Mendelian Inheritance and Exception and Extensions of Mendelian Inheritance

Tay-Sachs Disease Conner Died at 22 months

Mendel Performed experiments with pea plants in late 1850’s early 1860’s Created theories explaining dominance, segregation, and independent assortment Work not really noticed until after death Considered “Father” of genetics

Mendel’s Experiments Studied seven _______ traits Seed form (Round and wrinkled) Seed color (Yellow and green) Pod form (Smooth and constricted) Pod color (Green and yellow) Flower Position (Axial and terminal) Seed coat color (Gray and white) Stem length (Tall and short)

Mendel’s Experiments (cont) Mendel took a _____-breeding tall and ____-breeding short and cross-pollinated them (_____ generation) Result ________ tall (F 1 generation) Repeated with other traits Conclusion: one form of trait is _________ over the other Tall is dominant, short is ___________

Dominant vs Recessive These refer to an action or abundance of ___________ Recessive is often “_____ of function” If causes disorder, can be severe and early- onset Dominant can be “_______ of function”

Mendel’s Experiments (cont) Mendel self-pollinated the F 1 generation Result: ____ Tall, ___ short (F 2 generation) Repeated with other traits Conclusion: Each plant has two copies of trait that ___________ from each other during gamete formation; gamete used is chosen at random

Trait Nomenclature _________- form of a trait Dominant allele given capital; recessive is same letter, lower case (T= tall and t=short) Genotype- ______________________ Homozygous- same two alleles Homozygous dominant- two dominant (_________) Homozygous recessive- two recessive (_________) Heterozygous- two different alleles (_______) Phenotype- expressed trait Wild type- expression of most common form of the trait Mutant- expression of different form of trait resulting from mutation

Punnett Square Bookkeeping tool for genetic problems Gamete possibilities for each parent on each side

Independent Assortment Traits are independent of each other if on different ______________ Mendel got lucky Most of the seven traits used were on different chromosomes

Dealing with Two Traits __________ cross Two trait Punnett Square Still list all possible gametes on each side What are the possible gametes for a parent who is TtRr?

Dihybrid Cross

Probability Can be used to determine the outcome of inheritance Probability of Simple Events Probability of Independent Events Probability of Dependent Events

Pedigree Pictorial genealogy of a family showing the inheritance of a particular trait Individuals are shown and connected using symbols on pg 88 Can be used Determine if trait is dominant or recessive Determine probable carriers within family Determine probability of inheritance for future generations

Pedigree Analysis

Pedigree Analysis (cont)

Polydactyly

Beyond Mendelian Inheritance Sometimes inheritance doesn’t seem to follow Mendel’s laws

Lethal Alleles Sometimes the combination of two alleles is lethal (____________________) If death is during development, expected Mendelian ratio is not observed

Multiple Alleles Trait has more than _________ alleles Human Blood Groups- ________ system Three alleles I A (codes for an ___-type ID on blood cell) I B (codes for a ___-type ID on blood cell) i (codes for ____ ID on blood cell)

Incomplete Dominance Heterozygotes express phenotype __________ two homozygous phenotypes Snap dragon flowers RR= red Rr = ________ rr= white Pink is created because Rr plants don’t have as much pigment as RR plants do

Codominance Heterozygotes express _____________ within the phenotype Human Blood Groups I A I A - A blood (only A-type ID on blood cells) I A i- A blood (only A-type ID on blood cells) I B I B - B blood (only B-type ID on blood cells) I B i- B blood (only B-type ID on blood cells) ii- O blood (no ID on blood cells) I A I B - AB blood (both A-type and B-type ID on blood cells)

Epistasis One gene affects the __________ of another Bombay phenotype- encodes for glycoprotein on red blood cell needed to attach the A-type or B-type ID A person who is homozygous recessive for Bombay (____) will have ____ blood regardless of their ABO genotype

Penetrance Percentage of how often a genotype is expressed into a phenotype ____________ penetrance- person with affected genotype always expresses the phenotype ____________ penetrance- person with affected genotype may not show the phenotype

Expressivity Expresses the varying _________ of a phenotype being expressed

Pleiotropy Occurs when an inherited gene causes many effects within the body Can be difficult to trace because symptoms may vary from person to person

Phenocopy ___________________ creates symptoms that mimic a genetic phenotype

Genetic Heterogeneity Different genes can create the same ________________

Mitochondrial DNA Mitochondria contain a “mini-chromosome” with _______ genes mtDNA mutes rapidly because there is no DNA repair and high exposure to free radicals Only inherited from _________ (mother passes to ____ her children) Genes code mostly for machinery for protein synthesis

Mitochondrial Disorders Often affect most tissue with high amounts of mitochondria Heteroplasmy- individual has mitochondria with normal genes and mitochondria with mutant genes Creates a wide range of expressivity

Linkage Linked genes are on the same ___________ Linked traits do not show independent assortment Mixing of these traits can only occur during ______________

Linkage Nomenclature _________ inheritance- inheritance of allele combination in parents without crossing-over __________ inheritance- inheritance of allele combination created during crossing-over _____ formation- person heterozygous for both traits has both dominant alleles on one homolog and both recessive alleles on the other ______ formation- person heterozygous for both traits has one dominant and one recessive allele on each homolog

Linkage Map Linkage results can be used to map out relative positions of genes on chromosomes Distance between genes is measured in centimorgans (equal to the percentage of recombination occurring between the two)