You are examining a prepared slide with the 40x objective in place over the microscope. you rotate the 100x objective over the slide. when you look into the eyepiece, your specimen is gone. what happened?

A microscope is an instrument in biology that helps in viewing specimens which cannot be seen through the naked eyes. Objective lenses of microscopes (10x, 40x and 100x) help in magnifying a specimen.

When a specimen being observed with 40x objective lens in a microscope is rotated to 100x objective of the microscope, the specimen is lost because of the following reasons-

1. 100x objective is called the oil immersion objective which needs a special oil for observing specimens under it. Thus, specimens cannot be observed without the oil.

2. There are chances that the slide may be crushed due to this rotation and the specimen is damaged. Hence, using coarse adjustment knob of the microscope, the 40x objective has to be lifted away form the slide to some distance. A drop of oil should be placed on the slide and slowly the 100x objective should be brought into focus by using the fine adjustment knob of the microscope.

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.