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38 Cards in this Set
- Front
- Back
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genes
chromosome DNA genotype phenotype alleles |
-code for trait passed from 1 generation to next
-DNA organized into it -code for gene -allelic distribution of genes -outward appearance depends on genotype -different forms of gene |
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genotype vs phenotype
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-given genotype can predict phenotype NOT voce versa since dominant/recessive alleles
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true breeding
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-offspring have same traits as parents
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medel first law: SEGREGATION (4)
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-genes come in different forms ie alleles
-2 alleles/gene one from dad one from mom -meiosis separate 2 alleles into 1/gamete -if 2 alleles different, dominant expressed, recessive silenced |
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monohybrid cross
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one trait being studied
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P generation=
F generation= |
parent(ones being crossed), offspring
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use test cross
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-find unknown genotype
-tip: cross with homo recessive -also called back crosses |
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mendel 2nd law: INDEPENDANT ASSORTMENT
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-inheritance of one gene is independent (or unrelated) to inheritance of another gene
-refer as unlinked genes |
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phenotypically
3:1= genotypically 1:2:1= |
-3 purple 1 white
-1PP:2Pp:1pp *parents were Pp/Pp |
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9:3:3:1phenotype
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-parents TTPP x ttpp
-F1 TtPp self cross -F2 9:3:3:1 |
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genes linearly in chromosomes, diploid=
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-homologous pair of chromosomes
-one allele on one chromosome and other allele on other paired (homologous) chromosome |
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segregation and independent assortment (discuss meiosis)
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-before meiosis 1: genome replication, daughter DNA held to parent=sister chromatids
-metaphase 1: homologous chromosomes line up -anaphase 1: homologous separate but sister chromatids stay attached until meiosis 2 *meiosis 1=reductional division (cells haploid after) *independent assortment during meiosis 1 since homologous separate |
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nonindependant assortment and linkage
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-linked genes on same chromosome
-2 genes on same chromosome more likely to segregate during meiosis 1 together -tightly linked-->recombine at freq=zero -loosely linked-->recombine at freq around 50% ie same for independent assortment |
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crossing over
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-during prophase 1 when homologous paired into tetrads, and dna pieces exchanged between
-if genes initially linked may be unlinked if crossed over -if sister chromatids then no change in linkage freq (they identical) |
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degree of linkage
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-depends on distance between gene loci
-chance of cross over proportional to distance between genes *further apart more likely to get recombination |
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genetic map
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-construct by analyzing recombination freq
-shows distances between genes -1 map unit=1 % chance of recomb |
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mendalian genetics for simplicity except 100% recessive phenotype to be homozygous recessive
and if 100% dominant phenotype to be homo or hetero dominant but |
-have variations/different situations
-incomplete dominance, codominance, penetrance/expresstivity, inherited diseases |
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incomplete dominance
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-neither allele dominant
-get mixture of parental phenotypes ex) red flower+ white=all pink (hetero), self cross get 1:2:1 |
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codominance
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-2 criteria
1) multiple alleles for gene 2)more than 1 must be dominant when expressed with recessive -2 dominant present=expression of both phenotypes ex) blood |
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explain blood codominance
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blood type A and B dominant to O
if get both dominant alleles= IaIb genotype and phenotype AB blood (not mix but own phenotype) |
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penetrance
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-number of individuals with allele that actually express phenotype
-all or nothing (either have or dont) |
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expressivity
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-have varying expression of disease symptoms despite having identical genotype
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inherited diseases:
recessive dominant |
-need both recessive alleles to show disease phenotype, if hetero have no disease symptoms but called carrier
-one allele need for disease phenotype to be present |
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early acting vs late acting mutation
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-early: lethal before person can reproduce ie during development or as child
-late: lethal after genes passed on to offspring |
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sex determination
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-humans: 22 autosomes, 1 pair sex chromosomes
-female: XX -male: XY -meiosis: chromosomes pair for segregation -*father determines sex (mother gives X always) -50% chance either XY or XX NO MATTER # children had ie fertilization independent |
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Sex linked is__linked (unless told differently in ?)
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-x linked
-females hetero or homo for genetic condition -males: if X has mutation then=affected=hemizygous |
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x linked recessive seen more in
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males, since no other X to compensate
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if disease on x male fathers cannot pass sex linked disease to
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sons
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aneuploid
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-diploid #=46
-aneuploidy= variations from 46 *caused mainly by nondisjunction |
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nondisjunction
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-during meiosis 1 homologous chromosomes or meiosis 2 sister chromatids fail to separate
-extra genetic stuff in gamete |
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trisomy
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2N+1, extra chromosome
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monosomy
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2N-1, loss chromosome
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XO
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turner syndrome females
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XXX
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metafemales or superfemales
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XXY
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klinefelter male
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XYY
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male
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deletion
duplication translocation inversion |
-lose chromosome piece
-piece join homologous chromosome -piece join another chromosome -reinserts opposite orientation *if occur in germ cells can pass to offspring |
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whats worse aneuploidy of sex chromosomes or autosomes
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autosomes
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