mendelian inheritance and exception and extensions of mendelian inheritance
TRANSCRIPT
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 (F1 generation)Repeated with other traitsConclusion: 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 F1 generation
Result: ____ Tall, ___ short (F2 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 traitDominant 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
IA (codes for an ___-type ID on blood cell) IB (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 phenotypeHuman Blood Groups IA IA- A blood (only A-type ID on blood cells) IA i- A blood (only A-type ID on blood cells) IB IB- B blood (only B-type ID on blood cells) IB i- B blood (only B-type ID on blood cells) ii- O blood (no ID on blood cells) IA IB- 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)