3. Suppose there are 5 x 106 E. coli cells in a transformation reaction and you plate them all out to plates containing ampicillin. After incubating the plate at 37 deg C for 18 hours you observe 500 colonies. What fraction of the cells were transformed in this experiment

1/10^4

Explanation:

Given that 500 colonies were observed on ampicillin plate after transformation. 1 colony represents 1 transformed bacteria because each colony is assumed to have grown from one single bacteria. Hence, 500 bacteria had transformed from 5*10^6 bacteria.

Fraction of cells that got transformed = (Number of cells that were transformed/ Number of total cells)

= 500/(5*10^6)

= 1/10^4

Hence, 1/10^4 cells were transformed in experiment.

the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.

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.