7. Watermelons are exposed to a mutagen to produce a variety that has four sets of
chromosomes. The new variety is then crossed
with a normal watermelon to produce seedless
watermelons. What type of mutation is involved in
the growing of seedless watermelon?
a. point mutation
b. gene duplication
c. frameshift mutation
d. trisomy 21

The standard number of chromosomes in watermelon is 22. This is called the diploid number (di meaning two, as in dissect – cut in two). With this even number, cell division is highly regular and produces pollen and egg cells with 11 chromosomes that recombine to produce seed with the usual 22 chromosomes. Through a chemical process, the chromosome number can be doubled from 22 to 44 (tetraploid, tetra meaning four). Cell division in plants with 44 chromosomes is, again, highly regular and will produce pollen and egg cells with 22 chromosomes that recombine to produce seed having 44 chromosomes. However, if pollen from a plant with 22 chromosomes is placed on a female flower of a plant with 44 chromosomes, the resulting seed will have 33 chromosomes (triploid – three sets of the base number of 11 chromosomes). This odd number does not produce (or rarely produces) viable pollen and eggs in the resulting seedlings.            -Michigan State UN                                                 Explanation:

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

on the planet jupiter, the acceleration due to gravity is approximately 26 m s2 , roughly 2.7 times the acceleration due