Question

Correlate Mendel's four postulates with what is now known about homologous chromosomes, genes, alleles, and the process of meiosis.

Short answer

Short Answer: Mendel's Four Postulates relate to homologous chromosomes, genes, alleles, and the process of meiosis in the following ways: 1. The Law of Segregation states that organisms have two alleles for each trait, which separate during gamete formation in meiosis, ensuring each gamete carries only one allele for each trait. 2. The Law of Independent Assortment occurs during meiosis when homologous chromosomes line up independently along the metaphase plate, leading to different combinations of traits being passed onto the gametes. 3. The Law of Dominance correlates with alleles, as one version (allele) can be dominant over the other (recessive), resulting in the dominant trait being expressed even if there is only one copy of the dominant allele. 4. The Law of Unit Characters states that each trait is determined by a single gene, which serves as a useful starting point in understanding the relationship between genes and traits. However, it has limitations as many complex traits are influenced by multiple genes and their interactions.

Step-by-step solution

Mendel's Four Postulates

Mendel's four postulates are as follows: 1. The Law of Segregation: Each organism has two alleles for each trait, and these alleles separate during gamete formation, so each gamete carries only one allele for each trait. 2. The Law of Independent Assortment: The alleles of different traits are passed to offspring independently of each other. 3. The Law of Dominance: In a heterozygous individual, one allele can dominate the other allele, leading to the dominant trait being expressed in the organism. 4. The Law of Unit Characters: Each trait is determined by a single gene. Now, let's correlate each postulate with homologous chromosomes, genes, alleles, and the process of meiosis.

Postulate 1: Law of Segregation and Meiosis

During meiosis, a diploid cell divides twice to produce four haploid cells called gametes. In the first division (meiosis I), homologous chromosomes separate, with each daughter cell receiving one chromosome from each homologous pair. This process ensures that each gamete will carry only one allele for each trait, as stated in Mendel's Law of Segregation.

Postulate 2: Law of Independent Assortment and Meiosis

The Law of Independent Assortment states that the alleles of different traits are passed to offspring independently of each other. This occurs during meiosis I, when homologous chromosomes line up independently along the metaphase plate. The orientation of these chromosomes along the plate is random, which leads to different combinations of traits being passed onto the gametes.

Postulate 3: Law of Dominance and Alleles

The Law of Dominance states that in a heterozygous individual, one allele can dominate the other allele, leading to the dominant trait being expressed in the organism. This can be correlated with the concept of alleles, as each gene can have different versions called alleles. One version (allele) can be dominant over the other (recessive), meaning the dominant trait will be expressed even if there is only one copy of the dominant allele.

Postulate 4: Law of Unit Characters and Genes

The Law of Unit Characters states that each trait is determined by a single gene. In modern genetics, we understand that a gene is a segment of DNA containing the information necessary to produce a specific protein, which in turn influences the traits of an organism. While some traits are indeed determined by a single gene, it is important to note that many complex traits are actually influenced by multiple genes and their interactions, so this law has some limitations. However, for basic Mendelian traits, it still serves as a useful starting point in understanding the relationship between genes and traits.