Sexual life cycles alternate between meiosis, which halves the chromosome number, and fertilization, which restores it.
Correct Answer
True
True. Meiosis produces haploid cells, and fertilization fuses two haploid gametes into a diploid zygote, so the two processes balance each other across generations.
Category: Sexual Reproduction
Question 2
Most multicellular organisms reproduce only asexually.
Correct Answer
False
False. Multicellular organisms that rely only on asexual reproduction are exceedingly rare; most eukaryotes reproduce sexually at least some of the time.
Category: Sexual Reproduction
Question 3
In a haploid-dominant life cycle, the zygote divides by mitosis to form a multicellular diploid body.
Correct Answer
False
False. In a haploid-dominant life cycle, such as that of fungi, the zygote immediately undergoes meiosis to form haploid spores, and there is no multicellular diploid stage.
Category: Life Cycles
Question 4
In ferns, the large leafy plant that people usually recognize is the sporophyte generation.
Correct Answer
True
True. The familiar fern plant is the diploid sporophyte, which forms spores in structures called sporangia on the undersides of its leaves.
Category: Life Cycles
Question 5
Homologous chromosomes carry genes for the same traits at the same locations, with one homolog inherited from each parent.
Correct Answer
True
True. A diploid organism receives one member of each homologous pair from each parent, and the two homologs carry the same genes in the same order, though the versions of those genes may differ.
Category: Meiosis I
Question 6
Crossing over exchanges segments between the two sister chromatids of a single chromosome.
Correct Answer
False
False. Crossing over exchanges segments between non-sister chromatids of homologous chromosomes; swapping between identical sister chromatids would not create new combinations.
Category: Meiosis I
Question 7
After crossing over, a recombinant chromatid carries a mix of maternal and paternal DNA.
Correct Answer
True
True. Crossing over swaps segments between homologs, so the resulting recombinant chromatids combine DNA from the chromosome inherited from each parent.
Category: Meiosis I
Question 8
During metaphase I, all maternal homologs line up on one side of the cell's center and all paternal homologs on the other.
Correct Answer
False
False. Each homologous pair orients randomly at the center of the cell, independently of the other pairs, which is why gametes receive mixed combinations of maternal and paternal chromosomes.
Category: Meiosis I
Question 9
With 23 pairs of chromosomes, independent assortment alone allows a human to produce more than 8 million genetically different gametes.
Correct Answer
True
True. The number of possible combinations is 2 raised to the 23rd power, which is about 8.4 million, and crossing over adds even more variation.
Category: Meiosis I
Question 10
Chromosomes undergo another round of DNA replication during interkinesis.
Correct Answer
False
False. Interkinesis, the brief pause some species show between meiosis I and meiosis II, has no S phase, so the chromosomes are not duplicated again.
Category: Meiosis II
Question 11
The four cells produced by meiosis are typically genetically different from one another and from the parent cell.
Correct Answer
True
True. Crossing over and the random alignment of homologs mean that meiosis produces genetically unique cells, unlike mitosis, which produces identical copies.
Category: Meiosis Versus Mitosis
Question 12
In animals, meiosis produces cells used for growth and tissue repair.
Correct Answer
False
False. Growth and repair rely on mitosis; in animals, meiotic cells take part only in sexual reproduction, forming eggs and sperm.
Category: Meiosis Versus Mitosis
Question 13
Nondisjunction of a homologous pair during meiosis I leaves all four resulting gametes with an abnormal number of that chromosome.
Correct Answer
True
True. If a homologous pair fails to separate in meiosis I, two gametes get an extra copy of that chromosome and two get none, so none of the four is normal.
Category: Chromosome Errors
Question 14
A human zygote missing one copy of an autosome usually develops into a healthy infant.
Correct Answer
False
False. Monosomy of any autosome prevents a human zygote from developing to birth, because losing one copy of a whole chromosome halves the dose of hundreds of genes.
Category: Chromosome Errors
Question 15
The risk of having a child with trisomy 21 rises with maternal age.
Correct Answer
True
True. The chance of nondisjunction increases with the mother's age, and the risk of Down syndrome rises sharply after about age 35.
Category: Chromosome Errors
Question 16
Turner syndrome occurs in males who have one X chromosome and no second sex chromosome.
Correct Answer
False
False. Turner syndrome occurs in females who have a single X chromosome (X0); it can cause short stature, a webbed neck and sterility.
Category: Sex Chromosomes
Question 17
Tortoiseshell coat coloring in female cats arises from random X inactivation.
Correct Answer
True
True. Each cell randomly silences one X chromosome, and all of its descendants keep that same inactive X, so patches of fur express different coat color alleles carried on the two X chromosomes.
Category: Sex Chromosomes
Question 18
Polyploidy, having extra complete sets of chromosomes, is rare among plants.
Correct Answer
False
False. Polyploidy is common in plants, where polyploid individuals tend to be larger and more robust; it is rare in animals.
Category: Chromosome Errors
Question 19
In a reciprocal translocation, two nonhomologous chromosomes exchange segments with no net gain or loss of genetic information.
Correct Answer
True
True. A reciprocal translocation swaps pieces between two nonhomologous chromosomes, so the total genetic material stays the same, although a break inside a gene can still affect the person.
Category: Chromosome Errors
Question 20
Cri-du-chat syndrome results from an extra copy of chromosome 5.
Correct Answer
False
False. Cri-du-chat syndrome results from a deletion of most of the short arm of chromosome 5; affected infants have a high-pitched cry and nervous system abnormalities.
Category: Chromosome Errors