Question

What is the purpose of controlling the environment when testing a hypothesis?
It allows the scientist to determine the effect of the changed variable.
It allows samples and organisms to be tested under comfortable conditions.
It makes it easier for the scientist to perform the steps of the experiment.
It ensures that the scientist is undisturbed while performing the experiment.

Punnett squares are used to show possible combinations of alleles or to predict the probability of a trait occurring in offspring. A parakeet that is heterozygous for blue feathers (dominant) is crossed with a parakeet that is homozygous for white feathers (recessive).

A parakeet with white feathers. A parakeet with blue feathers.

According to the Punnett square for this cross, what percentage of offspring is predicted to have blue feathers?
25 percent
50 percent
75 percent
100 percent

Which are produced as a result of meiosis?
zygotes
chromosomes
tetrads
gametes

If the endoplasmic reticulum were removed from the cell, which organelle would not be able to function properly, and why?
mitochondria, because they rely on the ER as an energy source
ribosomes, because they receive proteins made by the ER
Golgi apparatus, because it packages proteins received from the ER
cytoplasm, because it relies on the ER for structural support

Mutations within an organism can occur in body cells or reproductive cells. Which type of mutation is seen in a sperm cell but not in a skin cell?
somatic mutation
missense mutation
nonsense mutation
germline mutation

Answer 1

1) What is the purpose of controlling the environment when testing a hypothesis?
- Answer: It allows the scientist to determine the effect of the changed variable.
- Reason: Controlling the environment keeps other factors constant so any observed effect can be attributed to the variable being tested.

2) Punnett square: heterozygous blue (dominant) x homozygous white (recessive). What percent of offspring predicted to have blue feathers?
- Answer: 50 percent.
- Reason: Cross Bb × bb yields Bb and bb offspring in a 1:1 ratio → half show the dominant blue phenotype.

3) Which are produced as a result of meiosis?
- Answer: gametes.
- Reason: Meiosis produces haploid sex cells (sperm or eggs); zygotes form by fertilization, tetrads form transiently during meiosis, chromosomes are not produced by meiosis.

4) If the endoplasmic reticulum were removed, which organelle would not be able to function properly, and why?
- Answer: Golgi apparatus, because it packages proteins received from the ER.
- Reason: The Golgi modifies, sorts, and packages proteins that are synthesized in/transported from the ER.

5) Mutation seen in a sperm cell but not in a skin cell?
- Answer: germline mutation.
- Reason: Germline mutations occur in reproductive cells and can be passed to offspring; somatic mutations occur in body (e.g., skin) cells.