Congrats! You’re Having A Baby!

Objective #1 Simulate the passing of alleles from parent to child by using a coin. Coin will be flipped twice to determine the genotype of child. The parents will both be heterozygous for the trait. Observe the genotype produced and identify the phenotype.

Lab Hints… Parents will be heterozygous for a given trait Simple Dominance – coin: head=D; tail=R Incomplete dominance – coin: head=D; tail=R Polygenic Inheritance – coin: head=D; tail=R Sex Determination – coin: head=X; tail=Y Each child receives two alleles which interact to control the phenotype.

Objective #2 Explore the various types of gene interactions which contribute to genetic diversity which is the source of evolution by natural selection. The way an organism looks is result of the way in which the two a alleles interact with each other. There are three different interactions: Simple Dominance, Incomplete Dominance and Codominance. Who has curly, wavy and straight hair? The one who inherits a dominant and a recessive allele.

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. The albino inherited a recessive allele from each parent.

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. What is the phenotypic ratio for the F1 Generation? 0 red flowers:4 pink flower:0 white flowers What is the phenotypic ratio for F2 Generation between two pink F1 flowers ? What is the phenotypic ratio for F2 Generation between a pink and a white flower? What are the phenotypes of the parent flowers? Notice that in this interaction, recognize that when the dominant & recessive allele get together they don’t produce the dominant phenotype like in simple dominance.

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. The arrangement of red & white hairs makes the cow look pink. This cow inherited a dominant R allele for red and the recessive r for white hairs so the cow’s genotype is heterozygous but the phenotype is not like the simple dominance or codominance interaction. Sickle Cell Anemia is a genetic disorder caused by a gene 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. Which genotype shows a phenotype with Two different blood cell shape? Why?

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. The fewer dominant alleles inherited, the lighter the skin. The white circles represent recessive alleles and black circles represent dominant alleles. There is a 1:64 chance of inherited all dominant alleles in this cross.

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

Here are two examples of a monohybrid cross which is a cross between two individuals with heterozygous genotypes.

Objective #2 Compare expected gender ratio with the observed gender ratio. Expected numbers or ratios come from using a Punnett square and simple mathematics. Observed numbers or ratios comes from sampling a population, which means physically counting individuals. Trait# Males Born# Females Born Ex (pected Male to Female Ratio Observed Male to Female Ratio Gender10 (observed) 12 (expected) 14 (observed) 12 (expected) 1:1 or 50%:50% 10:14 or The inheritance of a trait occurs by chance.

Conclusion: What did you learn after performing, analyzing and discussing the Congrats! You’re Having a Baby Genetics Lab?

Post Lab 1.Review all notes. 2.Complete all post lab questions. 3.Know the definitions of different gene interactions.

Agree or Disagree A person with a heterozygous genotype always shows the dominant phenotype. A person’s trait is always controlled by only one gene. All chromosomes are homologous pairs. There is a 100% chance of a child receiving a Y chromosome from dad.