Why are the brca1 and brca2 genes considered to be tumor-suppressor genes?

Explanation:

brca1 and brac2 genes are considered as tumor suppressor genes because these produce tumor suppressor proteins and this tumor suppressor protein repair the damaged DNA, prevent the uncontrolled growth and suppress the cell growth and regulates the cell division.

When the tumor suppressor gene does not function properly cell cannot control their growth that leads to tumor formation and result in cancer.

b is dominant over the allele for the white fur.

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.