Question
Which statement defines alleles?
A. They are the different forms of a gene that have the same effect on the phenotype.
B. They are the similar forms of a gene in different positions of a chromosome.
C. They are the various forms of a gene with slight differences in their base sequences.
D. They are the different forms of a gene coding for identical polypeptide chains.
Answer/Explanation
Question
The karyogram shown belongs to a human being.
What can be deduced from this karyogram?
A. The person is a male with Down syndrome.
B. The person is a female with Down syndrome.
C. The person is a male with a genetic disorder.
D. The person is a female with a missing chromosome.
Answer/Explanation
Question
The pedigree chart shows the inheritance of hemochromatosis, a genetic disease which causes an excessive accumulation of iron in the body.
What can be deduced about this genetic disease from the pedigree chart?
A. It is sex-linked.
B. It is autosomal dominant.
C. It is autosomal co-dominant.
D. It is autosomal recessive.
Answer/Explanation
Question
The table shows the estimated total number of genes in several organisms.
| Species | Estimated number of genes |
| Saccharomyces cerevisiae (a yeast) | 6000 |
| Escherichia coli (a bacterium) | 3200 |
| Drosophila melanogaster (fruit fly) | 14000 |
| Canis familiaris (domestic dog) | 19000 |
| Oryza sativ (rice) | 51000 |
| Homo sapiens (human) | 25000 |
What can be deduced from the information in this table?
A. Throughout evolution, the number of genes increases.
B. The domestic dog is more closely genetically related to the fruit fly than to the human.
C. The number of genes does not determine evolutionary success.
D. Humans produce about half as many proteins as rice.