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The Human Genome Chapter 14

The Human Genome Chapter 14. Donna Howell Biology I Blacksburg High School. Chromosomes. All human beings have 46 chromosomes: 23 from the egg, and 23 from the sperm. Two of those chromosomes are called sex chromosomes: the X and the Y. The other 44 are called autosomes.

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The Human Genome Chapter 14

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  1. The Human GenomeChapter 14 Donna Howell Biology I Blacksburg High School

  2. Chromosomes • All human beings have 46 chromosomes: 23 from the egg, and 23 from the sperm. • Two of those chromosomes are called sex chromosomes: the X and the Y. • The other 44 are called autosomes. • Females’ chromosomes are XX, and males’ chromosomes are XY.

  3. Karyotype • Scientists can take pictures of a cell’s chromosomes, and cut them out. • When they sort them out by chromosome number, they have created a karyotype. Human female karyotype

  4. Pedigree • A pedigree is a chart that shows the relationships within a family, and allows us to infer genotypes we may not know.

  5. Genes and the Environment • Some traits are not totally controlled by our genes; the environment contributes to some, such as height. • Mostly due to genes, but also dependent on nutrition.

  6. Blood Group Genes • Some of the first genes to be discovered were the human blood type genes. • There are 4 types of blood: A, B, AB and O.

  7. Recessive Alleles • Some genetic disorders are caused by recessive alleles. • Examples: albinism, cystic fibrosis, Tay-Sachs disease.

  8. Dominant Alleles • Some genetic disorders are caused by dominant alleles. • Examples: Huntington disease, Dwarfism

  9. Co-Dominant Alleles • Some genetic disorders are caused by co-dominant alleles – both alleles contribute to the disease. • Examples: sickle cell disease

  10. From Gene to Molecule • Sometimes, deletions in DNA can cause diseases. • One example is cystic fibrosis. • Three bases are deleted in the DNA, causing an amino acid to not be produced.

  11. From Gene to Molecule • Another example is sickle cell disease. • One base in DNA is changed, causing valine to be produced instead of glutamic acid.

  12. Sex-linked Genes • Because X and Y chromosomes are different, some genes reside on one and not the other. • These are called sex-linked genes.

  13. Sex-linked Genes • One example is colorblindness. • This gene is located on the X chromosome. • Because males only have one X, all colorblindness shows up in males, even if it is recessive.

  14. Chromosomal Disorders • Sometimes the cell makes errors when undergoing meiosis. • One common error is nondisjunction. • Causes abnormal number of chromosomes in gametes.

  15. Nondisjunction • One example is Down syndrome. • When a chromosome fails to separate during meiosis, cells may have an extra chromosome. • Called trisomy.

  16. Sex Chromosome Disorders • Disorders can also happen in the X and Y chromosomes. • In females, nondisjunction causes Turner’s Syndrome; in males, it causes Klinefelter’s syndrome.

  17. Turner’s Syndrome • Woman only inherits one X chromosome. • Unable to reproduce – are sterile. • Sex organs do not develop at puberty.

  18. Klinefelter’s Syndrome • Man has two X chromosomes and a Y chromosome. • Unable to reproduce – sterile.

  19. DNA Testing • Human DNA can be tested to find out a person’s genotype. • This can be used for family planning purposes.

  20. DNA Fingerprinting • A process where DNA from two or more sources can be matched. • Remember the Gene Machine? That was DNA fingerprinting! • Used for crimes, paternity, etc.

  21. Human Genome Project • In 1990, the Human Genome Project began. • This was an attempt to analyze the complete human DNA sequence. • Completed in 2000.

  22. Gene Therapy • Information about our genes can be used to replace an absent or faulty gene with a normal, working gene.

  23. The End

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