Viruses express tissue tropism and host specificity. In particular, the avian influenza strain H5N1 has rare incidences in humans due to the reduced distribution of alpha-2,3 sialic acids in the lower respiratory tract. As a consequence, when the H5N1 strain does infect a human, the disease is very severe due to the risk of pneumonia. In contrast, human influenza strains (H1N1, among others) attach to alpha-2,6 sialic acids, which are readily expressed in the upper and lower respiratory tract. Which of the following would not be true if a mutation were to allow the H5N1 strain to attach to alpha-2,6 sialic acids?Choose one:
A. The avian influenza strain could be transmitted easily from human to human.
B. An epidemic would likely ensue due to the lack of immunity to the new avian influenza strain.
C. The avian influenza strain could be transmitted directly from birds to humans.
D. The avian influenza strain would only infect the lower respiratory tract of humans.
Hint: Alpha-2,6 sialic acid is expressed throughout the human respiratory tract.
Of the mentioned statements, the incorrect one is option D.
The normal H5N1 strain or the bird flu virus when get attached with the alpha 2,3-sialic acid results in the infection of the lower respiratory tract in humans. The condition occurs very rarely. In comparison, the H1N1 or the human influenza strain gets attached with alpha-2,6 sialic acids and easily results in the infection of the upper and lower respiratory tract.
However, if the mutation takes place in the H5N1 strain, it can bind with the alpha-2,6 sialic acid and can result in the overall infection of the human respiratory tract. Now due to the occurrence of mutations in the H5N1 strain, bird flu can get transmit easily from birds to humans and from one human to another human. Also due to lack of immunity because of the emergence of new strain, the condition can become lethal as, like normal flu, the mutated strain can also result in the infection of the entire respiratory tract.
The theory of natural selection states that: a. individuals that live the longest are best adapted and selected for survival in the next generation b. the best-adapted individuals survive and reproduce, contributing the most genes to the next generation c. only the largest and strongest survive d. individuals that mutate in response to their environment will survive at the expense of those individuals who are genetically stable
Evolution may be defined as the change in the characteristics of the organism over several generation with respect to time. The natural selection acts as the main driving force for evolution.
Darwin is known as the father of evolution. According to natural selection, the individuals that are best adapted to their environment will survive and reproduce more and transfer their genes to the next generation.
Thus, the correct answer is option (b).
The correct answer is option b.
Natural selection generally illustrates that some of the individuals in a population get adapted significantly with their surroundings, and as a consequence, will thrive. Due to this, the genes get inherited on to the next generation, which may help the coming generation to get well adapted to the present environment. Therefore, the individuals that adapt adequately will thrive and reproduce and will pass on the majority of the genes to the next generation.
Erythrocytes might the best of example of form equals function because they lack many organelles. What organelles are absent in erythrocytes?
Mature mammalian red blood cells lack nuclei, mitochondria and rough endoplasmic reticulum, they do not contain DNA and consequently, cannot divide. They also cannot synthesise RNA nor synthesise any new proteins, and consequently, have a limited lifespan. Mature red blood cells circulate for about 100–120 days in the body before they are removed by the spleen.
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why do the processes and events dating back to the big bang eventually led to the existence of life on earth
Stars are formed such that their death led to the creation of life.
The Big Bang theory was developed in 1927. This theory helps to understand how the universe was created. According to this theory, hydrogen gas was created through a process of expansion and explosion. As a result, stars are formed such that their death led to the creation of life.
Earth formed around 4.54 billion years ago which is equal to approximately one-third of the age of the universe.
Some information about bacteria and viruses is arranged in this table.Which argument about bacteria and viruses is supported by this information?
A.Bacteria are larger than viruses but are still small enough to enter cells.
B.Both bacteria and viruses are surrounded by protective coverings, through the composition of each covering may be different.
C. Only bacteria can acquire new characteristics, which makes them more difficult to treat.
D.Bacterial infections such as diphtheria and tetanus cannot be prevented by vaccines.
Explanation: Bacteria are larger than viruses but are still small enough to enter cells.
The argument supported by the information in the table is that both bacteria and viruses are surrounded by protective coverings, but the composition of each covering may be different.
The argument supported by the information in the table is option B. Both bacteria and viruses are surrounded by protective coverings, but the composition of each covering may be different. For example, bacteria have a rigid cell wall made of peptidoglycan, while viruses have a protein coat called a capsid.
This difference in composition affects how bacteria and viruses interact with their environments and how they can be treated.