Aneuploidy can result in the final daughter cell if the spindle fibers fail to pull a chromosome toward the pole as in case of non-disjunction.
Explanation:
Aneuploidy is a condition which arises when one or more chromosome is missing in the final daughter cells.
Non-disjunction refers to the failure of chromosomal or chromatid segregation or separation during cell division. This results in erroneous meiosis or mitosis leading to the formation of final daughter cells or gametes with an extra or missing chromosome. This condition is aneuploidy.
Failure of separation or segregation of:
- Homologous chromosomes occur in Anaphase I, affects four daughter cells.
- Sister chromatids during Anaphase II, affects two daughter cells
This failure of separation leads to aneuploidy chromosomal abnormalities like monosomy, trisomy, etc which can cause diseases like Down’s syndrome, Turner’s syndrome etc.
Answer:
The correct answer is c) The first statement is true; the second is false.
Explanation:
To be able to perform its role, a hormone must bind a specific receptor in its target cell. The receptor can be located inside the cell (in cytosol) or in the surface of the cell (transmembrane receptor). By regulating the expression of the receptor, the target cell regulates the hormonal activity.
The number of hormone receptors in a cell is not constant, it can vary depending on sereral factors, such as the age of the organisms, the effect of several drugs, mutations or diseases.
Diversity is produced by mutation, it is what causes life to have advantages or disadvantages, and thus allow survival of the fittest to choose which mutation is the best suited for it's environment.
Answer:
The animals present body structure is due to evolution. It is seen in each part including the structure of the heart. The vertebrate heart becomes complex from a simpler form.
Invertebrates, the heart of fishes is two-chambered having one auricle and one ventricle. The deoxygenated blood gets purified in the gills. They are aquatic and no lungs for breathing. The hearts pump a mixture of oxygenated and deoxygenated blood to the body.
The amphibians and reptiles have 3 chambered heart as they lead terrestrial mode of life. The gills modified into the lungs. The left auricle receives pure blood and the right auricle receives deoxygenated blood. The blood purified in the lungs and in the ventricle, both types of blood get a mix. The ventricle pumps the mixed-blood throughout the body.
In the case of birds and mammal, the heart is 4 chambered and the oxygenated and deoxygenated blood are separated. These two are higher vertebrates. No mix of pure and impure blood, the body receives only the oxygenated blood.
This shows to construct the phylogenetic tree of vertebrates - the fishes should be in the bottom, and above it amphibians, reptiles, then, mammals and birds on the top branch of the tree. As the chambers and structure of the hearts modified one after another.
