Answer:
Explanation:
Meiosis is a form of cell division that occurs in the sex cells of organisms. It ensures the reduction of a diploid cell to an haploid cell to allow for the formation of a diploid zygote after fertilization (contribution of both parents haploid sex cells to give a diploid zygote). Thus, this process is very essential and important.
The reduction is accomplished by 2 divisions after the duplication of chromosomes
- first division: separation of homologous pairs of chromosomes (this reduces the total in half)
- second division: separation of sister chromatids of a chromosome.
The rearrangement in meiosis occurs by crossing over/genetic recombination.
This is the exchange of genetic material between homologous pairs of chromosome bringing about a rearrangement and genetic variation
An example of a chromosomal abnormality that arises as a result of defects in this process is the Down Syndrome which is caused by a nondisjunction of the chromosomes 21 pair in a sex cell.
This condition produces offsprings that have some characteristic facial features, short stature etc
I use save my exams
https://www.savemyexams.co.uk/gcse-biology-aqa-new/
And I also use past AQA papers but end of topic tests
Hope it helps :)
Answer:
Graded potentials are brought about by external stimuli (in sensory neurons) or by neurotransmitters released in synapses, where they cause graded potentials in the post-synaptic cell. Action potentials are triggered by membrane depolarization to threshold.
Explanation:
When Kai was hungry and his blood glucose level was decreasing, glucagon is the hormone which was secreted by the islets of pancreas to increase the blood sugar levels in his body. Glucagon forces the liver to release the stored glucose in it, which increases the blood glucose level in the body. When Kai ate the sugar cookies there was enough of blood glucose available for his body, also it exceeded the requirement and went high. Insulin was then secreted to control this excess glucose from the islets of pancreas. As it helps the body cells to absorb the glucose and lowers the amount of glucose in the blood. It makes the cell available with the glucose to produce energy and perform their activities.
In short, glucagon and insulin both are secreted by the same organ which is islets of pancreas. But they differ in their function, glucagon increases the blood glucose when the body needs it, whereas insulin helps to absorb the excessive glucose and stores that in the body. Both are the hormones which help in regulating the body glucose levels Hope this helps its all i can do for you.
