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Chapter 14 and 15 - Coggle Diagram

- - - - First: alternative versions of genes account for variations in inherited characters
        
        These alternative versions of a gene are called alleles
        
        Second: for each character, an organism inherits two alleles, one from each parent
        
        Third: if the two alleles at a locus differ, then one, the dominant allele, determines the organism’s appearance
        
        Fourth, the law of segregation: the two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes
        
        This segregation of alleles corresponds to the distribution of homologous chromosomes to different gametes in meiosis
        
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- - - - A pedigree is a family tree that describes the inheritance of a trait across generations
        
        Pedigrees can be used to make predictions about future offspring
  - - - Carriers are heterozygous individuals who carry the recessive allele but are phenotypically normal
        
        If a recessive allele that causes a disease is rare, it is unlikely that two carriers will meet and mate
        
        Most societies and cultures have laws or taboos against marriages between close relatives
- - - - Peas were available to Mendel in many different varieties
        
        He also started with varieties that were true-breeding (plants that produce offspring of the same variety when they self-pollinate)
        
        In a typical experiment, Mendel mated two contrasting, true-breeding varieties, a process called hybridization
        
        The true-breeding parents are called the P generation
        
        The hybrid offspring of the P generation are called the F1 generation
        
        When F1 individuals self-pollinate or cross-pollinate with other F1 hybrids, the F2 generation is produced
- - - - When Mendel crossed the F1 hybrids, many of the F2 plants had purple flowers, but some had white
        
        Mendel discovered a ratio of about three purple flowers to one white flower in the F2 generation
        
        Mendel called the purple flower color a dominant trait and the white flower color a recessive trait
        
        Mendel observed the same pattern of inheritance in six other pea plant characters, each represented by two traits
        
        What Mendel called a “heritable factor” is what we now call a gene
- - - - An organism with two different alleles for a gene is a heterozygote and is said to be heterozygous for the gene controlling that character
        
        Therefore, we distinguish between an organism’s phenotype, or physical appearance, and its genotype, or genetic makeup
- - - - Crossing two true-breeding parents differing in two characters produces dihybrids in the F1 generation, heterozygous for both characters
        
        dihybrid cross, a cross between F1 dihybrids, can determine whether two characters are transmitted to offspring together as a unit or independently
        
        It states that each pair of alleles segregates independently of any other pair of alleles during gamete formation
- - - - In codominance, two dominant alleles affect the phenotype in separate, distinguishable ways
- - - - An organism’s phenotype includes all aspects of its physical appearance, internal anatomy, physiology, and behavior
        
        An organism’s phenotype reflects its overall genotype and unique environmental history