Brief Description of Mendel's Law of Inheritence

• The law inheritance  explains that the traits in an individual are controlled by discrete units called factors. These factors  are present in pairs.

• The character that dominates appears in the first or consecutive generation   is called the dominant character, and the one that does not appear and may be masked  is the recessive character.

👌👌Remember The recessive character  is transmitted to the offspring in the same way as the dominant character.

• One trait is represented by a pair of allele . These two alleles  are brought together during Fertilization, where one of the alleles comes from the maternal gamete and the other from the parental gamete.

• The concept of dominance is strictly only used for genotypic characters and does not represent the phenotype of the individual.

• With new experiments on genetics, many researchers believe that the law of dominance doesn’t always hold true and that other patterns of inheritance also exist.

• Genes are the unit of inheritance and transmit through the gametes. The genes are present  within chromosomes. Each chromosome is always  in the pair and each chromosome comes from each parent.

• Homozygous individuals have two identical alleles like the AA The homozygous chromosomes are separated.

• During gametogenesis; both chromosomes are combined during the process of fertilization for the combing of both chromosome and characters. The offspring is  called heterozygous when they have two different alleles like Aa.

Mendel’s Law of Dominance

• This is the first law of dominance given by Mendel. When Mendel crossed by considering a single trait or monohybrid cross on a pea plant. 

• Mendel used allele TT for tall and allele tt for the short plant. After the crossing Mendel got tall plants with allele Tt in the first generation.

• After that Mendel made self pollination between the two  tall plants with Tt allele then he found three tall plants and one dwarf plant  in the Second generation.

• In the second generation he found a genotypic ratio -  TT : Tt : tt - 1:2:1 and phenotypic ratio is Tall : dwarf - 3:1.

• By  analyzing this result, Mendel used the term dominant for tall and recessive for short plants And propounded the first law of inheritance called Law of dominance. 

• Characters are controlled by the discrete unit called factors which are found in pair.

• In a dissimilar pair of factor or allele, one allele is dominant over the other.

• Law of Dominance explain the appearance of one parental character in first generation and appearance of both characters in Second generation.

• According to this law the characters that appear in the first generation are called dominant characters and the characters that do not appear are called recessive characters.

• It does not mean that recessive traits will never appear; it may appear in any generation.

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Law of Segregation or Law of purity of gamete 

• This law  states that alleles are separated at  random fashion  into gametes: When gametes are formed, each allele of one parent separates  randomly and each gamete receive one allele out of two allele.

• In a diploid organism, each  allele passes  in random  manner into gametes rather than offspring And offspring receives one allele from each parent.

Law of independent assortment

• Mendel's law of independent assortment reveals  that the alleles of two different traits  get  separated into gametes independently of one another.

• In other words, a gamete receives only one allele  and it  does not affect  the allele received for another gene.

• The Law of Independent Assortment states that in  a dihybrid cross ,the movement  of each pair of traits is independent of the other.

• In other words, during gamete formation, one pair of traits segregates from another pair of traits independently. 

• In the dihybrid cross, Mendel used  round-yellow seed with allele RRYY  and wrinkled green seed with allele of rryy and crossed them.

• He obtained only round yellow seeds with allele RrYy in the F1 generation. when he self-pollinated  the offspring of F1 progeny then he got four different combinations of seeds in the F2 generation.

• He obtained round-yellow, wrinkled-yellow, round green and wrinkled green seeds in the phenotypic ratio 9:3:3:1

Back  Cross: 

• The cross between the hybrid (Tt) and Either of the parents whether tall (TT) and dwarf (tt) is called Back cross.

• For example : Tt x TT and Tt and tt. In both type of cross the genotype ratio will be 1: 1

Test  Cross: 

• To know the genotype of tall plant in F2 generation, test cross is done.

• The cross between the dwarf  (tt) and Either of the tall plant  whether  (TT) and (Tt) is called test cross.

• For example : TT x tt and Tt and tt. The second one is similar to back cross therefore a back  cross can be test cross.