Answer:
Failure of chromosome to separate
Explanation:
The main essence of meiotic division is to form daughter cells with a reduced number of chromosomes that will maintain the correct chromosomal number in an organism. This is achieved when chromosomes separate during gamete formation (meiosis) to produce haploid (n) gametes.
However, a case may arise whereby chromosomes fail to separate during the anaphase stage of meiosis. This case is referred to as MEIOTIC NON-DISJUNCTION. As meiosis occurs in two stages i.e. meiosis I and II, so does meiotic nondisjunction. It can occur in meiosis I, where homologous chromosomes fail to separate or meiosis II, where sister chromatids fail to separate.
If it occurs in meiosis I, Two gametes will have a n-1 chromosome number i.e. one chromosome is missing while Two other gametes will have n+1 chromosome number i.e. one extra chromosome is added.
If it occurs in meiosis II, two normal haploid gametes (n) will be produced while the other two will have a n+1 and n-1 chromosome number respectively.
When these abnormal gametes (n+1, n-1) fuses with a normal gamete (n), the resulting organisms possess a chromosomal anomaly called ANEUPLOIDY i.e. a disorder in chromosomal number. The organisms will have 47 and 45 chromosomes depending on whether n+1 or n-1 gametes is involved respectively.
<h2>Kinase cascade </h2>
Explanation:
Normally, PK2 activates PK1
- PK1 and PK2 normally work sequentially in an intracellular signaling pathway
- If PK1 is permanently activated, a response is seen independently of whether or not PK2 is present
- If PK1 activated PK2, no response should be seen if PK1 were activated in the absence of PK2
- PK2 normally needs to activate PK1 for the cells to respond to the signal
- When PK2 is permanently activated in the absence of PK1, PK1 is not there to relay the signal
Answer:
There are two cell types: prokaryotes and eukaryotes. Prokaryotic cells are usually single-celled and smaller than eukaryotic cells. Eukaryotic cells are usually found in multicellular organisms, but there are some single-celled eukaryotes.
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Answer:
f. cyanobacteria
Explanation:
Cyanobacteria are a group of photosynthetic bacteria. They have the ability to use water as a source of an electron during the process of photosynthesis. Splitting of water produces molecular oxygen that is released into the surroundings. In this way, cyanobacteria release oxygen gas in the air. The primitive atmosphere of the earth was reducing and did not have oxygen gas. The first photosynthetic organisms that could split water during photosynthesis are supposed to be cyanobacteria. These prokaryotes added oxygen to the atmosphere of the early earth and gradually made it oxidative from reducing.
Algin<span> is a chemical taken from brown seaweeds. It is used to make medicine. </span>Algin<span> is used to lower cholesterol levels and to reduce the amount of heavy chemicals including strontium, barium, tin, cadmium, manganese, zinc, and mercury that are taken up by the body</span>
