Chapter 16. Simple patterns of inheritance

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1 Chapte 16 Simple pattens of inheitance 1

2 Genotpe and phenotpe 1) Allele A vaiant fom of a gene (e.g., Height of pea plant : tall, shot) 2) Genotpe -Genetic composition of individual -Homozgous (an individual with Two identical copies of an allele) -Heteozgous (an individual with Two diffeent alleles of a gene) 3) Phenotpe - Chaacteistics that ae the esult of gene expession - TT and Tt ae tall - tt is dwaf 4) Dominant vs ecessive 2

3 Seven Chaactes of pea plants that Mendel Studied 3

4 Stuctue of flowes in pea plants Pea flowe poduces Both male and female gametes : eceived pollen Spem migate To the ovules and fuse With egg : Egg cells ae fomed in ovules within the ova : spem fom in the pollen poduced within the stamen

5 Pea plants ae nomall self-fetilizing (a female gemete is fetilized b a male gamete fom the same plant. What Mendel did is coss-fetilization

6 Phenotpe : Tue-beeding line (a stain that continues to exhibit same taits afte seveal self-fetilization) phsical appeaance Offsping of P coss TALL Off sping of F 1 afte self-fetilizing 3/4 1/4 Law of Segegation 6

7 Each allele of a gene segegate fom each othe Law of segegation (elated to Meiosis)

8 Law of Segegation (to keep sepaate) Stating fom homozgous =>Tall is dominant 3 genotpes 2 phenotpes

9 How to pedict outcome of simple coss Punnett squae: Common method to pedict outcome of simple genetic cosses How to daw and use punnett squae Tt Female gametes T t Tt Male gametes T t TT Tt Tt tt Male paent female paent How to daw and use punnett squae Step 1. Wite down the genotpes of both paents Male paent: Tt Female paent: Tt Step 2. Wite down the possible gametes that each paent can make Male gametes: T o t Female gametes: T o t Afte Meiosis Step 3. Fill in the possible genotpes

10 How to detemine a genotpe of an individual with dominant phenotpe? Pefom Test coss Coss to detemine if an individual exhibiting a dominant tait is homozgous o heteozgous Coss with Tall plant Genotpe is not known could be TT o Tt Shot plant Onl possible genotpe is tt To detemine the genotpe If all offsping Genotpe will be TT ae tall Genotpe will be Tt If 1/2 is ae tall If 1/2 is ae shot

11 How to detemine a genotpe of an individual with dominant phenotpe? Pefom Test coss Coss to detemine if an individual exhibiting a dominant tait is homozgous o heteozgous Coss with Tall plant Genotpe is not known could be TT o Tt Shot plant Onl possible genotpe is tt

12 Inheitance patten of two taits Mendel conducted cosses in which he simultaneousl followed the inheitance of two diffeent taits => Two facto coss Taits followed :Seed colo and shape : ellow : geen : ound : winkled

13 Inheitance patten of two taits Mendel conducted cosses in which he simultaneousl followed the inheitance of two diffeent taits => Two facto coss Taits followed :Seed colo and shape : ellow : geen : ound : winkled Hpothesis 1) Genes fo seed colos and shape ae linked => vaiants found togethe in paents ae alwas inheited as a unit 3/4 : ellow/ound 1/4 : geen/winkled No new phenotpe poduced

14 Inheitance patten of two taits Mendel conducted cosses in which he simultaneousl followed the inheitance of two diffeent taits => Two facto coss Taits followed :Seed colo and shape : ellow : geen : ound : winkled Hpothesis 2) Genes fo seed colos and shape ae independent => alleles fo each gene ae andoml distibuted into gametes 4 possible genotpes of gametes 9/16 : ellow/ound 3/16 : ellow/winkled 3/16: geen/ound 1/16: geen/ winkled

15 Inheitance patten of two taits Mendel conducted cosses in which he simultaneousl followed the inheitance of two diffeent taits => Two facto coss Taits followed :Seed colo and shape : ellow : geen : ound : winkled Hpothesis 2) Genes fo seed colos and shape ae independent => alleles fo each gene ae andoml distibuted into gametes 4 possible genotpes of gametes 9/16 : ellow/ound 3/16 : ellow/winkled 3/16: geen/ound 1/16: geen/ winkled

16 Mendel s expeiments suppoted the second hpothesis => Law of independent Assotment Note: Not all of genes follow this law : if genes ae located in the same chomosomes the ll be inheited togethe 16

17 Meiotic pocess and patten of inheitance - Homologous chomosome pai caies an allele of the same gene at the same locus 17

18 Meiotic pocess and patten of inheitance Heteozgous (Tt) cell fom a tall plant Diploid cell t T Fou haploid cells t Chomosome eplicate t t Homologues paied with each othe tt T Homologous Chomosome segegate t t Sistechomatids segegate T Law of segegation T T T Alleles of a gene segegates duing tansmission fom Paents to offsping 18

19 Meiotic pocess and law of assotment Heteozgous diploid cell () to undego meiosis case1 eplication (S) and MetaphaseI alignment of Chomosomes (can occu in (Meta)diffeent was) case2 o andom Fou haploid cells Fou haploid cells 19

20 Inheitance of genes in Sex chomosomes Sex chomosomes X : lage, caies ove 1000 genes : small, caies less that 100 genes X-linked genes: Genes onl found in X chomosomes Males ae hemizgous fo X-linked genes (individual with onl one cop of a paticula gene) 24

21 X-linked genes Hemophilia A caused b ecessive X-linked gene Encodes defective clotting potein => blood does not clot nomall Female gametes X H X h-a X H X H Male gametes X H Nomal female X H X h-a Caie female X H Nomal male X h-a Male with hemophilia H : nomal allele H-A : ecessive allele fo hemophililia A If the mothe is heteozgous And fathe is nomal 1) Son has 50% chance of Having hemophilia 2) Daughte will have nomal phenotpe 25

22 Incomplete dominance Heteozgote has intemediate Phenotpe Neithe allele is dominant Pink fou-o clocks 50% of nomal potein not enough to give ed colo 26

23 Vaiations in inheitance Patten (Multiple alleles and codominance) Multiple alleles 3 o moe alleles in a population Phenotpe depends on which 2 alleles ae inheited ABO blood tpes in humans Thee alleles affecting blood tpe I A, I B i Based on which combinations of alleles ou have, BC expess diffeent tpes of suga molecules called Suface antigen Genotpe ii I A I A o I A i I B I B o I B i I A I B Blood tpe O A B AB

24 Vaiations in inheitance Patten I A o I B is dominant ove i allele I A and I B ae codominant Genotpe ii I A I A o I A i I B I B o I B i I A I B Blood tpe O A B AB