Difference between complete and incomplete dominance

Incomplete Dominance Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele. This results in a third phenotype in which the expressed physical trait is a combination of the phenotypes of both alleles.	Codominance Codominance is a form of dominance where in the alleles of a gene pair in a heterozygote On are fully expressed. This results in offspring with a phenotype that is neither dominant nor recessive.
The effect of one allele will be more than other.	Effect of both alleles will be equall.
A hybrid is formed which  is in the middle or intermediate of both alleles	Both alleles will express them independently
The expressed phenomenon won’t have any allele of its own	The expressed phenotype will show the combination of both alleles and phenotypes
Incompletely dominant allele will have quantitative effect	There will be no quantitative effect
E.g. Flower clour in snapdragon.	E.g. AB blood group in human.

Difference between Parenchyma, collenchyma and sclerenchyma

Parenchyma	Collenchyma	Sclerenchyma
It is made up of cells having very thin cell wall.	cells of collenchyma has unevenly thickened cell wall.	They are made up of cells having thick cell wall.
The cells are loosely packed.	Cells have little space between cells.	No intercellular spaces present between them, cells are tightly packed.
The cell wall is made up of cellulose.	The cell wall is made up of hemicelluloses and pectin.	The cell wall is made up lignin.
It is found in abundant.  Most of the plant tissues are made up of parenchyma cells.	Collenchymas cells make up the epidermal layers.	The outer woody stem portion of large trees is made up of sclerenchyma cells.
it constitutes  living cells.	It also constitutes  living cells.	Matured cells are dead.

Difference between Xylem and phloem

Xylem and Phloem both together constitutes the vascular bundles. They help in transporatation of food and minerals in plants.
The basic differences between xylem and phloem are :-

	Xylem	Phloem
Function	1. It transport of water and mineral from roots to other parts of the plant. 2. It forms vascular bundles with phloem 3.  It provides mechanical strength to plant due to presence of lignified cells.	1. It transport  food and nutrients from leaves to storage organs and growing parts of plant. 2.  It forms vascular bundles with xylem.
Location	Xylem is abundant in Roots, stems and leaves	Phloem is abundant in Roots, stems and leaves
Nature	Xylem is made up of three types of dead cells (vessels, tracheids, xylem fibres) and one type of living cells (xylem parenchyma)	Phloem contains only one type of dead cells (phloem fibres). and three types of living cells (sieve tube cells, companion cells and phloem parenchyma)
Made up of	Xylem constitutes of Tracheids, vessel elements, xylemparenchyma, xylem sclerenchyma.	Phloem constitutes of Sieve tubes, companion cells, phloem parenchyma, bast fibers, intermediary cells.
Physical structure	Xylem is tubular with hard walled cells	Phloem is also tubular but with soft walled cells
Movement	Unidirectional – Moves up the plant’s stem	Bi-directional – Moves up or down the plant’s stem

Transgenic animals

Transgenic animals are animals  that have had a foreign gene deliberately inserted into their genome.
The first successful production of transgenic mammals by the microinjection of genetically engineered constructs into the pronucleus of a mouse zygote was carried out .

 A laboratory mouse modified for lab purposes

 Nowadays a large number of transgenic animals (TAs) have been produced since for scientific purposes, to improve livestock and to produce RPs.
A question arises that what is the need to invent new transgenic animals.
Let us try and explore some of the common reasons:

(i) Normal physiology and development: Transgenic animals are be specifically designed to allow the study that how genes are regulated, and how they affect the normal functions of the body and its development, e.g., study of complex factors involved in growth such as insulin-like growth factor. By introducing genes from other species that alter the formation of this factor and studying the biological effects that result, information is obtained about the biological role of the factor in the body.

(ii) Study of disease: Many transgenic animals are designed to increase our understanding of how genes contribute to the development of disease. These are specially made to serve as models for human diseases so that investigation of new treatments for diseases is made possible. Today transgenic models exist for many human diseases such as cancer, cystic fibrosis, Alzheimer’s and many more.

(iii) Biological products: Medicines required to treat certain human diseases can contain biological products, but such products are often expensive to make. Transgenic animals that produce useful
biological products can be created by the introduction of the portion of DNA (or genes) which codes for a particular product such as human protein (α-1-antitrypsin) used to treat emphysema. Similar attempts are being made for treatment of phenylketonuria (PKU) and cystic fibrosis. In 1997, the first transgenic cow, Rosie, produced human protein-enriched milk. The milk contained the human alpha-lactalbumin and was nutritionally a more balanced product for human babies than natural cow-milk.

     The first modified transgenic cow, Rosie

(iv) Vaccine safety: Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans. Transgenic mice are being used to test the safety of the polio vaccine. If successful and found to be reliable, they could replace the use of monkeys to test the safety of batches of the vaccine.

(v) Chemical safety testing: This is known as toxicity/safety testing. The procedure is the same as that used for testing toxicity of drugs. Transgenic animals are made that carry genes which make them more
sensitive to toxic substances than non-transgenic animals. They are then exposed to the toxic substances and the effects studied. Toxicity testing in such animtals will allow us to obtain results in less time.

Disadvantages of Transgenic animals :-

1. Genetically engineered transgenic animals have a low survival rate
2. Transgenic animals usually leads to breeding problems. They have low reproductive rate.
3. This leads to mutations and functional disorders
4. These mutations in transgenic animals lead to  new dangerous and dreadful disease.

Why does cry protein or Bt Toxin not kill the Bacillus?

 Actually, the Bt toxin protein exist as inactive protoxins (as proenzyme ) but
once an insect ingest the inactive toxin, it is converted into an active form
of toxin due to the alkaline pH of the gut which solubilise the crystals.
The activated toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and eventually cause death
of the insect But as this protein do not get its favourable conditions in bacteria it remains inactive.

Polymerase chain reaction (PCR)

Polymerase chain reaction (PCR) is a technique used in molecular biology to amplify a single copy or a few copies of a segment of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence.

PCR machine

It was developed in 1983 by Kary Mullis, PCR is now a common and often indispensable technique used in clinical and research laboratories for a broad variety of applications.

Steps involved in PCR:-

steps involved in PCR

I. Denaturation:-
Denaturation refers to a structural change in macromolecules caused by extreme conditions
By raising the temperature of the PCR solution to just about 95°C, all the hydrogen bonds holding the complementary strands of DNA together are broken. This is known as the denaturation step in PCR.

II. Annealing :-
The process in which the temperature is lowered to about 50°C to enable the DNA primers to attach to the template DNA. In PCR, many man-made DNA primer molecules are already present in the PCR tube. During the second step of PCR, called the annealing step, the primers attach, or anneal, to the DNA template. PCR requires two different primers, one that can attach to each strand of the DNA molecule.

III. Extension/Elongation Step:-
During the extension, or elongation, step, Taq polymerase binds to each PCR primer and begins adding nucleotides. Note that Taq, like human DNA polymerase, can only add DNA nucleotides in one direction.

IV. PCR Cycling:-
To make millions of copies, we need to perform these three steps multiple times. The process of repeating the denaturation, annealing and extension steps of PCR is known as PCR cycling.
The amplified fragment if desired can now be used to ligate with a vector for further cloning

Advantages of PCR :-
PCR has a number of advantages.
1. It is fairly simple to understand and to use, and produces results rapidly.
2. The technique is highly sensitive with the potential to produce millions to billions of copies of a specific product for sequencing, cloning, and analysis.
3. It has its uses to analyse alterations of gene expression levels in tumours, microbes, or other disease states.

Limitations of PCR: –
1. One major limitation of PCR is that prior information about the target sequence is necessary in order to generate the primers that will allow its selective amplification.
2. Like all enzymes, DNA polymerases are also prone to error, which in turn causes mutations in the PCR fragments that are generated.

Disadvantages of Biotechnology

Biotechnology is very important branch of Biology . It can simply be explained as the exploitation of biological processes for industrial and other purposes, especially the genetic manipulation of microorganisms for the production of antibiotics, hormones, etc.
Yet biotechnology is very advance branch of the science but also has some drawbacks which are explained below :-

In Agriculture :-
• Genetically modified crops, also known as transgenic crops, may insert a plant gene into natural, unmodified varieties. For e.g. , a crop that is herbicide for resistant may transfer some of its traits to a weed, which would make the weed resistant to herbicides.

• There are also concerns that genetic engineering of crops would reduce their long-term biological potential.
Human risks :-
• The alteration of the genes of various organisms  from bacteria in the pharmaceutical industry to the animals in research to the plants in agriculture also raises concerns about its possible long-term consequences, which are still unknown.
• Genetically modified organisms may also escape into the wild, especially transgenic microorganisms, and these events may upset the balance of the ecosystem in nature. This may cause a decrease in the biodiversity, or the variety of organisms
• There are concerns that the use of genetic engineering in the food industry can increase sensitivity to certain allergens.

Related posts:
-advantages of biotechnology

advantages of Biotechnology

The use of biological processes for industrial and other purposes,  for the production of desirable products. Such as antibiotics, hormones, etc.
Advantages of Biotechnology:-

I. Genetically Engineered Insulin :-
A disease known as diabties is caused due to lack of a hormone insulin, which is a genetic disorder. Anciently insulin was extracted from pancreas of slaughtered cattle and pigs. Insulin from an animal source cause elergies in some patients. Modern Biotechnology solve this problem by gene cloning. Insulin consists of two polypeptide chains A and B linked by disulphide bonds. Chains A and B of human insulin are introduced them in plasmids of E. coli to produce insulin chains. They were produced and extracted separately, then combined by creating disulphide bonds to form human insulin.

II. Gene Therapy :-
If a person born with a hereditary disease , such diseases can be corrected by Gene Therapy
III. Molecular Diagnosis :-
Some techniques of diagnosis are used that serve the purpose of early diagnosis like Polymerase Chain Reaction (PCR) , Enzyme Linked Immuno Sorbent Assay (ELISA) , Recombinant DNA technology etc.

IV. Transgenic animals :-
These are those modified animals in which DNA is manipulated to possess and express an extra foreign genes. A lot of  transgenic animals like rats,  pigs , sheep , cows etc. are produced.

V. Transgenic Plants :-
Some plants are modified by introducing some extra foreign genes which plays an important role in green revolution. Such as Bt cotton , Bt mustard , Transgenic tomato etc.

VI.  In Agriculture :-

• Using biotechnology in the growth and production of fruits and vegetables has enabled scientists to change the way they ripen. Normally fruits and vegetables continue to ripen after harvesting; they must be rushed to market and sold quickly while they are fresh. Genetically modified crop can be harvested when ripe, and the ripening process stops, giving them a longer shelf life.
• These genetic modifications also increase a plant’s resistance to disease, pests, insecticides, herbicides and even extreme weather conditions. 
• Genetic engineering has also altered a plant’s nutritional makeup, making it richer in certain vitamins or minerals.

VII.  Environmental benefits :-
Biotechnology reduce agriculture’s impact on the land
• Conserve soil fertility, natural resources and energy
• Reduce greenhouse gases
• Minimize use of toxic pesticides  and herbicides by inventing new pest resistant plants like Bt. Cotton

Related posts:
disadvantages-of-biotechnology

contrasting pairs of characters of pea plant choose by mandel for hybridisation

In mid nineteenth century, Gregor Mendel ( Father of Genetics ) conducted hybridisation experiments on garden pea (pisum sativum) for seven years. Mendel choose such contrasting traits which do not blend at all . These traits are given below :-

Sr. No.	Characters	Contrasting pairs
		(Dominant)	(Recessive)
1.	Form of seed	Round (R)	Wrinkled(r)
2.	Color of cotyledons	Yellow(Y)	Green(y)
3.	Color of seed coat	Colored(C)	White(c)
4.	Form of pod	Inflated (I)	Constricted(i)
5.	Color of pod	Green(G)	Yellow(g)
6.	Position of flower	Axial(A)	Terminal(a)
7.	Height of plant (Length of stem)	Tall(T)	Dwarf(t)

Modern cell theory

Cell theory is the scientific theory that is used to describe the properties of cells. Theodor Schwann and Matthias Jakob Schleiden both together discussed Schwann’s hypothesis and they formulated cell theory. The postulates of cell theory are:
1) Postulate :
All organisms are made up of one or more cells.
2) Postulate :
Cells are basic units of structure and function in all organisms.
3) Postulate :
All cells come from pre existing cells.

After that modern cell theory came which include cell theory proposed by Theodor Schwann and Matthias Jakob Schleiden and some new postulates are also added to it which are mentioned below :-
1)  Postulate :
The cells within individuals of the same species are basically the same in chemical composition.
2)  Postulate :
Some organisms are made of only one cell. Unicellular is the term used to define such organisms.
3)  Postulate :
Other organisms are multicellular and are made of many cells.
4)  Postulate :
Heredity information is passed from parent to daughter cells during reproduction.