Genetics Answers

For centuries, people have searched for the fabled Fountain of Youth, said to confer the ability to

forestall old age and remain young forever. To gain insight into how tackling aging by targeting

telomerase might work, researchers looked at mice that lack a telomerase gene. These mice have

shorter telomeres than normal mice and age prematurely. However, when these mice were engineered

to express telomerase in their somatic cells, their telomeres lengthen and the effects of aging are

reversed. This observation suggests that a drug that stimulates the expression of telomerase in somatic

cells could prevent telomere shortening and stop the aging process. Consider how such a drug would

work and what may be some potential side effects of such a drug?

A conditional mutation expresses its mutant phenotype only under the restrictive conditions and expresses the normal phenotype under the permissive conditions. One type of conditional mutation is a temperature-sensitive mutation, which expresses the mutant phenotype only at certain temperatures. Strains of E. coli have been isolated that contain temperature-sensitive mutations in the genes encoding different components of the replication machinery. In each of these strains, the protein produced by the mutated gene is non-functional under the restrictive conditions. These strains are grown under permissive conditions and then abruptly switched to the restrictive condition. After one round of replication under the restrictive condition, the DNA from each strain is isolated and analysed. What characteristics would you expect to see in the DNA isolated from each strain with a temperature-sensitive mutation in its gene that encodes a) DNA polymerase III, b) primase and c) initiator protein?

The regulation of replication is essential to genomic stability, and, normally, the DNA is replicated just

once every eukaryotic cell cycle (in the S phase). Normal cells produce protein A, which increases in

concentration in the S phase. In cells that have a mutated copy of the gene for protein A, the protein is

not functional and replication takes place continuously throughout the cell cycle, with the result that

cells may have 50 times the normal amount of DNA. Protein B is normally present in G1 but disappears

from the cell nucleus in the S phase. In cells with a mutated copy of the gene for protein A, the levels of

protein B fail to disappear in the S phase and, instead, remain high throughout the cell cycle. When the

gene for protein B is mutated, no replication takes place.

Propose a mechanism for how protein A and protein B might normally regulate replication so that each

cell gets the proper amount of DNA. Explain how mutation of these genes produces the effects just

described.

What is sex chromosomes

1. A woman's sister has cystic fibrosis, a disease caused by recessive genes. Neither of her parents has the disease. What chance is there that her mother is a carrier (heterozygous) for the trait? What chance is there that the woman herself is a carrier for the trait?  

2. Huntington's disease is a degenerative disease of the nervous system which does not show up until age 40. It is caused by a dominant gene. John's father just began to show the symptoms. What is the chance that John will have the disease?

Achondroplasia is caused by a dominant allele. Two parents have achondroplasia, but their child does not. Explain how it is possible for the child not to have achondroplasia.

How much DNA is in a single cell? Put reference

Fill the blanks to complete the statements related to concepts important in Genetics

What is a gene?

1. Instruction manuals for our bodies are called ____.

2. Of the ____ genes in the body only a few are used for making hemoglobin.

3. Since genes contain instructions for building proteins, one example of a protein would be ____.

what is the possible genotype ratio among children with mother having a IAi and father having the genotype IAIB

Discuss the locations of each stage in protein synthesis, include exons, introns, splicing and amino acid activation.