Jack and Jill are twins. Because he is a boy, Jack’s parents encourage him to run. However, they discourage Jill from engaging in athletic activity. As a result, Jack is much faster at running up a hill than Jill. The difference in Jack and Jill’s behavior is best explained by .A) nonshared environmental influences.
B) active gene-environment relations.
C) polygenetic effects.
D) niche-picking.

What’s the student’s scientific question

14. which of the following codons code for threonine? a. ucg b. ugu c. cga d. aca

During crossing-over, a. genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles. b. nonsister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. c. one homologous chromosome of a tetrad is exchanged with another tetrad, resulting in new combinations of alleles. d. sister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. e. genetic material is exchanged between sister chromatids, resulting in new combinations of alleles.