Down syndrome, Turner syndrome, and Klinefelter syndrome constitute the most common chromosomal abnormalities encountered by primary care physicians. Down syndrome typically is recognized at birth, Turner syndrome often is not recognized until adolescence,and many men with Klinefelter syndrome are never diagnosed. Although each syndrome is caused by an abnormal number of chromosomes, or aneuploidy, they are distinct syndromes with learning disabilities and a predisposition toward autoimmune diseases,endocrinologic disorders, and cancers. 

The blood group characteristic in humans is controlled by three set of alleles, namely, I^A, I^B, and i. The alleles, I^A and I^B, are equally dominant whereas allele, i, is recessive to the other alleles. The individuals with genotype, I^A I^A and I^A i, have blood group A whereas the individuals with genotype, I^B I^B and I^B i, have blood group B. The persons with genotype I^A I^B have blood group AB while those with blood group O have genotype ii.

Alfred D. Hershey and Martha Chase (1952) used radioactive phosphorus (32P) and radioactive sulfur (35S) and showed that when bacteriophage T2​ infects its host cell, <i>Escherichia coli</i>, the phosphorus-containing DNA of the viral particle, not the sulfur-containing protein of the viral coat, enters the host cell and serves the genetic information for viral replication. For the purpose, they blended phage and bacteria together just after infection in a normal kitchen appliance to remove the phage coat. Following this, the viral DNA entered bacterial cell. It was established that DNA serves as genetic material for viruses.

LINKAGE AND RECOMBINATION

• Morgan carried out several dihybrid crosses in Drosophila to study genes that were ***-linked.
• Morgan hybridized yellow-bodied, white-eyed females to brown-bodied, red-eyed males and intercrossed those F₁
• According to him, two genes did not segregate independent of each other and F₂ ratio deviated from 9:3:3:1. This concluded that genes are linked. This process is called linkage.
• Recombination is the rearrangement of genetic material. The generation of non-parental gene combination during dihybrid cross is called recombination. When genes are located on same chromosome, they are tightly linked and show less linkage. This is responsible for variation.

• Translation refers to the process of polymerization of amino acids to form a polypeptide.
• The order and sequence of amino acids are defined by the sequence of bases in the mRNA and the amino acids are joined by a bond which is known as a peptide bond.
• Formation of a peptide bond requires energy and thus amino acids are activated in the presence of ATP and linked to their cognate tRNA by the process of charging of tRNA or aminoacylation of tRNA.
• If charged tRNAs are brought close enough, a peptide bond forms which is enhanced by the presence of a catalyst such as ribosome.
• Ribosome in its inactive state exists as two subunits; a large subunit and a small subunit.
• There are two sites in the large subunit, for subsequent amino acids to bind to and thus become close enough to each other for the formation of a

peptide bond.

• A translational unit in mRNA is the sequence of RNA that is flanked by the start codon (AUG) and the stop codon and codes for a polypeptide.
• An mRNA also has some additional sequences that are not translated and are referred as untranslated regions (UTR).
• The UTRs are present at both 5'-end (before start codon) and at 3'-end (after stop codon) which are required for efficient translation process.
• After activation of amino acids, translation starts with its three steps-
• Initiation
• Elongation
• Termination

Process of transcription

In prokaryotes

Transcription takes place in three steps

• Initiation
• RNA polymerase binds to promoter and initiates transcription.
• Initiation factor or sigma (σ) recognizes the promoter of the DNA.
• Elongation
• RNA polymerase facilitates opening of the helix and continues elongation.
• RNA polymerase uses nucleoside triphosphates as substrate and polymerizes in a template depended fashion following the rule of complementarity.
• Only a short stretch of RNA remains bound to the enzyme.
• Termination
• Once the polymerases reaches the terminator region RNA polymerase binds with the termination-factor (ρ) to terminate transcription.
• The nascent RNA falls off with the RNA polymerase which results in termination of transcription.
• The transcription and translation can be coupled in bacteria as the mRNA does not require any processing to become active, and also transcription and translation take place in the same compartment

In eukaryotes

• There are two additional complexities in eukaryotes.

1. The first complexity is that there are at least three RNA polymerases in the nucleus.

• The RNA polymerase I transcribes rRNAs (28S, 18S, and 5.8S)
• The RNA polymerase III is responsible for transcription of tRNA, 5srRNA, and snRNAs (small nuclear RNAs).
• The RNA polymerase II transcribes precursor of mRNA, the heterogeneous nuclear RNA (hnRNA).

1. The second complexity is that the primary transcripts contain both the exons and the introns and are non-functional.

• Primary transcripts are subjected to a process called splicing where the introns are removed and exons are joined in a defined order.
• hnRNA undergo two additional processing called as capping and tailing.
• In capping an unusual nucleotide (methyl guanosine triphosphate) is added to the 5'-end of hnRNA.
• In tailing, adenylate residues (200-300) are added at 3'-end in a template independent manner and the fully processed hnRNA is called mRNA
• mRNA is transported out of the nucleus for translation.

Significance of complexities

• The split-gene arrangements represent probably an ancient feature of the genome.
• The presence of introns is reminiscent of antiquity, and the process of splicing represents the dominance of RNA-world.

Dominance: The alleles IA and IB are dominant over allele i as IA and IB form antigens A and B, respectively, but i does not form any antigen.

Co-dominance: Both the alleles IA and IB are co-dominant as both of them are able to express themselves in the presence of each other in blood group AB (IAIB) by forming antigens A and B.

Multiple allelism: It is the phenomenon of occurrence of a gene in more than two allelic forms on the same locus.  The ABO blood group in humans is determined by three different allelic forms IA, IB and i.

The above three explanations prove that the inheritance of ABO blood group in humans shows dominance, co-dominance and multiple allelism.

ANSWER
Biopatent is a patent granted by the government to the inventor for biological entities and for products obtained from them. For example, basmati rice and neem based products are biopatents of India.

Chromatin is located in the nucleus of our cell. It is composed of DNA and proteins that condense to form chromosomes. It compresses the DNA structure into a compact unit so that it can fit within the nucleus.

The histone proteins organize the DNA into special structures called nucleosomes. The nucleosome further folds to form a chromatin fibre.

Biological Oxygen Demand is defined as the amount of dissolved oxygen required by aerobic microorganisms to breakdown the organic materials in a sample of water at a specific temperature & timeframe. In simpler words, The amount of oxygen needed by biological organisms such as bacteria in a given water sample for a breakdown of organic matter by oxidation process is called the Biochemical Oxygen Demand.

• BOD is the biological method used for the measurement of the total amount of dissolved oxygen (DO) used by microbes in the biological process of metabolizing organic molecules present in water.
• The total amount of oxygen gas present in the water is called the dissolved oxygen (DO). The non-compound oxygen present in water may either be a by-product of the photosynthesis of the aquatic plants or the dissolved atmospheric oxygen gas.

INSPIRATION:

a)The act of drawing air into the lungs.

b)Rib cages move forward and upward.

c) Contraction of external intercostals muscles and relaxations and internal intercostals muscles occur.

d) Increase in volume of the thoracic cavity.

e)Diaphragm contracts and becomes flattened.

f)Increase in volume of the thoracic cavity.

g) Air pressure in lungs is less than atmospheric pressure.

EXPIRATION.

a)Expulsion of air from the lungs.

b)Rib cages move downward and inward.

c)Relaxations of external intercostals muscles and Contraction of internal intercostals muscles occur

e) Diaphragm relaxes and becomes original dome-shaped.

f) The decrease in the volume of the thoracic cavity.

g) Air pressure in lungs is higher than atmospheric pressure.

DNA can be separated by agarose gel electrophoresis in which agarose is used as a matrix. DNA sample is added to the slot and current is applied to it. The smaller molecules move faster and the larger molecules are retarded. In this method, separation is based on charge and size of the DNA fragment. Isolation of DNA from agarose gels by electrophoresis can be done using the DEAE-cellulose membrane. It is done by transfer of all DNA fragments from an agarose slab gel onto DEAE-cellulose paper. Individual fragments of DNA are then eluted using 0.1 M NaCl.

<font face="Arial Narrow">RNA replication is the process by which new copies of genome-length RNAs are made
RNA replication occurs in the cytoplasm and is carried out by the viral RNA polymerase.
The full length plus strand is coated with nucleocapsid protein as it is made (mRNAs are not coated with this protein, which would interfere with the host protein translation machinery).</font>

<font face="Arial Narrow">The new positive strand is copied into full length minus strand, which is also coated with nucleocapsid protein as it is made. (Note: since the viral RNA polymerase synthesizes  mRNAs (transcription) and full-length RNA (replication), it is also sometimes called a transcriptase or a replicase, such names just focus on the different aspects of the polymerase activity.)</font>

Reproduction is a biological process of formation of new offsprings from the pre-existing organism. Reproduction becomes a vital process without which species cannot survive for long It ensures continuity of species generation after generations as older individuals undergo senescence and ultimately they die.

Life span – • The period from birth to the natural death of an organism represents its life span. Life span of organisms varies from few days (Butterfly-1to 2 weeks) to thousands of years (Banyan tree).

Types of Reproduction:
Based on whether there is one or two organisms taking part in the process of reproduction

• ASEXUAL REPRODUCTION
• SEXUAL REPRODUCTION

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<a data-ved="2ahUKEwj0_c3L69ztAhX_7HMBHUpWAXAQFjABegQIAhAC" href="https://mycbseguide.com/blog/reproduction-organisms-class-12-notes-biology/" ping="/url?sa=t&source=web&rct=j&url=https://mycbseguide.com/blog/reproduction-organisms-class-12-notes-biology/&ved=2ahUKEwj0_c3L69ztAhX_7HMBHUpWAXAQFjABegQIAhAC" rel="noopener" target="_blank">Reproduction in Organisms class 12 Notes Biology ...</a>

DNA replication is the biological process in which two identical copies of DNA are produced from one original DNA molecule.
The steps involved in the process of DNA replication are as follows:

1. The first step in DNA replication is to ‘unzip’ the double-helix structure of the DNA molecule.
2. This is carried out by an enzyme called helicase which breaks the hydrogen bonds holding the complementary bases of DNA together (A with T, C with G).
3. The separation of the two single strands of DNA creates a ‘Y’ shape called a replication ‘fork’. The two separated strands will act as templates for making the new strands of DNA.
4. One of the strands is oriented in the 3’ to 5’ direction (towards the replication fork), this is the leading strand. The other strand is oriented in the 5’ to 3’ direction (away from the replication fork), this is the lagging strand. As a result of their different orientations, the two strands are replicated differently.

I M R stands for Infant Mortality Rate

Infant Mortality Rate (or IMR) indicates the number of children that die before the age of one year as a proportion of 1000 live children born in that particular year.

The mitotic division called cleavage starts as the zygote moves through the isthmus of the oviduct towards the uterus and forms 2, 4, 8, 16 daughter cells called blastomeres. The embryo with 8 to 16 blastomeres is called a morula. The morula continues to divide and transforms into blastocyst as it moves further into the uterus. The blastomeres in the blastocyst are arranged into an outer layer caned trophoblast and an inner group of cells attached to trophoblast called the inner cell mass.

Packaging of DNA helix

• Length of DNA is found to be far greater than dimension of a typical nucleus

Total number of base pairs in a typical mammalian cell= 6.6 * 10⁹

Distance between two base pairs= 0.34nm

Therefore, Length of DNA= 0.34 *10^-9 *6.6 *10⁹ = 2.2m

Size of a nucleus is of the order of 10^-6m

So, Length of DNA is greater than the size of nucleus (It is as if the house is smaller than the person who wants to stay in).