If an individual is trisomic for chromosome 21, resulting in Down syndrome, and has an extra chromosome in each cell, what mutation must have occurred? A nondisjunction mutation in the gamete of one of the parents
A nondisjunction in both gametes of the parents
A nondisjunction in one of the first gamete cells of the individual
A nondisjunction mutation in body cells of both parents

What are the fixed alleles in the human species? o a. the alleles that are on the most chromosomes b. the alleles that change most often 000 c. the alleles that no one has d. the alleles that everyone has

What are the two causes of density in deep current waters? a. salinity (how much salt) of the water and high temperaturesb. salinity (how much salt) of the water and low temperatures c. oxygen content of the water and high temperatures. d. oxygen content of the water and low temperatures

Archeologists have discovered three sites showing conclusive evidence for the mastery of fire in tanzania, from a period slightly after the time that homo habilis was present in africa. these sites clearly were founded by homo erectus, the descendent species of homo habilis that migrated north, out of africa and into asia. homo erectus was known to have mastered fire, from ample evidence at sites in asia. there is no reason to attribute mastery of fire to homo ergaster, the descendent species of homo habilis that remained in africa.which of the following is an assumption on which the argument depends? (a) before their migration, homo erectus occupied african territory as far south as tanzania.(b) the strain of migration provided the selective pressure motivating homo erectus‘ mastery of fire.(c) homo ergaster would not have derived as much benefit from the mastery of fire as did homo erectus.(d) homo ergaster inherited all cultural knowledge from homo habilis, a species that did not have mastery of fire.(e) homo ergaster did not occupy regions as far south as tanzania until well after the time of these three sites.