Biology Mendelian Inheritance Patterns Flashcards
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Read the first 7 Biology Mendelian Inheritance Patterns flashcards as text
In a dihybrid cross between two heterozygous parents (AaBb × AaBb), what fraction of offspring are expected to be homozygous recessive for both traits (aabb)?
Answer: 1/16
Each trait independently produces 1/4 homozygous recessive offspring, so (1/4)(1/4) = 1/16 for both.
A man with blood type A (genotype I^A i) and a woman with blood type B (genotype I^B i) have children. What is the probability that a child will have blood type O?
Answer: 1/4
The cross I^A i × I^B i produces I^A I^B, I^A i, I^B i, and ii in equal 1/4 proportions, so 1/4 will be type O.
Which of the following best describes the concept of 'gene interaction' in the context of epistasis?
Answer: One gene masks or modifies the expression of another gene
Epistasis occurs when one gene's alleles suppress or alter the phenotypic expression of a different gene.
A plant with red flowers (RR) is crossed with a white-flowered plant (rr), producing all pink offspring (Rr). This pattern of inheritance is an example of:
Answer: Incomplete dominance
Incomplete dominance produces an intermediate phenotype (pink) because neither allele is fully dominant over the other.
In humans, the allele for attached earlobes (a) is recessive to free earlobes (A). Two parents with free earlobes have a child with attached earlobes. What are the genotypes of the parents?
Answer: Aa × Aa
Both parents must be Aa (carriers) to produce an aa child while themselves expressing the dominant phenotype.
The law of segregation states that:
Answer: Allele pairs separate during gamete formation so each gamete carries only one allele per gene
Mendel's law of segregation holds that the two alleles of a gene separate during meiosis, with each gamete receiving one allele.
If a trait is autosomal recessive, which of the following pedigree observations would be INCONSISTENT with that inheritance pattern?
Answer: An affected father passing the trait directly to all sons
An autosomal recessive trait is not sex-linked, so an affected father does NOT pass it to all sons — sons must also inherit a recessive allele from the mother.