Question

Molecular biology. Bio of the gene.

1. Describe the meaning of each of the following terms with regard to the structure of DNA. (2) a. Polymer b. Complimentary base pairing- c. Directionality - d. Hydrogen bonding- e. Antiparallel- f Major vs. minor groove - g. Genome- h. Gene - i. Chromosome- 2. What is the relationship between a molecule and a living organism?

Answer 1

Answer 1.

A. Polymer is formed by combining many monomers together. The monomer in case of DNA is nucleotide. A Nucleotide is composed of a base that can either be a purine or a pyrimidine, sugar-deoxyribose and phosphate. When many units of nucleotides are attached together then DNA strand is formed. Thus, DNA is a polynucleotidic structure.

B. Complimentary base pairing means a purine can bind to a pyrimidine by hydrogen bonding, as adenine can bind to Thymine by double hydrogen bonds and cytosine can bind to guanine by three hydrogen bonds and vice versa.

C. DNA is double stranded structure. The direction of one strand is 5 prime to 3 prime and that of the other 3 prime to 5 Prime. Thus, the 2 strands of DNA are antiparallel to each other.

D. The 2 strands are intact to each other due to the hydrogen bond between the bases. Adenine binds to Thymine by 2 H bonds and vice versa and cytosine binds to guanine by 3 H bonds and vice versa.

E. Same as part c

F. The double stranded DNA structure shows major and minor groove alternatively. They are present along the entire length of DNA and are helpful in DNA replication and transcription.

G. The number of genes present in a haploid cell are called as genome. For example sperm and ovum has genome but somatic cell has genes.

H. Genes are the unit of heredity that are passed from one generation to the other. Their alternative form is known as alleles.

I. The cell at the time of cell division shows the presence of chromosomes. The somatic cells usually has chromosomes in pairs thus they are Diploid or 2n. The gametic cells have half the chromosomes as that of the somatic cell thus they are haploid or n. They are confined to the nucleus and has genes on them.