Answer:
Bacteriophages (phages) are viruses that infect only bacteria and do not infect mammalian or plant cells. Phages are ubiquitous in the environment. Phages or bacteriophages were chosen as a model system for their simplicity, as they only contained protein-coated nucleic acid. Alfred D. Hershey and Martha Chase (who were part of the bacteriophage group) in 1952 studying the infection of the bacterium Escherichia coli by the T2 phage show that the information definitely resides in the DNA. They used phage with either [32P] -labeled DNA or [35S] -labeled proteins to infect the bacteria. Immediately afterwards, they centrifuged the sample so that the infected bacteria remain in the pellet and the virus capsids (proteins) remain in the supernatant. [35S] is found in the supernatant, whereas [32P] is found in bacteria. After one cycle of infection, it was observed that when phage labeled in the [35S] proteins were used, only 1% of the radioactivity was incorporated into the progeny. But when phages were [32P] labeled, more than 30% of the radioactivity was in the progeny. They showed directly that what is transmitted from one progeny to another is the DNA and not the proteins, despite having first "diluted" in a bacterium.
Explanation:
Bacteriophages are viruses that infect bacteria in a specific way. Bacteriophages, like other known viruses, are found in an intermediate zone between living organisms and inert matter. Bacteriophages bind to the host pathogenic bacterium, introduce their genetic material, replicate inside it and destroy it. Hersey, along with his assistant Martha Chase, used phages because they knew that T2 phages were made up of 50% proteins and 50% nucleic acids and that phages entered bacteria and reproduced. As the progeny carried the same infection traits, the genetic material of this had to be transmitted to the offspring, but the mechanism was unknown. These scientists carried out an experimental work with the T2 virus, a bacteriophage that infects the bacterium Escherichia coli, which it reproduces by attaching itself to the outer wall of the bacterium, injecting its DNA into it where it replicates and directs the synthesis of the phage's own proteins. Phage DNA is encapsulated within proteins and produces phages, which lyse or disrupt the cell and release phage from progeny. They infected a culture of bacteria with radioactively labeled phages: the protein coat with sulfur (35S) and its DNA with phosphorus (32P). After infection, they separated the phages from the bacteria by violent shaking using a mixer (hence the name of the experiment). By centrifugation the much smaller phages remained in the supernatant and the much larger bacteria in the pellet. 85% of the radioactivity corresponding to DNA appeared in the pellet and 82% of the protein in the supernatant. This result supported the idea that DNA was the only component of the bacteriophage that penetrated the interior of the bacteria and, having the ability to form new phages, constituted the genetic material.
Answer:
Part 1:
The mother’s genotype is ii, rr, MN
The father’s genotype is IAIA/IAi, Rr, MM
Part 2:
Approximately 1/32 (3.125%) of children can be expected to have the stated blood types.
Explanation:
Part 1:
The mother has blood types 0, Rh- and MN. Therefore, her genotype has to be ii, rr, MN.
The father has ABO type A. His ABO genotype may therefore be either IAIA or IAi, as both are compatible with type A offspring with a type 0 mother. His Rh genotype must be rr, since his Rh- child necessarily has to have inherited one r allele from each parent. Finally, his MN genotype has to be MM since both alleles are codominant.
Part 2:
Using the given data, we build the following Punnett chart:
IA R N IA r N i R N i r N
IA R M
IA R N
IA r M
IA r N
IB R M
IB R N
IB r M X
IB r N
Note that, of all 32 possible combinations, only a single one of them (marked with “X” produces a genotype which matches the desired blood type, as follows:
genotype: IBi, rr, MN
blood type: B, Rh-, MN
The circulatory system is used to transfer blood
Answer:
Due to less steps and requires less energy.
Explanation:
The bacterial cell is able to use glucose first as an energy source then switch to lactose because glucose requires less steps and less amount of energy for the break down as compared to lactose. If lactose is the only sugar available to the bacterial cells, then bacterial cells will use it as energy source for the production of energy. In order to use lactose, the bacteria must express the lac operon genes, which encode the main enzymes for lactose uptake and metabolism.
