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Ch. 29 Heredity
Marieb - Human Anatomy & Physiology 11th Edition
Marieb, Hoehn11th EditionHuman Anatomy & PhysiologyISBN: 9780136874034당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Marieb, Hoehn 11th EditionCh. 29 Heredity문제 4
29장, 문제 4

Suppose that the ability to taste PTC (phenylthiocarbamide) depends on the presence of a dominant gene T; nontasters are homozygous for the recessive gene t. This would be a case of classical dominant-recessive inheritance.
(a) Consider a mating between heterozygous parents producing three offspring. What proportion of the offspring are likely to be tasters? What is the chance that all three offspring will be tasters? Nontasters? What is the chance that two will be tasters and one will be a nontaster?
(b) Consider a mating between Tt and tt parents. What is the anticipated percentage of tasters? Nontasters? What proportion can be expected to be homozygous recessive? Heterozygous? Homozygous dominant?

검증된 단계별 안내
1
Understand the genetic basis: The ability to taste PTC is controlled by a dominant gene T. Tasters have at least one T allele (TT or Tt), while nontasters are homozygous recessive (tt).
For part (a), set up a Punnett square for two heterozygous parents (Tt x Tt). The possible genotypes of offspring are TT, Tt, and tt with probabilities 1/4, 1/2, and 1/4 respectively. Calculate the proportion of tasters by adding probabilities of TT and Tt.
Calculate the probability that all three offspring are tasters by raising the tasters' probability to the power of 3: \((\text{probability of taster})^3\). Similarly, calculate the probability that all three are nontasters by raising the nontaster probability to the power of 3.
Calculate the probability that exactly two offspring are tasters and one is a nontaster using the binomial probability formula: \(P = \binom{3}{2} \times (\text{probability of taster})^2 \times (\text{probability of nontaster})^1\).
For part (b), set up a Punnett square for parents Tt and tt. The possible offspring genotypes are Tt and tt with equal probabilities. Calculate the percentage of tasters (Tt), nontasters (tt), and identify the proportions of homozygous dominant (TT), heterozygous (Tt), and homozygous recessive (tt) offspring.

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Mendelian Dominant-Recessive Inheritance

This concept explains how traits are inherited through dominant and recessive alleles. A dominant allele (T) masks the effect of a recessive allele (t) in heterozygous individuals, so only those with two recessive alleles (tt) express the recessive trait. Understanding this helps predict offspring phenotypes based on parental genotypes.
추천 영상:
가이드 코스
03:39
Dominant vs. Recessive Alleles

Punnett Square and Genotypic Ratios

A Punnett square is a tool used to determine the possible genotypes of offspring from parental alleles. It helps calculate the expected proportions of homozygous dominant (TT), heterozygous (Tt), and homozygous recessive (tt) genotypes, which in turn predict phenotypic ratios such as tasters and nontasters.
추천 영상:
가이드 코스
06:36
Genotype & Phenotype

Probability in Independent Events

When considering multiple offspring, the probability of specific genotype or phenotype combinations is calculated by multiplying individual probabilities, assuming independent assortment. This allows determination of chances for all offspring being tasters, nontasters, or mixed combinations in a given number of offspring.
추천 영상:
가이드 코스
2:08
T Dependent & T Independent Antigens
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