What are some of the possible factors associated with aging?
What will be an ideal response?
The changes in immune system, hormone secretion, cellular and molecular changes in the cell, and the effects of free radicals have all been hypothesized to contribute to the aging process. Many developmental changes occur in the body throughout an individual's lifetime. Hormone levels change throughout a person's life; for example, growth hormone concentrations decline with age in both genders, and estrogen declines in females. The rate of cell division slows with age. One hypothesis is that telomeres, which protect the ends of the chromosomes, may influence the number of times cells can divide. Each time the DNA is copied before cell division, a tiny piece of telomere is sliced off. After a certain number of cell divisions, the telomere is gone, leaving the chromosome unprotected. Chromosomes that sustain such damage can no longer participate in cell division. Free radicals are another possible factor; they damage cells and thereby may also contribute to the aging process.
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The skin infection streptothrichosis is caused by members of the genus ________.
A. Streptomyces B. Streptococcus C. Dermatophilus D. Propionibacterium
The most likely explanation for the phenomenon where a protein may be found in different sub-cellular locations in different cells is
A. stabilization of the mRNA transcript B. alternative splicing C. RNA interference D. transport of mRNA from the nucleus to the cytoplasm
Enveloped viruses ____
a. generally lyse host cells as they are released b. synthesize envelope lipids as they replicate within the host cell c. acquire their envelope as they bud from the host cell d. acquire their envelope as they enter the host cell e. always contain DNA genomes
By what mechanism did allele frequencies change due to the asteroid?
A) Allele frequencies did not change because of the asteroid. B) The asteroid caused mutations in the fish population. C) The asteroid changed the environment, so fish with allele S2 had increased fitness. D) The asteroid killed fish because of their location, so the allele frequency changed by chance.