Question

How can you explain the laws of Mendel??

Answer 1

When a cell duplicates its DNA and divides twice to produce four gametes, or reproductive cells, the process is called meiosis. Most cells in the body are diploid, meaning they have two copies of each chromosome. But because gametes have gone through meiosis, they have one copy of each chromosome and are haploid. During sexual reproduction two gametes, called the egg and sperm, join together and form a diploid cell that will eventually become an individual organism. This diploid cell, called a zygote, received one copy of each chromosome from each parent. The appearance, or phenotype, of the new individual will depend on whether it inherited recessive or dominant copies of various alleles from its parents. Variant copies of genes are called alleles, and since plants and animals are diploid they have two alleles for each gene.

The Law of Dominance

A dominant trait is a trait whose appearance will always be seen in offspring. In other words, dominance describes the relationship between two alleles. If an individual inherits two different alleles from each of its two parents and the phenotype of only one allele is visible in the offspring, then that allele is said to be dominant. Mendel's law of dominance states that if one parent has two copies of allele A -- the dominant allele -- and the second parent has two copies of allele a-- the recessive allele -- then the offspring will inherit an Aa genotype and display the dominant phenotype.

The Law of Segregation

A parent may have two distinct alleles for a certain gene, each on one copy of a given chromosome. Mendel's second law, the law of segregation, states that these two alleles will be separated from each other during meiosis. Specifically, in the second of the two cell divisions of meiosis the two copies of each chromosome will be separated from each other, causing the two distinct alleles located on those chromosomes to segregate from one another.

The Law of Independent Assortment

Mendel's third law, the law of independent assortment, states that the way an allele pair gets segregated into two daughter cells during the second division of meiosis has no effect on how any other allele pair gets segregated. In other words, the traits inherited through one gene will be inherited independently of the traits inherited through another gene because the genes reside on different chromosomes that are independently assorted into daughter cells during meiosis.

Answer 2

The Law of Dominance

A dominant trait is a trait whose appearance will always be seen in offspring. In other words, dominance describes the relationship between two alleles. If an individual inherits two different alleles from each of its two parents and the phenotype of only one allele is visible in the offspring, then that allele is said to be dominant. Mendel's law of dominance states that if one parent has two copies of allele A -- the dominant allele -- and the second parent has two copies of allele a-- the recessive allele -- then the offspring will inherit an Aa genotype and display the dominant phenotype.

The Law of Segregation

A parent may have two distinct alleles for a certain gene, each on one copy of a given chromosome. Mendel's second law, the law of segregation, states that these two alleles will be separated from each other during meiosis. Specifically, in the second of the two cell divisions of meiosis the two copies of each chromosome will be separated from each other, causing the two distinct alleles located on those chromosomes to segregate from one another.

The Law of Independent Assortment

Mendel's third law, the law of independent assortment, states that the way an allele pair gets segregated into two daughter cells during the second division of meiosis has no effect on how any other allele pair gets segregated. In other words, the traits inherited through one gene will be inherited independently of the traits inherited through another gene because the genes reside on different chromosomes that are independently assorted into daughter cells during meiosis.