An onion body cell has 16 chromosomes arranged in 8 matching pairs. Where did the two chromosomes in each pair come from?

A person's liver cell and skin cell carry exactly the same DNA, yet they build different proteins and do different jobs. What best explains the difference?

A horse body cell contains 64 chromosomes. How many chromosomes are in one of that horse's sperm cells?

In dogs, a stretch of DNA at one position on a chromosome carries the instructions for coat length. What is this stretch of DNA called?

In a mouse, a gene on one chromosome carries instructions that fur cells use to build the molecule making dark pigment. What kind of molecule is built from those instructions?

A gardener cuts a tomato plant back so it stays short all summer. Seeds from that plant grow into tall plants. What does this show?

A parrot learns to copy its owner's whistle, and it also has bright green feathers. Which will it pass on to its chicks?

Order these three from largest to smallest: chromosome, gene, nucleus.

A strawberry plant sends out a runner that roots and grows into a new plant. How do the new plant's genes compare with the parent plant's genes?

A hydra in a pond grows a small bud on its side that breaks away and lives on its own. What kind of reproduction is this, and what does it produce?

A litter of puppies from the same two parents includes black, brown and spotted pups. What best explains the differences among them?

One bacterium is placed alone in a dish of nutrients, and a day later the dish is covered with millions of cells. What advantage of asexual reproduction does this show?

Aphids reproduce asexually all summer. In autumn, as cold weather arrives, they reproduce sexually instead. How does that switch help the population?

A greenhouse holds hundreds of orchids all grown as cuttings from one plant. A single fungus kills every one of them. Why did none survive?

Sea stars can regrow a whole body from a broken arm. A biologist finds two sea stars in one bay whose DNA is identical. What most likely happened?

A gardener wants every new rose bush to have exactly the same flower color as one prize bush. Which method should the gardener use?

In one person, a change to a single DNA base swaps one amino acid in a blood protein, and the protein's shape changes so it carries oxygen poorly. How is this mutation best described?

A mutation appears in the DNA of one skin cell on a woman's arm after years of sun exposure. Will her children inherit this mutation?

In a sprayed potato field, one beetle carries a mutation whose protein breaks down the pesticide, and its descendants become common. How is this mutation best described in this field?

A mutation changes one DNA base in a stretch of a plant's DNA that codes for no protein at all. What effect on the plant's traits is expected?

A mutation makes a cell stop building a protein partway, so the finished protein is missing the end that normally binds sugar. What is the likely result?

Students list mutations found in one fly population: several change no trait, one weakens a wing protein, and one improves a digestive enzyme. What does this list show about mutations?

Seeds are treated with radiation, and one grows into a plant with a flower color never seen in that species. What happened inside the seed's cells?

A mutation stops a corn plant's cells from building the protein that makes purple pigment in its kernels. What will those kernels look like?

Two purple-flowered pea plants are crossed, and some of their offspring have white flowers. What does this show about the two parents?

A pea plant carries the alleles Tt and grows a tall stem. Which word names the tall stem you can observe?

White-flowered plants of one species crossed with each other produce only white-flowered offspring, generation after generation. What does this indicate about the plants' alleles for flower color?

A guinea pig carries one allele for black coat (B) and one allele for white coat (b). Which word describes this pair of alleles?

In rabbits, fur color is controlled by one gene. A rabbit inherits fur-color alleles from its mother and its father. How many alleles for that gene does the rabbit have?

A black guinea pig may be BB or Bb, because black (B) is dominant to white (b). Which cross would reveal which genotype it has?

A pea plant carries one allele for round seeds and one for wrinkled seeds, and its seeds are round. What does this show about the round allele?

Two organisms that look the same for one trait must carry the same pair of alleles for it.

In rabbits, black fur (B) is dominant to brown fur (b). A Bb rabbit is crossed with a bb rabbit. What fraction of the offspring is expected to have brown fur?

In pea plants, tall (T) is dominant to short (t). Two Tt plants are crossed. What fraction of the offspring is expected to be tall?

A Punnett square for a cross between two Gg guinea pigs has four boxes. How many of those boxes show the genotype gg?

In cattle, black coat (B) is dominant to red coat (b). A BB bull is crossed with a bb cow. What genotype will all of the calves have?

Two Rr pea plants have already produced three round-seeded offspring in a row. What is the probability that the next offspring has wrinkled seeds?

A tall pea plant is crossed with a short pea plant, where tall (T) is dominant to short (t). Every offspring is tall. What was the tall parent's genotype most likely?

A Punnett square predicts the probability of each outcome rather than the exact traits of every individual offspring.

A white-flowered (pp) plant is crossed with a purple-flowered plant, and about half of their offspring are white. What is the purple parent's genotype?