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2.0: Genetics- form fou biology topic

2.0: Genetics- form fou biology topic

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Biology form four notes


 2. 0 GENETICS
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TOPIC OUTLINE
Concept of genetics
Genetics is the branch of science that deals with the study of heredity and variation among organisms
VARIATION is the differences among organisms of the same species
SPECIES is the group organisms which interbreed freely to produce fertile offspring
 
TERMINOLOGIES USED IN GENRTICS
1.     Heredity Is a passing of features (traits) from one generation to another generation parents to their young.
2.      A Trait is a heritable genetic characteristic that an orgasm possesses and can distinguishes one individual from another.
or
refers to the characteristic of an organism that can be passed from one generation to another. Examples of an organism's characters or traits include color, shape, height, texture, length and width of various body parts
.4.  Genotype
 Is the genetic constitution or make up of an organism?
 
 
5. Phenotype
 Is the outward or physical appearance of an organism
6. Gene
Is a part of chromosome that carries the genetic material called DNA? Are also referred to as nucleotide chemical units of inheritance arranged along the chromosomes. They are called hereditary factors.
OR

Gene is the unit of heredity that is transferred from the parent to offspring and carries information that determines the genetic characteristics of the offspring. The genetic Information’s are responsible for many genetically characteristics such as height, eye colour, blood type, hair colour, flower colour, branching patterns and leaf type.
 
11. Allele
Is an alternative form of a gene controlling the same characteristics but produce different effect Example: T-tallness and t- shortness?
10. Homozygous versus heterozygous
Homozygous Is a condition where by the two genes for a given trait are similar alike. example of a homozygous state is RR for rough coat and TT for smooth coat
OR
Homozygous is a genetic term that describes the state for an organism that possess identical alleles of a particular trait on similar loci of paired chromosomes. An example of a homozygous state is RR for rough coat and IT for smooth coat.
 
11.        Heterogeneous Is a condition where the two genes for a given trait are different
OR
heterozygous is a genetic term that describes the state for an organism that possess different or non-identical alleles of a particular trait. Example Tt
12.  CHROMOSOMES. Donny Company Resourceful Learning Centre Page 92 They are thread like structures found in the nucleus of the cell they are only visible when a cell nucleus is about to divide
13.  Locus
This is a specific position on a chromosome where a particular gene is located.
14.  HAPLOID
Is the condition of having one set of chromosomes?
-                   HAPLOID is denoted by letter "n". In human beings, which include gametes or reproductive cells implies 23 number of chromosomes
 
15.  DIPLOID Is the condition of having two set of homologous chromosomes
 
-DIPLOID is denoted by "2n" and implies 46 chromosomes. All somatic cells contain diploid number of chromosomes.
 
16.  . first filial generation (F1)
refers to the generation produced by pure parental.
-It is denoted as F1 generation.
 
17.  The second filial generation (F2) refers to the generation produced by crossing organisms from First filial generation
18.  -it is denoted as F2 generation
19.   parents
These are organisms that are capable of producing offspring’s
 
   21. Hybrid


A hybrid is an offspring resulting from crossing two parents of different breeds or varieties through sexual reproduction
22.  Dominance
Is the condition where one allele masks the expression of the another allele in the heterozygous. 
- TT is a homozygous tall individual, Tt is a heterozygous tall individual,
- An organism with Tt has a dominant allele for tallness (T) and a recessive allele for shortness (t).
 Dominant gene Is a gene that prevents the expression of another gene 6. Recessive gene Is a gene that is masked by another gene.
 
 Recessive gene Is a gene that is masked by another gene.
23.     Recessive is a condition where an allele can only express itself in a homozygous form, for example tt for dwarfness.
-Recessive genes tt
24.     Recessive allele is the allele masked by another allele in the heterozygous Tt
T- dominant allele
    t- recessive allele
25.      Pure breeding
Pure breeding is a kind of breeding in which the parents with particular genotype produces offspring only with the same genotype. Pure breed individuals are a group of identical organisms that always produce offspring of the same genotype when they are inter-crossed.
26.     Monohybrid inheritance is the inheritance which involves passage of single (traits) characteristic from one generation to another generation which is controlled by a single gene. Examples of this kind of inheritance include skin colour, hair texture or shape of an organism.
or
Monohybrid inheritance is the inheritance of single characteristic which is controlled by a single gene. Examples of this kind of inheritance include skin colour, hair texture or shape of an organism.
27.  Selfing is the crossing offspring of the same pair of parents.
28.  Dihybrid inheritance is the inheritance involves passage of two (traits) characteristics from one generation to another generation. Dihybrid crosses lead to dihybrid inheritance among organisms
Or
Dihybrid inheritance is the inheritance of two characteristics which are controlled by two genes. Dihybrid crosses lead to dihybrid inheritance among organisms
Qn necta 2006

1.      Use the words “homozygous”, “heterozygous”, “dominant”, “recessive” (where suitable) to describe the following combinations:  i) Bb    ii) BB   iii) bb

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