1. What is the structure of DNA?

DNA is a long molecule formed by two polynucleotide strands held together by hydrogen bonds. These bonds occur between complementary pairs of Nitrogen bases. The Deoxyribose Nucleic Acid (DNA) consists of four types of basic unit called nucleotides , Adenine (A), Thymine (T), Guanine (G) and Cytosine (C). Adenine pairs with thymine by two hydrogen bonds (A = T) and cytosine with guanine by three hydrogen bonds (C = G). The DNA strands are compared to a twisted ladder. The actual configuration of DNA is a double helix that looks some what like a spiral staircase. The structure of DNA is intimately related to its function.

2. Define mitosis.

The process of cell division where by the chromosomes are duplicated and distributed equally to the daughter cells is called mitosis.

3. Define meiosis.

Meiosis is a form of cell division happening in sexually reproducing organisms by which two consecutive nuclear divisions (meiosis- I and meiosis- II) occur without the chromosomal replication in between, leading to the production of four haploid gametes (sex cells), each containing one of every pair of homologous chromosomes (that is, with the maternal and paternal chromosomes being distributed randomly between the cells).

4. List of difference between mitosis and meiosis.

5. What is a chromatid?

At the start of mitosis each chromosomes contains two identical copies of its DNA molecules. Each copy is called a chromatid.

6. What is a gene?

A length of DNA which contains the instructions for making a single protein or polypeptide is called a gene.

7. Define nucleotides.

The basic building blocks of nucleic acid, such as DNA and RNA is called a nucleotide. It is an organic compound made up of nitrogen base, a sugar and a phosphate group.

8. Write the name of DNA molecule that carries the sequence of the four bases.

1. Adenine (A)
2. Thymine (T)
3. Guanine (G)
4. Cytosine (C)

9. Describe the important steps in the synthesis of proteins.

Proteins are polypeptides formed of many amino acids joined together by chemical bonds known as peptide bonds. There are 20 different amino acids in the formation of the polypeptide chains. Synthesis of proteins take place at tiny cytoplasm particles called ribosome. The type of protein to be synthesized in the ribosomes is determined by messenger RNA.

10. What is the structure of RNA?

RNA consists of a long chain of nucleotides. RNA usually has a single strand containing ribose. Sugar is ribose and not deoxyribose which contains uracil in place of thymine. Most RNAs are usually single stranded with partial double strand region due to folding back of single chain. RNA serves as the genetic material in many viruses.