Question

In: Anatomy and Physiology

List and describe the molecular (sexual) mechanisms that lead to genetic variation in gametes (offspring):

List and describe the molecular (sexual) mechanisms that lead to genetic variation in gametes (offspring):

Solutions

Expert Solution

  • In species that reproduce sexually, the behavior of chromosomes during meiosis and fertilization is responsible for most of the variation that arises in each generation.
  • Let's examine three mechanisms that contribute to the genetic variation arising from sexual reproduction:
    • Independent assortment of chromosomes.
    • Crossing over.
    • Random fertilization.

- Crossing over= a new combination of alleles.
- Random fertilization= nonspecific gamete selection.
- Random Mating= nonspecific mate selection.

● Independent assortment of cgromosomes.

Because each pair of homologous chromosomes is positioned independently of the other pairs at metaphase 1, the first meiotic division results in each pair sorting its maternal and paternal homologs into daughter cells independently of every other pair. This is called independent assortment. Each daughter cell represents one outcome of all possible combinations of maternal and paternal chromosomes.

● Crossing over.

Crossing over produces recombinant chromosomes, individual chromosomes that carry genes (DNA) derived from two different parents. In meiosis in humans, an average of one to three crossover events occur per chromosome pair, depending on the size of the chromosomes and the position of their centromeres.


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