Congrats! You’re Having A Baby!

Objective #1 Explore the various types of gene interactions which contribute to genetic diversity The way an organism looks is result of the way in which the alleles interact. The genotype determines the phenotype.

Simple Dominance is defined as when one allele completely expresses a trait and does not allow the other allele to express itself. Albinism is a disorder in which a person cannot make the pigment, melanin. A person who is “aa” has albinism. The “AA” and the “Aa” genotype produce normal skin pigment.

Incomplete Dominance is when both the dominant and the recessive cannot fully express the trait Snapdragons are flowers. Note that the dominant R allele will produce a red petal flower. When it combines with a recessive r allele, notice the petals are pink. The combination of R and r do not Allow for complete red. What is the phenotypic ratio for the F1 Generation? What is the phenotypic ratio for F2 Generation Between the F1 pink and white flower?

Codominance is defined as when two different alleles fully express the trait Roan Cattle have a lighter color almost pinkish appearance. It is not because they Have red hair. It is by the arrangement of red and white hairs. This cow inherited The dominant R allele for red and the recessive r for white hairs. Sickle Cell Anemia is a genetic Disorder caused by a point mutation. A person with this disorder would have red blood cells that are sickle shaped. Note the genotype is aa. Look at the Genotype AA, describe the normal cells.

Polygenic Inheritance is when many genes control a trait. As in the diagram below, skin color is controlled by (3) genes. Noticed the letters A, B, and C. These letters represent the (3) genes. The more dominant alleles inherited, the darker the skin.

Geneticists try to predict the possible genotypes and phenotypes of the next generation. Sometimes they use a simple Punnett square or the mathematics of probability. Below is a Punnett square for a monohybrid cross for flower color.

About the Lab Parents will be heterozygous for a given trait Simple Dominance – coin: head=D; tail=R Codominance – coin: head=D; tail=R Polygenic Inheritance – coin: head=D; tail=R Sex Determination – coin: head=X; tail=Y Read the directions carefully Complete Data for your two babies

Example of a Monohybrid Cross in Humans (both parents heterzygotes)

Objective #2 Compare expected phenotypic ratio to the observed phenotypic ratio Expected ratio comes from the punnett square. Observed ratio comes from sampling a population Trait# Dominant Individuals #Recessive individuals Observed Phenotypic Ratio Expected Phenotypic Ratio

Objective #3 Calculate the expected genotypic and observed genotypic ratios for a monohybrid cross for several types of gene interactions. In this part of the lab, you should realize that it is only the phenotypic ratio that change when the allele interaction no longer exhibits a simple dominance interaction.