the factors which determine an organisms phenotype

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Mapa Mental sobre the factors which determine an organisms phenotype, creado por freya hinks el 12/04/2017.
freya hinks
Mapa Mental por freya hinks, actualizado hace más de 1 año
freya hinks
Creado por freya hinks hace más de 7 años
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the factors which determine an organisms phenotype
  1. sex-linkage
    1. when the certain allele is located on a sex chromosome
      1. females have two X chromosomes and males have one X and one Y chromosome
        1. the Y chromosome is smaller so fewer genes are carried on it, so most genes are carried on the X chromosome
          1. if a gene is carried on a Y chromosome then a female will not inherit the gene, therefore it will not be expressed in her phenotype
          2. males only have one X chromosome so they often only have one allele for sex-linkage, so they often express the characteristic in thei phenotype even if it is recessive so males are more likely than females to show recessive phentoypes for genes that are sex-linked e.g. colour blindness
          3. dominant, recessive and codominant alleles
            1. dominant alleles
              1. an allele whose characteristic appears in the phenotype even when there is only one copy
              2. recessive alleles
                1. an allele whose characteristic only appears in the phenotype if tow copies are present
                2. codominant alleles
                  1. alleles that are both expressed in the phenotype
                3. epistasis
                  1. many different genes can control the same characteristics - they interact to form the phenotype
                    1. if genes are epistatic they can mask or be masked.
                  2. mutations
                    1. mutagenic agents
                      1. increase the rate of mutation
                        1. mutations occur randomly
                          1. Ultraviolet radiation, ionising radiation, chemicals and viruses
                            1. some chemicals called base analogs can substitute for a base during replication, changing the base sequence in the new DNA
                              1. some chemicals can delete or alter bases, changing the structure
                                1. some types of rediation can change the structure of DNA, which causes problems during DNA replication
                                2. substitution - base/s swapped for another
                                  1. deletion - base/s removed
                                    1. addition - base/s added
                                      1. duplication - base/s repeated
                                        1. inversion - a sequence of bases reversed
                                          1. translocation - a sequence of bases moved from one location to another on the genome
                                          2. monohybrid or dyhibrid genes
                                            1. monohybrid inheritance
                                              1. the inheritance of a characteristic controlled by a single gene
                                              2. dihybrid inheritance
                                                1. the genes that determine the two characteristics are located on different pairs of homologous chromosomes. Each of these genes can have two or more alleles.
                                              3. autosomal linkage
                                                1. genes on the same autosome are linked
                                                  1. they're on the same autosome so will stay together during independant segregation of chromosomes in meiosis 1
                                                    1. the alleles will be passed on the the offspring together
                                                    2. crossing over occurs in meiosis 1, and the closer the genes are, the less likely crossing over will split them up
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