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Genetics

Genetics. Ms Morin May 2008. TRAITS : Physical characteristics of an organism inherited from parents and passed on from one generation to the next. HEREDITY : The passing of the traits from parents to offspring. GENETICS : Study of heredity. Common Traits. Eye color seed color

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Genetics

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  1. Genetics Ms Morin May 2008

  2. TRAITS : Physical characteristics of an organism inherited from parents and passed on from one generation to the next. • HEREDITY: The passing of the traits from parents to offspring. • GENETICS: Study of heredity.

  3. Common Traits • Eye color seed color • Eye shape petal color • Hair color seed texture • Height blood type • Coat color Seed shape There are also MANY biochemical traits that are unseen (having certain enzymes, for example)

  4. The genetic diversity of James Bond

  5. http://www.athro.com/evo/gen/geframe.html

  6. Chromosomes & Genes • Our body cells have 46 chromosomes found in 23 pairs • Egg and sperm cells have 23 chromosomes each- no pairs. • There are a total of between 20,000 and 30,000 genes on our 23 pairs of chromosomes.

  7. Traits are controlled by genes. • Genes are segments of DNA on a chromosome that code for a specific trait • Each gene holds the DNA “code” to make one protein. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=gnd.TOC&depth=2

  8. Different forms of the same gene are called alleles. • Simple traits are controlled by 2 alleles of the same gene: we inherit 2 alleles of each gene for every simple trait. • 1 allele is inherited from female sex cell (the egg from the mom) • 1 allele is inherited from male sex cells (the sperm from the dad)

  9. Different forms of a gene • Different forms of genes are called alleles. Alleles can be dominant or recessive. • DOMINANT= trait is always expressed no matter what the other allele is.. • RECESSIVE = trait is only expressed if the other allele for that gene is also recessive. • We use a capital letter to represent a dominant allele and a lower case for recessive alleles

  10. Purebred or Hybrid? • PUREBRED: two identical alleles for a trait • HYBRID= two different alleles for a trait Example- Purebred Purebred Hybrid Dominant Recessive BB bb Bb

  11. PHENOTYPE- visible traits or physical appearance of an organism Examples- blue eyes, short, black fur • GENOTYPE- genetic makeup of an organism- its allele combination Examples- bb, Tt, GG

  12. Punnett Squares • What is it? A chart showing all the possible combinations of alleles. Geneticists use them to predict outcomes. (male) (female)

  13. Trait- Hitchhikers Thumb • Hitchhiker’s Thumb is dominant (H). No hitchhiker’s Thumb is recessive (h) • Cross- purebred Hitchhiker’s thumb female X non-Hitchhiker’s thumb male 4. Offspring predictions Genotype: ______%=4/4 = Hh Phenotype: _____%= 4/4= Hitchhiker’s Thumb

  14. Gregory Mendel • Father of genetics • Univ. of Vienna monk 1851 • Wondered why different pea plants had different characteristics • He observed that many pea plants’ traits were similar to their parents

  15. First generation F1 purebred tall X purebred short TT x tt Phenotype= Genotype= Second generation F2 Tt X Tt Phenotype= Genotype= Mendel’s Experiment

  16. Mendel’s Conclusions • When you cross 2 purebred plants • 1st generation only saw the dominant trait (Tall; Purple flowers- next slide) • 2nd generation showed purebred and hybrid. (Tall & short; Purple &White) • 1866- he presented his work but it wasn’t looked at by the scientific world until 1900!

  17. Probability and Genetics • PROBABILITY: A number that describes how likely it is that an event will occur # times event occurs= probability # possible outcomes *Results do not affect future results

  18. HOMOZYGOUS- 2 identical alleles: tt, TT same thing as purebred

  19. HETEROZYGOUS- 2 different alleles: Example: Tt same thing as hybrid

  20. Incomplete Dominance- • alleles are not dominant nor recessive • the phenotype is a blend of the two alleles. (Notice the use of all capital letters.)

  21. Codominance-* neither allele is dominant or recessive* the two different traits appear together in the organism* example: ABO blood type

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