Please give me the handwritten notes of Heridity and evolution.
Answers
Answer:
Revision notes on Heredity and Evolution
The study of heredity and variation is known as genetics. Heredity is defined as transmission of characteristics from parents to offspring's. The differences in characters of parents and offspring's is known as variation.
Answer:
In the simplest of words, heredity refers to the passing of traits or characteristics through genes from one generation (parent) to the other generation (offspring). ... Variation is important because it contributes to the evolution and forms the basis of heredity.Heredity
Sexual reproduction
The mode of reproduction that involves two individuals; one male and one female.
They produce sex cells or gametes which fuse to form a new organism.
Genes
Gene is the functional unit of heredity.
Every gene controls one or several particular characteristic features in living organisms.
Heredity
The process by which the features of an organism is passed on from one generation to another is called heredity.
The process is done by genes, which define the characters the organism.
Mendel’s work
Gregor Johann Mendel, known as ‘Father of Genetics’, was an Austrian Monk who worked on Pea plants to understand the concept of heredity.
His work laid the foundation of modern genetics.
He made three basic laws of inheritance – The Law of Dominance, The Law of Segregation and The Law of Independent Assortment.
Dominant traits
The traits that express themselves in an organism in every possible combination and can be seen are called Dominant traits.
In Mendel’s experiment, we see that tall trait in pea plants tends to express more than the short trait.
Therefore, the tall trait of the plant is said to be dominant over the short trait.
Recessive traits
A trait which is not expressed in presence of a dominant allele is known as recessive.
So, recessive character/trait is present in an organism but cannot be seen if a dominant allele exists.
Monohybrid cross
When only one character is considered while crossing two organisms, then such a cross is known as monohybrid cross.
The ratio of characters, arising out of this cross, at F2 generation is called monohybrid ratio.
E.g., If tall plant (TT) is crossed with a dwarf plant (tt), we get 3 tall:1 short plant at the end of the F2 generation.
So, 3:1 is monohybrid ratio.
Here, the height of the plant is considered at a time.
Dihybrid cross
When two characters are considered while crossing two organisms, then such a cross is known as a dihybrid cross.
The ratio of characters, arising out of this cross, at F2 generation is called dihybrid ratio.
E.g., If a plant with round and green pea is crossed with a plant with wrinkled and yellow pea,
The first generation plants would all have round and green pea.
On crossing the same for an F2 generation, we would observe four combinations of characters in the ratio of 9:3:3:1.
Thus, 9:3:3:1 is the dihybrid ratio.
Inheritance
In Biology, inheritance pertains to the transfer of traits from one generation to another.
Laws of Mendel
Law of Dominance says that a gene has two contrasting alleles and one always expresses itself in the organism.
It is called the dominant gene and it expresses in any possible combination.
Law of Segregation says that traits get segregated completely during the formation of gametes without any mixing of alleles.
Law of Independent Assortment says that the traits can segregate independently of different characters during gamete formation