receives neither.  when mitosis is complete; one cell has an extra chromosome, while the other is missing one.

In Meiosis I, a pair of homologous chromosomes does not separate due to non-disjunction.

So the resulting cells, one cell has two copies of a chromosome, while the other cell has no copies. The four total cells produced will all have chromosomal abnormalities.

 

In  Meiosis II, like mitosis;  a pair of sister chromatids fail to separate properly so  one daughter cell will have an extra chromosome and one daughter cell will be missing a chromosome.

 

Two abnormal cells are produced

Four abnormal cells are produced

Two normal & two abnormal cells are produced

 

Chromosome number of One cell:

2n+1 = (2*23) + 1= 46+1=47

Chromosome number of Another cell: 2n-1 = (2*23) - 1= 46-1=45

 

Chromosome number of two cells:

2n+1 = (2*23) + 1= 46+1=47

Chromosome number of Another two cell: 2n-1 = (2*23) - 1= 46-1=45

 

Chromosome number of normal cells are n=23

Chromosome number of abnormal cells  :

One cell : n+1 = 23+1=24

Another cell: n-1=23-1=22

 

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