Please hurry 1. Identify one environmental factor that could cause a base sequence in DNA to be changed to a different base sequence.

2. Explain why, in a mammal, a mutation in a gamete may contribute to change in the population of the organism while a mutation a body cell will not.

Explanation:

1     Long term exposure to harmful genotoxic chemicals or ionizing radiation can cause changes in the base sequence of DNA.Chemicals might induce DNA mutations, such as polycyclic hydrocarbons (fumes found in oil stations, or smoke from a tobacco cigarette), intercalating agents such as Ethidium Bromide (carcinogen), but also radiations such as UV-radiation (C and T bases are most vulnerable and would bind to identical bases unstead of their

2    Genetic changes that are described as de novo (new) mutations can be either hereditary or somatic. In some cases, the mutation occurs in a person’s egg or sperm cell but is not present in any of the person’s other cells. In other cases, the mutation occurs in the fertilized egg shortly after the egg and sperm cells unite. (It is often impossible to tell exactly when a de novo mutation happened.) As the fertilized egg divides, each resulting cell in the growing embryo will have the mutation. De novo mutations may explain genetic disorders in which an affected child has a mutation in every cell in the body but the parents do not, and there is no family history of the disorder.

Somatic mutations that happen in a single cell early in embryonic development can lead to a situation called mosaicism. These genetic changes are not present in a parent’s egg or sperm cells, or in the fertilized egg, but happen a bit later when the embryo includes several cells. As all the cells divide during growth and development, cells that arise from the cell with the altered gene will have the mutation, while other cells will not. Depending on the mutation and how many cells are affected, mosaicism may or may not cause health problems.

option a is correct i.e.

explanation:

in context to the membrane of nerve impulse, the outer membrane of neuron is semi permeable that is only sodium ions can pass through the membrane i.e. smaller ions can pass through the membrane while larger ions cannot pass through it.

answer: c. two haploid cells

explanation: