17 Questions
What is the genotypic ratio of the offspring from a cross between a homozygous dominant and a homozygous recessive parent?
All alike
In a monohybrid cross between a homozygous dominant and a homozygous recessive parent, what is the phenotypic ratio of the F1 generation?
All alike
In a monohybrid cross between two heterozygous parents (Rr x Rr), what is the genotypic ratio of the F2 generation?
1:2:1
In a monohybrid cross between two heterozygous parents (Rr x Rr), what is the phenotypic ratio of the F2 generation?
3:1
What is the purpose of a test cross?
To determine the genotype of an individual with a dominant phenotype
What is the genotype of the offspring from a cross between a homozygous dominant and a homozygous recessive parent?
All Tt
What is the probability of obtaining a tall offspring when a heterozygous tall plant (Tt) is crossed with another heterozygous tall plant (Tt)?
75%
In a dihybrid cross between rabbits that are heterozygous for both white fur (Ww) and long ears (Ee), what is the probability of obtaining an offspring with black fur and short ears?
25%
In a dihybrid cross between black, long-haired guinea pigs (Bbhh) and brown, short-haired guinea pigs (bbHh), what percentage of the offspring will have black fur and long hair?
50%
What is the genotype of the F1 generation when a homozygous tall plant (TT) is crossed with a homozygous short plant (tt)?
Tt
What is the expected phenotypic ratio of the F2 generation when a monohybrid cross is performed between two heterozygous tall plants (Tt x Tt)?
75% tall, 25% short
In a cross between a homozygous black rabbit (BB) and a heterozygous black rabbit (Bb), what are the possible genotypes of the offspring?
BB, Bb, and bb
If a plant homozygous for white fruit color (WW) is crossed with a plant homozygous for yellow fruit color (yy), what will be the phenotype of the F1 generation?
All white fruit color
In a monohybrid cross, what is the expected ratio of phenotypes in the F2 generation if the F1 generation is heterozygous for the trait?
3:1
What is the genotype of a true-breeding individual for a dominant trait?
Homozygous dominant (AA)
According to the Law of Independent Assortment, what happens when two different traits are considered in a genetic cross?
The alleles for each trait are distributed to gametes independently of the other trait
In a monohybrid cross between two heterozygous parents (Aa x Aa), what is the probability of obtaining an offspring with the recessive phenotype (aa)?
25%
Study Notes
Monohybrid Crosses
- A monohybrid cross is a cross between two plants that differ in one trait, such as seed shape.
- The cross between a round seed (RR) and a wrinkled seed (rr) produces all hybrid offspring (Rr) in the F1 generation.
- The F2 generation has a genotypic ratio of 1:2:1 (RR:Rr:rr) and a phenotypic ratio of 3:1 (round:wrinkled).
F1 and F2 Generations
- The F1 generation is the offspring of a cross between two parents with different traits.
- The F2 generation is the offspring of a cross between two F1 individuals.
Genotype and Phenotype
- Genotype refers to the genetic makeup of an individual (e.g., RR, Rr, rr).
- Phenotype refers to the physical characteristics of an individual (e.g., round or wrinkled seeds).
Law of Dominance
- The law of dominance states that when two parents with different traits are crossed, only one form of the trait will appear in the next generation.
- The dominant trait will be expressed in the phenotype.
Law of Segregation
- The law of segregation states that during gamete formation, the two alleles responsible for a trait separate from each other.
- Alleles for a trait are then recombined at fertilization, producing the genotype for the traits of the offspring.
Law of Independent Assortment
- The law of independent assortment states that alleles for different traits are distributed to sex cells and offspring independently of one another.
Test Cross
- A test cross is a cross between an individual of unknown genotype and a homozygous recessive individual.
- The test cross is used to determine the genotype of an individual.
Dihybrid Cross
- A dihybrid cross is a cross between two plants that differ in two traits.
- The genotype and phenotype ratios of a dihybrid cross can be predicted using the laws of Mendel.
Test your knowledge on monohybrid crosses involving seed shape traits. Understand how traits are inherited and expressed in the second filial generation through different genetic combinations.
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