Podcast
Questions and Answers
In snapdragons, red flowers (RR) crossed with white flowers (WW) produce pink flowers (RW). What phenotypic ratio is expected from a cross between two pink snapdragons?
In snapdragons, red flowers (RR) crossed with white flowers (WW) produce pink flowers (RW). What phenotypic ratio is expected from a cross between two pink snapdragons?
- All pink
- 3 red : 1 white
- 1 red : 1 pink : 1 white
- 1 red : 2 pink : 1 white (correct)
Which of the following scenarios best illustrates a polygenic trait?
Which of the following scenarios best illustrates a polygenic trait?
- A cat has either black or orange fur, determined by a single gene on the X chromosome.
- Human height shows a continuous range of variation, influenced by multiple genes. (correct)
- A certain butterfly species exhibits two distinct wing patterns, with one pattern completely dominant over the other.
- A plant species has three possible flower colors: red, white, and pink.
In a species of chickens, the allele for black feathers (B) and the allele for white feathers (W) are codominant. What would be the expected outcome if you cross a black chicken (BB) with a white chicken (WW)?
In a species of chickens, the allele for black feathers (B) and the allele for white feathers (W) are codominant. What would be the expected outcome if you cross a black chicken (BB) with a white chicken (WW)?
- All offspring will be black (BB).
- All offspring will be gray (BW). (correct)
- All offspring will be white (WW).
- 50% of offspring will be black (BB) and 50% will be white (WW).
A farmer crosses two breeds of chickens. One breed has red feathers (RR) and the other has yellow feathers (YY). Heterozygous offspring (RY) display orange feathers. If the farmer crosses two orange-feathered chickens, what percentage of their offspring will also have orange feathers?
A farmer crosses two breeds of chickens. One breed has red feathers (RR) and the other has yellow feathers (YY). Heterozygous offspring (RY) display orange feathers. If the farmer crosses two orange-feathered chickens, what percentage of their offspring will also have orange feathers?
In cattle, coat color exhibits codominance. Red coats are (RR), white coats are (WW), and roan coats (a mix of red and white hairs) are (RW). If a farmer breeds a roan cow with a white bull, what is the probability that their calf will have a red coat?
In cattle, coat color exhibits codominance. Red coats are (RR), white coats are (WW), and roan coats (a mix of red and white hairs) are (RW). If a farmer breeds a roan cow with a white bull, what is the probability that their calf will have a red coat?
Flashcards
Incomplete Dominance
Incomplete Dominance
Traits where heterozygotes show a blended phenotype, neither allele is dominant.
Polygenic Traits
Polygenic Traits
Traits controlled by multiple genes, leading to a wide range of phenotypes.
Codominance
Codominance
Both alleles are fully expressed in the phenotype.
Incomplete Dominance Example
Incomplete Dominance Example
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Codominance Example
Codominance Example
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Study Notes
Variations on Mendel Laws
- Some traits do not follow Mendelian genetics rules
- Some traits cannot be put into a Punnett Square to predict the offspring
Polygenic Traits
- Polygenic traits are controlled by two or more genes and can be called polyallelic
- A wide range of phenotypes is usually present
- Examples include: hair color, eye color, and skin color
Incomplete Dominance
- Traits are neither dominant nor recessive
- The heterozygous always blends in the colors
- Examples of blends: purple x white results in lavender, and red x yellow results in orange
Example problem
- In snapdragons, red flowers crossed with yellow flowers produce orange flowers
- Example: If a red snapdragon is crossed with an orange snapdragon, predict the offspring
Traits
- RR = red
- YY = yellow
- RY = orange
Parents
- RR x RY
- RR, RR, RY, RY
- 2/4 offspring will be red
- 2/4 offspring will be orange
Codominance
- Both genes or forms of the alleles are expressed
- This is seen in animals with multiple colors, such as chickens, calico cats, and zebras
- Human blood type is codominant
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Description
Explore non-Mendelian genetics including polygenic traits, where multiple genes influence phenotypes like hair or skin color and incomplete dominance, where heterozygous offspring show blended traits. Includes an example problem on predicting offspring color from snapdragon crosses.
