Questions and Answers
What is the expected frequency of mice with yellow fur when mating two mice with the genotypes AYaBb x AYaBb?
2/3
Match the phenotypes to the genotypes based on the effect of the third gene on fur color:
AaBbcc = albino AaBBCC = agouti black Aabbcc = albino AAbbCc = agouti brown aaBbCc = solid color, black AABBcc = albino
What is the probability that offspring will have solid black fur along with large patches of white fur in a cross between two mice that are heterozygous for agouti, black, color, and piebaldism?
9/256
If an individual has a genetic condition that neither parent has, what can be inferred about the mode of inheritance?
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What can be deduced about the genotypes of affected individuals in a rare, autosomal dominant condition?
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In autosomal recessive pedigrees, what is true about affected individuals?
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What is the probability that individual IV-1 will be affected given the conditions of her parents?
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How could the botanist best determine whether the genotype of the green-pod plant is homozygous or heterozygous?
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What do Punnett squares predict about the botanist's test cross?
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Which of Mendel's findings does the botanist's test cross illustrate if the original green-pod plant is heterozygous?
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During which part of meiosis do the two alleles of a gene separate?
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What is the ability to deduce an organism's genotype from the phenotype of its progeny?
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What are the expected frequencies of the four phenotypic classes in the progeny?
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What type of cross is exemplified by a study of two characters, such as eye color and skin color?
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What is the expected phenotypic ratio of the offspring when crossing heterozygous eye color, skin color, and number of eyes?
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What is the correct ratio of gametes produced by an AaBB individual?
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What would be the expected frequency of agouti brown offspring in a litter from two agouti black parents?
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What state of alleles interaction occurs when a dominant allele coexists with a recessive allele in a heterozygote individual?
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Which diagram represents anaphase I of meiosis?
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Which diagram(s) represent(s) anaphase II of meiosis?
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Which sample(s) of DNA might be from a skin cell arrested in G0 of the cell cycle?
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Study Notes
Genotype Identification and Test Cross
- Test cross involves crossing an unknown genotype with a homozygous recessive to determine its genotype.
- Testing the green-pod plant's genotype with a yellow-pod plant can reveal if it is homozygous or heterozygous.
Punnett Squares and Offspring Prediction
- Punnett squares illustrate all possible allele combinations from a genetic cross.
- Offspring probabilities for phenotype distribution can be observed, e.g., 50% green pods and 50% yellow pods when crossing a heterozygous plant.
Mendel's Law of Segregation
- This law states that alleles for a gene segregate during gamete formation.
- For a heterozygous plant, each gamete carries either the dominant or recessive allele, explaining phenotypic ratios in offspring.
Meiosis and Allele Separation
- Alleles separate in anaphase of meiosis I when homologous chromosomes are pulled apart.
Dihybrid Cross and Parental Genotypes
- Using offspring phenotypes from selfed pea plants aids in deducing parental genotypes.
- The cross of round yellow seeds with wrinkled yellow seeds helps predict progeny phenotype frequencies.
Quantitative Characters vs. Mendel's Traits
- Quantitative traits are influenced by multiple genes, unlike Mendel's focus on single-gene traits.
- These traits exhibit continuous variation within a population.
Diagrams of Chromosomes
- Identification of chromosome behavior during meiosis aids in understanding inheritance patterns.
- Specific stages like anaphase I and II can be illustrated through diagrams for clarity.
Allele Relationships and Phenotypic Outcomes
- Relationships between alleles, whether dominant or recessive, can be clarified through heterozygote analysis.
- Incomplete dominance leads to a mix of phenotypes, whereas codominance shows both phenotypes distinctly in heterozygotes.
Cross Genotypes and Expected Offspring Ratios
- The expected ratio of offspring from specific parental genotypes provides insight into inheritance patterns.
- Dihybrid crosses and the ratio of gametes produced by individuals exhibiting multiple traits reveal complexity in genetic inheritance.
Exploration of Epistasis and Multiple Genes
- Epistasis occurs when one gene masks the effect of another, showcasing complex interactions in traits like fur color in mice.
- Understanding how third and fourth genes affect fur color aids in predicting phenotypic outcomes in offspring.
Summary of Genetic Principles
- Mendel's laws of segregation and independent assortment underlie genetic predictions and outcomes.
- Accurate genotypic representation enhances the understanding of inheritance patterns across generations.### Genetics and Probability of Traits in Mice
- Cross of heterozygous mice results in a variety of fur colors and patterns.
- Solid black fur (aa genotype) probability is 1/4.
- Black fur (BB or Bb genotype) probability is 3/4.
- Colored fur (CC or Cc genotype) probability is 3/4.
- Piebaldism (pp genotype) probability is 1/4.
- Combined probability for solid black fur with large patches of white fur is 9/256 (1/4 x 3/4 x 3/4 x 1/4).
Inheritance Patterns in Autosomal Conditions
- Recessive genetic conditions appear without parents affected; dominant conditions require at least one affected parent.
- For rare conditions, the mode of inheritance that requires the least number of unrelated affected individuals is preferred.
Genotypes in Autosomal Dominant Pedigrees
- Affected individuals with one affected parent are heterozygous.
- Unaffected individuals are homozygous recessive.
- Affected individuals with unaffected children are heterozygous.
- Affected individuals with two affected parents may be homozygous dominant or heterozygous.
Genotypes in Autosomal Recessive Pedigrees
- Affected individuals are homozygous recessive.
- Unaffected children of affected parents are carriers (heterozygous).
- Both parents of affected individuals must have a recessive allele.
- In cases of carriers, unaffected children may be carriers or homozygous for the dominant allele.
- Assume individuals marrying into the family do not carry the recessive allele unless evidence is present.
Calculating Probabilities in Pedigrees
- Probability of an individual being affected depends on their carriers' status and allele transmission.
- Individual III-3's carrier probability is 2/3; individual III-4's is 1/2.
- The probability that individual IV-1 will inherit the condition (affected) involves calculations based on probabilities of parents being carriers and passing the recessive allele.
- The overall probability of IV-1 being affected is calculated as 1/12 using multiplication of individual probabilities.
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Description
Explore the fundamentals of genetics with this quiz on identifying genotypes from Mastering Biology Chapter 14. Test your knowledge on concepts like homozygous and heterozygous alleles through engaging flashcards. Perfect for biology students aiming to deepen their understanding of inheritance patterns.
