The complex tissues and organs of human body are made up of cells. The blueprint of genes in a cell for protein production is responsible for cell functionailty. The physical charactersitics and human traits are also dependent upon genes. Genome is a complete set of some 30,000 to 40,000 genes. The outer layer or cell membrane of a cell contains cytoplasm which consists of organelles like nucleus which controls the cells and maintains the genetic material in structures called chromosomes. Chromosomes serve as carrier for genetic and hereditary information in the form of strings called DNA (deoxyribonucleic acid). There are 22 pairs of chromosomes in a human body and a pair of sex chromosomes i.e. XX (females) and XY (males). DNA is of staircase shape called double helix. Each staircase is made up of DNA bases like A, C, T and G with some sequence for each gene. Human body consists of genes 50 % from father and 50% from mother. The Y chromosome is a sex determining chromosome. The men have Y and X combination while the women have both X chromosomes. The changes in DNA sequence are called Mutations. The genetic marker of a human is the one which passes down through generations. The natural selection process favours beneficial genetic mutations and limits harmful mutations. Genetic drift or genetic changes passes down from parents and its affect varies according to the population size.

The website is more beneficial for basic knowledge about human body, structure, cells, genes, chromosomes, and DNA.

Step # 2

The genome sequence is more detailed than the genome map. We can see the order of DNA bases through genmoe sequences while the other one is used to see the landmarks of a genome. In some cases mapping and sequencing are seen as differently e.g. without the intervention of sequencing we can determine the gene location and we can also map a gene. Both sequencing and mapping don’t tell anything about each other. The landmarks of mapping are actually the DNA sequences and both are approximately same.

Step # 3

The disease of disorder is the result of an abnormality in the DNA of and individual. Abnormalities can be casue of a small mutation in a gene. And there is the addition or subtracion of a chromosome or set of chromosomes.

Single gene disorder is the due to the effect of a mutation when an alteration or missing occurs in the protein product of a single gene.

The other abnormality or disorder called chromosome abnormality is due to the missing, duplication or due to the alteration of an entire choromosome or large segment of the chromosome.

The third abnormality called multifactor disorder is the result of mutations in multiple genes. These types of abnormalities are also casued due to the environmental effect on a human being or a living body.

The material is very helpful for the students of biological sciences and it provides a basic understanding of the human body, its structure, information about cells, DNA, the different abnormalities caused by chromosomes. However these websites are providing the basic knowledge about human body structures and chromosomal abnormalities but not detailed information and one must have to face difficulty in such unclear scenarios.

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