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Biology H-Mr.Willets
Genetics Problems-
1) Let's assume that hair color in humans is a simple genetic situation (it really isn't). Assume there are two alleles for hair color - a dominant allele for dark hair and a recessive allele for light hair. A dark haired woman whose father is light haired marries a light haired man. Use a Punnett Square to determine the expected phenotypes and genotypes of the children.
2) The gene for bent little fingers is dominant over the gene for straight fingers. Two bent fingered people have a straight fingered child. What are the genotypes of all three?
3) Brown eyes is dominant over blue eyes. Dark hair is dominant over light hair. The mother is brown eyed with light hair. The father is blue eyed with dark hair. The child is blue eyed with light hair. What are the genotypes of all three?
4) In short horned cattle, red is co-dominant with white . The hybrid is called roan. A roan mates with a roan. Use a Punnett Square to determine the expected phenotypes of the offspring.
5) The alleles for hair type show incomplete dominance One allele (c) is for curly hair. Another allele (s) is for straight hair. The hybrid is wavy. A wavy haired person marries a curly haired person. Use a Punnett Square to determine the expected phenotypes in the children.
6)Dark hair is dominant over light hair. A man with light hair has a dark haired daughter. What is the phenotype of the mother? The daughter marries a dark haired man. They have 20 children all with dark hair.
What is the most likely genotype of the husband?
7) In pigeons, ruffled feathers are dominant over smooth feather. A ruffled pigeon whose mother was smooth is crossed with a ruffled pigeon. The first chick has smooth feathers. What are the genotypes of the chick, its parents and the grandmother?
8) What gametes could the genotype BbRR produce? What gametes could the genotype BbRr produce.
Use a Punnett Square to determine the possible genotypes of their offspring. How many different genotypes are there? How many different phenotypes are there? (the answer here would describe the possibilities in terms of having the dominant or recessive trait for each pair of genes- for example, BbRR would be "dominant/dominant" whereas bbRR would be "recessive/dominant")
9) In summer squash, tan is dominant over yellow. Disc shape is dominant over sphere. Use a Punnett Square to determine the possible phenotypes for each cross below?
a) TtDd x ttDD b) TtDD x ttdd c) Ttdd x TTDd
#8 and 9 above are examples of Mendel's "Law of Independent Assortment" The inheritance of one set of genes does not affect the inheritance of another set.
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