Many human cells divide a finite number of times before going into permanent arrest, a phenomenon called Hayflick’s Phenomenon, which appears to be caused by the loss of telomeres.
Hayflick limit or Hayflick’s phenomena is defined as the number of times a normal cell population divides before entering the senescence phase.
Hayflick (1961) demonstrated that a population of normal human fetal cells divide in culture between 40 and 60 times before stopping.
This phenomenon is related to telomere length. Repeated mitosis leads to shortening of the telomeres on the DNA of the cell. Telomere shortening in humans eventually makes cell division impossible, and correlates with aging.
Telomeres are irrevocably shortened each time a cell divides. When the telomeres become too short, the cell can no longer divide.
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exposure to drugs causes mutations which produce drug-resistant populations of microbes.
<h3>What is the effect of using same type of drug?</h3>
Drug-resistant populations of microbes arise when the exposure to drugs causes mutations because this exposure produce resistance which leads to mutation in the organism. Due to this mutation, the drugs did not work on the organism anymore.
So we can conclude that exposure to drugs causes mutations which produce drug-resistant populations of microbes.
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Answer:
First
Explanation:
S-waves arrive first at a seismic station
Answer:
1/4 suffer from hemophilia
1/4 are heterozygous
Explanation:
So since they are normal but their son isn't it is assumed that the mom is the carrier since the dad has to be X^HY
X^HY x X^HX^h
Set up a pedigree
X^HX^H X^HX^h
X^HY X^hY
1/4 suffer from hemophilia (X^h)
1/4 are heterozygous (X^HX^h)