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Chapter 4: Problem 6

Three gene pairs located on separate autosomes determine flower color and shape as well as plant height. The first pair exhibits incomplete dominance, where color can be red, pink (the heterozygote), or white, The second pair leads to the dominant personate or recessive peloric flower shape, while the third gene pair produces either the dominant tall trait or the recessive dwarf trait. Homozygous plants that are red, personate, and tall are crossed with those that are white, peloric, and dwarf. Determine the \(P_{1}\) genotype(s) and phenotype(s). If the \(F_{1}\) plants are interbred, what proportion of the offspring will exhibit the same phenotype as the \(F_{1}\) plants?

Short Answer

Expert verified
Answer: 9/32

Step by step solution

01

Define genotype and phenotype symbols

Let's assign symbols to each gene and phenotype: Flower color: Incomplete dominance - Red (R₁R₁) - Pink (R₁R₂) - White (R₂R₂) Flower shape: Dominant personate and recessive peloric - Personate (P₁) - Peloric (P₂) Plant height: Dominant tall and recessive dwarf - Tall (T₁) - Dwarf (T₂)
02

Identify the P₁ genotypes and phenotypes

The problem states that the two parent plants have the following phenotypes: - Red, personate, and tall - White, peloric, and dwarf Using the symbols we defined earlier for genotypes and phenotypes, the \(P_{1}\) genotypes and phenotypes will be: Red, personate, and tall plant: R₁R₁P₁P₁T₁T₁ White, peloric, and dwarf plant: R₂R₂P₂P₂T₂T₂
03

Find F₁ genotypes after the cross

To find the genotypes of the \(F_{1}\) generation after the cross, we will perform a cross-pollination between the two \(P_{1}\) plants: R₁R₁P₁P₁T₁T₁ x R₂R₂P₂P₂T₂T₂ For each gene pair, the \(F_{1}\) offspring will inherit one allele from each parent, so the \(F_{1}\) genotype will be: Flower color: R₁R₂ (Pink) Flower shape: P₁P₂ (Personate) Plant height: T₁T₂ (Tall) The \(F_{1}\) genotype is: R₁R₂P₁P₂T₁T₂ The \(F_{1}\) phenotype is: Pink, personate, and tall
04

Interbreed F₁ plants and find proportions

When we interbreed the \(F_{1}\) plants, we will be performing the following genetic cross: R₁R₂P₁P₂T₁T₂ x R₁R₂P₁P₂T₁T₂ To find the proportion of offspring that have the same phenotype as the \(F_{1}\) plants (Pink, personate, and tall), we need to consider each gene pair separately: - Flower color: R₁R₂ x R₁R₂ Proportion of offspring with pink flowers: 2/4 (Only heterozygotes will be pink) - Flower shape: P₁P₂ x P₁P₂ Proportion of offspring with personate shape: 3/4 (Personate is the dominant trait) - Plant height: T₁T₂ x T₁T₂ Proportion of offspring with tall height: 3/4 (Tall is the dominant trait)
05

Determine the overall proportion

Now, we need to find the proportion of offspring that have all three required traits: pink flower color, personate flower shape, and tall height. We can find this by multiplying the proportions for each trait together: \(Proportion = \frac{2}{4} \times \frac{3}{4} \times \frac{3}{4} = \frac{9}{32}\) Thus, \(9/32\) of the offspring of the \(F_{1}\) plants will exhibit the same phenotypes as the \(F_{1}\) plants (Pink, personate, and tall).

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Most popular questions from this chapter

In this chapter, we focused on many extensions and modifications of Mendelian principles and ratios, In the process, we encountered many opportunities to consider how this information was acquired. Answer the following fundamental questions: (a) How were early geneticists able to ascertain inheritance patterns that did not fit typical Mendelian ratios? (b) How did geneticists determine that inheritance of some phenotypic characteristics involves the interactions of two or more gene pairs? How were they able to determine how many gene pairs were involved? (c) How do we know that specific genes are located on the sexdetermining chromosomes rather than on autosomes? (d) For genes whose expression seems to be tied to the sex of individuals, how do we know whether a gene is X-linked in contrast to exhibiting sex-limited or sex-influenced inheritance? (e) How was extranuclear inheritance discovered?

Morbid obesity in humans is an autosomal recessive disorder. Rett syndrome is a neurological disorder that is marked by the X.linked dominant allele, If two non-obese parents with Rett syndrome produce an obese, non-Rett son, what is the probability that their next child will be a female who is obese and also has Rett syndrome?

In cattle, coats may be solid white, solid black, or black-andwhite spotted. When true-breeding solid whites are mated with true-breeding solid blacks, the \(\mathrm{F}_{1}\), generation consists of all solid white individuals. After many \(\mathrm{F}_{1} \times \mathrm{F}_{1}\) matings, the following ratio was observed in the \(\mathrm{F}_{2}\) generation: \(12 / 16\) solid white \(3 / 16\) black-and-white spotted \(1 / 16\) solid black Rxplain the mode of inheritance governing coat color by determining how many gene pairs are involved and which genotypes yield which phenotypes. Is it possible to isolate a true-breeding strain of black-and-white spotted cattle? If so, what genotype would they have? If not, explain why not.

Two different genes, located on two different chromosomes, are responsible for color production in the aleurone layer of com kernels. For color production (either purple or red), the dominant alleles of these two genes \((C \text { and } R\) ) must come together. Furthermore, a third gene, located on a third chromosome, interacts with the \(C\) and \(R\) alleles to determine whether the aleurone will be red or purple. While the dominant allele ( \(P\) ) ensures purple color, the homozygous recessive condition (pp) makes the aleurone red. Determine the \(\mathrm{P}_{1}\) phenotypic ratio of the following crosses: (a) \(C C r r P P \times \operatorname{ccRRp} p\) (b) \(C c R R p p \times C C R r p p\) (c) \(\operatorname{CcRrPp} \times\) CcRrpp.

In goats, development of the beard is due to a recessive gene. The following cross involving true-breeding eoats was made and carried to the \(\mathrm{F}_{2}\) generation: \(\mathrm{P}_{1}=\) bearded female \(\times\) beardless male \(\mathrm{F}_{1}:\) all bearded males and beardless females \\[ \mathbf{F}_{1} \times \mathbf{F}_{1} \rightarrow\left\\{\begin{array}{l} 1 / 8 \text { beardless males } \\ 3 / 8 \text { bearded males } \\ 3 / 8 \text { beardless females } \\ 1 / 8 \text { bearded females } \end{array}\right. \\] Offer an explanation for the inheritance and expression of this trait, diagramming the cross. Propose one or more crosses to test your hypothesis.
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