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Degree: Psychology (Bachelors) - Bristol University
|Extended Project Qualification||A Level||£20 /hr|
|Psychology||A Level||£20 /hr|
In the first stage of Meiosis 1 - Prophase 1, after the chromosomes have coiled and condensed they ay touch each other at points known as chiasmata, and Crossing Over occurs. This is where genetic information is swapped between the pair of chromosomes. This results in a change in genetic code and thus, increases variation.
Also, in metaphase 1 and , chromosomes are arranged by random segregation and in Anaphase I and II chromosomes are independantly separated due to this random allignment and this, along with crossing over, means that the genetic code in each of the 4 haploid cells formed is different, thus creating varied cells.
Another way meiosis allows variation to happen is because during interphase, when DNA is replicated, mutations may occur, meaning the genetic code differs from that of the parent and so their DNA has changed.see more
There have been many studies into this area. For example, in 2008, Driessen and his team found that 30% of drug addicts and 15% of alcoholics suffered from post-traumatic stress disorder. This shows a clear link between the two, suggesting that those exposed to severe stress are more vulnerable to addictions.
However, Hajek et al suggested that this is not the case. They found that addictions, for example, smoking does not decrease stress and sometimes even increases levels of stress. Therefore, this contradicts that stress is a cause of addictions, yet they did note that the act of having another cigarette once someone is already addicted will reduce the stress induced by the addiciton itself.
Another study against the argument that stress leads to addiction was conducted by Cloniger. He stated that there is two types of alcoholics, type 1s who drink to reduce tension, and type 2s who drink to relieve boredom. Therefore, stress only explains the vulnerability of type 1s to becoming addictions. Since this shows that the explanation that stress causes addiciton does not apply to everyone, it reduces the validity of the explanation.see more
To do this, there are two rules, the Sine Rule and The Cosine Rule.
The sine rule is a/Sin A = b/Sin B = c/Sin C. (the lower and uppercase are very important. The rule also stands if you write the entire thing the other way up.
The sine rule is used when you either have the vlaue of two angles and one side, or two sides and one angle opposite one of those sides of a triangle.
Label the triangle clockwise starting with the angles. Use uppercase (A) to label the angles. Next, label the sides opposite each angle with its respective lowercase letter (a)
Then simply input the values you have into the correct places of the formula.
If you cannot use the sine rule, use The Cosine Rule:
a2 = b2 + c2 - 2bc cos A
b2 = a2 + c2 - 2ac cos B
c2 = a2 + b2 - 2ab cos C
You must work out which of these to use depending on what values you are given in your question.
To use the cosine rule you either need the length of all 3 sides, or the length of 2 sides and angle. Label your triangle in the same way as you would using the Sine rule. Then, input the numbers into the formula you have chosen.
If you are left with Cos/ Sin/ Tan x, remember to use the inverse to get the answer. E.g. if Cos A = 0.764, A is found by pressing the Cos-1 sign on your caluclated to find the inverse of Cos 0.764. I.e 40.2.see more