The result of the following cross indicates the orange eyes are ___ black eyes.
A cross between two aliens with black eyes. Their offspring have two phenotypes.
247 of them have black eyes, 86 of them are orange-eyed.
The total number of offspring is 333.
Answer
The result of the following cross indicates the orange eyes are recessive to black eyes
According to Mendel, a cross involving two heterozygous individuals for a dominant trait will yield offspring in the phenotype ratio 3:1, with the dominant trait accounting for about 75% of the phenotype and the recessive trait accounting for the remaining 25%.
In this case, the black eye color phenotype is 247, while the orange eye color phenotype is 86.
Calculating the percentage for each trait
Black eye = 247/333 x 100% = 74.1%
Orange eye = 86/333 x 100% = 25.8%
74.1:25.8 is approximately 3:1
Hence, it is evident that the orange eyes are recessive while the black eyes are dominant.
What number and types of chromosomes are found in a somatic cell in an animal with a diploid number of 48?
48 chromosomes (24 from each parent, including one sex chromosome from each)
What is the difference between heterozygous and homozygous individuals?
All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ.
When constructing a Punnett square, the symbols on the outside of the boxes represent _______, while those inside the boxes represent _______.
gametes, progeny
True or false? The same phenotype can be produced by more than one genotype.
true
True or false? In diploid organisms, a dominant phenotype will only be expressed if the individual is homozygous dominant for that trait.
false
If an organism with the genotype AaBb produces gametes, what proportion of the gametes would be Bb?
none
Two mice are heterozygous for albinism (Aa) . The dominant allele (A) codes for normal pigmentation, and the recessive allele (a) codes for no pigmentation. What percentage of their offspring would have an albino phenotype?
25
A tall, purple-flowered pea plant (TtPp) is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the “1” in the 9:3:3:1 ratio)?
ttpp
The result of the following cross indicates the orange eyes are _____ black eyes.
recessive too
If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the genotypic ratio of a cross between a heterozygous black-eyed MendAlien and an orange-eyed MendAlien?
0 homozygous black (BB): 1 heterozygote (black) (Bb): 1 homozygous orange (bb)
If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the phenotypic ratio of a cross between a heterozygous black-eyed MendAlien and an orange-eyed MendAlien?
1 black : 1 orange
The result of the following cross indicates that the genotype of the female parent is _____.
RR
The result of the following cross indicates that the genotype of the male parent is _____.
rr
The result of the following cross indicates that genotypically the offspring _____.
are all Rr
Which of these is a testcross?
A? x aa
That each gamete contains a single allele of the eye color gene is an illustration of _____.
Mendel’s law of segregation only
In his breeding experiments, Mendel first crossed true-breeding plants to produce a second generation, which were then allowed to self-pollinate to generate the offspring. How do we name these three generations? See Concept 14.1 (Page 270)
P … F1 … F2
Which of the following is true about a plant with the genotype AABbcc? See Concept 14.1 (Page 271)
It is homozygous at two loci.
What is an allele? See Concept 14.1 (Page 271)
an alternative version of a gene
How could the botanist best determine whether the genotype of the green-pod plant is homozygous or heterozygous?
Cross the green-pod plant with a yellow-pod plant.
Suppose that the botanist carried out the test cross described in Parts A and B and determined that the original green-pod plant was heterozygous (Gg). Which of Mendel’s findings does her test cross illustrate?
law of segregation
During which part of meiosis (meiosis I or meiosis II) do the two alleles of a gene separate? During which phase does the separation occur? State your answer as meiosis I or meiosis II followed by a comma and the name of the phase (for example, if your answer is meiosis II and metaphase, enter meiosis II, metaphase).
meiosis I, anaphase
Consider pea plants with the genotypes GgTt and ggtt . These plants can each produce how many type(s) of gametes? See Concept 14.2 (Page 277)
four … one
Two organisms with genotype AaBbCcDdEE mate. These loci are all independent. What fraction of the offspring will have the same genotype as the parents? See Concept 14.2 (Page 277)
1/16
You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered one. All of the F1 are pink. What does this say about the parental traits? See Concept 14.3 (Page 278)
Red shows incomplete dominance over white.
Height in humans generally shows a normal (bell-shaped) distribution. What type of inheritance most likely determines height? See Concept 14.3 (Page 281)
a combination of polygenic inheritance and environmental factors
Various procedures can be used to detect genetic disorders before birth. Among the tests discussed in this chapter, which is the least invasive (list first), and which two allow the chromosomes of the fetus to be examined? See Concept 14.4 (Page 288)
ultrasound imaging … chorionic villus sampling … amniocentesis
Which of the following do you expect if an individual is heterozygous for the sickle-cell trait? See Concept 14.3 (Page 285)
He or she will show some symptoms of the disease.
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