Pick the correct answer The recessive allele s causes Drosophila to have small w
ID: 212295 • Letter: P
Question
Pick the correct answer
The recessive allele s causes Drosophila to have small wings and the s1 allele causes normal wings. This gene is known to be X linked.
If a small-winged male is crossed with a homozygous wild-type female, what ratio of normal to small-winged flies can be expected in each sex in the F1?
50% small-winged in both sexes
If you observed a dicentric bridge at meiosis, what rearrangement would you predict had taken place? A dicentric bridge is the result of crossing over within the inversion loop of a pericentric inversion. A dicentric bridge is the result of improper chromosomal segregation of an inversion heterozygote. A dicentric bridge is the result of homologous centromeres connecting following crossing over within a pericentric inversion loop. A dicentric bridge is the result of crossing over within the inversion loop of a paracentric inversion.Explanation / Answer
1. If you observed a dicentric bridge at meiosis, what rearrangement would you predict had taken place?
ANSWER: A dicentric bridge is the result of crossing over within the inversion loop of a paracentric inversion.
2. What is Mendel's first law?
ANSWER: Also called the law of equal segregation, Mendel's first law states that during meiosis members of a gene pair segregate from each other and each gamete has an equal but random chance of obtaining one member of the gene pair.
3. From a large-scale screen of many plants of Collinsia grandiflora, a plant with three cotyledons was discovered (normally, there are two cotyledons). This plant was crossed with a normal pure-breeding wild-type plant, and 600 seeds from this cross were planted. There were 298 plants with two cotyledons and 302 with three cotyledons. What can be deduced about the inheritance of three cotyledons?
ANSWER: Half of the F1 progeny are mutant, suggesting that the three-cotyledon mutation is dominant and the original mutant was heterozygous.
4. Holstein cattle are normally black and white. A superb black-and-white bull, Charlie, was purchased by a farmer for $100,000. All the progeny sired by Charlie were normal in appearance. However, certain pairs of his progeny, when interbred, produced red-and-white progeny at a frequency of about 25 percent. Charlie was soon removed from the stud lists of the Holstein breeders. Why?
ANSWER: Charlie is not pure breeding, because in the F2 there were two types of progeny.
5. The recessive allele s causes Drosophila to have small wings and the s1 allele causes normal wings. This gene is known to be X linked. If a small-winged male is crossed with a homozygous wild-type female, what ratio of normal to small-winged flies can be expected in each sex in the F1?
ANSWER: 100% normal wings in both sexes