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24 terms

Chapter 13, 26

How do alleles segregate during gamete formation? According to Mendel's law of segregation, a gamete
always receives only one of the parent's alleles for each gene.
Does allele segregation determine gamete frequencies (i.e., proportions)? According to Mendel's law of segregation,
alleles segregate into gametes with equal frequency.
Parents - YY yy
F1 - Yy
When an F1 plant undergoes meiosis, what gamete types will it produce, and in what proportions?
1/2 Y and 1/2 y
Which statement correctly explains how to determine the frequencies of the F2 progeny?
The progeny frequencies are determined by the multiplication rule (multiplying the gamete frequencies together). Genotype frequencies are determined by applying the mutiplication rule to the gamete frequencies. For example, if the frequency of one particular male gamete is 1 and the frequency of one particular female gamete is ½, the frequency of those two gametes fusing to form the F2 progeny would be 1 x ½ = ½.
In peas, the allele for yellow seeds (Y) is dominant to the allele for green seeds (y). What would be the genotype and phenotype ratios of offspring from a cross between Yy and yy individuals?
Genotype: ½ Yy : ½ yy; Phenotype: ½ yellow : ½ green
Which theory was disproved when Mendel observed that the F1 generation of a monohybrid cross resembled one of the parents?
the theory of blending inheritance
When do you first learn which trait is dominant?
when observing the F1 generation of a monohybrid cross
If flower color in peas is genetically determined and you're speaking about the hereditary determinant that produces white instead of purple flowers, you're speaking about _____.
an allele
Which event in meiosis accounts for Mendel's principal of segregation?
separation of homologs at anaphase I. The physical separation of alleles on the two homologs in anaphase of meiosis I explains why each gamete contains one allele of each gene.
Which event in meiosis accounts for Mendel's principle of independent assortment?
Nonhomologous chromosomes line up independently during meiosis I.

This event explains why alleles on nonhomologous (different) chromosomes assort independently, and explains why gametes contain random assortments of maternal and paternal chromosomes.
Which concept(s) for identifying species cannot be applied to asexual or fossil species?
biological species concept. The criterion of reproductive isolation cannot be evaluated in fossil species or species that reproduce asexually.
Biological, morphological, and phylogenetic species concepts allow biologists to identify evolutionarily independent groups because they all rely on criteria indicative of _____.
no gene flow between populations
Which species concept would be most useful to a team of biologists conducting a biodiversity survey?
the morphospecies concept
Which mechanism causes postzygotic reproductive isolation?
hybrid sterility
Which of the following situations describes vicariance?
The Grand Canyon forms, separating two populations of squirrels on the North and South rims.
Which is the first step in allopatric speciation?
physical isolation of two populations
In the experiment testing whether new species can arise by hybridization, why did the researchers perform the crosses shown in steps 2 and 3? Sunflower experiment
to simulate matings that might have occurred naturally in the past. The researchers hypothesized that similar matings were involved in creating the naturally occurring species H. anomalus following hybridization between wild H. annuus and H. petiolaris.
Which description of reinforcement is correct?
Reinforcement is natural selection against interbreeding and production of hybrid offspring.
What occurs in a hybrid zone?
How did the sunflower species Helianthus anomalus originate?
How is a hybrid zone most likely to change over time if hybrid offspring have higher fitness than both parental populations?
It should expand into the ranges of both parental populations. Hybrid offspring should outcompete parental populations at least in the areas just outside the original hybrid zone, resulting in its expansion.
To promote genetic divergence, why is it important for the apple flies shown in the figure to mate on their food plants?
On apple trees, they are much more likely to encounter other apple flies than hawthorn flies. Because of the fruit preferences of the two populations little or no interbreeding occurs between apple flies and hawthorn flies, which reduces gene flow between them.
If autopolyploidy is responsible for the formation of a tetraploid grape (with extra-large fruit) from a diploid population (with smaller fruit), which of the following events must have occurred?
doubling of chromosome number in the diploid population. In autopolyploidy, reproductively isolated polyploid individuals are produced when chromosome number is doubled and all chromosomes come from the same species.
How do autopolyploidy and allopolyploidy differ?
The chromosomes of an autopolyploid individual come from the same species, whereas an allopolyploid individual has sets of chromosomes from different species.