Ib150 Final Continued

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Chapter 14: Who was Mendel?

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Grew up in Czech Republic, studied at university of vienna 1851-1853 Doppler and Unger(arose mendel's interest in variation of plants) helped him to develop scientifcally. Discovered the basic principles of heredity by breeding garden peas. He chose peas because they are available in many variety.
character: used for heritable feature.
Trait: each variant for a character, ex purple or white colors.
True-breeding: all offspring are of the same variety.
Hybridization: the crosing of two true breeding varieties.
P Generation: True breeding parents and hybrid offspring are F1 generation, and F1 hybrids produce F2 generations.

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Mendel's Hypothesis:
Law of segregation

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1; alternative versions of genes (alleles) account for variatiions in inherited characters.
2: For each character an organism inherits two alleles, one from each parent.
3: If the two allelas differ, then one, the dominant allele, is fully expressed in the organism's appearance; the other the recessibe allele, has no noticable effect on the organism's appearance.
4: The two alleles for each character segregate (separate) during gamete production.
Punnett square: a handy device for predicting the results of a genetic cross between individuals of known genotype.
Vocab
Homozygous~~having a pair of identical alleles for a character ex. (PP) for dominant and (pp) for recessive.
Heterozygous: having two different alleles for a gene (Pp).
Genotype: the genetic make up
Phenotype: the organism's traits ex. purple.
testcross: breeding of a recessibe homozygote with an organism of dominant pheontype but unknown genotype (devised by Mendel).

LAW OF INDEPENDENT ASSORTMENT

Monohybrids: hybrids produced in breeding experiments which follow only a single character, ex...color.
Dihybrids: following more than one character (two characters).

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Types of Dominance:

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Incomplete dominance: when f1 hybrids have an appearance somewhere inbetween the phenotypes of the two parental varieties.
Complete Dominance: the phenotype of the heterozygote and the homozygote are indistinguishable.
Codominance: the two alleles affect the phenotype in seperate distinguishable ways.
pleiotropy: The ability of a gene to affect an organism in many ways.
Epistasis: a gene at one locus alters the phenotypic expression of a gene at a second locus.
Polygenic inheritance: an addictive effect of two or more genes on a single phenotypic character.

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Patterns of inheritance

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Pedigree: a family's history for a particular trait.
Cystic fibrosis: strikes 2500 whites of european decent. It is a recessive allele.
Tay-sachs disease: recessive allele, one in 3600 births, occurs in people of jewish decent.
Sickle cell disease: one in 400 african americans. caused by the substitution of a single amino acid in the hemoglobin protein of red blood cells. this is also recessive.
Huntington's disease: dominantly inherited disease. it is a degenerative disease of the nervous system.

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Chapter 15: Linkage
Thomas Hunt Morgan

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Chromosome Theory of inheritance....genes have a specific loci on chromosomes, and it is the chromosome that undergo segregation and independent assortment.

Morgan::::He was the first to associate a specific gene with a specific chromosome. He was skeptical of both Mendelism and the chromosome theory.
Wild type: the normal phenotypr for a character ex...red eyes.
Genetic Recombination: production of offspring with new combinations of traits inherited form two parents.
Parental types: offsprings that resemble the parents.
Recombinants: off spring that have new combinatiions that do not resemble the parents.
Genetic map: an ordered list of the genetic locci along a particular chromosome.
linkage map: a map based on recombination frequencies.

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SEx Linked disorders in humans

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Duchenne muscular dystrophy: it has been tracked to a specific gene on the X chromosome.
Hemophelia: recessive sex linked trait.
Barr body; inactive X in each cell of a female condenses into a barr body, which lies along inside the nuclear envelope.
non disjunction:members of a pair of homologus chromosomes do not move apart properly during meiosis one, or sister chromatids fail to seperate during meiosis two.
aneuploidy: an abnormal chromosome number.
trisomic: having 2n plus 1 chromosomes.
Monosomic: having 2n-1 chromosomes.
Deletion: wh4en a chromosomal fragment lacking a ccentromere is lost during a cell division.
Inversion: a chromosomal fragment may also reattach to the original chromosome but in the reverse orientation.
Translocation: fragment joins non homologous chromosome.
Down syndrome: caused by a chromosomal alteration, it affects one in 700. .
Genomic imprinting: a gene on one chromosome is somehow silenced, while its allele on the homologous chromosome is left free to be expressed.
Fragile X syndrome: an X chromosome that hangs on to the rest of the chromosomes by a tin thread of DNA.

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Chapter 23: Gene Pool

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Population: a localized group of individuals belonging to the same species.
Species: a group of populations whose individuals have the potential to interbreed and produce fertile offspring.
gene pool: the total aggregate of genes in a population at any one time. It consists of all alleles at all gene loci in all individuals of the population.
Hardy Weinberg Theory: 500 plnts. 80% (.8) have R allele. 20% (.2) have r allele. .8*.8=.64, so 64% will have RR allele in the offspring. .2*.2=.04%, so 4% will have rr. .2*.8=.16, and .8*.2=.16, so a total of .32 or 32% will have Rr.
Hardy Weinberg equilibrium: which is saying that the frequencies would reman at .8 and .2 forever.
Hardy Weinberg Equation: p+q=1 then p=1-q, and q=1-p , so p^2 + 2pq + q^2 = 1. so all the percentages have to add up to one. .64 + .32 + .04 = 1

Assumptions of the theorum:::
~very large population size
~No migration
~No net mutations
~Random Mating
~No natural Selection.

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Microevolution

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Evolution is a generation to generation change in a population's freguencies of alleles.
Main causes of microevolution:(Genetic drift and natural selection)
Genetic DRift:which is the change in a population's allele frequencies due to chance. if a generation draws its alleles at random from the previous generation.
Bottleneck effect: disasters like fires, droughts, earthquakes, might reduce the size of a population, then some alleles are lost from the gene pool.
Founder effect: whenever a few individuals from a larger population colonize an isolated island, or some new habitat.
Gene flow: genetic exchange due to the migration of fertile individuals or gametes between populations (ex. windstorm blowing pollen)
Mutation: change in organism's DNA.
All part of Genetic drift, at least everything befor gene flow.

NATURAL SELECTION:
genetic Variation~~ths substrate for natural selction
polymorphism: when two or more discrete character are represented in a population.
Nucleotide diversity: measured by comparing nucleotide sequences of DNA sample from two individuals and then pooling the data from many such comparisions.
Geographic variation: differences in gene pools between populations or subgroups of populations.
Cline: type of geographic variation, a graded change in some trait along a geographic axis.
Mutation and Sexual recombination also play a part.
Balanced polymorphism: ability of natural selection to maintain stable frequencies of two or more phenotypic forms.
heterozygote advantage: individuals who are heterozygote at a particular locuz have greater survivorship and reproductive sucess than any type of homozygote.
Frequency dependent selection: survival and reproduction of any one morph declines if that phenotypic form becomes too common in the population.
Neutral variation: diversity of human fingerprints is one example, ...no selective advantage for some individuals over others.
Darwinian fitness; contribution an individual makes to the gene pool of the next generation.
Relative fitness: contribution of a genotype to the next generation compared to the contributions of alternative genotypes for the smae locus.
Directional Selection; most common during periods of environmental change or when members of a population migrate. it shifts the frequency curve for variations in one direction or the other by favoring a character.
Diversifying selection: environmental conditions are varied in a way that favors individuals on both extremess of a phenotypic range.
Stabilizing selection: acts againts extreme phenotypes and favors the more common intermediate variants.
Sexual dimorphism: example, males are larger than females. it can also be present in different colors, or male lions having manes as opposed to females and etc.
Intrasexual selection: selection within the same sex. example, males using antlers to battle other males.
NATURAL SELECTION CANNOT FASHION IF:
~~~~Evolution is limited
~~~~Adaptations are often compromises
~~~~Not all evolution is adaptive
~~~~Selection can only edit existing variations