Caspersprincess

Your lab partner was having difficulty observing cells in a slide of an onion root tip. On her parfocal microscope she switched from the low to high power objectives. She then used the fine focus knob to clarify her image, yet the entire field lacked brightness. She was unable to clearly distinguish any organelles. How would you suggest that she correct her focusing problem?

1. If a male who expresses a sex-linked disease mates with a female who is a carrier for the disease, what will the possible phenotypes of their offspring be?

2. If you do a test cross between a purple and a white flowered plant and get ½ white offspring and ½ purple offspring, what is the genotype of the purple parent (assume complete dominance)?

3. If a male and female who are both heterozygous for an autosomal dominant disease have children, what will the possible phenotypes of their offspring be? What are the parental phenotypes?

I have a test monday and I dont understand how to figure out these three sample questions.

1.If two parents were both heterozygous for a complete dominant trait, what is the probability that their child will express the recessive phenotype?

2.What are the genotypic frequencies of offspring produced by these two parents?

3.What are the phenotypic frequencies of offspring produced by these two parents?