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34 Cards in this Set
- Front
- Back
What are polygenetic traits
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controlled by more than one gene; ususally a complex character such as skin color, cancer cells
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continuous variation is also known as
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quantitative inheritance
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What is a continuous trait often the result of?
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polygenic ingeritance and is frequent multifactorial-multiple genes contributing to a trait and the environmental impact on the degree of expression. Example anger, addition.
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multifactorial trait
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phenotype that results from gene action and environmental influences
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meristic traits
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polygenic traits in which the phenotype is recorded by counting whole number. They are quantitative traits but do not have an infinite range of phenotypes. example; – eggs per clutch- you will not have 6.5 eggs-not infiniate range
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What is a threshold traits
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are polygenic and often multifactorial but have a small number of discrete phenotypic classes, an increasing number of diseases show this pattern of polygenic inheritance
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Cancer is result of what kind of trait?
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Threshold trait
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How can quantitative traits be explained in Mendelian terms?
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by many genes, each behaving individually in mendelian fashion, contributing to the phenotype in a cumulative or quantitative way
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corolla length in Nicotiana and grain color Triticum demonstrate what?
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Multifactorial hypothesis
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If you have a corolla length with one ranging 37-44mm and 91-97mm and you crossed them and get 61-67. What is the reasoning for this result in the F1? What happens in the F2?
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In the F1 population is it contribution of multiple genes influencing the trait, In the F2 population the variance increases and the mean is similar to what we started with however the spread is changed (variability changes). This show's Mendel's fist law of segregation of alleles
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What happens when you cross small with smalls, meds with meds, and large and large, overtime with the F3 generation?
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In the F3 generation the range is limited therefore the distribution is narrower and over time they become reproductively isolated from each other and diverge farther apart which can be speciation.
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In oncolor in wheat the contribution is noe the same as Mendel's dihybrid cross. Why?
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in this cross both of the alleles contribute to the same trait in the same way
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AABB has how many contributions? (oncolor in wheat)
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Has 4 contributions to the color and is most intense because it has 4 additive alleles the genotypic ratio is 1:4:6:4:1 and is approaching a bell shaped curve
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1 gene pair
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1:2:1
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2 gene pair
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1:4:6:4:1
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3 gene pair
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1:6:15:20:15:6:1
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4 gene pair
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1:8:28:56:70:56:28:8:1
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5 gene pair
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1:10:45:120:210:252:210:120:45:10:1
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For a low number of polygenes the number of additive loci can be estimated low?
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From the total number of possible phenotypes. These estimates assume that all of the additive alleles contribute equally and additively and that there are no significant environmental effects on the trait
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Number of phenotypic
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2n+1
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Polygenetic traits are usually measured how?
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sample of individuals that are large and representative of the population from which it is drawn from?
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How are the variences between F1 and F2 different?
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broader variance and is more spread out
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What does Hertatibility estimate?
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The genetic contribution to the phenotypic variability
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heritability describes what?
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the proportion of total phenotypic variation in a population due to genetic factors, but it does not indicate how much of a trait is genetically determined or the extent to which an individual’s phenotype is due to genotype
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Phenotypic variation has
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Genotypic variation
Environmental variation Genotype-by-environment interaction varience components |
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Broad sense heritability
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Measure the contribution of genotypic variance to the total phenotypic varience. The genotyic variance to the total phenotypic varience. The genotypic varience component includes all types of genetic variation in the population and assumes that the genotype-by environment varience component is negligible.
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Narrow sense heritability
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is the proportion of phenotypic varience due to the additive genotypic varience alone.
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Artificial selection
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the process of choosing specific individuals with preferred phenotypes from an initially heterogeneous population for future breeding. The purpose is to develop a population containing a high frequency of individuals with the desired traits.
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Give an example of artificial selection
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Dog species
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Realized heritability
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in selective breeding estimates the potential for artificial selection to be successful. An example is artificial selection for increased oil content in corn (figure in book).
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Twin studies allow what?
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An estimation of heritability in human. They are useful when they are maintained in the family, so the genetic variance should be 0 and the environmental should be similar so there is no dramatic differences between them. They are also useful subjects for examining genotypic vs. environmental varience for a multifactorial trait
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For monozygotic twins (identical) phenotypic variance equals what?
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environmental variance, since there is no genotypic variance.
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For dizygotic twins (fraternal) phenotypic variance differences represent what?
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both environmental variance and approximately half the genotypic variance.
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Comparison of phenotypic variances for the same trait in identical and fraternal twin sets provides what?
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estimate of broad-sense heritability for that trait. The difference in concordance for a given trait in identical versus fraternal twins suggests whether there is a strong genetic component involved in the determination of the trait
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