Sickle-cell anemia is an inherited chronic blood disease caused by an autosomal recessive allele. suppose a man who is homozygous recessive for the sickle-cell gene fathers a child by a woman who is a carrier for sickle-cell. what are the chances their children will exhibit the disease? (note: a punnett square may be useful.)

50%

Explanation:

Let's suppose that the allele "s" causes sickle cell anemia in homozygous condition. The genotype of the affected male=ss; the genotype of carrier female= Ss. The male will produce all the sperms carrying "s" allele while the female would produce gametes with either "S" or "s" in equal proportion.

A cross between affected male (ss) and carrier female (Ss) would give progeny in the following phenotype ratio= 1/2 normal child: 1/2 affected child. Therefore, there are 50% chances of their child to be affected by the disease.

i believe the answer is a or 1

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!