1. What are the gametes called in animals, and what are they called in plants ?
Answer
Gametes are referred to as sperm and egg cells in animals, and as pollen and egg cells in plants.
2. What is a "gene" ?
Answer
A gene is a small section of DNA on a chromosome.
3. What are the four bases that can be found in DNA ?
Answer
A, C, G and T.
4. In sexual reproduction, cells in the reproductive organs divide to form gametes. Describe the process of gamete formation.
Answer
Copies of the genetic information are made and the cell divides twice to form four gametes, each with a single set of chromosomes.
5. Describe some examples of organisms that uses both asexual and sexual reproduction.
Answer
The parasite that causes malaria reproduces asexually in the human host but sexually in the mosquito. Many fungi reproduce asexually by spores, but they also reproduce sexually to provide variation. Many plants produce seeds sexually, but they can also reproduce asexually by runners (as in strawberry plants) or by bulb division (as in daffodils).
6. DNA contains four different bases. State the way the bases pair together.
Answer
A always links to T (on the opposite strand) and C to G.
7. The genome is the entire genetic material of an organism. The whole human genome has now been studied and this has great importance for scientific understanding in the future, for example, in the search for genes linked to different types of disease. Describe some ways in which understanding the human genome is important.
Answer
The human genome is important in the search for genes linked to different types of diseases, in understanding and treating inherited disorders, and in tracing human migration patterns from the past.
8. Fur colour in mice is controlled by a single gene. If G = grey fur and g = white fur, what are the possible genotypes of a mouse with grey fur ?
Answer
The possible genotypes are GG and Gg.
9. XYZ is an inherited disorder caused by a dominant allele. A man with XYZ and a woman without XYZ have two children. One of the children has XYZ, while the other does not. Explain why the man must be heterozygous for XYZ.
Answer
The man has XYZ so has the dominant allele. One of the children does not have XYZ so must have two recessive alleles. The child without XYZ inherited a recessive allele from each parent.