question_answer

Who coined the term 'genetic code'? What does it mean? Define genetic material.

OR

Describe the origin and evolution of man.

 

Answer:

The term genetic code was coined by George Gamow. It means that a sequence of 3 successive bases specifies one amino acid in a polypeptide.

Genetic code is that by which genetic information in DNA controls the manufacture of specific proteins by the cell. The code takes the form of a series of triplets of bases in DNA, from which is transcribed a complementary sequence of codons in messenger RNA. The sequence of these codons determines the sequence of amino acids during protein synthesis. There are 64 possible codes from the combinations of the four bases present in DNA and messenger RNA and 20 amino acids present in body proteins: some of the amino acids are coded by more than one codon, and some codons have other functions.

A substance which stores biological information, transfers it to the next generation, and expresses it in the offspring is called genetic material. Gene is a unit of heredity composed of DNA. It can exist in different forms called alleles, which determine which aspect of the characteristic is shown (e.g. tallness or shortness for the characteristic of height). A gene occupies a specific position (locus) on a chromosome. In view of the discoveries of molecular genetics, it may be defined as the sequence of nucleotides of DNA (or RNA) concerned with a specific function, such as the synthesis of a single polypeptide chain or of a messenger RNA molecule, corresponding to a particular sequence of the genetic code. One or more of these structural genes, coding for protein, may be associated with other genes controlling their expression.

OR

The fossil evidences clearly indicate that origin of man occurred in Central Asia, China, Java and India (Shivalik Hills). It has been established that Dryopithecus is one of the oldest fossil which in turn evolved into apes and man. It lived about 20-25 million years ago. Fossils of Ramapithecus and Shivapithecus were found from Shivalik hills of the Himalayas. They lived about 14-15 million years ago. Australopithecus africnanus (African ape-man) lived about 4-5 million years ago in South Africa. He had human as well as ape features,

He was about 1.2 to 1.5 metres tall creature with bipedal locomotion. It gave rise to Homo habilis which lived in Africa about 2 million years ago. He was a more man like primate. He led community life in caves and used tools of stones. His brain volume was

650-800 cc. Homo erectus evolved from Homo habilis about 1.7 million years ago. He had a larger brain around 900 cc. Neanderthal man with a brain size of 1400 cc lived in near east and central Asia between 1,00,000-40,000 years back. They made tools, used animals hides as clothing, knew the use of fire, and burried their dead. They were replaced in Europe by modern man. Homo sapiens about 40,000 years ago.