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Questions and Answers
A tall plant of unknown genotype is test-crossed (meaning it is crossed with a recessive tt plant). Of the offspring, 869 are dwarf and 912 are tall. What is the genotype of the unknown parent, is it TT or Tt? Show the cross to prove it.
A tall plant of unknown genotype is test-crossed (meaning it is crossed with a recessive tt plant). Of the offspring, 869 are dwarf and 912 are tall. What is the genotype of the unknown parent, is it TT or Tt? Show the cross to prove it.
The genotype of the unknown parent is Tt.
In humans, tongue rolling is a dominant trait, those with the recessive condition cannot roll their tongues. Bob can roll his tongue, but his mother could not. He is married to Sally, who cannot roll her tongue. What is the probability that their first born child will not be able to roll his tongue?
In humans, tongue rolling is a dominant trait, those with the recessive condition cannot roll their tongues. Bob can roll his tongue, but his mother could not. He is married to Sally, who cannot roll her tongue. What is the probability that their first born child will not be able to roll his tongue?
50%
In goats, a recessive gene causes the goats to "faint" when they are startled. A farmer breeds two goats (that have never fainted) and their first offspring faints two days after its birth. What must the parent's genotypes have been? Show the cross to prove it.
In goats, a recessive gene causes the goats to "faint" when they are startled. A farmer breeds two goats (that have never fainted) and their first offspring faints two days after its birth. What must the parent's genotypes have been? Show the cross to prove it.
Both parents are heterozygous (Ff).
What parent genotypes are needed to result in 100% fainting goats?
What parent genotypes are needed to result in 100% fainting goats?
What parent genotypes will result in 1/4 of offspring being fainting goats?
What parent genotypes will result in 1/4 of offspring being fainting goats?
In guinea pigs, black eyes are dominant to red eyes. A male guinea pig that is heterozygous is crossed with a female that is eyed. What are the expected phenotypes of their offspring and in what proportion?
In guinea pigs, black eyes are dominant to red eyes. A male guinea pig that is heterozygous is crossed with a female that is eyed. What are the expected phenotypes of their offspring and in what proportion?
If out of 100 offspring 52 have red eyes and 48 have brown eyes, what are the probable genotypes AND phenotypes of the parents?
If out of 100 offspring 52 have red eyes and 48 have brown eyes, what are the probable genotypes AND phenotypes of the parents?
What is the genotype of the parent needed to produce 75% black eyed offspring when crossed with a heterozygous black eyed parent?
What is the genotype of the parent needed to produce 75% black eyed offspring when crossed with a heterozygous black eyed parent?
Flashcards
Test Cross
Test Cross
Mating an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype.
Genotype
Genotype
The genetic makeup of an organism, describing the alleles it carries for a particular trait.
Incomplete Dominance
Incomplete Dominance
When heterozygotes display a blended phenotype, neither allele is completely dominant.
Codominance
Codominance
When both alleles in a heterozygote are fully expressed, resulting in a phenotype that shows both traits.
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Phenotype
Phenotype
A display of traits or characteristics.
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Heterozygous
Heterozygous
Having two different alleles for a trait (e.g., Tt).
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Homozygous
Homozygous
Having two identical alleles for a trait (e.g., TT or tt).
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Dominant Trait
Dominant Trait
A trait that is expressed even when only one copy of the corresponding allele is present.
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Recessive Trait
Recessive Trait
A trait that is only expressed when two copies of the corresponding allele are present.
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- These notes cover monohybrid cross problems, incomplete dominance, codominance traits, and dihybrid cross practice problems
Monohybrid Cross Problems
- A tall plant with an unknown genotype is test-crossed with a recessive tt plant
- 869 of the offspring are dwarf and 912 are tall
- Need to determine the genotype of the unknown parent (TT or Tt) by showing the cross
- Tongue rolling is a dominant trait in humans, and the recessive condition means a person cannot roll their tongue
- Bob can roll his tongue, but his mother cannot
- He is married to Sally, who cannot roll her tongue
- Need to find the probability that their firstborn child will not be able to roll his tongue
- In goats, a recessive gene causes them to "faint" when startled
- A farmer breeds two goats (that have never fainted), but their first offspring faints two days after its birth
- Need to determine the parents' genotypes by showing the cross
- Task: Determine the parent genotypes needed to result in 100% fainting goats
- Task: Determine what parent genotypes will result in ¼ of offspring being fainting goats
- In guinea pigs, black eyes are dominant to red eyes
- A male guinea pig that is heterozygous is crossed with a female that has red eyes
- Need to find the expected phenotypes of their offspring and in what proportion
- Out of 100 offspring, 52 have red eyes and 48 have brown eyes
- Need to determine the probable genotypes and phenotypes of the parents
- Need to determine the genotype of the parent needed to produce 75% black-eyed offspring when crossed with a heterozygous black-eyed parent
Wizarding Genetics: Incomplete + Codominant Traits
Mandrakes
- Mandrakes can be yellow, blue, and green
- Y represents a yellow allele
- B represents a blue allele
- Yellow genotype: YY
- Blue genotype: BB
- Green genotype: BY
- A yellow Mandrake (YY) is crossed with a blue Mandrake (BB)
- Determine the chances of a yellow, blue, and green mandrake
- Determine if this is an example of incomplete or codominance
Merpeople
- Merpeople tails can be blue, green, or blue & green
- B represents the blue allele
- G represents the green allele
- Blue genotype: BB
- Green genotype: GG
- Blue & Green genotype: BG
- Cross a merperson with a green tail (GG) with a merperson with a blue/green tail (BG)
- Determine the chances of a merchild with a blue and green tail.
Phoenix
- Phoenix colors are red (R), blue (B), and purple
- A purple phoenix mates with a red phoenix
- Determine the possible offspring
House Elves
- House-elves can be tan, green, or spotted (tan with green spots)
- Dobby is tan, and Winky is spotted
- Determine the possible children
- Determine the probability that children will be spotted like Winky
- Determine the probability that children will be green like Winky's mother
Genetic Inheritance
- Hagrid's father was a 6-foot wizard
- Hagrid's mother was a 20-foot giantess
- Hagrid is 12 feet
- Task: Determine what type of genetic inheritance best describes how Hagrid's height was acquired (incomplete or codominance)
Dihybrid Crosses Practice Problems
Dobby and Dabbin
- Dobby the House Elf falls for Dabbin'
- Dobby's pointed ears are dominant, and he is heterozygous for ear shape
- Dabbin's ears are round
- Dobby's long nose is a recessive trait
- Dabbin is homozygous dominant for her stubby nose
- Determine the probability of having an elf child with a stubby nose and pointed ears using a Punnett square
Hagrid and Cerberus
- Hagrid is breeding Cerberus, his 3-headed dog
- Having three heads is dominant over having 2 heads
- Having chocolate brown fur is dominant to yellow fur
- Cerberus is heterozygous for both traits
- A female is also heterozygous for both traits
- Determine the expected frequency of 2-headed, yellow-furred dogs using a Punnett square
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