<span>Only one sperm normally fuses
with an egg because if more than one sperm fuses, through a process
called polyspermy, development of the zygote usually stops.
</span>
<span>Fertilization of one egg by
two sperm is possible, but the resulting zygote is almost never viable
because such a zygote would have three sets of chromosomes instead of
the normal two. This condition, called triploidy, is usually
incompatible with life. Those rare triploid infants that do survive to
term have severe and multiple birth defects and rarely live more than a
few days. </span>
Answer:
Make sure the lights are off if you are the last to leave the classroom, take shorter showers, and consume less meat and dairy products are all good ways you can reduce your personal footprint. Taking the time to get involved in conservation efforts in your area is a great way you can help fight climate change.
Answer:
256520
.........hope this helps!!!.............
Answer:
1 - Malaria
2- Typhoid fever and Tuberculosis
Explanation:
In case of malaria, the causal microorganism is Plasmodium falciparum, which target red blood cells of host. In humans who have defective sickle cell allele, have abnomral shaped red blood cells. So microorganism does not able to attach to abnormal shaped RBCs thus humans having sickle cell allele are more resistant to death caused by malaria.
In cystic fibrosis, mutation on that gene which encodes a protein known as cystic fibrosis transmembrane conductance regulator (CFTR).
Normally Salmonella typhi (bacteria responsible for typhoid fever) enters into intestinal cells by attaching with CFTR receptor. Carriers of cystic fibrosis mutant gene, have abnormal CFTR thus reduced rate of entry of bacteria into carriers.
Normally Mycobacterium tuberculosis (bacteria responsible for tuberculosis) adds sulfate in its cell walls. In carriers of cystic fibrosis, arylsulfatase B activity is reduced which incorporates sulfate. Thus reduced arylsulfatase activity makes bacteria unable to add sulfate in its cell walls thus decreases their virulence to carriers of cystic fibrosis.
