biology-class-12-unit-06-chapter-04-genetics-and-evolution-molecular-basis-of-inheritance-l-4-12-a85lm20rcag

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-4 </Success>
### <primary style="font-size:24px"> Question 2 What are the differences between positive and negative supercoilings? </primary>
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- **Answer-**
- Positive supercoiling is overwound and negative supercoiling is underwound
- Direction of the twisting i.e. if twisting is in direction of DNA helix, it is positive supercoiling and if it is opposite to the direction of DNA helix, then it is negative supercoiling
 
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<footer style = "font-size: 18px">Genetics and evolution Molecular basis of inheritance $\rightarrow$ Question 1 What are nucleoid? $\rightarrow$ <span style = "color:blue"> Question 2 What are the differences between positive and negative supercoilings? </span> $\rightarrow$ Question 3 Why DNA packaging is needed? $\rightarrow$ Question 4 What are the different proteins involved in nucleosome model? </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-4 </Success>
### <primary style="font-size:24px"> Question 3 Why DNA packaging is needed? </primary>
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- **Answer-**

- DNA packaging is an important process in living cells. Without it, a cell is not able to accommodate the large amount of DNA that is stored inside

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![image](/subject-images/iitpal/image/biology-class-12-unit-06-chapter-04-genetics-and-evolution-molecular-basis-of-inheritance-l-4_12-a85lm20rcag-03.jpg)

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<footer style = "font-size: 18px">Question 1 What are nucleoid? $\rightarrow$ Question 2 What are the differences between positive and negative supercoilings? $\rightarrow$ <span style = "color:blue"> Question 3 Why DNA packaging is needed? </span> $\rightarrow$ Question 4 What are the different proteins involved in nucleosome model? $\rightarrow$ Question 5 What are the different types of chromosome depending on their centromere position? </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-4 </Success>
### <primary style="font-size:24px"> Question 4 What are the different proteins involved in nucleosome model? </primary>
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- **Answer-**   
- $\text {Histones proteins:}$
  - $\text {It includes H1, H2A, H2B, H3 and H4.}$

- $\text {Non histones proteins:}$

- It includes scaffold proteins, DNA
- polymerase, heterochromatin protein1 and polycomb are common non-histone proteins

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![image](/subject-images/iitpal/image/biology-class-12-unit-06-chapter-04-genetics-and-evolution-molecular-basis-of-inheritance-l-4_12-a85lm20rcag-04.jpg)

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<footer style = "font-size: 18px">Question 2 What are the differences between positive and negative supercoilings? $\rightarrow$ Question 3 Why DNA packaging is needed? $\rightarrow$ <span style = "color:blue"> Question 4 What are the different proteins involved in nucleosome model? </span> $\rightarrow$ Question 5 What are the different types of chromosome depending on their centromere position? $\rightarrow$ Search of genetic material </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-4 </Success>
### <primary style="font-size:24px"> Question 5 What are the different types of chromosome depending on their centromere position? </primary>
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- **Answer-**

- 1. Metacentric

- 2. Sub metacentric
 
- 3. Acrocentric
- 4. Telocentric
- 5. Acentric
- 6. Dicentric and polycentric

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![image](/subject-images/iitpal/image/biology-class-12-unit-06-chapter-04-genetics-and-evolution-molecular-basis-of-inheritance-l-4_12-a85lm20rcag-05.jpg)

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<footer style = "font-size: 18px">Question 3 Why DNA packaging is needed? $\rightarrow$ Question 4 What are the different proteins involved in nucleosome model? $\rightarrow$ <span style = "color:blue"> Question 5 What are the different types of chromosome depending on their centromere position? </span> $\rightarrow$ Search of genetic material $\rightarrow$ Objective </footer>

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### <primary style="font-size:24px"> _Streptococcus pneumonia_ </primary>
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- There is one major difference between these two types; the III-S strain has a smooth polysaccharide coat which makes it resistant to the immune system of mice, whereas the II-R strain lacks this coat and so will be destroyed by the immune system of the host

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<footer style = "font-size: 18px">Features of genetic material $\rightarrow$ Griffith's experiment $\rightarrow$ <span style = "color:blue"> _Streptococcus pneumonia_ </span> $\rightarrow$ Griffith's experiment on rat $\rightarrow$ Griffith's experiment on rat </footer>

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### <primary style="font-size:24px"> Griffith's experiment on rat </primary>
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- Injected type IIR bacteria into mice, the mice lived, and no bacteria were observed in blood

- Injected type IIIS bacteria into mice, caused the mice to develop pneumonia and die, and bacteria were recovered from their blood

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<footer style = "font-size: 18px">Griffith's experiment $\rightarrow$ _Streptococcus pneumonia_ $\rightarrow$ <span style = "color:blue"> Griffith's experiment on rat </span> $\rightarrow$ Griffith's experiment on rat $\rightarrow$ Griffith's experiment on rat </footer>

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### <primary style="font-size:24px"> Griffith's experiment on rat </primary>
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- Injected large amounts of heat-killed type IIIS bacteria into mice, the mice lived and no type IIIS bacteria were recovered from their blood

- Injected mice with a small amount of living type IIR bacteria, along with a large amount of heat-killed type IIIS bacteria the mice became infected with pneumonia and died, examined blood from the hearts of these mice, he observed live type IIIS bacteria

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<footer style = "font-size: 18px">_Streptococcus pneumonia_ $\rightarrow$ Griffith's experiment on rat $\rightarrow$ <span style = "color:blue"> Griffith's experiment on rat </span> $\rightarrow$ Griffith's experiment on rat $\rightarrow$ Conclusion </footer>

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### <primary style="font-size:24px"> Conclusion </primary>
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- Griffith finally concluded that the type IIR bacteria had somehow been transformed, acquiring the genetic virulence of the dead type IIIS bacteria. This transformation had produced a permanent, genetic change in the bacteria
- Though Griffith didn't understand the nature of transforming substance so he called this substance the **transforming principle**
 
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![image](/subject-images/iitpal/image/biology-class-12-unit-06-chapter-04-genetics-and-evolution-molecular-basis-of-inheritance-l-4_12-a85lm20rcag-17.jpg)

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<footer style = "font-size: 18px">Griffith's experiment on rat $\rightarrow$ Griffith's experiment on rat $\rightarrow$ <span style = "color:blue"> Conclusion </span> $\rightarrow$ Avery, MacLeod, and McCarty experiment $\rightarrow$ Avery, MacLeod, and McCarty experiment </footer>

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### <primary style="font-size:24px"> Avery, MacLeod, and McCarty experiment </primary>
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- They homogenize the heat killed IIIS bacteria and filtered
- Collected filtrate
- Added proteinase enzymes such as trypsin and chymotrypsin, known to break down proteins
-They poured the extract in culture of type IIR bacteria
-Found the colonies of IIR as well as IIIS bacteria

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<footer style = "font-size: 18px">Griffith's experiment on rat $\rightarrow$ Conclusion $\rightarrow$ <span style = "color:blue"> Avery, MacLeod, and McCarty experiment </span> $\rightarrow$ Avery, MacLeod, and McCarty experiment $\rightarrow$ Conclusion of experiment </footer>

- Finally added Dnase enzymes, capable of destroying DNA, in the filtrate
- They poured the extract in culture of type IIR bacteria
- Found the colonies of only IIR bacteria
- There was no any IIIS bacteria developed in the culture

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<footer style = "font-size: 18px">Conclusion $\rightarrow$ Avery, MacLeod, and McCarty experiment $\rightarrow$ <span style = "color:blue"> Avery, MacLeod, and McCarty experiment </span> $\rightarrow$ Conclusion of experiment $\rightarrow$ Conclusion of experiment </footer>

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### <primary style="font-size:24px"> Conclusion of experiment </primary>
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- Enzymes such as trypsin and chymotrypsin, known to break down proteins, had no effect on the transforming substance
- Ribonuclease, an enzyme that destroys RNA, also had no effect Enzymes capable of destroying DNA, however, eliminated the biological activity of the transforming substance
- **Avery,** MacLeod, and McCarty showed that purified transforming substance precipitated at about the same rate as purified DNA and that it absorbed ultraviolet light at the same wavelengths as does DNA

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![image](/subject-images/iitpal/image/biology-class-12-unit-06-chapter-04-genetics-and-evolution-molecular-basis-of-inheritance-l-4_12-a85lm20rcag-049-1359.6.jpg)

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<footer style = "font-size: 18px">Avery, MacLeod, and McCarty experiment $\rightarrow$ Avery, MacLeod, and McCarty experiment $\rightarrow$ <span style = "color:blue"> Conclusion of experiment </span> $\rightarrow$ Conclusion of experiment $\rightarrow$ The genetic material in viruses </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-4 </Success>
### <primary style="font-size:24px"> The genetic material in viruses </primary>
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- **Hershey Chase experiment**

- Hershey and Chase worked with bacteriophages (viruses that infect bacteria, which in turn produce more viruses)
- Bacteriophages are made of DNA and protein. The scientists wanted to know which substance the genetic material in the bacteriophage was made of

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<footer style = "font-size: 18px">Conclusion of experiment $\rightarrow$ Conclusion of experiment $\rightarrow$ <span style = "color:blue"> The genetic material in viruses </span> $\rightarrow$ Structure of T2 Bacteriophage $\rightarrow$ Life cycle of Bacteriophage </footer>

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### <primary style="font-size:24px"> Why radioactive phosphorus and sulfur? </primary>
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- To Know the fate of protein and DNA, they used radioactive forms (isotopes) of phosphorus and sulfur
 - A radioactive isotope can be used as a tracer to identify the location of a specific molecule, because any molecule containing the isotope will be radioactive and therefore easily detected

- DNA contains phosphorus but not sulfur, so Hershey and Chase used 32P to follow phage DNA during reproduction
 - Protein contains sulfur but not phosphorus: so they used 35S to follow the protein

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<footer style = "font-size: 18px">Structure of T2 Bacteriophage $\rightarrow$ Life cycle of Bacteriophage $\rightarrow$ <span style = "color:blue"> Why radioactive phosphorus and sulfur? </span> $\rightarrow$ Hershey-Chase experiment $\rightarrow$ Hershey-Chase experiment </footer>

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### <primary style="font-size:24px"> Hershey-Chase experiment </primary>
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- First, Hershey and Chase grew E. coli in a medium containing 32P and infected the bacteria with T2 so that all the new phages would have DNA labeled with 32P

- **They grew a second batch of E. coli in a** medium containing 35S and infected these bacteria with T2 so that all these new phages would have protein labeled with 35S

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<footer style = "font-size: 18px">Life cycle of Bacteriophage $\rightarrow$ Why radioactive phosphorus and sulfur? $\rightarrow$ <span style = "color:blue"> Hershey-Chase experiment </span> $\rightarrow$ Hershey-Chase experiment $\rightarrow$ Hershey-Chase experiment </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-4 </Success>
### <primary style="font-size:24px"> Hershey-Chase experiment </primary>
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- After allowing time for the phages to infect the cells, they placed the _E. coli_ cells in a blender and sheared off the now-empty protein coats (ghosts) from the cell walls

- They separated out the protein coats and cultured the infected bacterial cells. Eventually, the cells burst and new phage particles emerged

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<footer style = "font-size: 18px">Hershey-Chase experiment $\rightarrow$ Hershey-Chase experiment $\rightarrow$ <span style = "color:blue"> Hershey-Chase experiment </span> $\rightarrow$ Conclusion $\rightarrow$ Griffith's experiment </footer>

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### <primary style="font-size:24px"> Conclusion </primary>
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- These results confirmed that DNA is the genetic material

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<footer style = "font-size: 18px">Hershey-Chase experiment $\rightarrow$ Hershey-Chase experiment $\rightarrow$ <span style = "color:blue"> Conclusion </span> $\rightarrow$ Griffith's experiment $\rightarrow$ Thank you </footer>

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### <primary style="font-size:24px"> Griffith's experiment </primary>
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- $ \text {II R}  $ - Non Virulent - $ \text {II R}  $  
- $ \text {III S}  $ - Virulent - $ \text {III S}  $

- 1. $ \text {II R} \longrightarrow $ mice $ \longrightarrow $ mice live
 
- 2. $ \text {III S} \longrightarrow $ mice $ \longrightarrow $ mice dead  
- 3. Heat killed $ \text {III S} \longrightarrow $ mice $ \longrightarrow $ mice live  
- 4. $ \text {II R}  $ + HK $ \text {III S} \longrightarrow $ mice $ \longrightarrow $ mice dead

- Chemical $ \Rightarrow $ **<ins>Transforming Principle</ins>**

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<footer style = "font-size: 18px">Hershey-Chase experiment $\rightarrow$ Conclusion $\rightarrow$ <span style = "color:blue"> Griffith's experiment </span> $\rightarrow$ Thank you $\rightarrow$  </footer>