Gaurav Gupta sir

2021-12-20 13:55:12 IMP TOPIC ....

Chromosomal Theory of Inheritance ........
Chromosomal theory of inheritance was given by Walter Sutton in 1902. This theory also explains the linear structure of chromosomes with genes in particular sites which was mentioned as loci while Boveri also studied this theory separately. So, this theory is also known as the Boveri-Sutton chromosome theory. According to this theory-

(i) Genes are found at specific locations on the chromosomes.

(ii) During meiosis the homologous chromosomes separate.

(iii) After fertilization the number of chromosomes becomes diploid.

(iv) Chromosomes segregate as well as assort independently.

Mutation...
The sudden changes in the sequence of DNA are known as mutations. The changes in the DNA may be heritable and will be passed onto the next generations affecting both the genotype, as well as the phenotype of an individual. The different types of mutation are frameshift mutations, insertions, deletions, duplications, substitutions, etc. Mutations may be harmful or may not affect at all.

(i) The addition or deletion of DNA bases will lead to changes in the reading frame called the Frameshift mutations.

(ii) The addition of DNA bases is known as insertions.

(iii) Removal of DNA bases is known as deletions.

(iv) If a piece of DNA is copied for more than one time is known as duplication.

Thus, these mutations will lead to a change in the DNA sequence resulting in the formation of the wrong protein. Open / Comment

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2021-12-20 10:14:18 𝙈𝙤𝙧𝙥𝙝𝙤𝙡𝙤𝙜𝙮 𝙛𝙪𝙧𝙩𝙝𝙚𝙧:-

Underground Stems:-

The stem of some plants lie below the soil surface. They are non-green, store food as means of perennation and vegetative propagation.

They are of following types:-

(a) Rhizome It is a prostrate thick stem growing horizontally beneath the soil surface. It has distinct nodes and internodes. The. nodes bear small scale leaves with buds in their axils, e.g., Zingiber (ginger officinale), Curcuma domestica (turmeric).

(b) Suckers These are non-green slender stem that grows horizontally in the soil and ultimately comes out to form a new aerial shoot. Each sucker contains one or more nodes with scale leaves and axillary buds, e.g., Mentha (podina), Chrysanthemum (guldaudi).

(c) Corm It is a swollen condensed form of rhizome which grows in the vertical direction in the soil. It stores a large amount of food, e.g., Amorphophallus, Colocasia (taro).

(d) Tuber It is a swollen end of underground stem branches. Each tuber has many notches on the surface called eyes or buds, which grow into new plants, e.g, Solanum tuberosum (potato).

(e) Bulb It is a highly reduced disc like stem. It bears a large number of fibrous adventitious roots at its base. Leaf bases form bulblets. The bulblets grow into new plants, e.g., Allium cepa (onion), Allium sativum (garlic). Open / Comment

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2021-12-19 23:00:02 Difference between Fimbriae and Pili

The fimbriae differ from the pili in the following ways:

Pili are fine hair like microfibers having pilin – a thick tubular structure while the fimbriae are tiny bristle-like fibers emerging from the surface of the bacterial cells

Pili are longer than fimbriae
Occurrence of the fimbriae in each cell is about 200-400 while the occurrence of pili are lesser than one to ten every cell

Fimbriae are found in the both the gram negative and positive bacteria both, pili are present in the gram negative bacteria only

The fimbriae are composed of fibrillin protein while the pilin protein makes up the pili

The fimbriae are less rigid compared to the pili

The formation of fimbriae is administered by the bacterial genes in the nucleoid area while the pili is administered by the plasmid genes

Fimbriae plays a role in attaching cells to the surface while pili are critical in bacterial conjugation Open / Comment

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2021-12-18 21:27:14 Handwritten

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