Basic Genetics | 10 Question Sci / Tech Multiple Choice Quiz

Answer: 23

Most cells in the human body have 46 chromosomes (23 pairs) in their nucleus. Gametes have a haploid number of chromosomes, which is half the diploid number, i.e. 23.

Answer: AIDS

AIDS is caused by the HIV virus, and is not genetically inherited. It can, however, be passed from mother to child through her breastmilk.

Answer: True

Point mutations can cause a single base to be lost or replaced by another base. An example of a genetic disease caused by a single point mutation is sickle cell anaemia.

Answer: False

An allele is a type of gene e.g. blue and brown are both genes for eye colour, but they are different alleles. A homozygote for a particular trait has only 1 type of allele in their genotype, e.g. BB or bb. A heterozygote has 2 different alleles in their genotype, e.g. Bb.

Answer: Each individual offspring has equal chance of getting one half of any gene pair or the other from a parent.

Mendel's First Law of segregation states that when a gamete is formed, the pair of alleles for a particular trait in the parent separates. Mendel's Second Law of independent assortment states that the segregation of one pair of alleles is independent of the segregation of any other pair of alleles.

Answer: False

For example, a bacteria gene which increases resistance to insect attack has successfully been introduced into corn plants.

Answer: red-green colour blindness

Sex-linked genetic diseases occur more often in one sex than another (usually males). This happens because females have the genotype XX, whereas males have the genotype XY. The genes which control diseases like haemophilia and colour blindness are located on the X chromosome. Usually, the normal allele is dominant and the allele causing the disease is recessive. Because females have 2 X chromosomes, both the chromosomes have to have the recessive allele in order for the disease to be expressed.

But because males have only 1 X chromosome, they only need 1 recessive allele that causes the disease for it to be expressed.

Answer: physical risk

The gene test usually involves only a blood sample, so the physical risks are minimal. The main thing that concerns people is how the results of a gene test will impact their lives. Discovering that a person is likely to develop a serious disease can cause depression, confusion and despair.

It can affect family relations, causing fear, anger or guilt in those who have or have not inherited particular genes. It can also lead to discrimination in areas like employment and health insurance e.g. an insurance company may refuse to cover you because you are likely to develop heart disease.

Answer: ADA deficiency

People with ADA (adenine deaminase) deficiency are less able to fight infections because many of their white blood cells die. In this study, bone marrow cells were taken from 2 ADA deficient girls and normal ADA genes were inserted into the cells. These were injected into the blood, from where they travelled back to the bone marrow.

It was hoped that the genetically engineered cells would multiply there, making cells which could produce the ADA enzyme. Today, the 2 girls are healthy and have fully functional immune systems.

Answer: gender

Continuous variation has people fitting in anywhere between two extremes. Discontinuous variation has traditionally classed people as fitting into definite categories, e.g. male or female. More recently, gender has been considered less as a binary distinction but existing along a spectrum.