Principle of Inheritance and variation ( imp. definitions) Flashcards
What is a character
ANy feature, internal or external of an organism
eg: eye colour, synthesis of a given enzyme in the body
what is a trait
Alternate forms of a character. It gives specific information about a character.
Eg: blue eyes/ brown eyes
what is a gene
It is a segment of DNA which carries information for a character. It is responsible for the inheritance and appearance of characters. It is the segment of dna which usually synthesises RNA and hence protein.
mendel used to call these elements/ factors
what is an allele
Alleles are alternative forms of genes. They contain information for traits present on homolgous chrosmomes.
There are mostly 2 alleles for a given character.
Notations for alleles
i) Mendel
First letter of dominant trait ( tall dom/ dwarf rec)
in capital for dom trait, in small for rec trait
T- tall t- dwarf
ii) International rules
First letter of recessive trait
in capital for dom trait, in small for rec trait
D- tall d-dwarf
ii) Morgan
first letter of recessive trait. + sign for dominance
d+ - tall d- dwarf
define homozygous/ pure line/ true breeding
why is it called true breeding
When both alleles are similar . They have information for the same trait.
If a homozygous plant is selfed, there will be offsprings having the same trait as parents, ie, it is true to its trait. Hence it is true breeding
define heterozygous/ hybrid
They are 2 dissimilar alleles for a gene. They contain information for 2 different traits.
When selfed, the offpsrings may or may not be similar to parents hence it is not true to its character
what is phenotype
External features of an organism
Pp and PP are both purple flowers
purple flower is phentoype
what is genotype
It is the genetic makeup/ genetic constitution of an organism, for a character.
Alleles give the genotype of the organism
