Jacob Syndrome In Hindi : Biology Blog

                                     Jacob Syndrome 

Jacob syndrome is due to presence of extra Y chromosome in males . This syndrome is also known as super male or criminal syndrome . Usually  in human being , there are 46 chromosomes but such a patients have extra Y chromosomes due to this the chromosome number changed from 46 to 47 . For more information click on this video . 


Visit the full video for Jacob or supermale syndrome .

   

Prokaryotes: Structure & Examples | Biology Blog

                              Prokaryotes

                    characteristics, cell structure , examples of prokaryotic cells                                    

Prokaryotes are consist of eubacteria and arceha. The Organism that comes under  Prokaryotes are microscopic, simple organisms and the cell lacks a true nucleus.   The major characteristics of prokaryotes are as below -


Features of prokaryotic Organism -

• True membrane-bound nucleus -   absent
  
  
• DNA complexed with histone - absent
  
  
• Number of chromosomes - One
  
  
• Ribosome - 70 S and 80 S
  
  
• Unit membrane-bound organelles- absent
  
  
• cell wall -  present in most of the prokaryotic cells and made up of peptidoglycan.
  
  
• Mitosis and meiosis - absent
  
  
• genetic recombination -  partial
  
  
• Mitochondria -  absent
  
  
• chloroplast - present 
  
  
• Sterol in Plasma membrane - Present 

Cell Structure Of Prokaryotes-  The word prokaryotes comes from the Greek word where Pro means before and Karyon means nucleus. The prokaryotic organism does not have true nucleus and nuclear membrane. there are following structure present in the cells of prokaryotes -

• Capsule - In most of the prokaryotes organisms like bacteria, an extra layer is present in addition to the cell wall that protects the organisms from any harm and also helps in moisture retention.
  
  
• Cell Wall - The cell wall is present in most of the prokaryotes and maintains the shape of the cell. In plants, the cell wall is made up of cellulose while in that of fungi it is made up of  Chitin.
  
  
• Cytoplasm- The gelly like structure distributed overall the cell is known as Cytoplasm. In the cytoplasm , cell organelles are present.
  
  
• Cell Membrane - The cell membrane is a layer that protects the entry and exit of the foreign substances in the cell.
  
  
• Ribosomes - Ribosomes are the protein factory of the cell. There are two types of ribosomes present in the prokaryotic cells one is 70 S and the other one is 80 S.
  
  
• Pilli - The hair-like outgrowth present on the capsule of the cell is known as pilli that further helps in reproduction. 

• Flagella- these are also hair-like structure helps in the movement of the cell.
  
  
• Plasmid - Plasmid is the extrachromosomal circular  DNA, it is also present in the prokaryotic cells.

Examples of Prokaryotes - Bacteria cells and Archebacteria cells are examples of Prokaryotes. Some features of bacteria and archebacteria are mentioned below - 

Bacterial Cells -

•  Bacterial cells are microscopic, relatively simple organisms.
  
  
• They do not have true nucleus present in them.
  
  
• Pilli, flagella, and capsule are some unique features of bacterial cells.
  
  
• The extrachromosomal DNA, also called plasmid are present in the cell.
  
  
• They have different types of shapes like - rod shape, cocci , vibrio, spirilla, and bacillus. 
  
  
• Generally, they are 0.2 to 0.5 in diameter but some bacteria are so large in size that are visible to the unaided eye. For example - Thiomargarita namibiensis.

Archebacteria - 

• Archebacteria are highly diverse with respect to morphology, reproduction, physiology, and ecology.
  
  
• They can be aerobic, anaerobic, facultative, and obligation.
  
  
• They do not have true nucleus.
  
  
• Ribosomes of the 70S are present.
  
  
• They are present in extreme aquatic or terrestrial habitats.    

Related Links - Difference between Prokaryotic and Eukaryotic cells 

What are Important Features of Flatworms

                                  Phylum Platyhelminthus 

Here are some important  features of phylum Platyhelminthus . Let's overview it . 

Important Characters -               

• They are acoelomate and triploblastic .
  
  
• Body is leaf like or in ribbon shape forms and do not have  segmentation .
  
  
• They do not any circulatory system .
  
  
•  Digestive system absent .
  
  
• They follow organ level system of  organisation .
  
  
• They are bilaterally symmetrical organism .
  
  
• Hermaphrodite .
  
  
• Nervous system comprises of  brain and two longitudinal nerve which is connected at intervals by transverse commissures .
  
  
• They have internal fertilization .
  
  
• Asexual reproduction through fission . 
  
  
• Flame cells are present in the form of excretory system .
  
  
• Example - Taenia (Tapeworms )  , Fasciola ( Liver Fluke ) . 
  

Chargaff's rule of DNA | Biology Guide

                                      Chargaff's Rule 

Erwin Chargaff's proposed two rules which are known as chargaff rules. This role plays a key role in double helix structure discovery. Here the rules are : -

Rule 1 -  In DNA structure the total number of purines is equal to a total number of pyrimidine .,i.e., the number of guanine units is equal to the number of cytosine unit and the number of adenine units is equal to thymine units.

Rule 2 -   In every species there is a unique composition of  DNA  is present in its body.

Hence ,  in double stranded structure of DNA
                                      A = T =  1
                                      G = C =  1
                Also, the percentage of C + G does not essentially equal to the percentage of A+ T     

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