Jackie read that aloe vera plants promoted healing of burned tissues. she decided to investigate the effect of varying amounts of aloe vera on the regeneration (regrowth) of planaria (a small water creature). she bisected the planaria to obtain 10 parts (5 heads and 5 tails) for each experimental group. she applied concentrations of 0%, 10%, 20% and 30% aloe vera to the groups. fifteen milliliters of aloe vera solutions were applied. all planaria were maintained in a growth chamber with identical food, temperature, and humidity. on day 15, jackie observed the regeneration of the planaria parts and categorized development as full, partial, or none. what is the purpose of the experiment? how many animals were in each experimental group? in the experiment above, what is the independent variable? in the experiment above, what is the dependent variable? in the experiment above, what are the constants? how did jackie measure the regeneration of the planaria? how could this experiment be improved?

it would be heredity

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.