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Inheritance, Variation and Evolution (Reproduction (Sexual (Meiosis (1)…
Inheritance, Variation and Evolution
DNA
Deoxyribonucleic Acid. A chemical that all of the genetic information in a cell is made up from. Coded Information. What's in your DNA determines the inherited characteristics you have. Found in the Nucleus. Long Structure called chromosomes.
Chromosomes come in pairs. DNA is a polymer. 2 strands coiled together. Double helix
Gene
Small section of DNA. Each gene codes for a particular sequence of amino acids which put together for a specific protein. 20 amino acids are used but make thousand of proteins. Gene tells us the order Determines what protein the cell produces e.g. haemoglobin, keratin.
Reproduction
Asexual
Asexual reproduction produces genetically identical cells. Only requires one parent. Mitosis - an ordinary cell makes a new cell by dividing in two. New cell has exactly the same genetic information as the parent cell. Clones. No fusion of Gamete. Bateria, some plants and some animals reproduce asexually
Sexual
Sexual reproduction is when genetic information from two organisms (mother and father) is combined to produce on offspring. Mother and father produce gametes by meiosis e.g. egg and sperm in animals. 23 chromosomes from each gamete. Fertilization they fuse together to form full chromosomes.
Produces variation in the offspring
Meiosis
1) Copies of the genetic information are made2) First division the chromosomes line up in the centre of the sell3) Pairs are pulled apart. Some of the father chromosomes and some of the Mothers join5) In the second division the chromosomes line up again6) All Gametes are genetically different from each other
23 pairs of chromosomes in human body. Of these 22 are matched pairs of chromosomes that control characteristics. The 23rd pair is labelled XY or XX. Determines the sex.
Males have X and Y chromosomes: XY
The Y chromosomes causes male characteristics
Females have two X chromosomes: XX
Genetic Diagrams
The recessive allele is represented by a lowercase letter.
The dominant allele is represented by an upper case letter.
Someone with two identical copies of an allele is homozygous for that particular gene
Someone with two different allele for a particular gene is heterozygous.
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Inherited
Diseases
Cystic fibrosis is disease of the membranes. An inherited disorder that mainly affects the lungs and pancreas. It is caused by a recessive allele. 1 in 4 chances of inheriting it.
Polydactyly is a genetic disorder where a baby is born with an extra finger and is caused by a dominant allele. 50% chance of inherited the disorder.
Genetic screening
During IVF embryos are fertilized in a lab and then implanted in the mothers womb. Before implanting it is possible to analyse its DNA to check any disorders.
Good and bad reasons - Implies that people with genetic diseases are undesirable, could increase prejudice. people are picking out the embryos they want. Expensive. Potential life is lost.
It will help stop people from suffering. There are laws to stop it from going to far.
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