A gene that has two alleles, A and a, is located on the same chromosome as a second gene that also has two alleles, B and b. Suppose a diploid individual has alleles AB on one copy of this chromosome and alleles ab on the other copy of this chromosome. For this individual, select the pair of recombinant genotypes that could result if crossing over occurs between these two chromosomes. A gene that has two alleles, A and a, is located on the same chromosome as a second gene that also has two alleles, B and b. Suppose a diploid individual has alleles AB on one copy of this chromosome and alleles ab on the other copy of this chromosome. For this individual, select the pair of recombinant genotypes that could result if crossing over occurs between these two chromosomes. Ab and ab AB and ab Ab and aB AB and aB

Ab and aB

Explanation:

Sometimes during meiosis, crossing over happens. During crossing over, homologous chromosomes pair and recombine, which means that the combination of alleles contained in the original, parental chromosomes changes.

If crossing over occurrs between these two genes chromosomes during meiosis, the dominant allele A, which in the parental chromosome was linked to the dominant allele B, after meiosis will be linked to the recessive allele b, which was originally in the other parental chromosome.

Likewise, another recominant chromosome resulting from crossing over will have the dominant allele B linked to the recessive allele a.

Therefore the recombinant genotypes would be Ab and aB.  

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.