<span>Genetic variation can be caused by mutation (which can
create entirely new alleles in a population), random mating, random
fertilization, and recombination between homologous chromosomes during
meiosis (which reshuffles alleles within an organism's offspring)</span>
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❖ B. Punnet Square is a chart used to show the possible outcomes of allele combinations that parents can pass on to their offspring.
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Answer:
1. Today instead of rotating upright, The earth's axis is tilted 23.5 degrees. The angle varies a little over time, but the gravitational pull of the moon prevents it from shifting by more than a degree so. This tilt is what gives us seasons.
2.The cooling effects of more indirect sunlight cause autumn and winter. Because of the earth's approximately 23.5° tilt, the season in the northern and southern hemispheres reversed, about six months apart from each other.
The correct answer is that "the T cell enters a state of anergy".
The activation of T cells requires two signals: (1) antigen specific signal presented by an antigen presenting cell (either a macrophage or a dendritic cell) that activates t cell receptors and (2) co-stimulatory signals that is not antigen specific but rather found in the plasma membrane of the antigen presenting cell (i.e. CD28). In the absence of a co-stimulatory signal, the t cell will enter a state of anergy or the inability to produce an immune response toward an offending antigen.
