BMST BMST - Basic Math and Science Genetics and Heredity Questions and Answers 5 — Questions and Answers
Question 1: In incomplete dominance, a red-flowered plant (RR) is crossed with a white-flowered plant (WW). What color will the F1 flowers be?
- Red
- White
- Pink (Correct answer)
- Spotted red and white
Correct answer: Pink
In incomplete dominance, heterozygotes (RW) show an intermediate phenotype, producing pink flowers.
Question 2: A mutation in a somatic cell (non-reproductive body cell) is:
- Always passed to offspring
- Never passed to offspring
- Passed only to female offspring
- Passed only through mitosis to daughter cells of that cell (Correct answer)
Correct answer: Passed only through mitosis to daughter cells of that cell
Somatic mutations affect only the cells that descend from the mutant cell via mitosis; they are not transmitted to the next generation.
Question 3: The law of independent assortment states that:
- Alleles for the same gene always separate together
- Genes on the same chromosome never separate
- Alleles of different genes are distributed independently during gamete formation (Correct answer)
- Dominant alleles mask recessive alleles in heterozygotes
Correct answer: Alleles of different genes are distributed independently during gamete formation
Mendel's law of independent assortment states that alleles of different genes segregate independently of one another during gamete formation.
Question 4: Which of the following best describes a test cross?
- Crossing two homozygous dominant individuals
- Crossing an organism of unknown genotype with a homozygous recessive individual (Correct answer)
- Crossing two F1 heterozygotes to produce F2 offspring
- Crossing two organisms of known genotype to confirm Mendel's ratios
Correct answer: Crossing an organism of unknown genotype with a homozygous recessive individual
A test cross reveals the unknown genotype by mating the organism with a homozygous recessive individual and analyzing the offspring.
Question 5: Down syndrome (Trisomy 21) results from:
- A deletion on chromosome 21
- Three copies of chromosome 21 due to nondisjunction (Correct answer)
- A translocation involving chromosome 21 only in females
- A point mutation on chromosome 21
Correct answer: Three copies of chromosome 21 due to nondisjunction
Down syndrome occurs when nondisjunction during meiosis results in an egg or sperm with two copies of chromosome 21, giving the offspring a total of three.
Question 6: If a trait is controlled by multiple genes (polygenic inheritance), you would expect the distribution of phenotypes in a large population to be:
- A simple 3:1 ratio
- Only two distinct phenotypes
- A continuous bell-shaped curve (Correct answer)
- Equally split between dominant and recessive phenotypes
Correct answer: A continuous bell-shaped curve
Polygenic traits, such as height and skin color, produce a continuous range of phenotypes that form a normal (bell-shaped) distribution in a population.
Question 7: In a dihybrid cross between two organisms that are both BbGg, what fraction of offspring are expected to be homozygous recessive for both traits (bbgg)?
- 1/16 (Correct answer)
- 1/4
- 3/16
- 9/16
Correct answer: 1/16
For each trait, the probability of a homozygous recessive offspring is 1/4; multiplying gives 1/4 × 1/4 = 1/16.
BMST BMST - Basic Math and Science Genetics and Heredity Questions and Answers 5
In incomplete dominance, a red-flowered plant (RR) is crossed with a white-flowered plant (WW).
What color will the F1 flowers be?