biology-class-12-unit-06-chapter-01-genetics-and-evolution-molecular-basis-of-inheritance-l-1-12-cequcogxhza

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-1 </Success>
### <primary style="font-size:24px"> Rosalind Franklin & Maurice Wilkins </primary>
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- In 1951, produced the X-ray crystallography pictures of DNA which Watson and Crick used to determine the structure of double-stranded DNA

- **Watson and Crick**

- Discoverered of the structure of DNA in 1953

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<footer style = "font-size: 18px">DNA $\rightarrow$ Discovery of DNA.... $\rightarrow$ <span style = "color:blue"> Rosalind Franklin & Maurice Wilkins </span> $\rightarrow$ Chemical nature of DNA $\rightarrow$ Nucleotide </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-1 </Success>
### <primary style="font-size:24px"> Watson and Crick model </primary>
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- DNA is a double stranded helix
 - DNA has two chains, twisted around each other on a common axis. It is commonly a right handed helix
- The two strands are polar with 5' and 3' ends
- The two strands are antiparallel, one strand runs in 5' to 3' and another in 3' to 5' direction
 - The two chains are not identical but complementary to each other due to base pairing

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<footer style = "font-size: 18px">Bonds within DNA... $\rightarrow$ Bonds between two strands of DNA $\rightarrow$ <span style = "color:blue"> Watson and Crick model </span> $\rightarrow$ Watson and Crick model $\rightarrow$ Watson and Crick model </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-1 </Success>
### <primary style="font-size:24px"> Watson and Crick model </primary>
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- Each turn of helix is 3.4 nm, with 10 pairs of nucleotides, each pair placed at a distance of 0.34nm and width of DNA is 2nm
- Each strand has hydrophilic deoxyribose phosphate back bone on periphery and hydrophobic bases stacked inside
- The two strands of helix are held by both hydrogen bonds between bases

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<footer style = "font-size: 18px">Bonds between two strands of DNA $\rightarrow$ Watson and Crick model $\rightarrow$ <span style = "color:blue"> Watson and Crick model </span> $\rightarrow$ Watson and Crick model $\rightarrow$ Different forms of DNA </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-1 </Success>
### <primary style="font-size:24px"> Different forms of DNA </primary>
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- B-DNA (Balanced DNA) duplex model proposed by Watson and Crick is right handed spiral

- Another right handed duplex model is A-DNA (Alternate DNA). Here, a single turn of helix has 11 base pairs

- C-DNA has 9 base pairs per turn of spiral and right handed

- D-DNA the number is only 8 base pairs and are also right handed

- Z-DNA (Zigzag DNA) is left-handed double helix with zigzag back-bone, alternate purine and pyrimidine bases, single turn of 45 A length with 12 base pairs

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<footer style = "font-size: 18px">Watson and Crick model $\rightarrow$ Watson and Crick model $\rightarrow$ <span style = "color:blue"> Different forms of DNA </span> $\rightarrow$ Functions of DNA $\rightarrow$ Differences between DNA & RNA </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-1 </Success>
### <primary style="font-size:24px"> Differences between DNA & RNA </primary>
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| Feature                               | RNA                                      | DNA                                      |
|----------------------------------------|------------------------------------------|------------------------------------------|
| Structure                             | Single-stranded (except in some viruses) | Double-stranded (except in few viruses)  |
| Sugar                                  | Ribose                                   | Deoxyribose                               |
| Bases                                 | Adenine, Guanine, Cytosine, Uracil       | Adenine, Guanine, Cytosine, Thymine       |
| Base Pairing                          | Adenine pairs with Uracil                | Adenine pairs with Thymine                |

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<footer style = "font-size: 18px">Functions of DNA $\rightarrow$ Differences between DNA & RNA $\rightarrow$ <span style = "color:blue"> Differences between DNA & RNA </span> $\rightarrow$ Differences between DNA & RNA $\rightarrow$ Lets answer these questions... </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-1 </Success>
### <primary style="font-size:24px"> Differences between DNA & RNA </primary>
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| Feature                               | RNA                                      | DNA                                      |
|----------------------------------------|------------------------------------------|------------------------------------------|
| Purine vs Pyrimidine                  | Purine is not equal to Pyrimidine        | Purine is equal to Pyrimidine (Chargaff's rule) |
| Complementary Nucleotides             | Form hairpin loops and helical structures | Throughout the length of DNA              |
| Genetic Material                      | Present in some viruses                  | Present in all living organisms          |
| Length                                | Short, consisting of only a few thousand nucleotides | Large, consisting of millions of nucleotides |

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<footer style = "font-size: 18px">Differences between DNA & RNA $\rightarrow$ Differences between DNA & RNA $\rightarrow$ <span style = "color:blue"> Differences between DNA & RNA </span> $\rightarrow$ Lets answer these questions... $\rightarrow$ Lets answer these questions... </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-1 </Success>
### <primary style="font-size:24px"> Lets answer these questions... </primary>
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- **Question 1.** Group the following as nitrogenous bases and nucleosides-
- Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine

- **Answer.** Nitrogenous bases present in the list are adenine, thymine, uracil, and cytosine.
- Nucleosides present in the list are cytidine and guanosine

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<footer style = "font-size: 18px">Differences between DNA & RNA $\rightarrow$ Differences between DNA & RNA $\rightarrow$ <span style = "color:blue"> Lets answer these questions... </span> $\rightarrow$ Lets answer these questions... $\rightarrow$ Lets answer these questions... </footer>

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### <primary style="font-size:24px"> Lets answer these questions... </primary>
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- **Question 2.** If a double stranded DNA has 20 per cent of cytosine, calculate the percent of adenine in the DNA

- **Answer.** We can use Chargaff's rule,

- G =  C(G + C = 40%)

- A =  T(A + T = 60%)

- Percentage of adenine molecule is 30%

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<footer style = "font-size: 18px">Differences between DNA & RNA $\rightarrow$ Lets answer these questions... $\rightarrow$ <span style = "color:blue"> Lets answer these questions... </span> $\rightarrow$ Lets answer these questions... $\rightarrow$ Questions you can answer... </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-1 </Success>
### <primary style="font-size:24px"> Lets answer these questions... </primary>
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- **Question 3.** If the sequence of one strand of DNA is written as follows -

- 5'-ATGCATGCATGCATGCATGCATGCATGC-3'

- **Answer.**  3'- TACGTACGTACGTACGTACGTACGTACG-5'

- **Question 4.** Which bond exist between

- $\quad$ A. Two Nucleotides
 
 - $\quad$ B. Two strands of DNA

- **Answer.**

- $\quad$ A. Phosphodiester Bond

- $\quad$ B. Hydrogen

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