is heritable and is a sex-limited autosomal recessive trait in dogs. Dogs with u

Question

is heritable and is a sex-limited autosomal recessive trait in dogs. Dogs with unilateral or bilateral undescended testes. A unilaterally dism this condition have either rchid animal can produce sperm, whereas a bilateral cryptorchid male usually does not and is sterile. Testes should be scrotal and thus 4 to 5 degrees cooler than produce sperm the body temperature to produce normal sperm. Even though unilateral cryptorchids produce abnormal sperm quality, due to adverse affect of high body temperature in the abdominal cavity, they are able to impregnate a female in estrus. A. Give the information in this question, identify and explain the necessary parental genotypes (if there is more than one possible cross, indicate as such) to yield a dog with the following conditions. You must also identify the phenotype and gender of the parents in your problem. i. Unilateral cryptorchidism. ii. Bilateral cryptorchidism. B. Describe, using the words "penetrance" and "expressivity" the specifics of cryptorchidisrm in dogs. C. Could this be a sex-influenced characteristic? Explain the logic behind your response. If your response is "NO then explain how sex-influenced inheritance works and provide an example of a characteristic that would be inherited in this manner (and walk through that example with genotypes and phenotypes). If your answer is "YES" then provide an example of how sex-influenced inheritance would occur in this instance

Explanation / Answer

Sex-limited genes are genes that are present in both sexes of sexually reproducing species but are expressed in only one sex and remain 'turned off' in the other. In other words, sex-limited genes cause the two sexes to show different traits or phenotypes, despite having the same genotype. This term is restricted to autosomal traits, and are different from sex-linked characteristics, which have to do with genetic differences on the sex chromosomes. Sex-limited genes are also distinguished from sex-influenced genes, where the same gene will show differential expression in each sex. Sex-influenced genes commonly show a dominant/recessive relationship, where the same gene will have a dominant effect in one sex and a recessive effect in the other.

A . As it is mentioned that cryptorchidism is a heritable and sex limited autosomal recessive trait, it could be stated that the affected individual is cc. This could be resulted from a cross between CC genotype/ Cc genotype with cc genotype. Now, if the cc genotype was in mother, she will be normal because it is a sex limited gene, but if the cc genotype was of father this dog was with cryptoorchidism. Phenotype of CC genotype/ Cc genotype in both father and mother dog will be normal, because it is a recessive trait.

Since, genetic information seperately on unilateral and bilateral cryptoorchidism is not given, it could be explained in terms of differential expressivity. In  bilateral cryptoorchidism, the degree of expression is more and in unilateral cryptoorchidism,  the degree of expression is less.

b. Penetrance is the proportion of individuals carrying a particular variant (or allele) of a gene (the genotype) that also express an associated trait (the phenotype).

Expressivity is the degree to which trait expression differs among individuals. The infertility related to cryptorchidism is not the same in all dogs.

c. No, it is mentioned that it is autosomal and since it is a matter of testis this influence is completely switched off in the females. In sex influenced genes, though differential the gene is expressed in both sexes (little or more). For example, pattern baldness in humans occurs more in men though the condition isn't restricted to males. This gene has two alleles, “bald” and “non-bald.” The behaviors of the products of these genes are highly influenced by the hormones in the individual, particularly by the hormone testosterone.

The baldness gene being on the X chromosome also explains why baldness is more common in men than in women. Baldness is recessive. None-baldness is dominant. So, the baldness gene, a male gets from his mother. Due to hormonal influences, it is more expressed in males.

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