Astudent was studying cell growth using cells grown in laboratory cultures. the cultures were synchronized so that all of the cells passed through the same stage of the cell cycle at the same time. the cells were examined during five different periods of time, intervals (a-e). the amount of dna present per cell was determined for each interval. the graph shows the result of this study.
1. most of the cells examined during interval a have half as much dna as those measured in interval c. therefore, most of the cells at interval b must have been in:
a. g0.
b. m phase.
c. s phase.
d. g1.
e. g2

C) S phase.

Explanation:

The cell cycle is a series of sequential events taking in a cell which represents how the cellular and nuclear contents of the cells are distributed in the new daughter cells.

The cell cycle takes place in two phases: Interphase in which cell prepares itself for nuclear division and Mitotic phase in which the cell divides its nuclear content especially the DNA. The interphase is divided into three phases that is G₁, S and G₂.

In the given question, since it is mentioned that at A interval the cell has half DNA than C, therefore, it could be concluded that a process is going on which doubles the amount of DNA in the cell which is known as DNA replication.  

The DNA replication occurs during the S phase or synthesis phase thus the cell observed at interval B is in S phase.

Thus, C) S phase is the correct answer.

c

explanation:

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.