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The Quick and Dirty Genetics Review
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Meiosis Forms sex cells called gametes
End with 4 haploid (only 23 chromosomes) cells that are not identical. Separates genes so only one allele gets passed on to offspring. Non-disjunction: chromosomes fail to separate. Offspring end up with more/less chromosomes. Nondisjunction causes genetics disorders like Down Syndrome (trisomy 21), Turners Syndrome (X), and Klinefelters (XXY)
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Mendelian Genetics Gregor Mendel studied inheritance patterns in pea plants. Major conclusion: Parents pass on traits to offspring. Only one copy gets passed on. The one the gets passed on is random. There are dominant and recessive genes.
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Genetic Terms Allele- Variation of a trait.
Homozygous: Having two of the same alleles (TT,tt). Heterozygous: Having two different alleles for traits (Tt). Punnett Squares show genetic probabilities.
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Non-Mendelian Genetics
We find that not everything follows Mendels rules: Sex-linked traits: traits that are carried on X and Y chromosomes. Males have XY and females have XX. Colorblindness is found on X chromosome so females are less likely to have it. Codominance: In a heterozygous, both traits get displayed. Example: Blood Type iAiB= AB Blood Incomplete Dominance: Hybrid has a blended phenotype. Red flower X White Flower= Pink Flowers
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Human Karyotypes Karyotypes can show: Normal has 46
Gender Abnormalities in chromosome (extra/missing/broken) Normal has 46 Arranged large -> small with sex chromosomes at the end.
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Pedigrees Sex-linked traits typically affect males, females are mostly carriers. Dominant traits are found more often in the family. If a kid has it, then a parent must have it. Recessive traits are less found. Two parents may not have the trait but have kids that do. -Track a single trait through a family. -Can determine if trait is dominant, recessive, or sex-linked.
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Genetic Engineering The Human Genome Project allowed us to sequence the entire human genome. Know where to look for certain genes. Possibility to fix/change/swap genes. Pros: Fix genetics disorders. Screen for diseases. Create more desirable traits (pesticide resist tomato plants). Cons: Unknown consequences of unnaturally hybridizing (combining) genes. Morality? Cost?
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