PCAT Genetics Flashcards
6 cards from real PCAT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 PCAT Genetics flashcards as text
If a carrier mother (X^A X^a) and a normal father (X^A Y) have sons, what percentage of sons will express the X-linked recessive trait?
Answer: 50%
Sons inherit their single X chromosome only from the mother; half of her X chromosomes carry the recessive allele, so 50% of sons are affected.
Which term describes the observable physical characteristics of an organism?
Answer: Phenotype
The phenotype is the physical expression of an organism's genetic information, influenced by both genotype and environment.
What is the specific location of a gene on a chromosome called?
Answer: Locus
A locus is the fixed chromosomal position of a gene; alleles are the alternative versions of the gene found at that locus.
Which nitrogenous base pairs with adenine in a DNA double helix?
Answer: Thymine
In DNA, adenine (A) pairs with thymine (T) via two hydrogen bonds, while guanine pairs with cytosine via three hydrogen bonds.
What term describes an organism that carries two identical alleles at a particular gene locus?
Answer: Homozygous
A homozygous organism carries two copies of the same allele (e.g., AA or aa) at a given locus.
During which phase of meiosis do homologous chromosome pairs separate and move to opposite poles?
Answer: Anaphase I
In Anaphase I of meiosis, homologous pairs are pulled apart to opposite poles, halving the chromosome number.