Biology: B1, B2, B3 Revision Summary

Ryan Hilton
Note by Ryan Hilton, updated more than 1 year ago
Ryan Hilton
Created by Ryan Hilton about 5 years ago


Biology: B1 You and Your Genes Revision Summary I'm currently revising for my GCSE's and would like to help others who have problems with Revising (like me) by providing summarized Revision Notes for various Subjects (Mainly Science) I do not know if these will help you however, i'd like to put them out there anyway. Thank you and Good Luck with Your Exams :)

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B1 – You and Your Genes (Even Smaller) Summary Genes: Genes make Proteins like Antibodies, Keratin and Hormones. Genes give characteristics such as Hair Colour, Height, Weight and Eye Colour. Environment effects characteristics, Height depending on your Diet. Chromosomes: Humans have 23 pairs of chromosomes. Total = 46. Each Chromosome Gene is in a Particular Position = same position on Partner Chromosome -> Also referred to as a Locus. Alleles: Dominant and Recessive alleles are given as either BB, Bb or bb. The Dominant version of the gene will mask the recessive version. ‘Aa’ the big ‘A’ would hide the effect of the little ‘a’ so all you would see is the effect of the dominant gene pair. Versions of a Gene are called Alleles. 2 of the same alleles either ‘AA’ or ‘aa’ are called Homozygous. ‘AA’ = Homozygous Dominant | ‘aa’ = Homozygous Recessive. One of each ‘Aa’ = Heterozygous. Genotype: What Genes you have ‘Aa’. Phenotype: What it looks like e.g. Dimples or No Dimples. Combining Genes: Sperm and Egg cells have a unique combination of Alleles. E.g. your Brother or Sister will have some similarities to you however, they are not identically the same. Different Characteristics = Different combination of alleles. Gender is Determined on the 23rd pair of Chromosomes. XX = Female & XY = Male. Genetic Disorders Huntington’s disease is caused by inheriting a dominant allele. ‘H’ - Huntington’s disease. ‘h’ = Healthy Person. Huntington’s disease --> ‘HH’ ‘Hh’. Healthy --> ‘hh’ Alleles. Symptoms: Memory Loss, Confusion, Tremors, Clumsiness and Loss of Balance. Does not appear until later ages --> Late 30’s 40’s and Even 50’s. Huntington’s disease is a Faulty Dominant Allele. Currently No Cure. Cystic Fibrosis is caused by inheriting a faulty recessive allele. ‘F’ = Healthy (FF & Ff). | ‘f’ = Cystic Fibrosis (ff). The middle Healthy Allele, ‘Ff’ is called the Carrier because the Dominant ‘F’ masks the Recessive ‘f’ Allele. Genetic Testing You can be tested as an adult for Genetic Testing --> Alleles you inherited when you were conceived = have for the rest of your life. You can test the Baby when it’s an Embryo this is called PGD (Pre-Implantation genetic diagnosis) this is where you would take out 1 of the cells from the 8 cell stage you could then see if it was carrying a Genetic Disease by looking at the Alleles. This method does not harm the Baby. Testing a Fetus = Risks such as infection to the mother and possible Miscarriage. Ethical Decisions --> Do you keep the Baby if you know it has a Genetic Disease or have an Abortion? In the future --> Test people using certain Drugs. Save Money + Lives. Ethics Some issues of Genetic Testing --> Who has access to this information E.g. If a Life Insurance company knows you have a Genetic Condition = increased price. If the Police arrest someone and take a sample = allowed to keep that sample on the database? Should people be able to have access to your information without your permission? Regulations and laws in place that are used to determine this kind of information like who has access this information and what they can do with it. Stem Cells Stem Cells --> found in the embryo. We can remove embryonic stem cells & use them to grow new organs for people with damaged tissue in organs. Not yet 100% effective. Adult Stem Cells --> found in tissues such as Bone Marrow, and Tooth tissue therefore not many Adult Stem Cells. Identical twins = examples of natural clones they are GENETICALLY identical not just similar. Some organisms reproduce asexually --> Strawberry plants and Potatoes.

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