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Let’s think about it…

Let’s think about it…. W hat are autosomes? What are sex chromosomes? What are the human autosomes and sex chromosomes? What are the chances of two parents conceiving a boy? A girl?. Ch 12 Inheritance patterns and Human Genetics . Human chromosome review. 23 pairs 1-22 = autosomes

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Let’s think about it…

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  1. Let’s think about it… • What are autosomes? • What are sex chromosomes? • What are the human autosomes and sex chromosomes? • What are the chances of two parents conceiving a boy? A girl?

  2. Ch 12 Inheritance patterns and Human Genetics

  3. Human chromosome review • 23 pairs • 1-22 = autosomes • 23rd pair = sex chromosome • What are they two sex chromosomes? • Female: XX • Male: XY • Y chromosome contains SRY gene • SRY: Sex determining Region Y- gene coding for production of male gonads (testes)

  4. Sex-linked genes and traits • Sex-linked traits: trait coded for by alleles on a sex chromosome • X chromosome much larger = many more gene than Y • Examples: • SRY (Y-linked) • Color blindness (X-linked) • Hemophilia (x-linked)

  5. Linked genes • Linked genes: pairs of genes that tend to be inherited together • Genes close to each other on chromosome • Example • If crossing over occurs, A & B are likely to be inherited together • A & E less likely

  6. Mutations • Change in nucleotide base sequence • Germ cell mutation: in gametes • does not affect organism • can be passed down to offspring • Somatic cell mutation: in body cells • Can affect organism • Lethal mutations: can cause death (usually before birth)

  7. Mutations • Chromosomes can be: • Deleted • Flipped around (inverted) • Moved to the wrong chromosome • DNA bases (& sequences) can be: • Deleted • Inserted • Substituted • Etc.

  8. Mutations • Two main categories: • Chromosomal (affect chromosome) • Nondisjunction: chromosomes fail to separate during meiosis • Down Syndrome

  9. 2. Gene (affect DNA sequence) • Frameshift: affects one codon and as a result, all codons downstream are changed (shifts the reading frame • ATC/GTA/GCT/GCT/ATT • ATC/GTT/AGC/TGC/TAT/T

  10. Chromosomal • Nondisjunction video

  11. Gene

  12. 12-2 Human genetics • Pedigree: diagram that shows how a trait is inherited over several generations

  13. Pedigrees used to: • See patterns of inheritance • See if trait is autosomal or sex-linked • Dominant or recessive

  14. Genetic Disorders and Diseases • http://www.youtube.com/watch?v=8s4he3wLgkM

  15. Genetic traits and disorders • Some traits have a single gene with two or more alleles • Blood type • Cystic fibrosis • Most human traits are polygenic: characters influenced by several genes • Skin color; 3-6 genes

  16. Genetic traits and disorders • Complex characters: influenced by environment and genes • Skin color exposed to sunlight • Height • Breast cancer • Diabetes • Heart disease

  17. Multiple alleles • Genes have more than three alleles • ABO blood type

  18. Incomplete dominance • Heterozygote is an intermediate phenotype

  19. X-linked traits • More common in males (x-linked recessive) • Males inherit X from mom and no other • No possibility of heterozygous • Colorblindness • http://www.youtube.com/watch?v=8Aaivktz8G0

  20. Single allele traits • Single allele of a gene controls these traits • <200 human traits • Huntington’s Disease • Autosomal dominant • Symptoms @30-40 y. o.

  21. Detecting genetic disease • Genetic screening: examination of a person’s genetic information • Need DNA from embryo • Amniocentesis: removal of amniotic fluid surrounding fetus • 14th-15th week • Chorionic villi sampling: sample of chorion villi (tissue surrounding developing embry) • 8th-10th week

  22. Open text to page 246 • Copy table in your notes • You only need the disorder, pattern of inheritance, and brief description of symptoms

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