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Biology - genetics (alleles and genes (alleles the different forms of the…
Biology - genetics
alleles and genes
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homozygous when both alleles are the same, heterozygous when both of the alleles are different
gamete an organism's reproductive cell, haploid e.g. egg cell
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DNA
this is a nucleotide
the base can be one of 4 - adenine cytosine guanine thymine (A,C,G,T)
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sexual reproduction
genetic information from 2 organisms combined to produce offspring which is genetically different to either parent
parents produce gametes, in animals are sperm and egg cells
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at fertilisation male&female gametes fuse to produce zygote/fertilised egg, zygote is diploid full set of chromosomes
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meiosis
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once gametes merge to form a zygot, the diploid cell divides by mitosis to form an ambryo and then these cells begin to differentiate
the work of mendel
crossed a tall plant and a dwarf plant, all offspring were tall
crossed 2 of the offspring, 3 were tall but 1 was dwarf
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it was difficult to understand his ideas then as there was no concept of genes. by hereditary units he meant genes
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causes of variation
genetic variation
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Sexual reproduction causes the offspring to have a new combination of characteristics from both parents
environmental variation
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E.g. a child who does not receive adequate nutrition will not grow to their full height potential, regardless of genetics
most phenotype features are the result of multiple genes acting together, not single genes being inherited
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protein synthesis
transcription
the mRNA is complementary to this strand and same bases are used, except thymine is replaced with uracil
using the template strand of DNA, the polymerase begins to produce mRNA
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translation
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here, there are tRNA molecules carrying a specific amino acid
the anti-codons complementary to the codons begin to attach together and the amino acid on the tRNA is released
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this forms a chain of amino acids called a polypeptide chain, which folds up to form a protein