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Reproduction (DNA Structure and Protein Synthesis (When the protein chain…
Reproduction
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The Best of Both Worlds
Sexual reproduction produces variation that helps survivla through natural selection if the environment changes. Natural selection is accelerated by humans in selective breeding.
Asexual reproduction needs only one parent is time and energy efficient is often faster than sexual reproduction and many identiacal offspring are produced when conditions are favourable
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Mny plants produce seeds sexually but also reproduce asexually for example by runner or bulb division.
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Inheritance in Action
Some characteristics are controlled by a signle gene. Each gene may have different forms called Alleles
The alleles present, or genotype operate at a molecular level to develop characteristics that can be expressed as the phenotype.
If the type alleles are the same the individual is homozygous for that trait but if the alleles are different they are heterozygous.
A dominant allele is always expreseed in the phenotype even if only one copy is present. A recesive allele is only expressed if two copies are present.
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Types of Reproduction
In asexual reproduction, there is no fusion of gametes and only one parent. There is no mixing of genetic information, leaidng to genetically identical offspring.
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Sexual reproduction involves the joining of male and female gametes formed my meiosis. Meiosis leads to the formation of non-indentical cells - sperm and egg cells in animals and pollen and egg cells in flowering plants.
In sexual reproduction there is a mixing of genetic information taht leads to variation in the offspring.
DNA and the Genome
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The whole human genome has now been studied and this wll have gret importance for medicine in the future
The genetic meterial in the nucleus of a cell is composed of DNA. DNA is a polymer made up of two strands forming a double helix
A gene is a small section of DNA on a chromosome. Each gene codes for a particular sequence of amino acids to make a specific protein.
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More About Genetics
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Ordinary human human body cells contain 23 pairs of chromosomes 22 control general body characteristic but only the sex chromosomes carry the gnees that determine sex.
Inherited Disorders
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Polydactyly is a dominant phenotype cause by a dominant allele that can be inherited from either or both parents.
Cystic fibrosis is a recesive phenotyupe and is casue by recessive alleles that must be inherited from both parents
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