Insertion and Deletion

 

Mutation that result in the missing DNA called deletions, and mutations that result in addition of extra DNA are called insertion.

Small scale: one or few insertion or deletion

Large scale: entire gene insertion or deletion 

Down syndrome

Down syndrome is set of mental and physical symptoms that result from having an extra copy of chromosome 21. Even though people with Down syndrome may have some physical and mental features in common, symptoms of Down syndrome can range from mild to severe. Usually, mental development and physical development are slower in people with Down syndrome than in those without it.
People with the syndrome may also have other health problems. They may be born with heart disease. They may have dementia. They may have hearing problems and problems with the intestines, eyes, thyroid and skeleton.
The chance of having a baby with Down syndrome increases as a woman gets older. Down syndrome cannot be cured. However, many people with Down syndrome live productive lives well into adulthood.

Central Dogma

Transcription of DNA to RNA to protein: This dogma forms the backbone of molecular biology and is represented by four major stages.
The DNA replicates its information in a process that involves many enzymes: replication.
The DNA codes for the production of messenger RNA (mRNA) during transcription.
In eucaryotic cells, the mRNA is processed (essentially by splicing) and migrates from the nucleus to the cytoplasm. 4. Messenger RNA carries coded information to ribosomes. The ribosomes "read" this information and use it for protein synthesis. This process is called translation.
Proteins do not code for the production of protein, RNA or DNA.
They are involved in almost all biological activities, structural or enzymatic.

Chromosome

A chromosome is an organized package of DNA found in the nucleus of the cell. Different organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes--22 pairs of numbered chromosomes, called autosomes, and one pair of sex chromosomes, X and Y. Each parent contributes one chromosome to each pair so that offspring get half of their chromosomes from their mother and half from their father. 
For most of the life of the cell, chromosomes are too elongated and tenuous to be seen under a microscope.Before a cell gets ready to divide by mitosis, each chromosome is duplicated (during S phase of the cell cycle).As mitosis begins, the duplicated chromosomes condense into short (~ 5 µm) structures which can be stained and easily observed under the light microscope.These duplicated chromosomes are called dadys.
When first seen, the duplicates are held together at their centromeres. In humans, the centromeres contains ~1 million base pairs of DNA. Most of this is repetitive DNA: short sequences (e.g., 171 bp) repeated over and over in tandem arrays.While they are still attached, it is common to call the duplicated chromosomes sister chromatid, but this should not obscure the fact that each is a bona fide chromosome with a full complement of genes.The kinetochore is a complex of proteins that forms at each centromere and serves as the attachment point for the spindle fiber that will separate the sister chromatids as mitosis proceeds into anaphase.The shorter of the two arms extending from the centromere is called the p arm; the longer is the q arm.Staining with the trypsin-giemsa method reveals a series of alternating light and dark bands called Gband.G bands are numbered and provide "addresses" for the assignment of gene loci. 

Point Mutation

A point mutation is a simple change in one base of the gene sequence.There are four main types of point mutation:

Missense mutation: changes of codons that cause substitution of one aa for another.

Nonsense mutation: converts an amino acid into a stop codon, UGA, UAA or UAG

Transition mutations:Purine replaces other purine (AT®GT) or pyrimidine replaces other pyrimidine (CT ® TT)Transversion mutations:Purine is replaced by a pyrimidine or vice versa, e.g. AG ® TG or AC

Eukaryotic Cells

 

 

A cell that contains membrane-bound compartments in which specific metabolic activities take place. Most important among these compartments is the nucleus, which houses the eukaryotic cell's . It is DNA this nucleus that gives the eukaryote – literally, "true nucleus" – its name. Eukaryotic organisms also have other specialized, membrane-bounded structures, called organelles, which are small structures within cells that perform dedicated functions. Eukaryotic cells are typically 10 to 100 micrometers across, or about 10 times the size of prokaryotic cells. The set of ideas most favored by biologists to explain how eukaryotic cells first came about is called the endosymbiotic theory. This theory is able to account well for the fact that two of the organelles found in eukaryotic cells, mitochondrias and chloroplasts, have their own DNA that is completely distinct from the DNA housed in the nucleus. According to the endosymbiotic theory, the eukaryotic cell evolved from a symbiotic community of prokaryotic cells. Specifically, the mitochondria and the chloroplasts are what remains of ancient symbiotic oxygen-breathing bacteria and cyanobacteria, respectively, whereas the rest of the cell seems to be derived from an ancestral archaean prokaryote cell.
The origin of the eukaryotic cell was a milestone in the evolution of life. Although eukaryotes use the same genetic code and metabolic processes as prokaryotes, their higher level of organizational complexity has permitted the development of truly multicellular organisms. Without eukaryotes, the world would lack mammals, birds, fish, invertebrates, fungi, plants, and complex single-celled organisms. 

 

Prokaryotic Cells

Cells that lack a membrane-bound nucleus are called prokaryotes (from the Greek meaning before nuclei). These cells have few internal structures that are distinguishable under a microscope. Cells in the monera kingdom such as bacteria and cyanobacteria (also known as blue-green algae) are prokaryotes.
Prokaryotic cells differ significantly from eukaryotic cells. They don't have a membrane-bound nucleus and instead of having chromosomal DNA, their genetic information is in a circular loop called a plasmid. Bacterial cells are very small, roughly the size of an animal mitochondrion (about 1-2µm in diameter and 10 µm long). Prokaryotic cells feature three major shapes: rod shaped, spherical, and spiral. Instead of going through elaborate replication processes like eukaryotes, bacterial cells divide by binary fission. Bacteria perform many important functions on earth. They serve as decomposers, agents of fermentation, and play an important role in our own digestive system. Also, bacteria are involved in many nutrient cycles such as the nitrogen cycle, which restores nitrate into the soil for plants. Unlike eukaryotic cells that depend on oxygen for their metabolism, prokaryotic cells enjoy a diverse array of metabolic functions. For example, some bacteria use sulfur instead of oxygen in their metabolism.

DNA translation

In the synthesis or production of proteins, a process of decoding the 'messenger Ribonucleic Acid' or mRNA takes place. It is the first step, and is known as translation. The mRNAs decoded in translation are obtained from a process known as transcription. The translation process takes place in the cell cytoplasm, specifically where the cell organelle, ribosome is present. Translation produces polypeptides as a result of decoding of the mRNA.

Transcription

DNA transcription is a process that involves the transcribing of genetic information from DNA to RNA. The transcribed DNA message is used to produce proteins. DNA is housed within the nucleus of our cells. It controls cellular activity by coding for the production of enzymes and proteins. The information in DNA is not directly converted into proteins, but must first be copied into RNA. This ensures that the information contained within the DNA does not become tainted.

DNA replication

DNA replication begins with the "unzipping" of the parent molecule as the hydrogen bonds between the base pairs are broken. Once exposed, the sequence of bases on each of the separated strands serves as a template to guide the insertion of a complementary set of bases on the strand being synthesized.

The new strands are assembled from deoxynucleoside triphosphates. Each incoming nucleotide is covalently linked to the "free" 3' carbon atom on the pentose (figure) as the second and third phosphates are removed together as a molecule of pyrophosphate (PPi). The nucleotides are assembled in the order that complements the order of bases on the strand serving as the template. Thus each C on the template guides the insertion of a G on the new strand, each G a C, and so on. When the process is complete, two DNA molecules have been formed identical to each other and to the parent molecule.

DNA structure

The structure was first described by James Watson and Francis Crick in 1953..The structure of DNA is illustrated by a right handed double helix, with about 10 nucleotide pairs per helical turn. Each spiral strand, composed of a sugar phosphate backbone and attached bases, is connected to a complementary strand by hydrogen bonding (non- covalent) between paired bases, adenine (A) with thymine (T) and guanine(G) with cytosine (C).
Adenine and thymine are connected by two hydrogen bonds (non-covalent) while guanine and cytosine are connected by three.