Chat with AIExam 5: Extensions and Modifications of Basic Principles
A mother with blood type B has a child with blood type O. Give all possible blood types for the father of this child.
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Discuss the difference between "cytoplasmic inheritance" and "genetic maternal effect."
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Answered by Examlex AI CopilotCytoplasmic inheritance and genetic maternal effect are both mechanisms of inheritance that involve the transmission of genetic information from the mother to her offspring, but they operate in different ways.
Cytoplasmic inheritance refers to the inheritance of genetic traits that are encoded by genes located in the cytoplasm of the cell, rather than in the nucleus where the majority of an organism's genetic material is found. These cytoplasmic genes are typically inherited exclusively from the mother, as the cytoplasm of the egg cell contains organelles such as mitochondria and chloroplasts, which have their own small genomes. This means that traits controlled by cytoplasmic genes are passed down from mother to offspring, and are not subject to the usual processes of genetic recombination and segregation that occur during sexual reproduction.
On the other hand, genetic maternal effect refers to the situation where the phenotype of the offspring is determined by the genotype of the mother, rather than by the offspring's own genotype. This occurs when the maternal genotype influences the development or expression of specific traits in the offspring, often through the provision of maternal gene products such as mRNA or proteins that are deposited in the egg during oogenesis. These maternal gene products can have a direct impact on the early development of the offspring, and can override the influence of the offspring's own genotype on certain traits.
In summary, the main difference between cytoplasmic inheritance and genetic maternal effect lies in the location of the genes involved and the mechanism by which they influence the phenotype of the offspring. Cytoplasmic inheritance involves the transmission of genetic traits encoded by cytoplasmic genes, while genetic maternal effect involves the influence of the maternal genotype on the development of specific traits in the offspring. Both mechanisms highlight the important role of the mother in determining the genetic and phenotypic characteristics of her offspring.
A geneticist is examining a culture of fruit flies and discovers a single female with strange spots on her legs. The new mutation is named melanotic. When a female melanotic fly is crossed with a normal male, the following progeny are produced: 123 normal females, 125 melanotic females, and 124 normal males. In subsequent crosses with normal males, melanotic females are frequently obtained but never any melanotic males. Provide a possible explanation for the inheritance of the melanotic mutation. (Hint: The cross produces twice as many female progeny as male progeny.)
(36) Answered by Examlex AI CopilotThe inheritance of the melanotic mutation in fruit flies can be explained by the fact that the mutation is located on the X chromosome. Since the cross produces twice as many female progeny as male progeny, this suggests that the melanotic mutation is recessive and located on the X chromosome.
When a female melanotic fly is crossed with a normal male, the resulting progeny show that the melanotic trait is inherited in a sex-linked manner. This means that the melanotic gene is located on the X chromosome, and since females have two X chromosomes, they can be carriers of the mutation without showing the phenotype. However, males only have one X chromosome, so if they inherit the melanotic mutation, they will exhibit the phenotype.
The fact that melanotic females are frequently obtained in subsequent crosses with normal males, but never any melanotic males, further supports the idea that the melanotic mutation is located on the X chromosome. This is because males only inherit one X chromosome from their mother, so if the X chromosome carries the melanotic mutation, they will exhibit the phenotype. However, since females have two X chromosomes, they have a higher chance of being carriers of the mutation without showing the phenotype.
In conclusion, the inheritance of the melanotic mutation in fruit flies can be explained by its location on the X chromosome, leading to a sex-linked inheritance pattern. This explains why melanotic females are frequently obtained in subsequent crosses with normal males, but never any melanotic males.
In rabbits, an allelic series helps to determine coat color: C (full color), cch (chinchilla; gray color), ch (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, cch is dominant to ch and c, ch is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > cch > ch > c.
- Indicate the phenotypic ratios expected of rabbits with the cross Cch × cc.
(36) In the yawncat (a rare hypothetical animal), the dominant allele R causes solid tail color, and the recessive allele r results in white spots on a colored background. The black coat color allele B is dominant to the brown allele b, but the B and b alleles can only be expressed if the animal has an mm genotype at a third gene locus. Animals that are M_ are yellow regardless of which allele from the B locus is present. A mating between a solid yellow-tailed male yawncat and a solid brown-tailed female yawncat produces 16 offspring with the following tail phenotypes: six solid yellow, two spotted yellow, three solid black, one spotted black, three solid brown, and one spotted brown.
-What is the MOST likely genotype of the female parent?
(42) A mother with blood type AB has a child with blood type B. Give all possible blood types for the father of this child.
(39) In the Mexican Hairless breed of dog, the hairless condition is produced by the heterozygous genotype (Hh). Normal dogs are homozygous recessive (hh). Puppies homozygous for the H allele are usually born dead. If the average litter size at weaning (after nursing) is six puppies in matings between hairless dogs, what would be the average expected number (not a ratio) of hairless and normal offspring at weaning from matings between hairless and normal dogs?
(32) Achondroplasia is a common cause of dwarfism in humans. All individuals with achondroplasia are thought to be heterozygous at the locus that controls this trait. When two individuals with achondroplasia mate, the offspring occur in a ratio of 2 achondroplasia : 1 normal. What is the MOST likely explanation for these observations?
(38) A yeast geneticist isolates two different haploid mutant yeast strains, strain A and strain B, which cannot grow unless the amino acid leucine is added to the growth media. Wild-type yeast strains can make their own leucine and do not require that it be added to the growth media. The geneticist discovers that each mutant yeast strain contains a single recessive mutation that leads to the observed leucine-requiring phenotype. When she crosses the two mutant strains together, she observes that the resulting diploid can grow without leucine added to the growth media. Explain the allelic relationship between the mutations in these two strains.
(37) In order to determine if mutations from different organisms in the same species that exhibit the same phenotype are allelic, which test would you perform?
(34) In chickens, comb shape is determined by genes at two loci (R, r and P, p). A walnut comb is produced when at least one dominant gene R is present at one locus and at least one dominant gene P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant gene is present at the first locus and two recessive genes are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive genes are present at the first locus and at least one dominant gene is present at the second (genotype rr P_). If two recessive genes are present at the first and the second locus (rr pp), a single comb is produced.
-Give genotypes for comb shape of the parents in the following cross: Rose crossed with pea produces 20 walnut offspring.
(40) You are studying body color in an African spider and have found that it is controlled by a single gene with four alleles: B (brown), br (red), bg (green), and by (yellow). B is dominant to all the other alleles, and by is recessive to all the other alleles. The bg allele is dominant to by but recessive to br. You cross a pure-breeding brown spider with a pure-breeding green spider.
-Predict the genotype of the progeny.
(36) A homozygous strain of corn that produces yellow kernels is crossed with another homozygous strain that produces purple kernels. When the F1 are interbred, 280 of the F2 are yellow and 70 are purple.
(38) In domestic chickens, some males display a plumage pattern called cock feathering. Other males and all females display a pattern called hen feathering. Cock feathering is an autosomal recessive trait that is exhibited in males only.
-What type of inheritance is exhibited by this trait?
(40) A mother with blood type A has a child with blood type AB. Give all possible blood types for the father of this child.
(26) In chickens, comb shape is determined by genes at two loci (R, r and P, p). A walnut comb is produced when at least one dominant gene R is present at one locus and at least one dominant gene P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant gene is present at the first locus and two recessive genes are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive genes are present at the first locus and at least one dominant gene is present at the second (genotype rr P_). If two recessive genes are present at the first and the second locus (rr pp), a single comb is produced.
- Give genotypes for comb shape of the parents in the following cross: Rose crossed with single produces 31 rose offspring.
(41) You are studying a coat color gene (B, brown) in Mexican bats. You have isolated a recessive allele (b) that causes yellow coat color, but you suspect that the phenotype may be sensitive to environmental conditions. To test your hypothesis, you examine the segregation ratio of phenotypes in F1 progeny from a cross between two heterozygotes. You do this once at normal laboratory temperatures (28°C) and once at temperatures closer to their native habitat (34°C) and record the following data: Brown Yellow 2 153 47 3 170 30 a. What ratio do you expect in each experiment if temperature does not affect the phenotype?
b. What test can you use to determine if the ratio you observed is significantly different from the expected ratio?
c. Using that statistical test, is either observed ratio more different from the expected ratio than one would expect from chance alone? If so, suggest a biological explanation.
(37) Explain how a phenotype like height in a tree can be due to the influence of both genes and environment.
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