Answer;
Semi-permeability means that only certain molecules are allowed to pass through.
Explanation;
-Semi-permeability is one of the features of a cell membrane, which means that the membrane allows selective movement of materials in and out of the cell; that is only certain molecules can enter or leave the cell.
-For example smaller molecules such water and ions such as potassium and sodium ions are able to leave and enter the cell, while other molecules that are large such as protein molecules can not enter or leave the cell.
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:
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:
Neanderthals
Explanation:
Homo sapiens encountered neanderthals in europe and had offspring.
