DAT DAT - Dental Admission Biology: Genetics and Heredity 2

Question 1

In a testcross, an organism of unknown genotype is crossed with which individual?

Accepted Answer

A homozygous recessive individual

Answer

A testcross uses a homozygous recessive individual to reveal the genotype of an organism expressing a dominant phenotype.

Question 2

For an X-linked recessive trait, which parent passes the allele to an affected son?

Accepted Answer

Mother only

Answer

Sons inherit their single X chromosome from their mother, so an X-linked recessive trait is passed from a carrier mother to affected sons.

Question 3

A standard dihybrid cross (AaBb × AaBb) produces which classic phenotypic ratio?

Accepted Answer

9:3:3:1

Answer

The dihybrid cross produces a 9:3:3:1 phenotypic ratio when both genes show complete dominance and independent assortment.

Question 4

Genes that are physically located on the same chromosome are described as:

Accepted Answer

Linked

Answer

Linked genes reside on the same chromosome and tend to be inherited together unless separated by crossing over during meiosis.

Question 5

The recombination frequency between two genes is used to estimate:

Accepted Answer

The physical distance between genes on a chromosome

Answer

Higher recombination frequency indicates greater physical distance between genes, measured in centimorgans (cM), forming the basis of genetic maps.

DAT Practice Test