Podcast
Questions and Answers
In a scenario where both parents are heterozygous for a particular trait (Aa), what is the probability that their offspring will express the recessive phenotype?
In a scenario where both parents are heterozygous for a particular trait (Aa), what is the probability that their offspring will express the recessive phenotype?
- 100%
- 75%
- 25% (correct)
- 50%
A plant has the genotype AaBb, where A is dominant for tallness and B is dominant for purple flowers. What phenotypes could potentially appear in the offspring if this plant is self-pollinated?
A plant has the genotype AaBb, where A is dominant for tallness and B is dominant for purple flowers. What phenotypes could potentially appear in the offspring if this plant is self-pollinated?
- Tall with purple flowers and dwarf with white flowers only.
- Dwarf with white flowers only
- Tall with purple flowers only
- Tall with purple flowers, tall with white flowers, dwarf with purple flowers, and dwarf with white flowers. (correct)
If a person with type AB blood (co-dominant alleles) has children with a person with type O blood, what blood types are possible in their offspring?
If a person with type AB blood (co-dominant alleles) has children with a person with type O blood, what blood types are possible in their offspring?
- AB or O
- A, B, AB, or O
- A, B, or O
- A or B (correct)
In a certain species of bird, feather color is determined by a single gene with two alleles: $F$ for green feathers and $f$ for blue feathers. If a population of these birds consists of 64% green-feathered birds and 36% blue-feathered birds, and blue is recessive, what can you infer about the genotypes of the green-feathered birds?
In a certain species of bird, feather color is determined by a single gene with two alleles: $F$ for green feathers and $f$ for blue feathers. If a population of these birds consists of 64% green-feathered birds and 36% blue-feathered birds, and blue is recessive, what can you infer about the genotypes of the green-feathered birds?
A scientist is studying a new species of beetle. They notice that some beetles have spots and some do not. After breeding several generations, they find that the trait for spots does not follow a simple dominant/recessive pattern. Instead, heterozygous beetles have fewer spots than homozygous dominant beetles. What type of inheritance is most likely at play?
A scientist is studying a new species of beetle. They notice that some beetles have spots and some do not. After breeding several generations, they find that the trait for spots does not follow a simple dominant/recessive pattern. Instead, heterozygous beetles have fewer spots than homozygous dominant beetles. What type of inheritance is most likely at play?
In a co-dominant inheritance pattern, what is the expected phenotype of an offspring that inherits two different dominant alleles for a specific trait?
In a co-dominant inheritance pattern, what is the expected phenotype of an offspring that inherits two different dominant alleles for a specific trait?
How did Mendel's cross-pollination experiments with pea plants, which naturally self-fertilize, enable him to make key discoveries about inheritance?
How did Mendel's cross-pollination experiments with pea plants, which naturally self-fertilize, enable him to make key discoveries about inheritance?
Why did the recessive trait reappear in Mendel's F2 generation, even though it was not present in the F1 generation?
Why did the recessive trait reappear in Mendel's F2 generation, even though it was not present in the F1 generation?
In the context of Mendelian genetics, what is the significance of allele segregation during the formation of sex cells?
In the context of Mendelian genetics, what is the significance of allele segregation during the formation of sex cells?
Consider a monohybrid cross between two pea plants, both heterozygous for a trait (Aa). What genotypic ratio would you expect to observe in the offspring?
Consider a monohybrid cross between two pea plants, both heterozygous for a trait (Aa). What genotypic ratio would you expect to observe in the offspring?
Flashcards
Co-dominance
Co-dominance
When both alleles are dominant and both traits are fully expressed in the phenotype.
P-generation
P-generation
The original pair of parents in a genetic cross.
F1-generation
F1-generation
The first generation of offspring from a cross between the P-generation.
Principle of Dominance
Principle of Dominance
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Punnett Square
Punnett Square
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Gamete
Gamete
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Allele
Allele
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Genotype
Genotype
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Phenotype
Phenotype
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Dominant Allele
Dominant Allele
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Study Notes
- Sexual reproduction and genetic variation are key drivers of species evolution
- Offspring from the same parents can vary genetically because each gamete (sperm or egg) is genetically unique
Alleles, Genotypes, and Phenotypes
- Offspring inherit genes (genetic information packed into chromosomes) from each parent
- Alleles are different versions of each gene
- Genotype: The genetic code or set of alleles within a gene/group of genes
- Phenotype: The physical manifestation of an organism's genotype
- Genotypes can be homozygous (alleles are the same, e.g., "aa") or heterozygous (alleles are different, e.g., "Aa")
Dominant, Recessive, and Co-dominant Alleles
- Phenotype depends on the dominant/recessive relationship between alleles
- Dominant alleles: Expressed as the phenotype if at least one is present in the genotype
- Recessive alleles: Expressed as the phenotype only if the genotype is homozygous recessive
- Blue eyes in humans are recessive, resulting from a lack of pigment, while green, hazel, or brown eyes are dominant
- Co-dominance: Both or all alleles are dominant, resulting in a phenotype where both traits are exhibited (e.g., spotted fur in cows)
Gregor Mendel and Pea Plant Traits
- Gregor Mendel: Father of Genetics, experimented with pea plants in his monastery garden
- Pea plants usually self-fertilize, producing identical offspring
- Mendel concluded that an individual's traits are passed down from one generation to the next
- Mendel cross-pollinated pea plants to create hybrids and study traits like seed color, seed texture, and plant height
- P-generation: true-bred original parents
- F1-generation: first offspring from cross-pollination
Mendel's Conclusions
- F1-generation: Showed characteristics of only one parent
- Principle of dominance: Some alleles are dominant, others are recessive; dominant phenotype is expressed if at least one dominant allele is present
- F2-generation: Variations in characteristics reemerged, recessive traits reappeared in approximately a fourth of the offspring
- Alleles for each gene are segregated during sex cell (pollen and seeds in plants) formation, with each sex cell carrying only one allele for that gene
- During fertilization, alleles for the same gene recombine
- Two heterozygous parents can produce offspring with a homozygous recessive genotype, expressing the recessive trait
Punnett Squares
- Mendel used Punnett squares to predict the probabilities of phenotypes from given parents
- Monohybrid crosses: Study the inheritance of a single pair of alleles or a single trait (e.g., height), using a four-box Punnett square
- Dihybrid crosses: Study the inheritance of two different alleles or a pair of traits (e.g., seed color and texture), requiring a larger Punnett square
- In a monohybrid cross with both parents having genotype Aa, there's a 25% chance of AA, 25% chance of aa, and 50% chance of Aa
- In dihybrid crosses, alleles are segregated so each sperm/egg has one allele per trait; a SsbB cross has a 6.25% chance of the offspring being homozygous recessive for both traits
Why Study Parental Genotypes?
- Allows geneticists to predict offspring genotypes/phenotypes using Punnett squares
- Useful for determining the probability of offspring inheriting genetic disorders
- Knowing the offspring's genotype can help deduce possible parental genotypes
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Description
Sexual reproduction and genetic variation are key drivers of species evolution. Offspring inherit genes from each parent. Alleles are different versions of each gene, and phenotypes depend on the dominant/recessive relationship between alleles.
