Chapter Extending Mendelian Genetics. Incomplete Dominance. Incomplete Dominance. R = red R = white. Incomplete Dominance (alt)

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female / eggs Colonie High AP Biology Chapter 12.2 12.

with a simple system peas are genetically simple most traits are controlled by a

the other The relationship between genotype & phenotype is rarely that simple

hybrids have in between appearance RR = red flowers rr = white flowers Rr = pink

generation (P) 1 st generation (F 1 hybrids) RR true-breeding red flowers X 100%

100% RR Rr rr 2 nd generation (F 2 ) red 50% white pink 1:2:1 Incomplete

Co-dominance this time, both alleles are epressed, but they are NOT blended

1 female / eggs Colonie High AP Biology Chapter Beyond Mendel s Laws of Inheritance Etending Mendelian Genetics Mendel worked with a simple system peas are genetically simple most traits are controlled by a single gene each gene has only 2 alleles, 1 of which is completely dominant to the other The relationship between genotype & phenotype is rarely that simple Incomplete Dominance when one allele is partially dominant over the other hybrids have in between appearance RR = red flowers rr = white flowers Rr = pink flowers make 50% less color RR R R R = red R = white Incomplete Dominance Parent generation (P) 1 st generation (F 1 hybrids) RR true-breeding red flowers X 100% pink flowers self-pollinate R R true-breeding white flowers 4 O clock flowers 100% RR Rr rr 2 nd generation (F 2 ) red 50% white pink 1:2:1 Incomplete Dominance (alt) C R male / sperm C R C R C R C R % genotype 50% % phenotype 50% Co-dominance this time, both alleles are epressed, but they are NOT blended together RR = red coat color RR rr = white coat color WW Rr = pink roan coatcolor? RW R = red W = white C W C W C W C W C W 1:2:1 1:2:1

Co-dominance 2 alleles affect the phenotype in separate,

both I A & I B are dominant to i allele I A & I B alleles are

oligosaccharides/antigens on the surface of red blood cells

groups critical for blood transfusions A person produces

blood type donor s blood has A or B oligosaccharide that is

foreign molecules cause donated blood cells to clump together

Blood Type Compatibility genotype phenotype phenotype status I

type O type A oligosaccharides on surface of RBC type B

oligosaccharides on surface of RBC no oligosaccharides on

Most genes are pleiotropic one gene affects more than one

2 Co-dominance 2 alleles affect the phenotype in separate, distinguishable ways ABO blood groups 3 alleles I A, I B, i both I A & I B are dominant to i allele I A & I B alleles are co-dominant to each other determines presences of oligosaccharides/antigens on the surface of red blood cells Blood Type Compatibility Matching compatible blood groups critical for blood transfusions A person produces antibodies against oligosaccharides in foreign blood wrong blood type donor s blood has A or B oligosaccharide that is foreign to recipient antibodies in recipient s blood bind to foreign molecules cause donated blood cells to clump together can kill the recipient Karl Landsteiner ( ) Blood Types Blood Type Compatibility genotype phenotype phenotype status I A I A I A i type A I B I B I B i type B I A I B type AB i i type O type A oligosaccharides on surface of RBC type B oligosaccharides on surface of RBC both type A & type B oligosaccharides on surface of RBC no oligosaccharides on surface of RBC universal recipient universal donor Pleiotropy Most genes are pleiotropic one gene affects more than one phenotypic character wide-ranging effects due to a single gene: dwarfism (achondroplasia) gigantism vs. acromegaly Acromegaly: André the Giant

Pleiotropy It is not surprising that a gene can affect

intricate molecular & cellular interactions responsible

build up in many organs sickle cell anemia sickling of

in mice = 2 genes pigment (C) or no pigment (c) more

matter B allele 9:3:3:1 becomes 9:3:4 Epistasis in Labs

pigment will be: black (B) to brown (b) Epistasis in

Inheritance Some phenotypes determined by additive

phenotypes on a continuum human traits skin color

vs. Nurture Phenotype is controlled by both environment

soil ph Human skin color is influenced by both genetics

3 Pleiotropy It is not surprising that a gene can affect a number of organism s characteristics consider the intricate molecular & cellular interactions responsible for an organism s development cystic fibrosis mucus build up in many organs sickle cell anemia sickling of blood cells Epistasis One gene masks another coat color in mice = 2 genes pigment (C) or no pigment (c) more pigment (black=b) or less (brown=b) cc = albino, no matter B allele 9:3:3:1 becomes 9:3:4 Epistasis in Labs 2 genes: E & B pigment (E) or no pigment (e) how dark pigment will be: black (B) to brown (b) Epistasis in People Johnny & Edgar Winter albino Africans Polygenic Inheritance Some phenotypes determined by additive effects of 2 or more genes on a single character phenotypes on a continuum human traits skin color height weight eye color intelligence behaviors Nature vs. Nurture Phenotype is controlled by both environment & genes Color of Hydrangea flowers is influenced by soil ph Human skin color is influenced by both genetics & environmental conditions Coat color in arctic fo influenced by heat sensitive alleles

It all started with a fly Chromosome theory of inheritance eperimental evidence from improved microscopy & animal breeding led us to a better understanding of

Sturtevant in the Drosophila stockroom at Columbia University 1910 1933 Thomas Hunt Morgan embryologist at Columbia University 1 st to associate a specific gene with a

mutant white-eyed male traced the gene for eye color to a specific chromosome Eplanation of Se Linkage female all offspring white eye male 100% of females have s 50% of

Se-linked Traits Although differences between women & men are many, the chromosomal basis of se is rather simple In humans & other mammals, there are 2 se chromosomes:

4 It all started with a fly Chromosome theory of inheritance eperimental evidence from improved microscopy & animal breeding led us to a better understanding of chromosomes & genes beyond Mendel Drosophila studies A. H. Sturtevant in the Drosophila stockroom at Columbia University Thomas Hunt Morgan embryologist at Columbia University 1 st to associate a specific gene with a specific chromosome Drosophila breeding prolific 2 week generations 4 pairs of chromosomes XX=female, XY=male Morgan s First Mutant Wild type fly = s Morgan found a mutant white-eyed male traced the gene for eye color to a specific chromosome Eplanation of Se Linkage female all offspring white eye male 100% of females have s 50% of males have white eyes How is this possible? Se-linked trait! Se-linked Traits Although differences between women & men are many, the chromosomal basis of se is rather simple In humans & other mammals, there are 2 se chromosomes: X & Y 2 X chromosomes develops as a female: XX redundancy an X & Y chromosome develops as a male: XY no redundancy Se Linked Traits because the Y chromosome is actually smaller than the X chromosome, men only have one copy of certain genes so if the X chromosome has a recessive allele, that has to be epressed because that is all that is there! X Y but haploid here diploid here but haploid here

female / eggs Colonie High AP Biology Eplanation of Se Linkage female 100% of females have s all offspring white eye male 50% of

Genes on Se Chromosomes Y chromosome SRY: se-determining region master regulator for maleness turns on genes for production of

X chromosome Contains a gene called DAX1, an antitestes factor SRY inhibits DAX1 other traits beyond se determination hemophilia

chromosome Se-Linked Traits XHH H Y XHh H X h X H X H Y Y X H 2 normal parents, but mother is carrier for a se-linked trait male

5 female / eggs Colonie High AP Biology Eplanation of Se Linkage female 100% of females have s all offspring white eye male 50% of males have white eyes How is this possible? Se-linked trait! Genes on Se Chromosomes Y chromosome SRY: se-determining region master regulator for maleness turns on genes for production of male hormones pleiotropy! X chromosome Contains a gene called DAX1, an antitestes factor SRY inhibits DAX1 other traits beyond se determination hemophilia Duchenne muscular dystrophy color-blind Human X Chromosome Se-linked usually X-linked more than 60 diseases traced to genes on X chromosome Se-Linked Traits XHH H Y XHh H X h X H X H Y Y X H 2 normal parents, but mother is carrier for a se-linked trait male / sperm X H Y X H X H X H Y X H X h X H X h X h X H X h X h Y Se-Linked Traits Hints X-linked follow the X chromosomes males get their X from their mother trait is never passed from father to son Y-linked very few traits only 26 genes trait is only passed from father to son females cannot inherit trait

fission rapid growth generation every ~20

dominant form of life on Earth incredibly

burgdorferi Lyme disease Treponema pallidum

genetically identical to parent where does

Conjugation Direct transfer of DNA between

joined results from presence of F plasmid

6 Bacteria Bacteria review one-celled organisms prokaryotes reproduce by binary fission rapid growth generation every ~20 minutes 10 8 (100 million) colony overnight! dominant form of life on Earth incredibly diverse Bacterial Diversity Borrelia burgdorferi Lyme disease Treponema pallidum Syphillis Escherichia coli O157:H7 Hemorrhagic E. coli Enterococcus faecium skin infections Binary Fission Replication of bacterial chromosome Aseual reproduction offspring genetically identical to parent where does variation come from? Conjugation Direct transfer of DNA between 2 bacterial cells that are temporarily joined results from presence of F plasmid with F factor F for fertility DNA E. coli male etends se pilli, attaches to female bacterium cytoplasmic bridge allows transfer of DNA

Beyond Mendel s Laws of Inheritance

Chapter 14. Beyond Mendel s Laws of Inheritance 1 Extending Mendelian genetics Mendel worked with a simple system peas are genetically simple most traits are controlled by a single gene each gene has only