Chromosomal Theory of Inheritance
Biology: IB Diploma Higher Level, topic 3.1.1
Chromosomal Theory of Inheritance
Proposed independently by Sutton and Boveri in the early 1900s, the Chromosomal Theory of Inheritance states that chromosomes are vehicles of genetic heredity.
Chromosomal Inheritance
- Scientists began to reevaluate Mendel's models in terms of the behavior of chromosomes in cell division.
- In 1902, Theodor Boveri observed that proper embryonic development of sea urchins does not occur unless chromosomes are present.
- That same year, Walter Sutton observed the separation of chromosomes into daughter cells during meiosis.
- These observations led to the development of the Chromosomal Theory of Inheritance, which identified chromosomes as the genetic material responsible for Mendelian inheritance.
Observational evidence
- The Chromosomal Theory of Inheritance was consistent with Mendel’s laws and was supported by the following observations:
- 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.
Observational evidence - 2
- Further observational evidence includes:
- 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.
- Collectively, these processes of segregation, independent assortment, and fertilization result in genetic variation.
Experimental evidence
- Despite the correlations between the behavior of chromosomes during meiosis and Mendel’s laws, the Chromosomal Theory of Inheritance was proposed before there was any direct evidence.
- Critics pointed out that individuals had far more independently segregating traits than they had chromosomes.
- It was only after years of carrying out crosses with the fruit fly, Drosophila melanogaster, that Thomas Hunt Morgan provided experimental evidence to support the Chromosomal Theory of Inheritance.
Test yourself on Chromosomal Theory of Inheritance
Thomas Hunt Morgan performed genetic crosses using which of the following organisms to produce evidence for the Chromosomal Theory of Inheritance?