GENETICS Subtopics

GENETICS Subtopics. -Hereditary material -Genetic code -Protein synthesis - Mendelian principle of inheritance -Non- Mendelian inheritance -Mutation -Genetic engineering.

Introduction. Definition Genetics is the study of heredity and variation. Variation Is the difference among individuals of the same species. Species Is a group of organisms which have the same karyotype(number and appearance of chromosomes) Heredity Is the passage of characteristics(traits) from one generation to another.Heredity is controlled by hereditary materials..

HEREDITARY MATERIAL. Hereditary material or genetics materials are carriers of hereditary/genetic information from one generation to another. Genaral characteristics of hereditary material. 1.Metabolically stable: Hereditary material are chemically inert,ideally suited for storage of genetic information. 2.Constant within a cell: Within a cell of a given species does not vary in number.

Cont…. 3.Mutations: Genetic material can be affected by mutagens and causing mutation 4.Linearity: Genetic materials are linear in structure.so the information they store occur in linear array 5.Self replication Hereditary material are capable of undergoing self replication..

LOCATION OF HEREDITARY MATERIAL IN THE CELL. Cytology studies have revealed that the genetic materials are located in the nucleus due to the following evidences. 1.Universal occurrence of the nucleus. In most cells or at some stages of life cycle of the cell,suggests that it has essential roles,one of which is to control heredity. 2.Fertilization.During fertilization the nuclear of the gametes fuse to form zygote.The latter develop in to an individual organism with various characteristics that are derived from the parents.This shows that the fused nuclear had hereditary materials from the parents..

Cont….. 3.Nuclear division. One of the significance of meiosis is that it brings variations.However the latter,are controlled by hereditary materials.This suggests that is the manipulation of the hereditary materials in the nucleus which bring about variation.

LOCATION OF THE HEREDITARY MATERIAL IN THE NUCLEUS.

Cont…. 2.Mutation. Mutation of the chromosomes ,leads to the change in the genetic make up of an organism.This suggests the presence of hereditary material in the chromosomes. 3.Fertilization: The sex of the individual to be born depend on the fused sex chromosomes during fertilization.If X and Y chromosomes fuse produce a male but if X and X fuse produce female.Thus since sex is genetically controlled,then the fused chromosomes have hereditary material..

Cont... 4.Nuclear division: During diplotene stage of prophase 1,there is crossing over formation at which there is breaking of chromatids and reunion of chromatids of homologous chromosomes which results to variation.This implies that the process is associated with the exchange of hereditary materials and hence new gene combination in reunited chromatids..

Prepared by M,basher.

TYPES OF HEREDITARY MATERIALS. Hereditary materials exists in two forms A.Ribonucleic acid (RNA) B.Deoxyribo nucleic acid(DNA).

GENERAL CHEMISTRY OF HEREDITARY MATERIAL. Hereditary materials are polymers of nucleotide(monomers).The nucleotide consists of:- (i) Pentose sugar, in which DNA has deoxyribose sugar and RNA has ribose sugar (ii) Phosphate group: This give acid nature of the hereditary material. (iii)Nitrogenous bases:They are derived from purines and pyrimidines. Purine bases have two rings,are of two types adenine(A) and guanine(G)..

Cont….. Pyrimidines bases have one ring,which include Thymine(T),cytosine(C) and uracil(U). Note:There is no uracil(U) in DNA and there is no thymine(T) in RNA. Chemical bonds in hereditary material There are hydrogen bonds between complementary base pairs in DNA,since it has two strands and in RNA(tRNA) also phosphodiester bonds that hold the nucleotide together..

Chemical structure of nucleotide component. Prepared by M,basher.

Nucleotide formation. Prepared by M,basher.