There are choices for this question namely:
<span>A) B cells produce IgE antibodies
B) B cells release cytokines
C) cytotoxic T cells present the class II MHC molecule-antigen complex on their surface
D) helper T cells release cytokines
The correct answer is "helper T cells release cytokines". Cytokines are released by helper T cells when B cells attach to them via receptors. These T cells "help" these B cells to differentiate by secreting certain cytokines. When B cells differentiate, they are converted to plasma cells and able to secrete antibodies to the antigen presented to the T cells. </span>
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.
I believe proteins are synthesized from amino acids during synthesis reactions.
Protein synthesis starts with transcription of mRNA from a DNA gene in the nucleus.Various types of RNA may have been synthesized using the appropriate DNA. The RNAs migrate from the nucleus to the cytoplasm where the process of translation takes place. During the process the mRNA with the codons (three nucleotide bases that code for a specific amino acids) is interpreted by the anticodons in the tRNA , thus forming amino acids with together forms polypeptides and then proteins are formed.
Answer:
The theory of evolution was proposed by Charles Darwin and was first formulated in his book, "Origin of Species" in 1859. It focuses on the changes in species and populations over time
