You are traveling in the Netherlands and overhear a tulip breeder describe a puzzling event. Tulips normally have two outer whorls of brightly colored petal-like organs, a third whorl of stamens, and an inner (fourth) whorl of carpels. However, the breeder found a recessive mutant in his field in which the outer two whorls were green and sepal-like, whereas the third and fourth whorls both contained carpels. What can you speculate about the nature of the gene that was mutated?

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Hey, everyone. Let's take a look at this question together in a family of six, the father has a long sharp nose and is tall while the mother has a small round nose and is short. Their two daughters have small round noses and short heights and their son has a long sharp nose and is tall. What can be inferred about the nature of genes and their expression in the phenotype? Is it that the traits are controlled by a single gene with a dominant and recessive allele, they are controlled by multiple genes with each gene having a large effect. They are controlled by multiple genes with each gene having a small effect or gene expression is determined solely by the environment. Let's work this problem out together to try to figure out what can be inferred about the nature of these genes and their expression in the phenotype. So from the question, we know that we have a father and a son that both have long and sharp noses as well as they are tall in height. And we know that the mother as well as the two daughters have small round noses and are short in height. And from this information, we are able to infer that the genes and the expression in this family of six are not consistent with a dominant and recessive a little pattern. Since the father and the son have the same phenotype and the mother and the two daughters have the same phenotype. So since we are able to infer that it is not consistent with that dominant and recessive allele pattern, we can go ahead and eliminate answer choice. A and we can also eliminate answer choice. D since we know that gene expression being determined solely by the environment is not something that we can determine from the question because we don't have enough information. And so it is either that the traits are controlled by multiple genes with each gene having either a large effect or a small effect. And since the offspring have the exact same phenotype as one of the parents, we are able to determine that the inheritance pattern of these genes is polygenic inheritance, which describes many genes that have small effects on the phenotype making. Answer choice. C traits are controlled by multiple genes with each gene having a small effect is the correct answer. Since we are able to infer that the inheritance pattern observed in this family is not consistent with that dominant and recessive allele pattern as well as gene expression being determined solely by the environment. So it is either that the traits are controlled by multiple genes with each gene having a large effect or a small effect. However, the inheritance pattern of these genes and their expression is consistent with that polygenic inheritance, which describes many genes with small effects. So answer choice C is the correct answer. I hope you found this video to be helpful. Thank you and goodbye.

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Key Concepts

Flower Structure and Whorls

Dominance and Recessiveness in Genetics

Homeotic Genes and Floral Development