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Genetics since mendel
Genetics since mendel
Genetics since mendel
Genetics since mendel
Genetics since mendel
Genetics since mendel
Genetics since mendel
Genetics since mendel
Genetics since mendel
Genetics since mendel
Genetics since mendel
Genetics since mendel
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Genetics since mendel


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  • 1. Genetics Since Mendel
    In science, there is an exception to every rule, particularly in Genetics
  • 2. Incomplete Dominance
    Neither allele for a trait is dominant
    The phenotype produced is intermediate between the two homozygous parents
    Ex: The four-o’ clock
    plants showed pink
    flowers when a
    homozygous white
    and homozygous red
    plant were crossed
  • 3. Multiple Alleles
    More than two alleles that control a trait are called multiple alleles
    Traits controlled by multiple alleles produce more than three phenotypes
    Ex: Bloodtype
    Alleles for bloodtype are A, B, and O
    Possible genotypes are: AB, AA, AO, B, BO, OO
  • 4. Blood Type Cross
  • 5. Polygenic Inheritance
    A group of gene pairs acts together to produce a trait, which creates more variety in phenotypes
    Many human traits are controlled by polygenic inheritance, such as hair and eye color and the effects of so many alleles acting together produces a wide variety of phenotypes
  • 6. An example of this is human stature.
    NOTE:  whether an individual achieves his or her genetically programmed height is significantly affected by human growth hormones (HGH) produced in the pituitary gland.  A deficiency in the amount of these hormones during childhood and puberty can result in stunted growth.  Too much of them can cause excessive growth resulting in exceptional height.  Differences in diet and other environmental factors during the crucial growth years can also be important in determining stature and other complex traits.  Usually, about 10% of an individual's height is due to the environment.
  • 7. Genetics and the Environment
    Your environment plays a role in how some of your genes are expressed or whether they are expressed at all.
    Ex: skin cancer: if you are genetically predisposed to this cancer, using sunscreen can prevent it and overexposure can cause it
    Environmental factors can affect how large organisms grow
  • 8. Mutations – genes that are altered or copied incorrectly
    A mutation can be harmful, beneficial, or have no effect
    Chromosome disorders – caused by more or fewer chromosomes than normal
    Down’s syndrome –
    caused by an extra copy of
    chromosome 21
  • 9. Genetic Disorders Video
  • 10. Recessive Genetic Disorders
    Both parents have a recessive allele responsible for the disorder and pass it to their child
    Because the parents are heterozygous, they don’t show any symptoms
    Cystic fibrosis is a recessive disorder
  • 11. Sex Determination
    Chromosomes that determine the sex of an organism are XX in females and XY in males
    Females produce eggs
    with an X chromosome
    only. Males produce
    sperm with either an X
    or a Y chromosome
  • 12. Sex-linked disorders
    An allele inherited on an X or Y chromosome is a sex-linked gene
    Color blindness is a sex-linked disorder caused by a recessive allele on the X chromosome
    A pedigree follows a trait through generations of a family