17.2 - Monohybrid Inheritance Flashcards
How are genetic crosses usually represented as
- represented in a standard form of shorthand
Why do you chose the first letter of one of the contrasting features in a genetic cross, e.g. G (green) Y(yellow)
- easy to identify which letter refers to which characteristic when you’re considering multiple
Using a punnet square. The dominant Allele A codes for breathing fire and recessive allele a codes for breathing lightning. If a female dragon that breaths fire (with one parent that was able to breathe lighting) breeds with a male dragon that breeds lighting. What is the probability that the child will breathe lightning
What is monohybrid inheritance?
- Monohybrid inheritance is the inheritance of a single gene.
- It involves the study of how a specific characteristic, determined by one gene, is passed from parents to offspring.
- Gregor Mendel’s experiments with pea plants, particularly the color of pea pods, are a classic example of monohybrid inheritance.
What is an example of monohybrid inheritance in pea plants?
- One example of monohybrid inheritance is the color of pea pods, which come in two basic colors—green and yellow.
- This trait is determined by a single gene with two alleles, where the allele for green pods is dominant and the allele for yellow pods is recessive.
What does “pure-breeding” mean in the context of inheritance?
- “Pure-breeding” refers to organisms that, when bred with each other, consistently produce offspring with the same characteristic.
- For example, pure-breeding green-pod pea plants will always produce offspring with green pods.
- This occurs because the plants are homozygous for the gene controlling that characteristic, meaning they have two identical alleles for the trait.
What happens when pure-breeding green-pod pea plants are crossed with pure-breeding yellow-pod pea plants?
- When pure-breeding green-pod plants are crossed with pure-breeding yellow-pod plants, all the offspring in the first generation (the F₁ generation) produce green pods.
- This occurs because the allele for green pods is dominant over the allele for yellow pods, which is recessive.
What is the genetic composition of the first filial (F₁) generation in a monohybrid cross?
- The first filial (F₁) generation consists of heterozygous plants, meaning each plant has one allele for green pods and one allele for yellow pods (Gg).
- Since the green allele is dominant, all the plants in the F₁ generation express the green pod phenotype.
What happens when the heterozygous F₁ plants are crossed with each other?
- When heterozygous F₁ plants (Gg) are crossed with each other, the offspring in the second generation (the F₂ generation) exhibit a phenotypic ratio of approximately 3:1.
- This means that for every three plants with green pods, there is one plant with yellow pods.
What is the law of segregation?
- “in diploid organisms, characteristics are determined by pairs of alleles. During gamete formation, only one allele from each pair is included in a single gamete.”
- This means that each gamete carries just one allele for each gene.
How does Mendel’s experiment with pea pod color illustrate dominant and recessive alleles?
- In Mendel’s experiment, crossing pure-breeding green-pod plants with pure-breeding yellow-pod plants resulted in an F₁ generation where all plants had green pods, indicating that the allele for green pods is dominant.
- When F₁ heterozygous plants were intercrossed, the F₂ generation exhibited a 3:1 ratio of green to yellow pods, showing the recessive yellow allele only appeared in the phenotype when two copies were present.
Inhumans, Huntington’s disease is caused by a dominant, mutant allele of a gene. Draw a genetic diagram to show the possible genotypes and phenotypes of the offspring produced by a man with one allele for the disease and a woman who does not suffer from the disease.
