Because while species of mosquitoes eat the carcasses of insects that drown in the water, the mosquito larvae feed on the waste products, making nutrients such as nitrogen available for the plant community to thrive.
Answer: D. Frameshift mutation
Explanation:
A nonsense mutation is one in which a codon codifying for an amino acid is replaced by a stop codon, resulting in a premature end to translation (e.g. TAT [Tyrosine] >> TAG [stop]).
A missense mutation is one in which a codon is altered in such a way that it ends up codifying for a <em>different</em> amino acid (e.g. AUA [Isoleucine] >> AUG [Methionine]).
A point mutation is any mutation which involves the altering of a single nucleotide (such as the examples given above), <em>regardless</em> of its effect on the resulting protein.
Finally: a frameshift mutation is one which alters the <em>reading frame</em> of a gene, which results in a whole different set of nucleotides being treated as individual codons by the translation machinery. The consequence of this is a significant change in the resulting amino acid sequence. Frameshift mutations may be the result of several mechanisms which include insertions and deletions. The example given in the picture appears to show an example of one such mutation.
Answer: The probability of having an offspring with type A blood is 1/4.
Explanation: Since each of the parents have a recessive allele for blood type O, their genotypes are IAi and IBi for the father and mother respectively. A cross between them will produce four offsprings: one with type AB blood, one with type A blood, one with type B blood and one with type O blood.
See the attached punnet square for more information
The tetrad occurs during the first phase of meiosis. It is the foursome of chromatids that forms when replicated homologous chromosomes align. It must be formed for crossing over to occur. It is broken apart when the homologous chromosomes separate in meiosis I