Lethal genes (genes that result in the failure to develop a vital organ or metabolic pathway) are nearly always recessive. animal breeders who discover a unique trait and selectively breed to increase the occurrence of that trait often encounter a noticeable increase in lethal genes. why? a. the lethal recessive gene may be incompletely dominant. b. spreading the gene among offspring of both sexes will increase the likelihood it will be sex-linked and expressed. c, the selective-mating of closely related individuals, or inbreeding, increases chances that two recessive genes will "meet" in offspring. d. "pleiotropy" - the gene that is being selected for this trait may have the second effect of being lethal. e. "epistasis" - selection for the desired trait may result in "uncovering" the lethal gene.

C

Explanation:

When breeders notice a unique trait of interest and selectively breed to increase their population, there is tendency of also increasing the population of lethal genes. This happens via a situation known as inbreeding depression. There is a tendency to mate closely related individuals in a bid to increase the occurrence of a desired phenotype. However, in a situation where these animals have a recessive lethal gene, it may result in a double recessive thus becoming obvious in the population.

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!