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B12 - Reproduction - Coggle Diagram
B12 - Reproduction
Types of reproduction
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Meiosis leads to the formation of non-identical cells - sperm and egg cells in animals, and pollen and egg cells in flowering plants.
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In sexual reproduction there is a mixing of genetic information that leads to variation in the offspring.
Asexual reproduction - no fusion of gametes and one parent. No mixing genetic information, leads to genetically identical offspring.
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Inheritance in action
If the two alleles are the same, the individual is homozygous for all that trait, but if the alleles are different they are heterozygous.
A dominant allele is always in the phenotype, even if only one is present, a recessive allele is only expressed if two copies are present
The alleles present (genotype) operate at a molecular level to develop characteristics that can be expressed as the phenotype.
Most characteristics are the result of multiple genes interacting, instead of a signal one.
Some characteristics are controlled by a signal gene. Each gene may have different forms called alleles.
More about genetics
Ordinary human body cells contain 23 pairs of chromosomes;22 control general body characteristics only but the sex chromosomes carry the genes that determine sex.
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In human females that sex chromosomes are the same (XX) while in males the sex chromosomes are different (XY)
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Inherited disorders
Polydactyly is a dominant phenotype cause by a dominant allele that can be inherited from either or both parents.
Cystic fibrosis is a recessive phenotype and is caused by recessive alleles that must be inherited both parents.
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DNA and the genome
DNA
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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.
Genome
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The whole human genome has now been studied and this will have great importance for medicine in the future.