To study the molecular mechanism of dna replication, you incubated soluble e. coli extracts with a mixture of datp, dttp, dgtp, and dctp, all of which are labeled with the -phosphate group. after a while, the incubation mixture was treated with trichloroacetic acid, which precipitate the dna but not the nucleotide or very short oligonucleotides. the precipitate was collected and the extent of the radioactively label nucleotide incorporation into the dna was determined.
a.) if any one of the four nucleotides is omitted from the incubation mixture, would you detect radioactivity in the precipitate? explainb.) would 32p be incorporated into the dna if only dttp is labeled? explainc.) would radioactivity be found in the precipitate if 32p labeled the β and γ rather than the α phosphate of the deoxyribonucleotides? explain.

Explanation:

A) Since, mixture of dATP, dTTP, dGTP, and dCTP all were labeled; radioactivity can be detected even if one of the four nucleotides is omitted from the incubation mixture. This is because all other three nucleotides contain labeled phosphate and hence, radioactivity can be detected.

B) Yes. If 32P is labeled only dTTP, it can be detected in DNA. Since, dTTP can pair with 'A' nucleotide in DNA.

C) Mostly radioactivity can be detected in DNA when the alpha or terminal phosphates are labeled. It is difficult to detect radioactivity when phosphate groups other alpha like beta or gamma phosphates are labeled. Even if the radioactivity is detected it can be detected in rare cases like 5`end labeling of DNA on gamma phosphate.

an individual’s sex (i.e., whether they are a male or female) is determined by the sex chromosomes. most people have two sex chromosomes, one that is inherited from their mother and one that is inherited from their father. typically, females have two x chromosomes (xx) and males have one x chromosome and one y chromosome (xy). conditions caused by changes (“mutations”) in genes located on the x chromosome are considered x-linked.

x-linked recessive inheritance

most x-linked conditions are recessive. this means that in a person with two x chromosomes (most females), both copies of a gene (i.e., one on each x chromosome) must have a change or mutation whereas in a person with one x chromosome (most males), only one copy of a gene must have a mutation. a female with a mutation in one copy of a gene on the x chromosome is said to be a “carrier” for an x-linked condition. a male with a mutation in a gene on the x chromosome is typically affected with the condition. because females have two copies of the x chromosome and males have only one x chromosome, x-linked recessive diseases are more common among males than females. however, x-linked recessive diseases can occur in both males and females.

for x-linked recessive disorders, an unaffected carrier mother who has a mutation in a gene on the x chromosome can transmit either the x chromosome with this mutation or a “normal” x chromosome to her children. if the father is unaffected, none of her daughters will be affected and all of her daughters will be unaffected—since they will inherit at least one normal x chromosome from their father. however, each daughter will have a 50% chance of being an unaffected carrier like her mother and a 50% chance of both x chromosomes being normal.