question_answer

What are salient features of HGP? What are the prospects of this project?

OR

List 5 factors of modern concept of evolution. How vertebrate hearts show homology?

 

Answer:

Human genome project was launched in 1990 for sequencing human genome. Human genome has 3 x 10 bp and the cost of sequencing human genome was estimated approximately 9 billion US dollars. The project was 13 year old project coordinated by U.S. Department of Energy and National Institute of Health. Various countries like Japan, France, Germany, China contributed to this project. The project completed in 2003.

The salient features are -

(i) The human genome contains 3164.7 million nucleotide bases.

(ii) The average gene consists of 3000 bases, but sizes vary greatly with the largest known human gene being dystrophy at 2.4 million bases.

(iii) The total number of genes is estimated as 30,000-much lower than previous estimates of 80,000 to 1,40,000 genes. Almost all (99.9 per cent) nucleotide bases are exactly the same in all people.

(iv) The functions are unknown for over 50 per cent of discovered genes.

(v) Less than 2 per cent of the genome codes for proteins.

(vi) Repeated sequences make up very large portion of the human genome.

(vii) Repetitive sequences are stretches of DNA sequences that are repeated many times, sometimes hundred to thousand times. They are thought to have no direct coding functions, but they shed light on chromosome structure, dynamics and evolution.

(viii) Chromosome 1 has most genes (2968), and the Y has the fewest (231).

(ix) Scientists have identified about 1.4 million locations where single base DNA differences (SNPs - single nucleotide polymorphism, pronounced as 'snips') occur in humans. This information promises to revolutionise the processes of finding chromosomal locations for disease-associated sequences and tracing human history.

The discovery of human genome is a great achievement of man. It will show new ways to diagnose, treat many human diseases.

It will help in healthier living and give knowledge about designer drugs, genetically modified foods and our genetic identity also.

It will also help us to sequence the genomes of some other organisms like Drosophila, yeast, bacteria, plants etc.

OR

The factors of modern concept of evolution are:

(i)   Genetic variation

(ii) Adaptation

(iii) Differential reproduction

(iv) Accumulation of genetic variation

(v) Speciation

The organs which have same fundamental structure but are different in functions are called homologous organs. These organs follow the same basic plan of organisation during their development but in adult they perform different functions. E.g; forelimbs of frog, lizard, pigeon, whale, horse and man have same basic structural plan but different functions. The hearts of different vertebrate also show homology. The heart is two chambered in fishes, consisting of one auricle and one ventricle. In amphibians, it is three chambered and in lower reptiles the heart is partially four chambered. In higher reptiles, birds and mammals heart is four chambered and the oxygenated and deoxygenated bloods are completely separated. This presents a gradual modifications in the heart of vertebrate series while the fundamental structure of heart remains same in all the groups.