Genetic Inheritance

Clarissa Mackay
Mind Map by Clarissa Mackay, updated more than 1 year ago
Clarissa Mackay
Created by Clarissa Mackay almost 6 years ago
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Genetic inheritance

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Genetic Inheritance
  1. Definitions
    1. Gene- The smallest unit of heredity corresponding to section of DNA that codes for a specific mRna that is, a section of DNA located between a start codon and a stop codon
      1. Chromosome- The structures that are formed within the nucleus of a cell by the super-collided DNA - 46 chromosomes (23 pairs of homologous chromosomes) 44 = autosomes 2 = sex chromosomes
        1. Locus- the specific point at a chromosome where a gene is located
          1. Allele -Two matched genes at same location (locus)on chromosome
            1. Homozygous- If two alleles code for same trait (FF, ff)
              1. Heterozygous-If two alleles different (Ff)
                1. Genotype-The genetic composition of an individual (ff,FF,Ff)
                  1. Phenotype – The physical expression of a genotype (Brown hair)
                    1. Dominant - If allele masks or suppresses the expression of the other allele it is said to be dominant (represented by capital letter)
                      1. Recessive-The allele masked is said to be recessive (represented by lowercase letter)
                      2. Autosomal Dominant
                        1. Genes that will dominant a recessive gene (FF, Ff - phenotype will show)
                          1. Normal skin pigment, freckles, ability to roll tongue. normal arches, dimples, unttached earlobs (FF,Ff)
                        2. Autosomal Recessive
                          1. Gene that will only show with two homozygous recessive gene
                            1. Albinsm, No freckles, no tongue roll,no dimples, flat feet, attached earlobes (ff)
                          2. Sex-Linked Inheritance
                            1. Inherited traits determined by genes on sex chromosome • A gene found only on X-chromosome = X-linked • A gene found only on Y-chromosome = Y-linked • If recessive not masked – so will be expressed in males
                              1. If recessive not masked – so will be expressed in males - Color blind,haemophilia
                            2. Multiple Allele Inheritance
                              1. Some genes exhibit more than two allele forms e.g. blood group
                                1. Ia, Ib are co-dominant; i is recessive
                                  1. You can be blood group A, B, O or AB
                              2. Incomplete Dominance
                                1. Both alleles expressed in heterozygous to produce a different phenotype to either homozygous trait, often an intermediate
                                  1. inheritance of hair texture, flower colours – CC is curly hair cc is straight hair – Cc is wavy hair
                                2. Polygenic Inheritance
                                  1. Some traits require several gene pairs
                                    1. Skin colour based on three gene pairs, each with 2 alleles Phenotype is continuous from very fair to very dark
                                  2. Genetic Diseases
                                    1. Cystic Fibrosis – autosomal recessive • Sickle cell anaemia- co-dominance • Haemophilia- X-linked recessive • Down syndrome - Trisomy 21 – chromosomal abnormality
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