biology-class-12-unit-06-chapter-02-genetics-and-evolution-molecular-basis-of-inheritance-l-2-12-c4gywiag2zu

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-2 </Success>
### <primary style="font-size:24px"> Nucleotide and nucleoside </primary>
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- Sugar + Nitrogenous base + Phosphate

- $\quad  \quad \quad  \quad  \quad$ $\darr$

- $ ~ ~ \quad \quad \quad$Nucleotide

- $\quad  \quad \quad  \quad  \quad$ $\darr$

- $ \quad \quad \quad$ Nucleic Acid(DNA,RNA)

- $ \quad \quad \quad$ Nucleoside

- $ \quad \quad \quad$ Sugar + Nitrogenous base

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<footer style = "font-size: 18px">Ribose $\rightarrow$ Nitrogenous bases $\rightarrow$ <span style = "color:blue"> Nucleotide and nucleoside </span> $\rightarrow$ Nucleotide $\rightarrow$ Polynucleotides </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-2 </Success>
### <primary style="font-size:24px"> Uncommon nucleotides </primary>
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- **1. Pseudouridine**

- Isomerization occurs when the uracil base is rotated 180 ± through an N3 - C6 diagonal axis (circular arrow)

- In pseudouridine (right), the C-5 position of uracil (arrowhead) is linked to the C-10 position of the sugar, resulting in an increase in hydrogen bonding capacity (to one acceptor and two donors) compared with that in U

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<footer style = "font-size: 18px">Structure of RNA $\rightarrow$ Structure of RNA $\rightarrow$ <span style = "color:blue"> Uncommon nucleotides </span> $\rightarrow$ Uncommon nucleotides $\rightarrow$ Uncommon nucleotides </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-2 </Success>
### <primary style="font-size:24px"> Uncommon nucleotides </primary>
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- **2. Ribothymidine**

- **3. Dihydrouridine (DHU)**

- It is a pyrimidine which is the result of adding two hydrogen atoms to a uridine, making it a fully saturated pyrimidine ring with no remaining double bonds

- It is found in tRNA and rRNA

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<footer style = "font-size: 18px">Structure of RNA $\rightarrow$ Uncommon nucleotides $\rightarrow$ <span style = "color:blue"> Uncommon nucleotides </span> $\rightarrow$ Uncommon nucleotides $\rightarrow$ Types of RNA </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-2 </Success>
### <primary style="font-size:24px"> Uncommon nucleotides </primary>
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- **4. Inosine**

- Hypoxanthine is a naturally occurring purine derivative
- It is occasionally found as a constituent of nucleic acids, where it is present in the anticodon of tRNA in the form of its nucleoside inosine
- It has a tautomer known as 6-hydroxypurine

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<footer style = "font-size: 18px">Uncommon nucleotides $\rightarrow$ Uncommon nucleotides $\rightarrow$ <span style = "color:blue"> Uncommon nucleotides </span> $\rightarrow$ Types of RNA $\rightarrow$ Types of RNA </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-2 </Success>
### <primary style="font-size:24px"> Other RNAs </primary>
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- Small Nuclear RNAs

- It plays a critical role in gene regulation by way of RNA splicing

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![image](/subject-images/iitpal/image/biology-class-12-unit-06-chapter-02-genetics-and-evolution-molecular-basis-of-inheritance-l-2-12-c4gywiag2zu-22a.jpg)

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<footer style = "font-size: 18px">Function of tRNA $\rightarrow$ Ribosomal RNA $\rightarrow$ <span style = "color:blue"> Other RNAs </span> $\rightarrow$ Other RNAs $\rightarrow$ Other RNAs </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-2 </Success>
### <primary style="font-size:24px"> Other RNAs </primary>
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- Small Interfering RNAs

- Small interfering RNAs (siRNAs) are yet another class of small RNAs

- Although these molecules are only 21 to 25 base pairs in length, they also work to inhibit gene expression

- Specifically, one strand of a double-stranded siRNA molecule can be incorporated into a complex called RISC

- This RNA-containing complex can then inhibit transcription of an mRNA molecule that has a sequence complementary to its RNA component

![image](/subject-images/iitpal/image/biology-class-12-unit-06-chapter-02-genetics-and-evolution-molecular-basis-of-inheritance-l-2-12-c4gywiag2zu-24a.jpg)

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<footer style = "font-size: 18px"> $\rightarrow$ Other RNAs $\rightarrow$ <span style = "color:blue"> Other RNAs </span> $\rightarrow$ Other RNAs $\rightarrow$ Other RNAs </footer>

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### <primary style="font-size:24px"> Other RNAs </primary>
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- Small Nucleolar RNAs

- Inside the eukaryotic nucleus, the nucleolus is the structure where rRNA processing and ribosomal assembly take place

- Molecules called small nucleolar RNAs (snoRNAs) were isolated from nucleolar extracts because of their abundance in this structure

- These molecules function to process rRNA molecules, often resulting in the methylation and pseudouridylation of specific nucleosides

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![image](/subject-images/iitpal/image/biology-class-12-unit-06-chapter-02-genetics-and-evolution-molecular-basis-of-inheritance-l-2-12-c4gywiag2zu-25.jpg)

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<footer style = "font-size: 18px">Other RNAs $\rightarrow$ Other RNAs $\rightarrow$ <span style = "color:blue"> Other RNAs </span> $\rightarrow$ Other RNAs $\rightarrow$ Why thymine instead of uracil in DNA? </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-2 </Success>
### <primary style="font-size:24px"> Why thymine instead of uracil in DNA? </primary>
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- Despite uracil's tendency to pair with adenine, it can also pair with any other base, including itself

- By adding a methyl group (which is hydrophobic) and turning it into thymine, its position is reorganized in the double-helix, not allowing those wrong pairings to happen

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<footer style = "font-size: 18px">Other RNAs $\rightarrow$ Other RNAs $\rightarrow$ <span style = "color:blue"> Why thymine instead of uracil in DNA? </span> $\rightarrow$ Why thymine instead of uracil in DNA? $\rightarrow$ Why thymine instead of uracil in DNA? </footer>

- Cytosine can deaminate to produce uracil

- Only difference between them is the change from an O in uracil to an NH2 in cytosine

- The problem is that, if uracil were a component of DNA, the repair systems would not be able to distinguish original uracil from uracil originated by deamination of cytosine

- So using thymine instead makes it way easier and more stable, as any uracil inside DNA must come from a cytosine and so it can be replaced by a new cytosine

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<footer style = "font-size: 18px">Other RNAs $\rightarrow$ Why thymine instead of uracil in DNA? $\rightarrow$ <span style = "color:blue"> Why thymine instead of uracil in DNA? </span> $\rightarrow$ Why thymine instead of uracil in DNA? $\rightarrow$ Which evolved first DNA or RNA? </footer>

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<footer style = "font-size: 18px">Why thymine instead of uracil in DNA? $\rightarrow$ Why thymine instead of uracil in DNA? $\rightarrow$ <span style = "color:blue"> Why thymine instead of uracil in DNA? </span> $\rightarrow$ Which evolved first DNA or RNA? $\rightarrow$ Which one more stable DNA or RNA? </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-2 </Success>
### <primary style="font-size:24px"> Which evolved first DNA or RNA? </primary>
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- During the earliest times of life, eventually an error changed uracil for thymine and it was found to be more stable to carry information, since such a molecule wouldn't be destroyed so easily and thus would succeed in passing its "layout" to the next generation

- Deoxyribose Sugar in DNA is more Stable than Ribose Sugar of RNA

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<footer style = "font-size: 18px">Why thymine instead of uracil in DNA? $\rightarrow$ Why thymine instead of uracil in DNA? $\rightarrow$ <span style = "color:blue"> Which evolved first DNA or RNA? </span> $\rightarrow$ Which one more stable DNA or RNA? $\rightarrow$ Answer these Questions </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-2 </Success>
### <primary style="font-size:24px"> Which one more stable DNA or RNA? </primary>
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- RNA has a 2'OH

- The result is that under basic conditions, the hydroxyl group may be deprotonated and may act as an nucleophile and hydrolyze the phosphate bond

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<footer style = "font-size: 18px">Why thymine instead of uracil in DNA? $\rightarrow$ Which evolved first DNA or RNA? $\rightarrow$ <span style = "color:blue"> Which one more stable DNA or RNA? </span> $\rightarrow$ Answer these Questions $\rightarrow$ Thank you </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-2 </Success>
### <primary style="font-size:24px"> Answer these Questions </primary>
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- **Question 1 -** What are the differences between DNA & RNA?

- **Question 2 -** Write the RNA Sequence of this given DNA

- $\quad \quad \quad \quad $  sequences:5 'ATCCGTAATCGTTC 3'

- **Question 3 -** Give the function of following RNA -

- a. mRNA

- b. tRNA

- c. rRNA

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<footer style = "font-size: 18px">Which evolved first DNA or RNA? $\rightarrow$ Which one more stable DNA or RNA? $\rightarrow$ <span style = "color:blue"> Answer these Questions </span> $\rightarrow$ Thank you $\rightarrow$  </footer>