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Biology Revision Notes

B1- You and Your Genes

Differences in individuals are called variations
Variation can be effected by genetics and environment
Genes carry the genetic information for every living organism.
Different genes control different characteristics, e.g. eye colour
Genes come in long strips called chromosomes
Chromosomes are made of…

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Dominant alleles controls the development of the characteristic even if you only
inherit them from one parent
Recessive alleles can only control the characteristic if you inherit them from both
Dominants are displayed by capital letters and Recessive by lower case letters
Most characteristics are determined by different genes…

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If one parent is healthy and not a carrier, the disorder cannot be passed on, but if
both parents carry the disease they have a 75% chance of their child either
developing the disease or becoming a carrier
It is possible to test a person for faulty alleles
If tests…

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Then left to divide up till the 8 cells stage, before being screened for alleles which
cause specific genetic disorders
Any healthy embryos are implanted back into the uterus and the pregnancy goes
ahead as normal
There are concerns about this technique and how it plays nature
People believe it…

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Then make a decisions depending on what will benefit the majority of people


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