Write a short essay that correlates Mendel's four postulates with what is now known about genes, alleles, and homologous chromosomes.

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1. Begin by briefly stating Mendel's four postulates: (1) Unit factors in pairs, (2) Dominance and recessiveness, (3) Segregation, and (4) Independent assortment.
2. Explain how Mendel's concept of 'unit factors' corresponds to genes, which are discrete units of heredity located on chromosomes.
3. Describe how alleles are different versions of a gene, relating to Mendel's idea of dominant and recessive traits, where one allele can mask the expression of another.
4. Connect the principle of segregation to the behavior of homologous chromosomes during meiosis, where alleles separate so that each gamete receives only one allele of each gene.
5. Discuss independent assortment in terms of how genes located on different chromosomes are inherited independently due to the random orientation of chromosome pairs during meiosis I.

Key Concepts

Mendel's Four Postulates

Mendel's four postulates describe the basic principles of inheritance: the existence of discrete hereditary units (genes), the segregation of allele pairs during gamete formation, independent assortment of different gene pairs, and dominance relationships between alleles. These principles laid the foundation for classical genetics.

Genes and Alleles

Genes are segments of DNA that code for specific traits, while alleles are different versions of a gene found at the same locus on homologous chromosomes. Alleles can be dominant or recessive, influencing the phenotype expressed in an organism.

Homologous Chromosomes and Meiosis

Homologous chromosomes are pairs of chromosomes, one from each parent, that carry the same genes but may have different alleles. During meiosis, these chromosomes segregate independently, explaining Mendel's postulates of segregation and independent assortment at the molecular level.