In fungi and plants, meiosis produces single cells that can grow into a new multicellular organism without fusing with another cell; these cells are called spores.
Missing Word
spores
Spores are reproductive cells that develop directly into a new organism; in haploid-dominant and alternation-of-generations life cycles they form by meiosis.
Category: Life Cycles
Question 2
Cells with two complete sets of chromosomes, one set from each parent, are described as diploid.
Missing Word
diploid
Diploid (2n) cells carry two sets of chromosomes; human body cells are diploid, with 23 pairs.
Category: Chromosome Sets
Question 3
Eggs and sperm produced by meiosis contain one set of chromosomes and are therefore haploid.
Missing Word
haploid
Haploid (n) cells carry a single set of chromosomes, so two of them can fuse at fertilization to restore the diploid number.
Category: Chromosome Sets
Question 4
A chromatid that carries both maternal and paternal DNA after crossing over is described as recombinant.
Missing Word
recombinant
Recombinant chromatids result from the exchange of segments between homologs in prophase I, creating new combinations of alleles.
Category: Meiosis I
Question 5
Spindle microtubules attach to each chromosome at a protein structure called the kinetochore, which forms where sister chromatids are joined.
Missing Word
kinetochore
The kinetochore is the attachment point for spindle microtubules; in meiosis I one homolog attaches to each pole.
Category: Meiosis I
Question 6
Sister chromatids are held together at a constricted region of the chromosome called the centromere.
Missing Word
centromere
The centromere joins sister chromatids; it holds them together through meiosis I, and they separate at anaphase II.
Category: Meiosis I
Question 7
The division of the cytoplasm that follows each nuclear division in meiosis is called cytokinesis.
Missing Word
cytokinesis
Cytokinesis splits the cytoplasm, by a cleavage furrow in animal cells and a cell plate in plant cells, producing separate daughter cells.
Category: Meiosis II
Question 8
An individual whose cells have an incorrect number of chromosomes, such as one extra or one missing, is described as aneuploid.
Missing Word
aneuploid
Aneuploidy is an abnormal chromosome number that is not a whole extra set, usually caused by nondisjunction.
Category: Chromosome Errors
Question 9
A condition in which a cell has only one chromosome of what should be a homologous pair is called monosomy.
Missing Word
monosomy
Monosomy is the loss of one chromosome from a pair; in humans, monosomy of any autosome prevents development to birth.
Category: Chromosome Errors
Question 10
Having three copies of a particular chromosome instead of the usual two is called trisomy.
Missing Word
trisomy
Trisomy is the gain of one chromosome; the extra gene dose disrupts development, and trisomy 21 causes Down syndrome.
Category: Chromosome Errors
Question 11
A rearrangement in which a chromosome segment breaks off, rotates 180 degrees and reinserts into the same chromosome is called an inversion.
Missing Word
inversion
An inversion reverses the order of genes in a segment without adding or removing genetic material, so its effects are often mild unless the break disrupts a gene.
Category: Structural Changes
Question 12
An organism with three complete sets of chromosomes, which in animals is usually sterile because meiosis cannot divide an odd number of sets evenly, is described as triploid.
Missing Word
triploid
Triploid (3n) organisms are a form of polyploidy; with an odd number of sets, homologs cannot pair evenly in meiosis, so viable gametes are rarely produced.
Category: Chromosome Errors
Question 13
A chromosomal rearrangement in which a segment of a chromosome is lost is called a deletion.
Missing Word
deletion
A deletion removes genes along with the lost segment; cri-du-chat syndrome is caused by a deletion on chromosome 5.
Category: Structural Changes
Question 14
A rearrangement in which a segment of a chromosome is copied so that it appears twice is called a duplication.
Missing Word
duplication
A duplication adds an extra copy of the genes in a segment, which can upset normal gene dosage.
Category: Structural Changes
Question 15
Asexual reproduction in which a new individual grows as an outgrowth of the parent and then detaches, as in yeast and hydra, is called budding.
Missing Word
budding
Budding is a form of asexual reproduction that produces offspring genetically identical to the parent, without the need for a mate.
Category: Sexual Reproduction