Genetics Chapter 10—pages 258-285

Genetics the study of heredity Heredity the study of characteristics from parent to offspring Terms Each gene has 2 alleles (forms) Ex.: The gene for teeth health is found on chromosome 6 Each person has 2 alleles for each gene—one from mom and one from dad

Each baby will get an allele for each gene from each parent If a father has the alleles T and t for teeth health… If a mother has the alleles t and t for teeth health… T = healthy teeth (dominant trait) t = rotten teeth (recessive trait)

What is the father’s genotype for this trait? __________ What is the father’s phenotype for this trait? __________ What is the mother’s genotype for this trait? __________ What is the mother’s phenotype for this trait? __________

Primary Sperm Cell = Possible sperm cells =

Primary Egg Cell = Possible egg cells =

Determine the % chance that this couple, EACH TIME they get pregnant, will have a healthy baby with healthy teeth, and the % chance that they will have unhealthy teeth. Punnett Square:

Parents have the genotype Bb and Bb for eye color Parents have the genotype Bb and Bb for eye color. Determine the % chance that their children will have a certain color of eyes (brown eyes are dominant over blue eyes).

The dominant trait will be the capital letter and the recessive trait will be the lowercase form of the same letter when dealing with traits that display dominance!

Show all of the following when determining probabilities: Parents’ phenotype: Letters: Parents’ genotype: Punnett square: Ratio:

IV. Terms Heterozygous or Hybrid (Carrier) = Tt; one of each, so phenotype is dominant Homozygous or Purebred (Normal) = TT or tt—both letters are the same * The only way you can receive the recessive trait is to have 2 “littles” for a genotype!

Carrier We use the term carrier instead of the word heterozygous when working with a trait that is a disease. Cystic fibrosis is the most common inherited disease in white people. 1 in 20 are carriers and 1 in 2,000 babies are born with cystic fibrosis.

V. Another practice problem Cross a carrier of cystic fibrosis with a normal person. Parents’ phenotype: Letters: Parents’ genotype: Punnet square: Ratio:

Cross a carrier with a carrier: Parents’ phenotype: Letters: Parents’ genotype: Punnett square: Ratio: