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Questions and Answers
What is the cause of colour blindness?
What is the cause of colour blindness?
Which gender is more commonly affected by colour blindness?
Which gender is more commonly affected by colour blindness?
Individuals with colour blindness are unable to distinguish which shades?
Individuals with colour blindness are unable to distinguish which shades?
Colour blindness is a genetic condition linked to which chromosome?
Colour blindness is a genetic condition linked to which chromosome?
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Which genetic pattern of inheritance does colour blindness follow?
Which genetic pattern of inheritance does colour blindness follow?
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Which alleles are codominant with each other?
Which alleles are codominant with each other?
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Which blood type is possible for an individual with IAi genotype?
Which blood type is possible for an individual with IAi genotype?
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Which blood type results from the genotype ii?
Which blood type results from the genotype ii?
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What is the relationship of the O allele in blood type inheritance?
What is the relationship of the O allele in blood type inheritance?
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Which genes are most commonly associated with sex-linked traits?
Which genes are most commonly associated with sex-linked traits?
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What genotype corresponds to females?
What genotype corresponds to females?
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Which condition is caused by a recessive gene on the X chromosome?
Which condition is caused by a recessive gene on the X chromosome?
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What is a common consequence of hemophilia?
What is a common consequence of hemophilia?
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What is the result of incomplete dominance in the F1 generation?
What is the result of incomplete dominance in the F1 generation?
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In codominance, what is the phenotypic expression of heterozygous alleles?
In codominance, what is the phenotypic expression of heterozygous alleles?
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Which of the following examples represents incomplete dominance?
Which of the following examples represents incomplete dominance?
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How are alleles typically represented in incomplete dominance?
How are alleles typically represented in incomplete dominance?
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What does the 'R' and 'R'' notation represent in incomplete dominance?
What does the 'R' and 'R'' notation represent in incomplete dominance?
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How many different alleles can exist for a gene showing multiple alleles?
How many different alleles can exist for a gene showing multiple alleles?
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Which blood type system is an example of multiple alleles in humans?
Which blood type system is an example of multiple alleles in humans?
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Which of the following is represented by two capital letters indicating codominant alleles?
Which of the following is represented by two capital letters indicating codominant alleles?
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Study Notes
ABO Blood Type
- ABO blood type follows both codominant and dominant inheritance patterns
- The A and B alleles are codominant with each other, while both are dominant over the O allele
- The O allele is recessive
ABO Blood Type Genes and Alleles
- The blood type gene is represented by the letter I
- The I gene has three alleles: IA, IB, and i
- The alleles are expressed in heterozygous individuals, resulting in different blood types
- The possible blood types are:
- A: IAIA or IAi
- B: IBIB or IBi
- AB: IAIB
- O: ii
Mendel's Luck
- Mendel's experiments were successful because he studied traits in garden peas that behaved simply
- These traits were not linked or lethal, had only two alleles, and displayed complete dominance
- Other scientists, including Darwin, were conducting similar experiments, but they were using species with more complex patterns of heredity
Sex-linked Traits
- Traits are located on the sex chromosomes, X and Y
- Females have an XX genotype, while males have an XY genotype
- Many sex-linked traits are carried on the X chromosome
Hemophilia
- Hemophilia is a recessive gene on the X chromosome that causes a bleeding disorder
- There are approximately 20,000 hemophilia patients in the United States
- The severity of hemophilia is related to the amount of clotting factor in the blood
- About 70% of hemophilia patients have severe hemophilia, with less than 1% of the normal amount of clotting factor
Color Blindness
- Color blindness is a recessive sex-linked condition caused by a lack of color receptors in the eye
- It results in an inability to see some colors correctly
- Color blindness is more common in males
- Individuals with color blindness are unable to distinguish between certain shades of red and green
Exceptions to Mendel's Laws
- Incomplete dominance: alleles appear blended in the phenotype
- Codominance: both alleles are expressed equally
- Multiple alleles: some genes have more than two alleles
Incomplete Dominance
- Incomplete dominance occurs when neither allele is fully dominant over the other
- The two alleles are represented as two capital letters, one with an apostrophe to indicate the different allele
- Example: snapdragons (flower)
- F1 hybrids have an appearance that is a mixture of the two parental varieties
Codominance
- Codominance occurs when both alleles of a gene are dominant and the heterozygous phenotype has both traits equally expressed
- The two alleles are represented as two capital letters: the first letter of one trait and the first letter of the other trait
- Example: ABO blood type
Multiple Alleles
- Blood type is an example of multiple alleles, with three alleles: A, B, and O
- Each person has two of these alleles in their DNA
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Description
Learn about the inheritance patterns of ABO blood types, including codominant and dominant relationships between alleles and the resulting blood types.
