"tryptophan self-controls its synthesis." justify this statement.
a. if a lesser amount of tryptophan is present in a cell, tryptophan acts as an inducer and binds to a repressor, leading to the synthesis of enzymes required for its production and thus its synthesis.
b. if an excess amount of tryptophan is present in a cell, tryptophan acts as a promoter, preventing the further synthesis of necessary enzymes for its production and thus its synthesis.
c. if an excess amount of tryptophan is present in a cell, tryptophan acts as a co-repressor, preventing the further synthesis of necessary enzymes for its production and thus its synthesis.

Option C, If an excess amount of Tryptophan is present in a cell, Tryptophan acts as a co-repressor, preventing the further synthesis of nessary enzymes for its production and thus its synthesis.

Explanation:

When level of tryptophan is high it attache to the trp repressor  and this duo together act as a repressor. Binding of tryptophan changes the shape of the repressor and thus convert it into the active DNA binding form. This duo of tryptophan and trp repressor attaches with the operator and block binding of RNA polymerase to the promoter. In this way further transcription of the operon is prevented.

Hence, option C is correct

1. glaciers are melting

2. more water going into ocean (water's such as fresh waters, etc)

an individual’s sex (i.e., whether they are a male or female) is determined by the sex chromosomes. most people have two sex chromosomes, one that is inherited from their mother and one that is inherited from their father. typically, females have two x chromosomes (xx) and males have one x chromosome and one y chromosome (xy). conditions caused by changes (“mutations”) in genes located on the x chromosome are considered x-linked.

x-linked recessive inheritance

most x-linked conditions are recessive. this means that in a person with two x chromosomes (most females), both copies of a gene (i.e., one on each x chromosome) must have a change or mutation whereas in a person with one x chromosome (most males), only one copy of a gene must have a mutation. a female with a mutation in one copy of a gene on the x chromosome is said to be a “carrier” for an x-linked condition. a male with a mutation in a gene on the x chromosome is typically affected with the condition. because females have two copies of the x chromosome and males have only one x chromosome, x-linked recessive diseases are more common among males than females. however, x-linked recessive diseases can occur in both males and females.

for x-linked recessive disorders, an unaffected carrier mother who has a mutation in a gene on the x chromosome can transmit either the x chromosome with this mutation or a “normal” x chromosome to her children. if the father is unaffected, none of her daughters will be affected and all of her daughters will be unaffected—since they will inherit at least one normal x chromosome from their father. however, each daughter will have a 50% chance of being an unaffected carrier like her mother and a 50% chance of both x chromosomes being normal.