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Chromosomal Inheritance
Overview of chromosomal inheritance.
The chromosome theory of inheritance states that the Mendelian genes are present at specific locations (loci) on chromosomes
It is the chromosomes themselves that are subject to segregation and independent assortment.
Wild-type genes and traits are those that are most commonly found within a natural population.
Steps of chromosomal inheritance via Independent Assortment:
- The genotypes of two parental organisms are big D, big D, big R, big R and little d, little d, little r, little r.
- The genotypes of the F1 generation gametes are Big D, big R; big D, little r; little d, big R; little d, little r.
- Thus, we see that each genotype has an equal chance (1 in 4) of occurring.
Exceptions:
Linked Genes
- Because a single chromosomes contain many genes, depending on the traits studied, some genes may be linked by being on the same chromosome.
- Linked genes are located on the same chromosome and so, are inherited together.
- Crossing over is a process in which the physical connection of genes on the same chromosome is broken.
- These are the results of meiosis and normal segregation of chromosomes.
- But sometimes during meiosis 1, bits of two chromatids are broken off and are rejoined to the other chromatid.
Sex-linked genes are those located on either sex chromosome.
- These genes exhibit special inheritance patterns.