DNA and Genes /detailed information

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 Certainly! Here's an in-depth explanation of DNA and genes, including their structure, function, processes, and importance in genetics and biology.

🧬 DNA and Genes – Full Detailed Information

🧬 PART 1: DNA (Deoxyribonucleic Acid)

🔹 1. What is DNA?

DNA is the hereditary material in almost all living organisms.

It carries the instructions needed for the growth, development, functioning, and reproduction of all life forms.

🔹 2. Location of DNA

Found in the nucleus (nuclear DNA) and mitochondria (mitochondrial DNA).

Each cell in the human body contains about 6 billion base pairs of DNA.

🔹 3. Chemical Composition

DNA is a polymer made up of repeating units called nucleotides.

Each nucleotide contains:

A phosphate group

A deoxyribose sugar

A nitrogenous base (A, T, C, or G)

🔹 4. Nitrogenous Bases

BasePairing RuleTypeAdenine (A)Pairs with Thymine (T)PurineThymine (T)Pairs with Adenine (A)PyrimidineCytosine (C)Pairs with Guanine (G)PyrimidineGuanine (G)Pairs with Cytosine (C)Purine 

A-T forms 2 hydrogen bonds, C-G forms 3 hydrogen bonds.

🔹 5. Structure: Double Helix

Proposed by Watson and Crick (1953).

Looks like a twisted ladder:

Sugar-phosphate backbone forms the sides.

Base pairs form the rungs.

🧬 PART 2: GENES

🔹 1. What is a Gene?

A gene is a segment of DNA that contains the code for making a specific protein.

Genes are the basic units of heredity.

🔹 2. Location

Genes are located on chromosomes.

Humans have 20,000–25,000 genes, spread across 46 chromosomes (23 pairs).

🔹 3. Structure of a Gene

PartFunctionPromoterStart signal for transcriptionExonsCoding sequences (expressed)IntronsNon-coding sequences (removed during RNA processing)TerminatorEnd signal for transcription 

🔹 4. Types of Genes

Structural Genes: Code for proteins (e.g., enzymes, keratin).

Regulatory Genes: Control gene expression.

Housekeeping Genes: Constantly active for basic cell function.

Non-coding RNA Genes: Produce tRNA, rRNA, miRNA, etc.

🔄 GENE EXPRESSION PROCESS

🧭 Central Dogma of Molecular Biology:

DNA → RNA → Protein

1. Transcription (in nucleus)

DNA is transcribed into mRNA by RNA polymerase.

mRNA is a single-stranded copy of the gene.

2. RNA Processing (Eukaryotes)

Splicing removes introns.

5' cap and poly-A tail are added.

3. Translation (in cytoplasm)

mRNA is decoded by ribosomes into a chain of amino acids.

Amino acids form proteins, which perform cellular functions.

🧬 CHROMOSOMES

Chromosomes are tightly coiled DNA molecules with proteins (histones).

Humans have:

22 pairs of autosomes

1 pair of sex chromosomes (XX in females, XY in males)

⚠️ MUTATIONS

What is a Mutation?

A change in the DNA sequence.

Can occur naturally or due to radiation, chemicals, or viruses.

Types of Mutations:

TypeDescriptionExamplePoint MutationChange in a single nucleotideSickle Cell AnemiaInsertion/DeletionAddition or removal of basesCystic FibrosisChromosomal MutationStructural changes in chromosomesDown Syndrome (Trisomy 21) 

🧪 MODERN APPLICATIONS OF DNA AND GENES

1. Genetic Engineering

Altering DNA for desired traits.

Includes GMOs, gene therapy, and CRISPR.

2. DNA Fingerprinting

Used in forensic science and paternity testing.

3. Personalized Medicine

Tailoring treatments based on a person's genetic profile.

4. Gene Therapy

Treating diseases by correcting defective genes.

🧠 EPIGENETICS

Study of heritable changes in gene expression that do not involve changes to the DNA sequence.

Influenced by:

Environment

Lifestyle

Nutrition

Mechanisms include DNA methylation and histone modification.

🌍 GENOME

A genome is the entire set of DNA in an organism.

The Human Genome Project mapped all human genes (completed in 2003).