What happens if a homologous pair of chromosomes fails to separate, and how might this contribute to genetic disorders such as down syndrome

If a homologous pair of chromosomes fails to separate, gametes with abnormal chromosome number are formed. Down syndrome is caused due to trisomy chromosome 21.

Explanation:

During anaphase-I of meiosis-I, homologous chromosomes separate from each other and move to the opposite poles. If one or more chromosomes fail to do so, this is called non-disjunction. Non-disjunction of chromosomes results in the formation of gametes with abnormal chromosome numbers and causes many genetic disorders.

For example, when chromosome 21 fails to separate from its homolog during anaphase-I, some of the resultant gametes have two copies of this chromosome and some lack chromosome 21 at all. The fertilization of gamete carrying two copies of chromosome 21 with normal gamete results in the formation of a zygote with three copies of this chromosome and causes Down's syndrome.

it has to be understood that the sea water contains a huge amount of sodium and chlorine ions and if they enter the cell of the atlantic cod fish, the cell will shrivel and the fish will die. to avoid such a condition, the fish uses active transport for the purpose of removing the ions against the gradient.

explanation:

the atlantic cod is not a maritime osmoconformer. its native application of salts is less than that of the seawater it lives in. it is continually falling water from the gills to the ocean via osmosis.

countering that, the fish is going to be swallowing seawater. but since its internal collection of salts is lower than seawater, the fish will want to go free of excess salt, and since that's going upon a gradient, then active transport, requiring energy, must be used to pump out the salt. much marine fish use the organs to filter out the salt and these fish discharge very straight urine.