PCAT PCAT Genetics

Question 1

What is the probability of two heterozygous parents (Aa × Aa) producing a homozygous recessive offspring?

Accepted Answer

25%

Answer

In a monohybrid cross of Aa × Aa, the offspring ratio is 1 AA : 2 Aa : 1 aa, giving a 25% chance of the aa genotype.

Question 2

Which type of mutation involves the insertion or deletion of a nucleotide that causes a shift in the reading frame?

Accepted Answer

Frameshift mutation

Answer

Frameshift mutations result from insertions or deletions that shift the codon reading frame, altering all downstream amino acids.

Question 3

In incomplete dominance, what is the phenotype of a heterozygous individual?

Accepted Answer

An intermediate phenotype

Answer

Incomplete dominance produces a blended intermediate phenotype in heterozygotes, such as pink flowers from red and white parents.

Question 4

What term describes genes located on the same chromosome that tend to be inherited together?

Accepted Answer

Linked genes

Answer

Linked genes are physically located on the same chromosome and are transmitted together unless separated by crossing over.

Question 5

Which RNA molecule carries genetic information from the nucleus to the ribosomes?

Accepted Answer

mRNA

Answer

Messenger RNA (mRNA) is transcribed from DNA in the nucleus and carries the coding sequence to ribosomes for translation.

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