Heredity and Evolution, Slides of Biology

Download Heredity and Evolution and more Slides Biology in PDF only on Docsity!

Heredity and Evolution

Part-

• (^) Inheritance/ heredity- The process by

which characters are transferred from one

generation to the next generation.

Ear Lobe Rolling tongue

Gregor Johann Mendel

Mendel’s Experiment

1. He conducted artificial pollination/cross-pollination experiments using several true-breeding varieties having contrasting traits. A true breeding line is the one that having undergone continuous self pollination for several generations, shows the stable trait inheritance and expression for several generations

Monohybrid cross Q1. Axial flower Terminal flower Q2. Violet flower White flower Interesting Case

• (^) F1 generation : This term was given by Bateson. It is the generation of hybrids produced from a cross between the genetically different individual called parents eg. “Tt” individuals are produced F1 generation from a cross between “TT” and “tt” parents.
• (^) F2 Generation- (Bateson, 1905) F2/Second filial generation is the generation of individuals which arises as a result of inbreeding or interbreeding amongst individual of F1 generation
• (^) Genome -It is the entire genetic constitution of a prokaryote/ virus or haploid genetic constitution of a eukaryote.
• (^) Gene: Unit of inheritance(Term given by Johansen,1909) Gene Allele A gene is a segment of DNA which controls a specific trait Alternate forms of the same gene which are present on the identical locus of the same gene A gene determines a particular character Two or multiple alleles bring variation to the trait Gene controls the character “height of the plant” This gene has 2 forms “T” & “t”

Dominant trait Recessive trait The phenomenon where one allele expresses itself exclusive of the presence of other allele. The phenomenon where an allele expresses itself in the absence of its dominant allele but remains masked in its presence. Dominant allele forms a complete functional enzyme due to which complete polypeptide is formed to express completely Recessive allele forms incomplete or defective, or non-functional polypeptide is formed and fails to express completely

Dihybrid cross

• Cross between plants differing in two traits

/cross involving study of inheritance of 2

genes or characters.

• Genotypic ratio: RRYY 1: RRYy 2: RRyy 1: RrYY 2: RrYy 4: Rryy 2: rrYY 1: rrYy 2: rryy

Mendel’s laws of inheritance

Law of dominance

• (^) Characters are controlled by discrete units called factors
• (^) This law states that when two alternative forms of a trait or character (gene or alleles) are present in an organism, only one factor expresses itself in F1 progeny and is called dominant while the other that remains masked is called recessive. Law of segregation (Universal law)
• (^) This law states that the factors or alleles of a pair segregate from each other during gamete formation, such that a gamete receives only one of the two factors. They do not show any blending. Law of independent assortment
• (^) According to this law the two factors of each character assort or separate out independent of the factors of other characters at the time of gamete formation and get randomly rearranged in the offsprings producing both parental and new cominations of characters.

XX-XY type

• (^) Seen in many insects ( Drosophila) and mammals including humans.
• (^) Males have X and Y chromosomes along with autosomes and females have a pair of X chromosomes.