Answer:
1) the genes and chromosomes do not double after each generations because parental sex cells are haploid and only contain one set of chromosomes. During fertilization the two cells fuse to form a diploid zygote with two copies of genes and chromosomes. For example a normal human has 46 chromosomes (2 copies of 23 chromosomes) during reproduction gametes which contain 23 chromosomes (haploid) fuse to form an offspring with the correct number of chromosomes ( 23 + 23 = 46).
2) offspring only receive one set of chromosomes from each parent so to maintain the chromosome number of humans. If this did not happen you would not be the same species.
Sediment pollution is the single most common source of pollution in U.S. waters. Approximately 30% is caused by natural erosion, and the remaining 70% is caused by human activity. ... Sediment pollution can have long-term impacts on aquatic insects, fish and other wildlife in affected waterways
The answer is stabilizing selection.
<span>Sickle-cell anemia is a recessive disorder caused by the presence of two recessive alleles "s", so genotype is "ss". This disorder is characterized by sickle hemoglobin. In an area with malaria, heterozygous individuals "Ss" (with one dominant allele and one recessive allele) have an advantage. These individuals will have both normal and sickle hemoglobin. But pathogen that causes malaria affect only normal hemoglobin, so heterozygous individuals will have half of the hemoglobin resistant to the pathogen and those individuals are resistant to malaria.</span>
Stabilizing selection favors heterozygotes Ss, disruptive selection favors dominant (SS) and recessive (ss) homozygotes, while directional selection favors dominant (SS) or recessive (ss) homozygote. Since in this example, people with genotype Ss (heterozygotes) are in advantage, then this is an example of stabilizing selection.
Answer:
killer T
Explanation:
helper T activates killer T cells which literally kill the virus or bacteria. memory T are the subset of an infection.
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