DECODE The Script of LIFE

  Chromosomal Theory of Inheritance The chromosomal theory of inheritance was proposed independently by Walter Sutton and Theodore Boveri in 1902. They stated that behavior of chromosomes was parallel to behavior of genes and used chromosome movement to explain Mendel’s laws. The hereditary factors are carried in the nucleus. Like the Mendelian alleles, chromosomes are also found in pairs. The sperm and eggs having haploid sets of chromosomes fuse to re-establish the diploid state. Morgan extensively worked on fruit flies, Drosophila melanogaster and provided experimental evidence to support the chromosomal theory of inheritance. Comparison between the behavior of Genes and Chromosomes Genes Chromosomes Occurs in Pairs. Occurs in Pairs. Segregate at the time of gamete formation such that only one of each pair is transmitted to a gamete. Segregate at gamete formation and only one of each pair is transmitted to a gamete. It has independent pairs segregate independently of each other. It

  Types Of Mutations Quick Navigation Summary box for Types of Mutations The role of DNA sequences –a reminder Types of mutations Point mutations Substitution Insertions and deletions Consequences of point mutations and examples Missense mutations Sickle Cell Anaemia Nonsense mutations Duchenne muscular dystrophy Frameshift mutations Frequently Asked Questions What are the major types of mutations? What are point mutations? What are frameshift mutations? What is a nonsense mutation? Summary box for Types of Mutations Mutations occur through various mechanisms that can impact genes, chromosomes, and outcomes differently. Mutations can occur on a single nucleotide scale (at the level of point mutations), or on a much larger scale (where segments of whole chromosomes are affected. Substitution of nucleotides can be synonymous (silent) or non-synonymous (change amino acid). The resulting mutations can be missense (amino acid change in sequence) or nonsense (premature stop codon is encoded.