Unit 6: Genetics Day 1

Learn genetics inheritance patterns with Punnett squares & pedigrees!

Write your first and last name in the space below. Watch this video if you need to review how to create a Punnett Square for simple dominant inheritance. Watch this video if you need to review incomplete dominance, codominance, and polygenic traits. Watch this video if you need to review blood types and multiple allele traits. Watch this video if you need to review sex-linked traits. Genetics Vocabulary: Match each genetics vocabulary term to its definition. You can click on the box for the vocabulary term and then click on the corresponding box for the definition. You do not need to drag the line across to connect them. Allele Letter that represents the different versions of a gene Homozygous Genotype made up of two of the same allele (ex: BB or bb) Heterozygous Genotype made up of two different alleles (ex: Bb) Genotype Gene combination (ex: BB, Bb, or bb) Phenotype Physical characteristic (ex: brown eyes) Types of Inheritance Table: Use the description and example to help you identify each type of genetic inheritance. Complete Dominance One allele is completely dominant over another allele Example: In pea plants, the allele for green pods (G) is completely dominant over the allele for yellow pods (g). Incomplete Dominance Heterozygous individuals show a blended, intermediate form of the trait Example: In snapdragons, the allele R codes for red flowers the allele W codes for white flowers. Individuals with the genotype RW are pink. Codominance Heterozygous individuals express BOTH forms of the trait Example: In cattle, the allele R codes for red hairs and the allele W codes for white hairs. Individuals with the genotype RW have both red AND white hairs. Multiple Allele Trait Trait controlled by more than two alleles Example: In humans, ABO blood type is controlled by 3 different alleles. Sex-linked Trait Gene for the trait is located on the X or Y chromosome Example: In humans, the gene for hemophilia is located on the X chromosome. Polygenic Trait Trait is controlled by more than one gene Example: In humans, eye color and skin color are controlled by many genes. Complete Dominance Punnett Square: Two fish meet at the coral reef, fall madly in love, and get married the same night. They decide to have children right away. The mom fish has a big, fluffy tail (TT) and the dad fish has a flat tail (tt). What is the probability that their first child will have flat tail? Complete the Punnett square below for this cross by typing in either TT, Tt, or tt for each box. Tt Tt Tt Tt In the Punnett Square above, what is the probability that their first child will have a flat tail? 0% 25% 50% 75% Incomplete Dominance Punnett Square: In snapdragons, the allele for red flower color (R) is INCOMPLETELY DOMINANT over the allele for white flower color (W). Complete the Punnett Square below to show a cross between a red flowered plant and a white flowered plant. Type the genotype into each box as either RR, RW, or WW. RW RW RW RW According to the Punnett Square above, 100% of the offspring in this cross will have _ flower. red white pink red and white Codominance Punnett Square: In cattle, the allele for red hair (B) is CODOMINANT with the allele for white hair (W). Individuals who are roan (BW) have both red AND white hairs. What phenotypic results would we expect if two roan cattle are crossed? Complete the Punnett square below by typing BB, BW, or WW in each box. BB BW BW WW According to the Punnett square above, what phenotypic results would we expect if two roan cattle are crossed? 25% red, 25% roan, and 25% white 50% red, 50% roan, and 0% white 25% red, 50% roan, and 25% white 0% red, 75% roan, and 25% white In humans, hemophilia is a sex-linked trait located on the X chromosome. Normal blood clotting (XH) is dominant over hemophilia (Xh). Observe the Punnett square below which shows a cross between a carrier mom and a normal dad. Which statement is true of the results of this cross? We would expect 50% of their children to have hemophilia (males and females affected) We would expect 25% of their children to have hemophilia (only females affected) We would expect 0% of their children to have hemophilia We would expect 25% of their children to have hemophilia (only males affected) Watch this video if you need to review pedigrees. Use this pedigree to answer the questions that follow: How many generations are shown in this pedigree? 1 2 3 4 How many individuals in this family express the trait being traced? 6 (3 males and 3 females) 5 (2 males and 3 females) 6 (4 males and 2 females) 5 (3 males and 2 females) Use the pedigree inheritance flow chart below to answer each question in the next section. Use the flow chart above. What type of inheritance does this pedigree show? Autosomal Dominant Autosomal Recessive Sex-linked Recessive Use the flow chart above. What type of inheritance does this pedigree show? Autosomal Dominant Autosomal Recessive Sex-linked Recessive Use the flow chart above. What type of inheritance does this pedigree show? Autosomal Dominant Autosomal Recessive Sex-linked Recessive Use the pedigree below to answer the final two questions. The pedigree shows the inheritance of cystic fibrosis in a family. Cystic fibrosis is an autosomal recessive trait. The allele F represents normal and the allele f represents cystic fibrosis. What genotype would the shaded individual in this pedigree have? FF Ff ff F- What genotypes must the parents of the shaded individual have? Mom = FF and Dad = ff Mom = ff and Dad = Ff Mom = Ff and Dad = FF Mom = Ff and Dad = Ff