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40 Cards in this Set
- Front
- Back
Blending
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idea that genetics of 2 parents mixes (like paint in a bucket)
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Particulate
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idea that 2 parents pass on distinct units of inheritance that retain their separate identities in offspring
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Gregor Mendel
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-monk
-studied botany and math before he decided he wanted a simple life and not a "real world" job |
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the garden pea plant (Why is it good for genetic testing?)
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-many varieties
-self pollinating but can be cross-pollinates -true breeding -reproduce quickly |
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pollination
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transfer of pollen from the stamen to the pistil
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self-pollination
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fertilization occurs w/in a single plant
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cross pollination
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transferring pollen from one strain of pure plant to another strain that is pure for the contrasting trait
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Mendel's Experiement
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P Generation
-true breeding -"parent generation" F1 Generation -offspring resulting from P generation -"first filial generation" -hybrids F2 Generation -offspring from F1 -"second filial generation |
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Mendel's Conclusion
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2 fundamental principles of heredity
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Law of Independent Assortment
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each allele is independent from the other during meiosis
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Law of Segregation
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the 2 alleles for a character separate randomly during gamete production
-anaphase 1 |
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Mendel's F2 Cross Results
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dominant - recessive ratio of 3:1
-3 purple, 1 white |
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How did Mendel explain the constant pattern?
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1. alternate forms of genes (alleles) account for variations of inherited characteristics
2. organisms inherit 2 alleles - one from each parent 3. if 2 alleles are different, then one is expressed (dominant) 4. the 2 alleles for a character separate during gamete production |
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test cross
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-punnett square used to determine probable outcome
-not always spot on but if there is a big difference = mutation of something else is wrong |
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pleitropy
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one gene affects an organism in multiple ways
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Genetics of Sickle cell Anemia
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two alleles
1. Hb^a : normal 2. Hb^s : sickle cell |
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Pleiotrophic affects of two sickle cell alleles
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-at low O2 levels, blood cells with only Hb^s hemoglobin "sickle"
-causes blood cells to stick together -impedes oxygen delivery -over time, it causes damage throughout body |
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epistasis
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multiple genes affect 1 phenotype
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albinism
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phenotype produced when pathway for melanin is completely blocked
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tyrosinase
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-An enzyme in the melanin synthesizing pathway
-Without an active tyrosinase melanin production is halted |
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polygenic inheritance
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many genes plus environmental factors affect phenotype
-the greater number of genes and environmental factors that affect a trait, the more continuous the variation in versions of that trait -examples include: height, weight, eye and skin color - |
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Genetic disorders
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Inherited conditions that cause mild to severe medical problems
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Why don't genetic disorders disappear?
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-mutation introduces new rare alleles
-in heterozygotes harmful allele is masked so it can still be passed on to offspring -late onset: there already old enough to have had children by the time the disease is present -heterozygous carrier -beneficial |
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Huntington's disease
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-Autosomal dominant allele
-Causes involuntary movements, nervous system deterioration, death -Symptoms don't usually show up until person is past age of 30 -People often passed the allowing before they know they have it |
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Multi-factorial disorders
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Many people are susceptible to diseases that have a multi-factorial basis
-A genetic component plus a significant environmental influence Heart disease, diabetes, cancer, alcoholism, manic-depressive disorder, schizophrenia |
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Phenotypic treatments
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Symptoms of many genetic disorders can be minimized or suppressed by:
dietary controls, adjustments to environmental conditions, and surgeries or hormonal treatments |
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Homologous chromosomes
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-Homologous autosomes identical in length, size, shape, and gene sequence
-Sex chromosomes are nonidentical but still homologous -Homologous chromosomes Interact (crossing over), then segregate from one another during meiosis |
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Thomas Hunt Morgan
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First to associate the specific gene with a specific chromosome
-He selected drosophila melanogaster because they are prolific breeders, have only four chromosomes, and have many variants |
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Linked groups of genes
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Linked genes tend to be inherited together because they're located close together on the same chromosome and I passed along other unit
-Close together equals less chance they will separate during crossover |
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Full linkage
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No crossing over
Very close to centromere |
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Incomplete linkage
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Crossing over
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Crossover frequency
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Morgan's student predicted that the further apart two genes are the higher the probability that a crossover will occur and therefore the higher the recombination frequency
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The Y chromosome
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You were than two dozen genes identified
One is the master gene for male sex determination (SRY gene) -SRY present = tester -SRY absent = ovaries |
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the x chromosome
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carries more than 2300 genes
most genes deal with non-sexual traits -genes on x chromosome can be expressed in both males and females |
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Deletion
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Loss of some segment of a chromosome
Most are lethal or cause a serious disorder |
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Duplication
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Gene sequence that is repeated several to hundreds of times
Duplications a car normal chromosomes May have adapted advantage Useful mutations may occur and copy |
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Inversion
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A linear stretch of DNA is reversed
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Translocation
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A piece of one chromosome becomes attached to another nonhomologous chromosome
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Aneuploidy
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Individuals have an abnormal number of chromosomes
Trisomy: 2n +1 monosomy: 2n -1 Major cause of human reproductive failure Most human miscarriages are aneuploids |
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Polyploidy
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Individuals have three or more of each type of chromosome
Common in flowering plants Lethal for humans 99% die before birth or newborns die soon after |