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GENETIC TERMS

GENETIC TERMS. Key definitions. GENE A part of a chromosome which controls a specific feature of an individual. Key definitions. ALLELE Different forms of a gene, e.g. the gene for eye colour may include and blue allele and a brown allele. Key definitions. DOMINANT

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GENETIC TERMS

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  1. GENETIC TERMS

  2. Key definitions • GENE • A part of a chromosome which controls a specific feature of an individual.

  3. Key definitions • ALLELE • Different forms of a gene, e.g. the gene for eye colour may include and blue allele and a brown allele.

  4. Key definitions • DOMINANT • An allele which is expressed (switched on) while another allele is switched off. Usually identified as a capital letter, e.g. R.

  5. Key definitions • RECESSIVE • An allele which is not expressed (switched off) while another allele is switched on. Usually identified as a lower case letter, e.g. r.

  6. Key definitions • HOMOZYGOUS • An individual who has inherited two identical alleles, e.g. RR or rr

  7. Key definitions • HETEROZYGOUS • An individual who has inherited two different alleles, e.g. Rr or Rr

  8. Key definitions • GENOTYPE • A description of the genes an individual carries, e.g. your genotype may be RR, rr, or Rr

  9. Key definitions • PHENOTYPE • A description of the feature an individual shows, e.g. your phenotype may be tongue roller or non-tongue roller.

  10. The inheritance of eye colour • A person with the genes BB will have brown eyes. • A person with the genes bb will have blue eyes. • A person with the genes Bb will have brown eyes.

  11. The inheritance of eye colour • In a person with the genes Bb only the effect of gene B shows. • The effect of gene B dominates the effect of gene b. • Gene B is dominant to gene b. • Gene b is recessive to gene B.

  12. B is the gene for brown eyes b is the gene for blue eyes

  13. B is the gene for brown eyes b is the gene for blue eyes Parents Body cell in father with a pair of genes for brown eyes Body cell in mother with a pair of genes for blue eyes BB bb

  14. B is the gene for brown eyes b is the gene for blue eyes Parents Body cell in father with a pair of genes for brown eyes Body cell in mother with a pair of genes for blue eyes BB bb Gametes

  15. B is the gene for brown eyes b is the gene for blue eyes Parents body cell in father with a pair of genes for brown eyes body cell in mother with a pair of genes for blue eyes BB bb Gametes each sperm has a gene for brown eyes B B

  16. B is the gene for brown eyes b is the gene for blue eyes Parents body cell in father with a pair of genes for brown eyes body cell in mother with a pair of genes for blue eyes BB bb Gametes each sperm has a gene for brown eyes each ovum has a gene for blue eyes b b B B

  17. B is the gene for brown eyes b is the gene for blue eyes Parents body cell in father with a pair of genes for brown eyes body cell in mother with a pair of genes for blue eyes BB bb Gametes each sperm has a gene for brown eyes each ovum has a gene for blue eyes b b B B At fertilization There are 4 possible ways of joining a sperm to an ovum

  18. B is the gene for brown eyes b is the gene for blue eyes Parents body cell in father with a pair of genes for brown eyes body cell in mother with a pair of genes for blue eyes BB bb Gametes each sperm has a gene for brown eyes each ovum has a gene for blue eyes b b B B At fertilization There are 4 possible ways of joining a sperm to an ovum B B

  19. B is the gene for brown eyes b is the gene for blue eyes Parents body cell in father with a pair of genes for brown eyes body cell in mother with a pair of genes for blue eyes BB bb Gametes each sperm has a gene for brown eyes each ovum has a gene for blue eyes b b B B At fertilization There are 4 possible ways of joining a sperm to an ovum B B

  20. B is the gene for brown eyes b is the gene for blue eyes Parents body cell in father with a pair of genes for brown eyes body cell in mother with a pair of genes for blue eyes BB bb Gametes each sperm has a gene for brown eyes each ovum has a gene for blue eyes b b B B At fertilization There are 4 possible ways of joining a sperm to an ovum b b B B

  21. B is the gene for brown eyes b is the gene for blue eyes Parents body cell in father with a pair of genes for brown eyes body cell in mother with a pair of genes for blue eyes BB bb Gametes each sperm has a gene for brown eyes each ovum has a gene for blue eyes b b B B At fertilization There are 4 possible ways of joining a sperm to an ovum b b B B

  22. B is the gene for brown eyes b is the gene for blue eyes Parents body cell in father with a pair of genes for brown eyes body cell in mother with a pair of genes for blue eyes BB bb Gametes each sperm has a gene for brown eyes each ovum has a gene for blue eyes b b B B At fertilization There are 4 possible ways of joining a sperm to an ovum b b B B All the children of this F1 generation have genotype Bb and phenotype brown eyes

  23. Parents father with brown eyes mother with brown eyes Gametes At fertilization

  24. Parents father with brown eyes mother with brown eyes Bb Bb Gametes At fertilization

  25. Parents father with brown eyes mother with brown eyes Bb Bb Gametes B b B b At fertilization

  26. Parents father with brown eyes mother with brown eyes Bb Bb Gametes B b B b B b At fertilization B b

  27. Parents father with brown eyes mother with brown eyes Bb Bb Gametes B b B b B b At fertilization B b

  28. Parents father with brown eyes mother with brown eyes Bb Bb Gametes B b B b B b At fertilization B b A child who inherits the genes BB will have brown eyes A child who inherits the genes Bb will have brown eyes A child who inherits the genes bb will have blue eyes

  29. Parents father with brown eyes mother with brown eyes Bb Bb Gametes B b B b B b At fertilization B b A child who inherits the genes BB will have brown eyes A child who inherits the genes Bb will have brown eyes A child who inherits the genes bb will have blue eyes In the F2 generation the ratio of brown eyed children to blue eyes will be 3 to 1

  30. The work of Gregor Mendel • Just over 100 years ago a monk called Gregor Mendel tried to discover how characteristics are inherited. • For one of his experiments Mendel used pea plants which are either tall or dwarf (short)

  31. The work of Gregor Mendel • Flowers on tall plants were pollinated with pollen from tall plants. • Flowers on dwarf plants were pollinated with pollen from dwarf plants. • The seeds were collected. • The seeds were planted. • If all the new plants looked the same as the parent plants they were pure breeding (true breeding)

  32. The work of Gregor Mendel • Using these pure breeding plants he pollinated flowers on a tall plant with pollen from a dwarf plant. • The plants grown from these seeds were called the F1 generation. • All the F1 were tall, tallness was the dominant gene. • The F1 were called hybrids because they inherited different characteristics from each parent.

  33. The work of Gregor Mendel • Mendel then pollinates one hybrid flower from the F1 with the pollen from another hybrid F1 flower. • The seeds were grown into the F2 generation.

  34. The work of Gregor Mendel • Three quarters of the flowers in the F2 generation were tall. • One quarter of the F2 were dwarf. • The dwarfness reappeared in the F2 generation. • Dwarfness was the recessive characterisitic.

  35. The work of Gregor Mendel

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