Answer:
All of these choices are correct.
Explanation:
Cell cycle is the process of growth and division of cell. It comprises of interphase and mitosis. In interphase the cell grows, replicates its genomic content and prepares itself for division. In mitosis the division occurs.
Cell cycle is controlled by a group of kinases called as Cyclin dependent Kinases (CDKs). They act by phosphorylating their substrates. They are of various types like Cdk1, Cdk2, Cdk4 etc. They become active when they bind to a regulatory protein called cyclin. They are also of various types like Cyclin A, Cyclin B, Cyclin C etc. Level of cyclin and corresponding CDK increases and decreases according to the stage of cell cycle. For example in S phase of cell cycle concentration of cyclin A and E shoots up. CDK2 is able to bind to these cyclin molecules and hence it becomes active.
Cell cycle has major checkpoints where the condition of cell is analysed before it proceeds to the next stage of cycle. If any abnormality is detected, repair mechanism is activated or the cell is killed. Checkpoints do not allow cell cycle to proceed in damaged cells.
p53 is a tumor suppressor protein which can halt cell cycle when it detects some abnormality in cell. It usually acts in G1/S checkpoint (before the DNA replication starts in cell) and G2/M checkpoint (before the cell division begins). Hence, all of the above statements are true.
Answer:
<em>The correct option is C) AS</em>
Explanation:
Sickle cell anaemia is a recessive disorder in which the blood of the person is not able to clot properly. For sickle cell to occur, both the alleles for the trait have to be recessive. A person who has a dominant and a recessive allele will be heterozygous, showing the dominant characteristics. But such a person will be a carrier for the disease. There will be chances for the offsprings of that person to actually have the disease.
Answer;
D. The birds have different mating seasons.
Explanation;
-Different species of birds have different mating or breeding seasons. Evolution has played a role in adjusting the timing of avian(birds) breeding seasons to maximize the number of young produced. The breeding season depends on a number of factors, for example In the temperate, subarctic, and arctic zones, the overriding factor is the availability of food. This varies across all different species of birds, irrespective of other similarities they may have.
Impact of the use of fossil fuels during the industrial revolution was it made possible a huge increase in the amount of productive energy available to humans.
The development of machines, including steam engines and the internal combustion engine, made it possible to exploit vast new resources of energy stored in fossil fuels, specifically coal and oil. The fossil fuels revolution greatly increased the energy available to human societies during industrial revolution.
Contrary to this fossil fuel have some disadvantages like when fossil fuels are burned, they release large amounts of carbon dioxide, a greenhouse gas, into the air. Greenhouse gases trap heat in our atmosphere, causing global warming.
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Answer:
1. C
2. I
3. B
4. I
5. A
Explanation:
1. Nonrenewable resources include oil, natural gas, coal, and nuclear energy.
2. Nonrenewable resources cannot be readily replaced at the speed with which they are being consumed.
3. Renewable sources include biomass energy (such as ethanol), hydropower, geothermal power, wind energy, and solar energy. Biomass refers to organic material from plants or animals, etc.
4. Because they take a very long time to form. They are not replaceable.
5. Corn can be used for ethanol fuel, and a new crop of corn can be grown and harvested each year. Corn is a renewable resource. Also, renewable resources <u>cannot</u> be replaced in our lifetime.
