DAT - Dental Admission Biology: Genetics and Heredity Flashcards
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In a testcross, an organism of unknown genotype is crossed with which individual?
Answer: A homozygous recessive individual
A testcross uses a homozygous recessive individual to reveal the genotype of an organism expressing a dominant phenotype.
For an X-linked recessive trait, which parent passes the allele to an affected son?
Answer: Mother only
Sons inherit their single X chromosome from their mother, so an X-linked recessive trait is passed from a carrier mother to affected sons.
A standard dihybrid cross (AaBb × AaBb) produces which classic phenotypic ratio?
Answer: 9:3:3:1
The dihybrid cross produces a 9:3:3:1 phenotypic ratio when both genes show complete dominance and independent assortment.
Genes that are physically located on the same chromosome are described as:
Answer: Linked
Linked genes reside on the same chromosome and tend to be inherited together unless separated by crossing over during meiosis.
The recombination frequency between two genes is used to estimate:
Answer: The physical distance between genes on a chromosome
Higher recombination frequency indicates greater physical distance between genes, measured in centimorgans (cM), forming the basis of genetic maps.
Human skin color is determined by multiple genes contributing to a continuous range of phenotypes — this is an example of:
Answer: Polygenic inheritance
Polygenic inheritance involves multiple genes each contributing to a trait, producing a continuous bell-curve distribution of phenotypes in a population.