biology-class-12-unit-06-chapter-03-genetics-and-evolution-molecular-basis-of-inheritance-l-3-12-mxkyzecx0k4

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-3 </Success>
### <primary style="font-size:24px"> Genome organization & chromosome </primary>
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- Genome means "the complete set of Chromosome or genetic material present in a cell or organism"

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<footer style = "font-size: 18px"> $\rightarrow$ Genetics and evolution $\rightarrow$ <span style = "color:blue"> Genome organization & chromosome </span> $\rightarrow$ Genome organization & chromosome $\rightarrow$ Why genome organization is required? </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-3 </Success>
### <primary style="font-size:24px"> Features of viral genome </primary>
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- One molecule or segmented genome (many pieces)

- Viruses with RNA genome are called retroviruses

- Genome size two thousand basepairs (2Kb) - 2 million basepairs (2 Mb)

- No special organization of the genome

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<footer style = "font-size: 18px">Genome organization in virus $\rightarrow$ Features of viral genome $\rightarrow$ <span style = "color:blue"> Features of viral genome </span> $\rightarrow$ Features of bacterial genome $\rightarrow$ Features of bacterial genome </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-3 </Success>
### <primary style="font-size:24px"> Features of bacterial genome </primary>
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- **Most genomes are** -

-  1. Single molecule
-  2. One circular chromosome  
-  3. Double stranded DNA 
-  4. Some have small additional circular DNA that can replicate independently (plasmid)

- Genome is organized in a structure called (Nucleoid)

- The size of Bacterial chromosomes ranges from 0.6 Mbp to over 10 Mbp

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<footer style = "font-size: 18px">Features of viral genome $\rightarrow$ Features of bacterial genome $\rightarrow$ <span style = "color:blue"> Features of bacterial genome </span> $\rightarrow$ Genome organization in bacteria $\rightarrow$ Genome organization in bacteria </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-3 </Success>
### <primary style="font-size:24px"> Genome organization in bacteria </primary>
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- To fit within the bacterial cell, the chromosomal DNA must be compacted about a 1000-fold  
 
- This involves the formation of loop domams  
- The number of loops varies according to the sizeof the bacterial chromosome and the species
 - _E.coli_ has 50-100 with 40,000 to 60,000 bp in each
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<footer style = "font-size: 18px">Features of bacterial genome $\rightarrow$ Genome organization in bacteria $\rightarrow$ <span style = "color:blue"> Genome organization in bacteria </span> $\rightarrow$ Genome organization in bacteria $\rightarrow$ Genome organization in bacteria </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-3 </Success>
### <primary style="font-size:24px"> Genome organization in bacteria </primary>
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- **DNA supercoiling is a second important way to compact the bacterial chromosome**

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<footer style = "font-size: 18px">Genome organization in bacteria $\rightarrow$ Genome organization in bacteria $\rightarrow$ <span style = "color:blue"> Genome organization in bacteria </span> $\rightarrow$ Genome organization in bacteria $\rightarrow$ Enzymes associated with supercoilings </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-3 </Success>
### <primary style="font-size:24px"> Genome organization in bacteria </primary>
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<footer style = "font-size: 18px">Genome organization in bacteria $\rightarrow$ Genome organization in bacteria $\rightarrow$ <span style = "color:blue"> Genome organization in bacteria </span> $\rightarrow$ Enzymes associated with supercoilings $\rightarrow$ Enzymes associated with supercoilings </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-3 </Success>
### <primary style="font-size:24px"> Enzymes associated with supercoilings </primary>
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- The control of supercoiling in bacteria is accomplished by two main enzymes -

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- 1. DNA gyrase (also termed DNA topoisomerase II)

- Introduce negative supercoils using energy from ATP
 - It can also relax positive supercoils when they occures

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<footer style = "font-size: 18px">Genome organization in bacteria $\rightarrow$ Genome organization in bacteria $\rightarrow$ <span style = "color:blue"> Enzymes associated with supercoilings </span> $\rightarrow$ Enzymes associated with supercoilings $\rightarrow$ Chromosome function is influenced by DNA supercoiling </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-3 </Success>
### <primary style="font-size:24px"> Chromosome function is influenced by DNA supercoiling </primary>
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- The chromosomal DNA in bacteria is negatively supercoiled  
 - In _E. coli_, there is one negative supercoil per 40 turns of the double helix

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<footer style = "font-size: 18px">Enzymes associated with supercoilings $\rightarrow$ Enzymes associated with supercoilings $\rightarrow$ <span style = "color:blue"> Chromosome function is influenced by DNA supercoiling </span> $\rightarrow$ Chromosome function is influenced by DNA supercoiling $\rightarrow$ Eukaryotic genome </footer>

- Negative supercoiling has two major effects

- Helps in the compaction of the chromosome

- Creates tension that may be released by DNA strand separation

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<footer style = "font-size: 18px">Enzymes associated with supercoilings $\rightarrow$ Chromosome function is influenced by DNA supercoiling $\rightarrow$ <span style = "color:blue"> Chromosome function is influenced by DNA supercoiling </span> $\rightarrow$ Eukaryotic genome $\rightarrow$ Levels of DNA packaging </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-3 </Success>
### <primary style="font-size:24px"> Levels of DNA packaging </primary>
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<footer style = "font-size: 18px">Chromosome function is influenced by DNA supercoiling $\rightarrow$ Eukaryotic genome $\rightarrow$ <span style = "color:blue"> Levels of DNA packaging </span> $\rightarrow$ Proteins involved in DNA Packaging $\rightarrow$ Proteins involved in DNA Packaging </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-3 </Success>
### <primary style="font-size:24px"> Proteins involved in DNA Packaging </primary>
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- Histones proteins -

- It includes H1, H2A, H2B, H3 and H4

- Non Histones Proteins-

- It includes Scaffold proteins, DNA polymerase, Heterochromatin Protein1 and Polycomb are common non-histone proteins

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<footer style = "font-size: 18px">Eukaryotic genome $\rightarrow$ Levels of DNA packaging $\rightarrow$ <span style = "color:blue"> Proteins involved in DNA Packaging </span> $\rightarrow$ Proteins involved in DNA Packaging $\rightarrow$ Nucleosome </footer>

<h6><b>Histones</b></h6>

- Proteins around which DNA coils to form chromatin

- Contain positively charged R-groups which bind to the negatively charged DNA (phosphate groups)
 - DNA backbone has a negative charge  
 - Histones have a positive charge

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<footer style = "font-size: 18px">Levels of DNA packaging $\rightarrow$ Proteins involved in DNA Packaging $\rightarrow$ <span style = "color:blue"> Proteins involved in DNA Packaging </span> $\rightarrow$ Nucleosome $\rightarrow$ Nucleosome </footer>

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### <primary style="font-size:24px"> Looped domain formation (300nm) </primary>
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<footer style = "font-size: 18px">Nucleosome $\rightarrow$ Formation of chromatin fibre $\rightarrow$ <span style = "color:blue"> Looped domain formation (300nm) </span> $\rightarrow$ Formation of heterochromatin (700nm) $\rightarrow$ DNA compaction </footer>

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### <primary style="font-size:24px"> DNA compaction </primary>
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- Euchromatin is uncoiled and active, whereas heterochromatin condensed and is inactive

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<footer style = "font-size: 18px">Formation of heterochromatin (700nm) $\rightarrow$ DNA compaction $\rightarrow$ <span style = "color:blue"> DNA compaction </span> $\rightarrow$ Formation of metaphase chromosome (1400nm) $\rightarrow$ Formation of metaphase chromosome (1400nm) </footer>

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### <primary style="font-size:24px"> Formation of metaphase chromosome (1400nm) </primary>
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<footer style = "font-size: 18px">DNA compaction $\rightarrow$ Formation of metaphase chromosome (1400nm) $\rightarrow$ <span style = "color:blue"> Formation of metaphase chromosome (1400nm) </span> $\rightarrow$ Chromosome $\rightarrow$ Different parts of chromosome </footer>

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### <primary style="font-size:24px"> Different parts of chromosome </primary>
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- Pellicle and matrix

- Chromonemata

- Chromomeres

- Centromere

- Secondary constrictions

- Satellite bodies

- Telomeres

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<footer style = "font-size: 18px">Formation of metaphase chromosome (1400nm) $\rightarrow$ Chromosome $\rightarrow$ <span style = "color:blue"> Different parts of chromosome </span> $\rightarrow$ Structure of chromosome $\rightarrow$ Structure of chromosome </footer>

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### <primary style="font-size:24px"> Structure of chromosome </primary>
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- Chromonemata
 - Two identical, spirally coiled threads

- Chromomeres
 - Beadlike bodies over the chromonemata

- Centromere (Primary Constriction)
 - A lighter staining region appears as a constriction or thinner segment of the chromosome and is usually called centromere or primary constriction

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<footer style = "font-size: 18px">Different parts of chromosome $\rightarrow$ Structure of chromosome $\rightarrow$ <span style = "color:blue"> Structure of chromosome </span> $\rightarrow$ Structure of chromosome $\rightarrow$ Types of chromosomes </footer>

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### <primary style="font-size:24px"> Structure of chromosome </primary>
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- Secondary constrictions
 - Nucleoli are assembled

- Satellite bodies
 - Present beyond the secondary constriction

- Telomere  
 - The tips or the terminal ends of chromosomes are called telomeres
 - It has a unique property that it prevents the ends of the chromosomes from sticking to each or one another

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<footer style = "font-size: 18px">Structure of chromosome $\rightarrow$ Structure of chromosome $\rightarrow$ <span style = "color:blue"> Structure of chromosome </span> $\rightarrow$ Types of chromosomes $\rightarrow$ Metacentric </footer>

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### <primary style="font-size:24px"> Metacentric </primary>
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- Centromere is present near about in the middle of the chromosome

- Chromosomes have equal arms metacentric chromosomes are V- shaped

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<footer style = "font-size: 18px">Structure of chromosome $\rightarrow$ Types of chromosomes $\rightarrow$ <span style = "color:blue"> Metacentric </span> $\rightarrow$ Sub-Metacentric $\rightarrow$ Acrocentric </footer>

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### <primary style="font-size:24px"> Acentric </primary>
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-  If centromere is lacking, the chromosome is termed as acentric

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<footer style = "font-size: 18px">Acrocentric $\rightarrow$ Telocentric $\rightarrow$ <span style = "color:blue"> Acentric </span> $\rightarrow$ Dicentric and polycentric $\rightarrow$ Functions of chromosomes </footer>

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### <primary style="font-size:24px"> Functions of chromosomes </primary>
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- They contain hereditary information in the form of genes and act as hereditary vehicle

- They control division, growth, metabolism and differentiation of cell

- Sex chromosomes determine sex of the individuals

- Crossing over and aberrations of chromosomes introduce variations in population

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<footer style = "font-size: 18px">Acentric $\rightarrow$ Dicentric and polycentric $\rightarrow$ <span style = "color:blue"> Functions of chromosomes </span> $\rightarrow$ Lets summarize $\rightarrow$ Test yourself </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-3 </Success>
### <primary style="font-size:24px"> Questions </primary>
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- **Question 1.** What are Nucleoid?

- **Question 2.** What are the difference between positive and negative supercoilings?

- **Question 3.** Why DNA Packaging is needed?

- **Question 4.** What are the different proteins involved in Nucleosome Model?

- **Question 5.** What are the different types of chromosome depending on their centromere position?

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![image](/subject-images/iitpal/image/biology-class-12-unit-06-chapter-03-genetics-and-evolution-molecular-basis-of-inheritance-l-3_12-mxkyzecx0k4-56.jpg)

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<footer style = "font-size: 18px">Lets summarize $\rightarrow$ Test yourself $\rightarrow$ <span style = "color:blue"> Questions </span> $\rightarrow$ Answers of questions asked $\rightarrow$ Answers of questions asked </footer>

### <Success style="font-size:25px"> Genetics And Evolution Molecular Basis Of Inheritance L-3 </Success>
### <primary style="font-size:24px"> Answers of questions asked </primary>
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- **Question 1.** What are the differences between DNA & RNA?

- **Answer**

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<footer style = "font-size: 18px">Test yourself $\rightarrow$ Questions $\rightarrow$ <span style = "color:blue"> Answers of questions asked </span> $\rightarrow$ Answers of questions asked $\rightarrow$ Answers of questions asked </footer>