Chapter 14 Questions Flashcards
Which choice below is a basic difference between Mendel’s particulate hypothesis and the hypothesis of blending inheritance?
The blending inheritance hypothesis, but not the particulate hypothesis, maintained that after a mating, the genetic material provided by each of the two parents is mixed in the offspring, losing its individual identity.
If a plant variety is true-breeding for a dominant trait, then _____.
if the plant were allowed to self-pollinate, all of the progeny would have the dominant trait
-All the progeny would show the same phenotype.
A = big apples; R = red apples; a = small apples; r = yellow apples. You have one tree that produces big yellow apples and another tree that produces small red apples. When the two are crossed, you find that half of the new trees produce big red apples and half produce big yellow apples. What are the genotypes of the parents?
AArr and aaRr
-Trees that produce big yellow apples could be AArr or Aarr. Trees that produce small red apples could be aaRR or aaRr. Because all the offspring are big, the big parent must be homozygous for A. Because half the apples are red and half are yellow, the red parent must be heterozygous for red. The conclusion is that the cross must be AArr x aaRr.
Assume tall (T) is completely dominant to dwarf (t) in a certain species of plant. If a homozygous dominant individual is crossed with a homozygous dwarf, the offspring will _____.
all be tall
-The tall allele is completely dominant to the dwarf allele.
The F1 generation differed from the F2 in Mendel’s experiments in that _____.
all of the F1 showed the dominant phenotype, but only three-fourths of the F2 did
Physically, what are different alleles?
Different alleles are different DNA sequences found at the same locus on homologous chromosomes.
-Unless a mutation has occurred during DNA synthesis, sister chromatids will always carry the same allele.
In a certain plant, the alleles A, B, and C are completely dominant to the alleles a, b, and c. A plant with the genotype AABbcc will have the same phenotype as a plant with the genotype _____.
AaBBcc
Pea plants are tall if they have the genotype TT or Tt, and they are short if they have genotype tt. A tall plant is mated with a short plant. Which outcome below would indicate that the tall parent plant was heterozygous?
The ratio of tall offspring to short offspring is 1:1.
-If one parent has the genotype Tt and the other parent has the genotype tt, about half of the offspring will be tall.
What is indicated when a single-character testcross yields offspring that all have the dominant phenotype?
The parent with the dominant phenotype was homozygous.
-If all the progeny show the dominant phenotype, the parent must have been homozygous, transmitting the dominant allele to all of the offspring.
If an organism that is homozygous dominant is crossed with a heterozygote for that trait, the offspring will be _____.
all of the dominant phenotype
-The offspring of an AA x Aa cross are either AA or Aa. All will express the dominant phenotype.
In Mendel’s monohybrid cross of purple-flowered and white-flowered peas, all members of the F1 generation had the _____ phenotype because their genotype was _____ at the flower-color locus.
purple-flowered … heterozygous
If the two traits that Mendel looked at in his dihybrid cross of smooth yellow peas with wrinkled green peas had been controlled by genes that were located near each other on the same chromosome, then the F2 generation _____.
would have deviated from the 9:3:3:1 phenotypic ratio that is predicted by the law of independent assortment
In carrying out his breeding studies, Mendel examined characters that had which of the following properties?
- They were controlled by loci that were (or behaved as if they were) on different chromosomes.
- It was possible to isolate true-breeding varieties for each trait.
- The traits varied in an either-or fashion.
- The characters each were controlled by a single gene.
The law of independent assortment _____.
- states that the alleles at different loci segregate independently from one another during a dihybrid cross
- can account for a 9:3:3:1 ratio seen in the F2 generation
- applies only to genes that are present on different chromosomes (or behave as if they were)
Homologous pairs of chromosomes often _____.
contain different alleles
-Pairs of homologous chromosomes carry the same genes.
If each parent can produce 100 genetically distinct gametes, how many genetically distinct offspring can two parents produce?
10,000
-100 × 100 = 10,000. The rule of multiplication applies to these independent events.
Pea flowers may be purple (P) or white (p). Pea seeds may be round (R) or wrinkled (r). What proportion of the offspring from the cross PpRr x PpRr will have white flowers and wrinkled seeds?
1/16
An AABbccDdEeFF individual is crossed with an individual with the genotype AaBBCCDdEeff. What is the probability that their offspring will have the genotype AaBBCcddEEFf?
1/64
If a heterozygous plant is allowed to self-pollinate, what proportion of the offspring will also be heterozygous?
1/2
An individual with the genotype AABbCcDD can make how many different kinds of gametes?
4
A red bull is crossed with a white cow and all of the offspring are roan, an intermediate color that is caused by the presence of both red and white hairs. This is an example of genes that are _____.
codominant
Flower color in snapdragons is an example of incomplete dominance. When a red-flowered plant is crossed with a white-flowered plant, the F1 generation has pink flowers. If a pink-flowered plant is crossed with another pink-flowered plant, the progeny plants will be _____.
25% red, 50% pink, and 25% white
Which choice below describes the expression of Tay-Sachs disorder in humans at the biochemical level?
incompletely dominant
Human blood groups are governed by three alleles, A, B, and O. A and B are codominant and O is recessive to both. A man who has type B blood and a woman who has type A blood could have children of which of the following phenotypes?
A, B, AB, or O
Which of the following matings cannot produce a child with blood type O? The letters refer to blood types (phenotypes).
O × AB
-Both parents could be I^Ai.
A woman with type O blood is expecting a child. Her husband is type A. Both the woman’s father and her husband’s father had type B blood. What is the probability that the child will have type O blood?
50%
A single genetic locus that controls more than one trait is said to be _____.
pleiotropic
Color in squash is controlled by epistatic interactions in which color is recessive to no color. At the first locus white squash (W) is dominant to colored squash (w). At the second locus yellow (Y) is dominant to green (y). What is the phenotype of a squash with the genotype wwYy?
yellow
