Question

1)Draw a chromosome and indicate where urban centers,deserts,genes,promoters and terminators would be located.
2)Name the two major molecules that are found in a chromosome
3)Describe how DNA is packed into a chromosome using the following terms:
a)DNA double helix
b)Histones
c)Nucleosomes

3)Define and contrast chromosomes and gene;
4)State the function of a gene.
5)Describe how Gene's are distributed along a chromosome (urban centers and deserts), and which base pairs tend to be most prevalent in coding and non-coding regions.

Answer 1

ans 1.

2. The two major molecules are Proteins and Deoxyribonucleic acid ( DNA ) found in choromosome .

3. The mechanism of DNA packing -

1. At the simplest level , chromatin is a double stranded helical structure of DNA.
2. DNA is complexed with histones to form nucleosome.
3. Each nucleosome composed of eight histone proteins around which the DNA wraps 1.65 times.
4. A chromosome consist of a nucleosome and H1 histone.
5. The nucleosome fold up to form 30 nm fibre.
6. That forms loops averaging 300 nm fibre.
7. The 300 nm fibres are compressed and folded to produce a 250 nm wide fibre.
8. Tight coiling of the 250 nm wide fibre produces the chromatid of a chromosome

4. Definition of chromosome and gene -

• Chromosome- The chromosome of a cell are in a cell nucleus . They carry the genetic information. Chromosomes are made up of DNA and proteins combined as chromatin. Each chromosome contain many genes , when they duplicate , chrmosome looks like the letter " X ".
• Gene - A gene is the basic physical and functional unit of heredity . Genes are made up of DNA . Some gene act as instructions to make molecules called proteins,
• contrast chromosome and gene-

Chromosome	GENE
Most condensed structure of DNA.	It is a locus on a chromosome.
Always composed of DNA	Composed of either DNA or RNA
Mutation leads to chromosomal abnormalities such as deletion , duplication etc.	Mutation include point mutation , frameshift mutation etc.
Mutations occur in homologus recombination	Mutation occur in DNA replication.

5. Function of a gene -

Gene gives instruction for living beings to make molecules called proteins.

6.Gene dense urban centres are composed of DNA building blocks G and C . Gene deserts are rich in DNA building blocks A and T. Genes concentrated in random areas along the genome , with vast expanses of non coding DNA between.