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