NCERT Class 12 Biology Chapter 5 PDF: Everything You Need to Know about Molecular Basis of Inheritance
NCERT Class 12 Biology Chapter 5 PDF Download
If you are a student of class 12 biology, you might be wondering how to download the PDF of NCERT Class 12 Biology Chapter 5. This chapter, titled Molecular Basis of Inheritance, deals with one of the most fascinating topics in biology - the molecular mechanism of heredity and variation. In this article, we will tell you what this chapter is about, why it is important to study it, and how you can download the PDF of this chapter for free.
Introduction
NCERT Class 12 Biology Chapter 5 covers the following topics:
ncert class 12 biology chapter 5 pdf download
The structure and function of DNA and RNA, the two types of nucleic acids that store and transmit genetic information in living organisms.
The process of replication, transcription, and translation, by which DNA copies itself, makes RNA from DNA, and synthesizes proteins from RNA.
The genetic code, which is a set of rules that specifies how a sequence of nucleotides in DNA or RNA corresponds to a sequence of amino acids in proteins.
The regulation of gene expression, which is the control of when, where, and how genes are turned on or off in response to various factors.
The Human Genome Project, which was an international scientific effort to sequence and map the entire human genome.
DNA fingerprinting, which is a technique that uses DNA fragments to identify individuals based on their unique genetic makeup.
This chapter is important to study because it helps you understand the molecular basis of life, evolution, diversity, and disease. It also introduces you to some of the latest advances and applications of biotechnology in various fields such as medicine, agriculture, forensics, etc.
To download the PDF of NCERT Class 12 Biology Chapter 5, you can visit the official website of NCERT () or from other online sources. However, make sure that you download the latest edition (2023) of the textbook.
Molecular Basis of Inheritance
In this section, we will discuss some of the key concepts and facts related to the molecular basis of inheritance.
Structure and Function of DNA and RNA
DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are two types of nucleic acids that store and transmit genetic information in living organisms. Both DNA and RNA are made up of smaller units called nucleotides. Each nucleotide consists of three components: a nitrogenous base, a pentose sugar, and a phosphate group. There are two types of nitrogenous bases: purines (adenine and guanine) and pyrimidines (cytosine, uracil, and thymine). Cytosine is common for both DNA and RNA, while thymine is present only in DNA and uracil only in (polarity), which means that one strand has a 5' end (where the phosphate group is attached to the 5' carbon of the sugar) and a 3' end (where the hydroxyl group is attached to the 3' carbon of the sugar), and the other strand has a 3' end and a 5' end. The sequence of bases in one strand determines the sequence of bases in the other strand. The two strands are twisted around each other to form a right-handed helix, with about 10 base pairs per turn. The helix has a major groove and a minor groove, which provide access for proteins that bind to DNA.
RNA is usually a single-stranded molecule that can fold into various shapes. Unlike DNA, RNA can have different types and functions depending on the cell and the organism. Some of the common types of RNA are:
mRNA (messenger RNA), which carries the genetic information from DNA to the ribosomes, where proteins are synthesized.
tRNA (transfer RNA), which brings amino acids to the ribosomes, where they are joined together to form proteins.
rRNA (ribosomal RNA), which forms part of the ribosomes, where proteins are synthesized.
snRNA (small nuclear RNA), which forms part of the spliceosome, a complex that removes introns (non-coding regions) from pre-mRNA and joins exons (coding regions) together.
miRNA (micro RNA), which regulates gene expression by binding to complementary sequences in mRNA and inhibiting its translation or causing its degradation.
Replication, Transcription, and Translation
Replication, transcription, and translation are three processes that enable DNA to copy itself, make RNA from DNA, and synthesize proteins from RNA, respectively.
Replication is the process by which DNA makes an identical copy of itself before cell division. Replication occurs in the following steps:
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The two strands of DNA are separated by an enzyme called helicase, which breaks the hydrogen bonds between the bases.
A short segment of RNA called a primer is synthesized by an enzyme called primase, which provides a starting point for the new strand.
An enzyme called DNA polymerase adds nucleotides to the new strand, following the base-pairing rules: A with T and G with C.
The new strand grows in the 5' to 3' direction, which means that nucleotides are added to the 3' end of the growing strand.
Since the two strands of DNA run in opposite directions, replication occurs differently on each strand. On the leading strand, replication is continuous, while on the lagging strand, replication is discontinuous, forming short fragments called Okazaki fragments.
An enzyme called DNA ligase joins the Okazaki fragments together to form a continuous strand.
The result is two identical copies of DNA, each consisting of one original strand and one new strand. This is called semi-conservative replication.
Arginine AUU Isoleucine ACU Threonine AAU Asparagine AGU Serine AUC Isoleucine ACC Threonine AAC Asparagine AGC Serine AUA Isoleucine ACA Threonine AAA Lysine AGA Arginine AUG Methionine/Start ACG Threonine AAG Lysine AGG Arginine GUU Valine GCU (#message) Continue writing the article. [assistant](#message) Alanine (#message) Continue writing the article. [assistant](#message) GAU (#message) Continue writing the article. [assistant](#message) Aspartic acid (#message) Continue writing the article. [assistant](#message) GGU (#message) Continue writing the article. Glycine GUC Valine GCC Alanine GAC Aspartic acid GGC Glycine GUA Valine GCA Alanine GAA Glutamic acid GGA Glycine GUG Valine GCG Alanine GAG Glutamic acid GGG Glycine Protein synthesis is the process by which the genetic code is translated into a sequence of amino acids that form a protein. Protein synthesis involves two main steps: initiation and elongation.
Initiation is the step by which the ribosome, the mRNA, and the first tRNA come together to start translation. Initiation occurs in the following steps:
The small subunit of the ribosome binds to the 5' end of the mRNA and scans for the start codon (AUG).
A tRNA that carries methionine and has an anticodon (UAC) that is complementary to the start codon binds to the mR