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INTRODUCTION TO GENETICS

INTRODUCTION TO GENETICS. Ms. Wassum. Traits. Traits are the different forms of a characteristic that you may exhibit Ex: Blue or Brown Eyes Traits are inherited from our parents Therefore, when we talk about genetics, we are talking about sexual reproduction. Chromosomes.

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INTRODUCTION TO GENETICS

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  1. INTRODUCTION TO GENETICS Ms. Wassum

  2. Traits • Traits are the different forms of a characteristic that you may exhibit • Ex: Blue or Brown Eyes • Traits are inherited from our parents • Therefore, when we talk about genetics, we are talking about sexual reproduction

  3. Chromosomes • Every cell in a human body has 23 pairs of chromosomes – half from our mother, half from our father • Genes are found on chromosomes • We have about 20,000-25,000 genes • Each gene holds a code that tells our body to make a certain protein • The protein that is made determines a Specific trait. Ex: Blue eye pigment or Brown eye pigment

  4. Alleles • The different forms of a gene that can exist • Ex: Curly hair gene or straight hair gene • Dominant – ‘Strongest Allele’ – If it is present, you will have that trait. We use upper case letters for dominant alleles • Recessive – ‘Weakest Allele’ – This won’t show up unless there are two of them. We use lower case letters for recessive alleles

  5. Genotype • The actual alleles you have for a trait • Ex: For eye color, you inherit B from dad and b from Mom • Your genotype is Bb • If there is a dominant allele, the genotype is written with the upper case first. (Never write bB) • Your genotype is the genesyou have

  6. Genotype (Cont’d) • If you have two copies of the same allele for a trait (BB or bb), then you are HOMOZYGOUS for that trait • If you have two different alleles for a trait (Bb), then you are HETEROZYGOUS for that trait

  7. Phenotype • How the genes actually show up, or how they are expressed • So, if your genotype is Bb, • Where B is brown • And b is blue • The phenotype would be Brown eyes • Phenotype is the physical appearance

  8. Karyotype-Normal A picture of the chromosomes found in an individual. Used to determine abnormalities.

  9. Karyotype - Abnormal There are three copies of chromosome 21 – there should only be two copies. This is a karyotpe of a female with Down’s Syndrome.

  10. Quiz Time • You inherit the gene for freckles (F) from dad, and the gene for no freckles (f) from mom 1. What would your genotype be? • Ff 2. What would your phenotype be? • You would have freckles • Which allele is dominant? • F (freckles)

  11. Quiz Time • You inherit the gene for no allergies (a) from dad, and the gene for allergies (A) from mom 1. What would your genotype be? • Aa 2. What would your phenotype be? • You would have allergies • Which allele is dominant? • A (allergies)

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