BIOLOGY FORM FOUR TOPIC 2: GENETICS

Concept of Genetics
The concept of the Genetics
Explain the concept of the genetics
Genetics is the study of heredity and variations in organism. Through this statement there are two common words that are heredity and variation.
Heredity is the passing on of characteristics from parents to the off spring.
Variation is the observable differences in organisms from the same species.
The hereditary characteristics are passed from parents to their offspring through distinct units called genes.
Genes are hereditary materials or factors, which determine a specific characteristic or trait in an organism.
Common terms used in Genetics
State common terms used in genetics
First filial generation (F1)
This is arising from the crossing of two pure breeds
Second filial generation (F2)
This is the generation obtained by crossing individuals of the first filial generation.
Genotype
This is the genetic makeup of an organism or an individual
Phenotype
This is the outward appearance determined by a gene
Haploidy (n)
Having one set of unpaired chromosomes in the nucleus
Diploidy (2n)
Having two sets of homologous (similar) chromosomes in the nucleus
Alleles
It is the alternative number of genes in the nucleus or in the same position
Homozygosity
The state of possessing two identical forms of a particular gene, one inherited from each parent. For example, a girl who is homozygous forcystic fibrosis(CF) received the cystic fibrosis gene from both of her parents and therefore she has cystic fibrosis.
Heterozygosity
Thestateofbeingheterozygous;havingtwodifferentallelesofthesamegene
Dominance
This is a condition where an allele can express itself in the presences of other alleles. Example: ‘Tt’ where ‘T’ is the dominant that expresses its effect in the presence of ‘t’.
Recessiveness
A condition where an allele can only express itself when they are in homozygous form but does not express its effect on the presence of other alleles.
Mutation
A sudden random change in the genetic make up of a cell, causing it and all cells derived from it to differ from normal cells.
Mutagen
This is an agent capable of increasing the rate of mutation in an organism like formaldehyde and nitrous acid.
Selfing
It is the crossing offspring of the same pair of parents.

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