How can the banding patterns on Drosophila polytene chromosomes be used to aid deletion mapping of genes on the chromosomes?
What will be an ideal response?
The unexpected expression of a recessive trait caused by pseudodominance (the loss of a dominant allele) can be correlated with changes in band number and physical appearance of the polytene chromosomes. For example, in a polytene X bearing wild-type alleles, deletions in certain regions can be visually observed. These can be correlated with the appearance of pseudodominant phenotypes for those alleles. The alleles can then be mapped to those missing regions on the chromosome.
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Which one of the following statements about rickettsias is false?
A) Diseases caused by rickettsias are arthropodborne. B) Rickets is caused by a Rickettsia species. C) Rickettsia species cause typhus and typhuslike diseases. D) Rickettsias have leaky membranes.
Vacuoles for ingesting food and regulating their water balance are characteristic of
A. sporozoans. B. trypanosomes. C. ciliates. D. algae. E. spirochetes.
Which one of the following is not among the four most abundant elements in living organisms?
A) Carbon B) Hydrogen C) Nitrogen D) Oxygen E) Phosphorus
During the pre-embryonic period, a single sperm passes through the zona pellucida. In the vast majority of cases, where does this process occur?
A) in the oviduct (fallopian tube) B) in the placenta C) in the uterus D) in the ovary