Monday, January 7, 2008

4 - forensic medicine mcqs - 21 to 25

21-The route of administration of Amyl Nitrate in Cyanide poisoning is

a. Intra Muscular
b. Intra Venous
c. Sub dermal
d. Inhalation


The correct Answer is D

Amyl nitrate is chemically related to nitroglycerin and has been used for many years to treat angina pectoris. It is also effective in the emergency management of cyanide poisoning by causing the oxidation of hemoglobin to the compound methemoglobin. Methemoglogbin reacts with the cyanide ion to form cyanomethemoglogin, which has less affinity for oxygen, thus freeing hemoglogin to react with oxygen.

Onset of action: 30 seconds inhaled
Supplied: 0.3 ml/glass ampule (capsule covered with woven gauze).
Adult: Glass ampule should be broken and inhaled for 30-60 seconds. Repeat as necessary
Pediatric: same as adult


22-The Commonest type of abrasion seen in road traffic accidents is

a. Scratch abrasions
b. Grazed Abrasions
c. Contact Abrasions
d. Imprint Abrasions


The Correct Answer is B

Abrasions are commonly caused by a 'glancing' impact across the surface of the skin, but if the force is directed vertically down onto the skin surface it may be termed a 'crush' injury.

These wounds are seen where an object has struck the skin (eg a blow from a fist), or where the injured person has fallen onto a rough surface, such as road.

Abrasions may be 'linear', or commonly known as a single 'scratch', whereas if a broader surface is affected, it is called a 'graze' or 'brush abrasion' (eg where a motorcyclist is thrown from their vehicle, and comes into contact with the road surface in a skidding fashion). Such an abrasion often covers a relatively large area of skin, and is often called a 'friction burn' in lay language.


23-In a case of disputed paternity, Father's blood group is A, Mother's blood group is B, the child's blood is

a. A only
b. B only
c. AB only
d. A,AB,B or O


The correct Answer is D

Around 1900 it was discovered that there are at least 4 different kinds of human blood. This is based on the fact that on the surface of the red blood cells there may be one or more proteins, called antigens. These antigens are called A and B. Antibodies are produced in the blood plasma against these A and B antigens, and continue to be produced throughout a person’s life.

The antigens determining the four blood groups are the result of the expression of three alleles; O, A and B; the latter two being dominant to O. The genotypes AA and AO, and the genotypes BB and BO cannot be distinguished serologically and are classified as group A and B respectively. Thus only four phenotypes (A, B, AB, and O) can be recognized, although six genotypes occur.

A person’s blood type is inherited from their parents, just like any other genetic trait.
Persons with blood type A have inherited one or two copies of the gene for the A antigen, one from each parent. Persons with blood type B have inherited one or two copies of the gene for the B antigen. Persons with blood type AB have inherited on copy of the A antigen from one parent and one copy of the B antigen gene from the other parent. Persons with blood type O inherited neither A nor B genes from their parents.

Blood typing can be used in legal situations involving identification or disputed paternity. In paternity cases a comparison of the blood types of mother, child, and alleged father may be used to exclude a man as the possible parent of a child. For example, a child with the blood type AB whose mother is type A could not have a father whose blood type is A or O. The father must have blood type B.


24-For DNA test liquid blood is preserved in

a. Sodium Citrate
b. Pot. Oxalate
d. Sodium Fluoride


The correct Answer is C

DNA in biological samples is very stable and can tolerate room temperature storage conditions very well. However, over an extended period of time, frozen storage is generally considered to be the optimum storage condition for biological samples. This means that evidence, such as bloodstained clothing, should be held frozen. Liquid blood samples, stored in glass or plastic containers, should be held in the refrigerator since these samples can break in the freezer. Liquid blood samples containing preservatives (e.g. EDTA) are stable for a very long period of time in the refrigerator.

Certain buffers (e.g. those containing EDTA) are designed to inhibit the activity of nucleases that can breakdown DNA and these can preserve DNA in liquid form better than other liquid extractants.


25-Caput Succedaneum in a new born is

a. Collection of blood under the pericranium
b. Collection of Sero-sanguineous fluid in the scalp
c. Oedema of the scalp due to grip of the forceps
d. Varicose veins in the scalp


The Correct Answer is B

Caput Succedaneum is a collection of blood/fluid in subQ tissues of scalp

* not limited by bony sutures
* benign, self-limited, resolves in days

Collection of bloodunder the pericranium is a Cephalhematoma

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