Mendel's work on inheritance went largely unnoticed until it was rediscovered around 1900.
Correct Answer
True
True. Mendel published his pea results in the 1860s, but the scientific community largely ignored them until other scientists rediscovered the work in 1900.
Category: Mendel's Experiments
Question 2
In Mendel's flower color crosses, the white trait disappeared in the F1 generation and never reappeared in later generations.
Correct Answer
False
False. The white trait was hidden in the F1 generation but reappeared in the F2 generation, in about one quarter of the plants.
Category: Mendel's Experiments
Question 3
Mendel obtained the same results whether the violet-flowered plant or the white-flowered plant supplied the pollen.
Correct Answer
True
True. Mendel performed reciprocal crosses, switching which parent provided the pollen, and the offspring ratios were the same, showing the traits did not depend on the sex of the parent.
Category: Mendel's Experiments
Question 4
Mendel studied traits that showed continuous variation, such as a wide range of plant heights.
Correct Answer
False
False. Mendel chose traits with discontinuous variation, which appear in clearly distinct forms, such as tall or dwarf plants and violet or white flowers.
Category: Mendel's Experiments
Question 5
Mendel studied seven characteristics of pea plants, each of which appeared in two contrasting forms.
Correct Answer
True
True. Mendel tracked seven characteristics, including flower color, seed color, seed texture and plant height, and each had two clearly different forms.
Category: Mendel's Experiments
Question 6
Mendel's pea plants took several years to reach maturity.
Correct Answer
False
False. Garden peas mature within one growing season, which let Mendel follow several generations in a relatively short time.
Category: Mendel's Experiments
Question 7
A recessive trait is expressed only when an individual has no dominant allele for that gene.
Correct Answer
True
True. A dominant allele hides a recessive one in a heterozygote, so the recessive trait appears only in individuals that are homozygous recessive.
Category: Genetic Terms
Question 8
An organism's phenotype includes the alleles it carries but does not express.
Correct Answer
False
False. The genotype includes all of an organism's alleles, expressed or not; the phenotype is only the observable traits.
Category: Genetic Terms
Question 9
In a Punnett square, the possible gametes of each parent are listed along the top and side, and each box shows a possible offspring genotype.
Correct Answer
True
True. A Punnett square combines every possible gamete from one parent with every possible gamete from the other to show the expected offspring genotypes and their frequencies.
Category: Monohybrid Crosses
Question 10
Crossing a homozygous dominant individual with a homozygous recessive individual produces dominant and recessive offspring in a 1:1 ratio.
Correct Answer
False
False. Every offspring of such a cross is heterozygous and shows the dominant trait; a 1:1 ratio appears only when the dominant-looking parent is heterozygous.
Category: Monohybrid Crosses
Question 11
The F2 offspring of a monohybrid cross between true-breeding parents show a genotypic ratio of 1:2:1.
Correct Answer
True
True. Self-crossing the heterozygous F1 gives one homozygous dominant to two heterozygous to one homozygous recessive offspring.
Category: Monohybrid Crosses
Question 12
Mendel's law of dominance states that in a heterozygote, the two traits blend into an intermediate form.
Correct Answer
False
False. The law of dominance states that in a heterozygote one trait conceals the other, so only the dominant trait is seen; recessive traits appear only in homozygous recessive individuals.
Category: Laws of Inheritance
Question 13
The farther apart two genes are on a chromosome, the less often crossing over separates them.
Correct Answer
False
False. Greater distance between genes gives more room for crossovers, so distant genes are separated more often; this is why recombination frequency can be used to map genes.
Category: Gene Interactions
Question 14
A population can contain many alleles of a gene, even though each diploid individual carries at most two.
Correct Answer
True
True. A diploid organism has only two copies of each gene, one on each homolog, but across a population there can be many different alleles, as with the three ABO alleles.
Category: Dominance Variations
Question 15
In epistasis, two alleles of the same gene blend to produce an intermediate phenotype.
Correct Answer
False
False. Epistasis is an interaction between different genes, in which one gene masks or interferes with another; an intermediate phenotype from two alleles of one gene is incomplete dominance.
Category: Gene Interactions
Question 16
In fruit flies, the red-eye allele is the wild type and is dominant to the white-eye allele.
Correct Answer
True
True. In Drosophila, red eye color is the wild type and is dominant to white; the gene is carried on the X chromosome.
Category: Sex-Linked Traits
Question 17
Thomas Hunt Morgan identified the first X-linked trait, an eye color gene, in garden peas.
Correct Answer
False
False. Morgan identified the first X-linked trait, eye color, in the fruit fly Drosophila melanogaster.
Category: Sex-Linked Traits
Question 18
X-linked recessive disorders such as hemophilia appear more often in males than in females.
Correct Answer
True
True. A male has only one X chromosome, so a single recessive allele causes the disorder, while a female needs two copies.
Category: Sex-Linked Traits
Question 19
A mother who is homozygous for an X-linked recessive allele passes it to half of her sons.
Correct Answer
False
False. Both of her X chromosomes carry the allele, so she passes it to all of her sons, and every son will show the trait.
Category: Sex-Linked Traits
Question 20
In birds, females have the nonmatching pair of sex chromosomes, so recessive sex-linked traits appear more often in females.
Correct Answer
True
True. In birds the sex chromosome pattern is reversed compared with mammals, so the female is the sex with one copy of sex-linked genes and shows recessive sex-linked traits more often.
Category: Sex-Linked Traits