Chromosomal theory of inheritance
Walter Sutton and Theodor Boveri are credited with developing the Chromosomal Theory of
Inheritance, which states that chromosomes carry the unit of heredity (genes).
• During meiosis, homologous chromosome pairs migrate as discrete structures that are
independent of other chromosome pairs.
• The sorting of chromosomes from each homologous pair into pre-gametes appears to be
random.
• Each parent synthesizes gametes that contain only half of their chromosomal complement.
• Even though male and female gametes (sperm and egg) differ in size and morphology, they
have the same number of chromosomes, suggesting equal genetic contributions from each
parent.
• The gametic chromosomes combine during fertilization to produce offspring with the same
chromosome number as their parents.
Thomas Hunt Morgan provided experimental evidence to support the Chromosomal Theory of Inheritance.
asexual reproduction: which produces offspring genetically identical to the parent
(starfish or cactus)
sexual reproduction: sex cells (gametes) from two parents combine in the process of
fertilization, leading to the formation of a new, genetically distinct individual.
life cycle features in common, such as meiosis (the production of haploid cells from diploid ones)
and fertilization (the fusion of haploid gametes to form a diploid cell called the zygote).
Types of sexual life cycles
diploid-dominant: the multicellular diploid stage is the most obvious life stage, and the only
haploid cells are the gametes. Humans and most animals have this type of life cycle.
haploid-dominant: life cycle, the multicellular (or sometimes unicellular) haploid stage is the
most obvious life stage and is often multicellular. In this type of life cycle, the single-celled
zygote is the only diploid cell. Fungi and some algae have this type of life cycle.
alternation of generations: both the haploid and the diploid stages are multicellular,
though they may be dominant to different degrees in different species. Plants and some
algae have this type of life cycle.
diploid-dominant
Haploid-dominant life cycle
Alternation of generations