AP BIOLOGY GENETICS | COMPLETE QUESTIONS AND ANSWERS | 2025/2026
LATEST UPDATE| ALREADY GRADED A+
Which syndrome is characterized by the XO chromosome abnormality? Turner syndrome
Details: Turner syndrome is characterized by a chromosome pattern of XO, or one X
chromosome and no Y chromosome.
What kind of cell results when a diploid and a haploid gamete fuse during fertilization? A
triploid cell has three sets of chromosomes: the two from the diploid gamete and the one from
the haploid gamete
Of the following chromosomal abnormalities, which type is most likely to be viable in humans?
Trisomy
Details: Some trisomies are viable in humans, they result in developmental abnormalities, such
as Down syndrome (trisomy 21). Only humans with trisomies of the small chromosomes
(13,18,21) or the sex chromosomes survive past birth.
If a diploid cell undergoes meiosis and produces two gametes that are normal, and one with n −
1 chromosomes, and one with n + 1 chromosomes, what type of error occurred? A
nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome
migrated to the same pole of the cell.
If a diploid cell undergoes meiosis and produces two gametes with n + 1 chromosomes and two
gametes with n− 1 chromosomes, what type of error occurred? A nondisjunction error
occurred in meiosis I, in which both members of a homologous pair migrated to the same pole
of the cell.
Details: When this type of error occurs, half of the gametes receive one too many
chromosomes, and the other half receive one too few. When all of the gametes are affected,
the error probably occured in meiosis I.
, Height in humans generally shows a normal (bell-shaped) distribution. What type of inheritance
most likely determines height? A combination of polygenic inheritance and environmental
factors
Details: Several genes (polygenic inheritance) control height in humans, giving an overall normal
distribution. Environmental factors such as nutrition smooth out the curve.
Quantitative characters vary in a population along a continuum. How do such characters differ
from the characters investigated by Mendel in his experiments on peas? Quantitative
characters are due to polygenic inheritance, the additive effects of two or more genes on a
single phenotypic character. A single gene affected all but one of the pea characters studied by
Mendel.
Select the correct explanation for the fact that a carrier of a recessive genetic disorder does not
have the disorder. In a recessive disorder, only a single functioning allele is necessary to
determine a normal phenotype.
- read about degrees of dominance
When a dominant allele coexists with a recessive allele in a heterozygote individual, how do
they interact with each other? They do not interact at all.
Details: An allele is called dominant because it appears in the phenotype of a heterozygote, not
because it subdues a recessive allele.
A black guinea pig crossed with an albino guinea pig produces 12 black offspring. When the
albino is crossed with a second black one, 7 blacks and 5 albinos are obtained.
What is the best explanation for this genetic outcome? Albino (b) is a recessive trait; black
(B) is a dominant trait.
Using previous info
LATEST UPDATE| ALREADY GRADED A+
Which syndrome is characterized by the XO chromosome abnormality? Turner syndrome
Details: Turner syndrome is characterized by a chromosome pattern of XO, or one X
chromosome and no Y chromosome.
What kind of cell results when a diploid and a haploid gamete fuse during fertilization? A
triploid cell has three sets of chromosomes: the two from the diploid gamete and the one from
the haploid gamete
Of the following chromosomal abnormalities, which type is most likely to be viable in humans?
Trisomy
Details: Some trisomies are viable in humans, they result in developmental abnormalities, such
as Down syndrome (trisomy 21). Only humans with trisomies of the small chromosomes
(13,18,21) or the sex chromosomes survive past birth.
If a diploid cell undergoes meiosis and produces two gametes that are normal, and one with n −
1 chromosomes, and one with n + 1 chromosomes, what type of error occurred? A
nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome
migrated to the same pole of the cell.
If a diploid cell undergoes meiosis and produces two gametes with n + 1 chromosomes and two
gametes with n− 1 chromosomes, what type of error occurred? A nondisjunction error
occurred in meiosis I, in which both members of a homologous pair migrated to the same pole
of the cell.
Details: When this type of error occurs, half of the gametes receive one too many
chromosomes, and the other half receive one too few. When all of the gametes are affected,
the error probably occured in meiosis I.
, Height in humans generally shows a normal (bell-shaped) distribution. What type of inheritance
most likely determines height? A combination of polygenic inheritance and environmental
factors
Details: Several genes (polygenic inheritance) control height in humans, giving an overall normal
distribution. Environmental factors such as nutrition smooth out the curve.
Quantitative characters vary in a population along a continuum. How do such characters differ
from the characters investigated by Mendel in his experiments on peas? Quantitative
characters are due to polygenic inheritance, the additive effects of two or more genes on a
single phenotypic character. A single gene affected all but one of the pea characters studied by
Mendel.
Select the correct explanation for the fact that a carrier of a recessive genetic disorder does not
have the disorder. In a recessive disorder, only a single functioning allele is necessary to
determine a normal phenotype.
- read about degrees of dominance
When a dominant allele coexists with a recessive allele in a heterozygote individual, how do
they interact with each other? They do not interact at all.
Details: An allele is called dominant because it appears in the phenotype of a heterozygote, not
because it subdues a recessive allele.
A black guinea pig crossed with an albino guinea pig produces 12 black offspring. When the
albino is crossed with a second black one, 7 blacks and 5 albinos are obtained.
What is the best explanation for this genetic outcome? Albino (b) is a recessive trait; black
(B) is a dominant trait.
Using previous info
