Question

A. If eradication of disease is the reason for the actions of the Eugenics movement leaders, their efforts would not be successful. Give two reasons why genetic diseases are difficult to eliminate.

Hint: One reason is how genetic diseases arise (give specifics), and the other reason is the difficulty of identifying all individuals with the disease-generating allele especially if the disease is recessive (explain why identification is difficult).

A third reason that it is not ethical to eradicate unfit traits like how the Nazis tried to do is not a reason I would like you to report as the answer to this question.

B.

The genes involved in these multifactorial traits are identified by looking at populations of people, and if one is lucky, by animal models. Mouse models are how scientists identified the ob and db genes.

What do each of these genes code for and how do the gene products interact?

C.

The mutations in the ob and db genes (LP and LEPR, respectively, in humans) only account for ~5% of cases of obesity. The other 95% are due to other genes. Scientists are hunting for these genes by doing a genome-wide association study (GWAS) on a large number of people in the population. Phenotype (obese or not) is compared to SNPs in haplotypes.

How do SNPs arise in genomes of people in the population? Think about what happens to DNA.

D.

When hunting for genes, scientists will look for a high LOD score between the haplotype and the trait of a disease (e.g., obese).

1. Why does the scientist want a high LOD score?
2. What does linkage between the haplotype and the trait mean about the location of the gene that causes the disease?

Answer 1

a. The two reasons why genetic diseases are difficult to eliminate from a population are-

A genetic disorder is a disease caused in whole or in part by a change in the DNA sequence away from the normal sequence. Genetic disorders can be caused by a mutation in one gene (monogenic disorder), by mutations in multiple genes (multifactorial inheritance disorder), by a combination of gene mutations and environmental factors, or by damage to chromosomes (changes in the number or structure of entire chromosomes, the structures that carry genes). Thus in order to know a genetic disease, its origin should be now which is a difficult task.

Another factor is a recessive genetic disease arise when there is a mating of two people who are heterozygous for the genetic trait. In heterozygous people or the carriers, symptoms of the disease are not present until they mate with a similar person who is a carrier to produce an offspring who posses that recessive trait. Thus identification of carriers of the traits is a difficult process.

Nazis killed people indiscriminately so this could not be the method followed i.e killing people who possess the unfit trait should not be followed.

B. The "Diabetes" (Db) Gene of the Mouse Codes for a Mutated Leptin Receptor.

The ob gene, an adipose-specific gene believed to encode a satiety factor that regulated food intake and energy expenditure, has recently been discovered in mice. Two separate mutations in the mouse ob gene result in the development of morbid obesity.

C. Cells sometimes make mistakes during the copying process - kind of like typos. These typos lead to variations in the DNA sequence at particular locations, called single nucleotide polymorphisms, or SNPs. If more than 1% of a population does not carry the same nucleotide at a specific position in the DNA sequence, then this variation can be classified as an SNP. If an SNP occurs within a gene, then the gene is described as having more than one allele. In these cases, SNPs may lead to variations in the amino acid sequence.

D. Linkage studies provide a statistical measure, referred to as a lod score (logarithmic odds), that measures the probability that the genetic marker is closely associated with the measured trait. A high lod score suggests that the genetic marker and a gene for the trait are located close to each other on a chromosome.