The Phenotype of a Dog Can Be Determined by
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A brood of canis familiaris can be either of ii colors. In this breed, brown is ascendant to yellowish. A brown dog mates with a yellowish dog and produces a litter of six brown dogs. What is the genotype of the parental brown dog?
Possible Answers:
Unable to determine from the given data
Homozygous dominant
Heterozygous
Homozygous recessive
Correct answer:
Unable to determine from the given data
Explanation:
We know that the yellow canis familiaris must exist homozygous recessive and that the brown canis familiaris must be either heterozygous or homozygous dominant. If B is used to represent the dominant brown allele and b is used to represent the recessive yellow allele, this means that the yellow parent must be bb and the brown parent could be either BB or Bb.
We know that all of the puppies must carry a dominant allele, since they all express the ascendant phenotype. The yellow parent only carries the recessive allele. This indicates that every puppy must have inherited a ascendant allele from the dark-brown parent. The about likely genotype of the brown parent would be homozygous ascendant, which would lead to all puppies being heterozygous and brown.
BB ten bb
All offspring will be Bb and express the dominant brown phenotype.
Note, however, that we cannot determine the genotype of the brown parent for certain. Due to contained array, it is possible that a heterozygous chocolate-brown parent gave the recessive allele to all offspring by risk.
Bb x bb
One-half offspring will be Bb and one-half will be bb.
The probability of getting half dozen brown puppies from this cantankerous would be equal to half to the sixth power, or 1.56%. While this is a very pocket-sized take a chance, it is not impossible and we cannot rule out a heterozygous genotype for the brown domestic dog.
In a species of lizard, light-green coloration is dominant to blue coloration. A breeder wants to produce as many bluish lizards as possible from ane cross. Which of the post-obit crosses volition produce the highest percentage of blue lizards?
Possible Answers:
Cc x cc
Cc ten Cc
CCx cc
cc x cc
Explanation:
The question tells usa that light-green is dominant to blue. This ways that the C allele must correspond to green and the c allele must correspond to blue. We are looking for the cross that will produce the about blue offspring. Since blue is recessive, all blue offspring will exist homozygous recessive; thus, we are substantially looking for the cantankerous that carries the most recessive alleles.
Of the given crosses, cc x cc contains the greatest number of recessive alleles. Every offspring from this cross will be homozygous recessive and brandish the blue phenotype. This cross thus gives the highest percentage of blue offspring, with that percentage beingness 100%.
If a homozygous brown rat mates with a heterozygous dark-brown rat, what pct of the offspring will have white fur?
Correct respond:
Explanation:
Heterozygous organisms carry one dominant allele and one recessive allele. The dominant allele is expressed over the recessive allele, giving the organism the ascendant phenotype. If the heterozygous rat in the question is brown, then we can conclude that brown is ascendant to white.
The cross of these 2 rats would be:
Parents: BB (brown) x Bb (brown)
Offspring: one-half BB (dark-brown), half Bb (brown)
Though half of the offspring will be homozygous and half will be heterozygous, all offspring will exist brown. None of the offspring from this cantankerous will evidence the white phenotype.
If a male is heterozygous for the dimples allele and marries a female who does non possess the allele needed for dimples, what is the chance their child will have dimples? Dimples are an autosomal dominant trait.
Explanation:
By creating a Punnett square in which the male carries the characterization Dd and the female person has the label dd, one tin see the possible combinations of alleles that the kid may have. D will symbolize the allele for dimples, and d will symbolize the allele for no dimples. The cross will exist Dd x dd.
There is a 50% chance that the child does not obtain the allele needed for dimples (dd), and a l% chance that the child is heterozygous (Dd). Because dimples is an autosomal dominant trait, heterozygosity will express dimples, leading to a 50% risk that the kid will have dimples.
A new species of insect was recently discovered. Scientists have found that orangish coloration is recessive to yellow coloration. If a heterozygous yellow insect is mated to an orange insect, what are the expected phenotypic percentages of the offspring?
Possible Answers:
100% xanthous
100% orange
75% yellowish, 25% orangish
50% yellow, l% orange
25% yellow, 75% orange
Right answer:
50% yellow, 50% orange
Explanation:
We are told that the yellow parent is heterozygous, so we can set up a elementary cross. Nosotros know that the orange insect must exist homozygous recessive due to the fact that it displays the orange phenotype.
In our cross, nosotros will use A every bit the dominant allele and a equally the recessive allele. This gives the yellow parent a genotype of Aa and the orange parent a genotype of aa.
Aa x aa
Possible offspring: Aa, Aa, aa,aa
Nosotros can come across that in that location are only two possible genotypic results. Half of the offspring will be Aa and half will be aa. The Aa offspring will be xanthous and the aa offspring volition be orange, giving a 1:1 phenotypic ratio.
In pea plants, tall is dominant for height, greenish is dominant for colour and round is dominant for pea shape.
A tall dark-green plant is crossed with a short yellow plant. fifty% of the offspring are tall and green, and 50% are tall and yellowish.
What are the genotypes of the parent plants?
Possible Answers:
Alpine-dark-green: ttgg
Short-yellow: TTGg
Tall-greenish: TTGg
Curt-yellow: ttgg
Tall-green: TtGg
Short-yellow: ttgg
Tall-green: TtGG
Brusque-yellow: ttgg
Tall-greenish: TTGG
Short-yellow: ttgg
Correct answer:
Alpine-green: TTGg
Brusk-yellow: ttgg
Explanation:
Let's look at each trait individually. We tin can see that all of the offspring from this cantankerous will be tall; the tall allele must exist dominant over the recessive allele. We too know that one parent must be homozygous dominant for the tall allele, since it is passed to every single offspring. The parent genotypes for height areTT(tall) andtt(short). The short found must be homozygous recessive to show the recessive phenotype.
Now, let'southward expect at color. Half of the offspring are light-green and one-half are yellow. This tells the states that whichever parent displays the dominant phenotype is also heterozygous, allowing the recessive phenotype to announced in the offspring. Since nosotros know that dark-green is ascendant, we know that the green establish must be heterozygous. In order to display the recessive yellow phenotype, the yellow plant must be homozygous recessive. The parent genotypes for colour must beGg (greenish) andgg (xanthous).
Together, we can see that the tall-light-green establish will beTTGg and the curt-yellow institute will bettgg.
A biologist genetically crosses two cats, both with black fur, which is dominant over white fur. The pair take 12 kittens, 9 with blackness fur and 3 with white fur. What is the parental cross?
Possible Answers:
bb X BB
BB X Bb
Bb X Bb
BB X BB
bb X bb
Explanation:
The ratio of kittens with blackness fur to kittens to white fur is iii:1. Since the recessive phenotype is shown in the offspring, we know that both of the parents are carriers of the recessive genotype and are thus both heterozygous,Bb.
Assume that in the organism in question, the allele for brownish fur (B) is ascendant to the allele for white fur (b). Too assume that the allele for curly fur (C) is dominant to the allele for direct fur (c). Finally, assume these genes are independent.
Given parents with the genotypes BBCc and Bbcc, what fraction of offspring will display straight, brown fur?
Correct answer:
Explanation:
Each parent will contribute i allele at random from each of the two genes. The odds of having brown fur, given the parental genotypes, is 100% because all children will receive a dominant allele for brown fur (B) from the first parent. This ways that the odds of having brown direct fur will depend only on the odds of having direct fur. Having straight fur requires one recessive allele (c) from each parent. The second parent volition always contribute a recessive allele while the first will contribute a recessive allele half the time. Thus, the odds of straight fur is l%, as are the odds of straight, chocolate-brown fur. Alternatively, a Punnett square may be used. The foursquare beneath shows the l% offspring combinations with straight, chocolate-brown fur highlighted in blood-red.
If two parents are heterozygous for a trait and they accept children, what is the percentage of the children that are heterozygous for the trait?
Explanation:
For simplicity, nosotros volition assign the letter "a" for the factor of interest. Thus, the heterozygous genotype is Aa. You may sketch a punnet square of the cross: Aa x Aa to help illustrate that the combinations result in fifty% run a risk of heterozygous offspring.
In a cross in which both parents are heterozygous, what would be the percentage of offspring that are homozygous recessive for the trait?
Caption:
Arbitrarily, nosotros may assign the letter "b" for the factor of interest. The cross and then is as follows: Bb x Bb. Each parent has a 50% chance of altruistic a recessive (b) allele to the offspring. We must multiply these probabilities to become the chance of a homozygous recessive offspring.
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