Question

1. Based on your understanding of sex-linked recessive traits, would it be possible for the phenotype to skip one or more generations before reappearing? Explain your answer.

2. Proteomics is the study of the number of different proteins that a gene produces. Why might this be a more complete snapshot of human genetics than genomics?

3. If the Huntington’s disease trait is dominant, why is it not more prevalent in the population?

Answer 1

1. Sex-linked recessive traits usually affect males, as they only have one X-chromosome whereas females have two copies of X chromosomes and hence, the allele is compensated in females because, recessive traits require two copies of the mutant allele to be expressed in females, whereas males require only one mutant allele as they only have one X chromosome. Therefore, if a female parent is carrier, then half of her sons will have the disorder and half of her daughters will be carriers. But if a female parent has the disorder i.e. homozygous, then all her sons will acquire the disorder and all her daughters will be carriers. If a male parent has the disorder, then all his daughters will be carriers, but the sons are unaffected. Hence, sex linked recessive traits do not skip generations, as they either found in the sons or the daughters.

2. Genomics is the molecular characterisation of whole genome. Proteome is the set of protein coding gene products. Genome provides information about DNA sequences but it does not provide any information regarding when the genes are expressed or what cells they are expressed in, expression patterns, stability of proteins and post-translational modifications. Genome is invariant in every cell of an organism, whereas proteome varies by cell type, developmental stage, environmental conditions and disease response.

3. Huntington disease is an autosomal dominant disease, which requires one dominant allele for its expression. But, a dominant trait need not be common in population. The prevalence of the trait depends upon how many copies of the allele are present in the population. "Dominant " term refers to the fact that the allele is expressed over another allele. The dominant allele of a person shows affect only when that person marries and have kids. But, people with huntington disease have a short life span and die due to other complications of the disease like pneumonia and heart diseases.