Week 3 Notes
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This 5 page Class Notes was uploaded by Nikki Hovland on Wednesday October 14, 2015. The Class Notes belongs to Biol 180 at University of Washington taught by Scott Freeman in Summer 2015. Since its upload, it has received 36 views. For similar materials see Introductory Biology in Biology at University of Washington.
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Date Created: 10/14/15
INTRODUCTORY BIOLOGY 180 Thursday October 15 2015 Week 3 Notes Lecture 8 Extensions to Mendel linkage vs sexlinkage linked genes are on same chromosome and sexlinked just means its on a sex chromosome genes can be linked AND sexlinked linkage mapping Sturtevant found that the percentage of recombinants is proportional to the physical distance between genes called centiMorgans recombinant when an offspring has a new combination of alleles as a result of crossing over mechanism multiple allelism when there are more than just 2 alleles for a particular gene polymorphic trait when there are more than just 2 phenotypes expresses in the population due to having multiple alleles example blood type is a polymorphic trait because you can have A blood B or AB codominance when two phenotypes are simultaneously expressed due to having two different alleles in a heterozygote both alleles expressed not just the dominant allele phenotype again blood type is example of codominance incomplete dominance heterozygotes have a phenotype that is between the two different traits of the homozygous parents note this is much like Mendel s initial hypothesis of blending inheritance example a red flower mates with white flower and the offspring has a pink phenotype pleiotropic genes that can influence many traits basically one gene is not only responsible for influencing one phenotype it can influence multiple an individual s phenotype is usually a result of both environmental factors and its genotype genebygene interaction one trait is influenced by many differentgenes example the rooster comb example in the book is great because it shows how the two different phenotypes in a parent can produce offspring with their phenotypes INTRODUCTORY BIOLOGY 180 Thursday October 15 2015 as well as different phenotypes due to other genes that are expressed IN ADDITION and leads to the creation of new phenotypes genebyenvironment interaction when a trait corresponding to a particular genotype is also affected by environmental conditions example an individual may have the genotype for diabetes but the individual may not show the phenotype of diabetes if they are not in an environment that would promote this like poor eatinghigh or low extreme sugar intake or vise versa quantitative traits traits that are continuous and do not fall into discrete categories unlike Mendel s traits he worked withwhich were discrete population distributions usually follow a bellshaped normal curve with qualitative traits LECTURE 9 Human Genetic Disease Review genes will act as if they are independent even if they are on the same chromosome if they are more than 50 cM apart crossing over is at least 50 likely to happen How do patterns of inheritance and natural selection affect human genetic disease Transmission selection dynamics and selection on lateonset illnesses all factors mode of transmission when trait is described as autosomal or sexlinked and gives the type of dominance to allele this allows us to track genotypes and phenotypes through generations for certain traits and predict likelihood of offspring receiving a particular genotype pedigree a family tree allows to mark relationships between parents and offspring as well as sex of individual and whether the individual is affected a carrier or unaffected shaded half shaded or empty carrier when an individual carries an allele for a particular disease or trait but does not express it in his or her phenotype INTRODUCTORY BIOLOGY 180 Thursday October 15 2015 in sexlinked traitsdiseases females can only be carriers never malesthey are either affected or not affected because they have two X chromosomes that can mask the disease allele key characteristic of Xlinked recessive traits is that males often express the trait more than females only have one X chromosome females are often carriers and mask the recessive allele appearance of Xlinked recessive trait usually skips a generation in pedigrees bad alleles that have low fitness in a particular environment often are beaten out of a population the slowestwhile codominant and dominant alleles are beaten out faster roughly equal since both express their phenotypes because they undergo natural selection more often than the recessive alleles that can hide and skip generations LECTURE 10 Data Analysis and Statistics Types of data categorical discrete with no inbetweens like color bar charts can represent categorical on x axis and continuous data on y axis continuous like time or distance dependent variable usually on the xaxis while independent is on the yaxis scatterplot is used for continuous data which can have values over a range not for discrete data which go in categories don t extrapolate conclusions when analyzing graphs only conclude things that you can take directly from the graph example can make a conclusion about relationship between growth or something between two variables measured based on data points but can t extrapolate and come up with some reason you think is the reason for why these data occurs only say what the data tells you bar charts are used when you have data that is discrete it fits into distinct categories instead of over a range ie like different treatment groups INTRODUCTORY BIOLOGY 180 Thursday October 15 2015 histograms are used usually for frequencies in a population divided by certain intervals like how many students have certain intervals of heights box and whisker plots are used for determining where most of the data falls allows you to see big chunks lower 25 middle 50 and upper 25 and to see extremes probability measure of likeliness that a particular event will occur and is a number between 0 not likely and 1very likely the higher the probability of an event the more certain we are that the event is going to occur standard error quantifies how confident you are that the average you found is the actual average you would observe in a really huge population under the same test measures precision and is denoted by an I on top of the categories in the graph statistical test create a null hypothesis if there is no affect calculate a test statistic that determines the size of the difference between the treatment groups ie freshman are on average 2 inches shorter than seniors determine the probability of getting the same test statistic or higher by chance done by using reference distribution which suggests the probability of getting different values of the test statistic is the null is correct biologists refer to a difference among treatment groups as being statistically significant usually if there is less than 5 chance of observing the same result by chance having a p value of 005 or less if pvalue is too high it doesn t mean our experiment is wrong all we need to do is increase sample size which will help reduce our pvalue if we get a pvalue less than 005 then we reject our null because the data is statistically significant and the data supports our hypothesis then we continue science by revising our hypotheses to find out more information when trying to figure out the probability of getting at least a certain number out of a given number of tries like getting 2 heads out of 4 flips DRAW OUT ALL POSSIBILITIES using the both andeither or rule can mess you up combining probabilities INTRODUCTORY BIOLOGY 180 Thursday October 15 2015 both and rule if you want to find probability of two independent events occurring at the same time multiply the two probabilities together either or rule if you want to find probability of an event happening if there are multiple ways for it to happen getting a 1 OR a 3 when rolling a die then add the two probabilities together
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