Question 1

Which of the following best explains how a change in the DNA nucleotide sequence can result in a nonfunctional protein?

Accepted Answer

A change in the DNA sequence can alter the mRNA codons, which may result in a different amino acid sequence and thus a protein with altered structure and function.

Question 2

Given the DNA template strand sequence TAC-GGA-CTT, what is the complementary mRNA sequence produced during transcription?

Accepted Answer

AUG-CCU-GAA

Question 3

Which process ensures that daughter cells produced during mitosis have the same chromosome number and genetic information as the parent cell?

Accepted Answer

DNA replication occurs before mitosis, ensuring each daughter cell receives an identical set of chromosomes.

Question 4

A model shows cells dividing rapidly without responding to normal cell-cycle checkpoints. What is a likely consequence for the organism?

Accepted Answer

Uncontrolled cell division can lead to tumor formation and possibly cancer.

Question 5

Which of the following is the correct word equation for photosynthesis?

Accepted Answer

carbon dioxide + water $$\rightarrow$$ glucose + oxygen

Question 6

A plant receives sufficient water and light, but the amount of carbon dioxide available decreases. What is the most likely effect on photosynthesis?

Accepted Answer

The rate of photosynthesis will decrease because carbon dioxide is a reactant required to produce glucose.

Question 7

Which of the following best explains why organisms need elements such as nitrogen, phosphorus, or sulfur in addition to carbon, hydrogen, and oxygen?

Accepted Answer

These elements are required to build proteins and nucleic acids, which cannot be formed from carbon, hydrogen, and oxygen alone.

Question 8

Which of the following is the correct word equation for aerobic cellular respiration?

Accepted Answer

glucose + oxygen $$\rightarrow$$ carbon dioxide + water + energy (ATP)

Question 9

During intense exercise, muscle cells may not receive enough oxygen. How do these cells continue to produce ATP, and why is this process less efficient?

Accepted Answer

They switch to anaerobic respiration (fermentation), which produces less ATP per glucose molecule because it does not fully break down glucose.

Question 10

A pond's fish population rises from 100 to 250, then falls to 140 after a drought. What is the most likely explanation for this change?

Accepted Answer

The drought reduced water availability, lowering the pond's carrying capacity and causing a decrease in the fish population.

Question 11

Which of the following best describes how photosynthesis and cellular respiration contribute to the cycling of carbon in ecosystems?

Accepted Answer

Photosynthesis removes carbon dioxide from the atmosphere and incorporates it into glucose, while cellular respiration releases carbon dioxide back into the atmosphere.

Question 12

Which of the following human activities can reduce biodiversity, and how does it affect an ecosystem?

Accepted Answer

Habitat destruction reduces available living space, leading to population declines and possible extinction.

Question 13

How can meiosis and sexual reproduction result in offspring with genetic combinations different from either parent?

Accepted Answer

Meiosis involves crossing over and independent assortment, creating new combinations of alleles in gametes, which combine during fertilization.

Question 14

A scientist finds a heritable trait in a population that was not observed in earlier generations. Which two genetic sources could explain this variation?

Accepted Answer

A new mutation or a new combination of alleles from sexual reproduction; genetic analysis can distinguish between a novel mutation and recombination.

Question 15

In pea plants, tallness (T) is dominant to shortness (t). If two heterozygous plants (Tt × Tt) are crossed, what are the expected genotype and phenotype ratios?

Accepted Answer

Genotype ratio: 1 TT : 2 Tt : 1 tt; Phenotype ratio: 3 tall : 1 short

Question 16

Two parents are heterozygous for a recessive condition (Aa × Aa). What is the probability that their child will have the genotype aa?

Accepted Answer

25% ($$\frac{1}{4}$$), as shown by a Punnett square with one aa out of four possible combinations.

Question 17

Which of the following best explains how environmental factors can influence the expression of traits in a population?

Accepted Answer

Environmental factors such as temperature, nutrition, or sunlight can affect gene expression, leading to variation in phenotypes even among individuals with the same genotype.

Question 18

Which of the following is NOT a correct pairing of a biological macromolecule with one of its primary functions?

Accepted Answer

Carbohydrates: form cell membranes

Question 19

A student claims that plants use glucose only for energy and cannot use it to build cellular structures. Which scientific reasoning best refutes this claim?

Accepted Answer

Plants use glucose as a building block to synthesize cellulose for cell walls and other macromolecules, not just for energy.

Biology 1 Test #4 Study Guide – Step-by-Step Guidance

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