Chpt. 13 Mendel And The Gene

Front 1

model organism

Back 1

-individuals are small, short-lived, inexpensive to care for, able to produce large numbers of offspring, and easy to manipulte experimentally

Front 2

Blending inheritance is wrong

Back 2

-Mendel's first cross of truebreeding round and wrinkle lines yields all round F1 progeny

Front 3

reciprocal cross

Back 3

for heterozygous-heterozygous cross, crossing male dominant w/female recessive and female dominant and male recessive to ensure no sex linkage of a trait

Front 4

theory of particulate inheritance

Back 4

hereditary determinants do not blend - they maintain their integrity from generation to generation

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gene

Back 5

hereditary determinant for a trait

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alleles

Back 6

different versions of the same gene

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genotype

Back 7

the alleles found in an individual

Front 8

principle of segregation

Back 8

-to explain Mendel's F2 3:1 ratio, alleles must segregate into the different gamete cells during the formation of eggs and sperm
-each gamete carries only one allele for a particular gene (wrinkle/round), because alleles have segregated during meiosis

Front 9

monohybrid cross

Back 9

cross btwn male and female that are heterozygous at the gene in question (3:1 progeny)

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principle of independent assortment

Back 10

-alleles from different genes are transmitted independently from one another (for genes located on different chromosomes)
-different genes assort independently because they are located on different chromosomes

Front 11

testcross

Back 11

-cross btwn individual with unknown genotype with truebreeding(homozygous), recessive individual

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locus

Back 12

where a gene is located

Front 13

chromosome theory of inheritance

Back 13

-Mendel's rules can be explained by the independent alignment and separation of homologous chromosomes at meiosis I

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wild type

Back 14

-individuals with the most common phenotype
-"w+"

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mutation

Back 15

a change in a gene

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X-linked inheritance
(X-linkage)

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-a gene that resides on a the X-chromosome, where the Y-chromosome does not carry an allele for that gene
-the discover of X-linked inheritance convinced most biologists that the chromosome theory of inheritance was correct

Front 17

linkage

Back 17

-genes found on the same chromosome
-should violate principle of independent assortment (doesn't always, do you know why?)

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NOTATION

Back 18

writing genotype (listing relevant alleles that are present):
-use a / to separate homolouse alleles that are linked
i.e. wy+/w+y

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recombinant

Back 19

combination of alleles on in progeny that are different than combination of alleles found in parental generation
-result of crossing over

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genetic mapping

Back 20

-diagram that shows the relative positions of genes along a particular chromosome
-found by looking at frequency of genetic recombinants
-19% recombinant progeny = 19 map units apart for genes

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crossing over

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-the farther apart two genes are on a chromosome, the more of a chance there is that crossing over will occur
-breaks up linkage and makes it appear as if independent assortment is occuring
-genes behave as if independently assorted when more than 50 or more map units apart

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multiple allelism

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-more than two alleles for the same gene

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polymorphic

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-when more than two distinct phenotypes are present for a trait in a population due to multiple allelism
i.e. B-globin inhumans

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incomplete dominance

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-heterozygotes have an intermediate phenotype
-1:2:1 genotype and phenotype
i.e. lavender four-o'clocks

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codominance

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-heterozygotes have the phenotype associated with both alleles present
-both alleles represented in phenotype

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pleotropic

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-a gene that influences many traits, rather than just one
i.e. Marfan syndrome

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epistasis

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-an allele of one gene masks the effect of an allele @ another gene
i.e. pepper color, chicken comb

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discrete traits

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-characteristics that are qualitatively different
i.e.seed color is either yellow or green

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quantitative traits

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-quantitative variation - individuals differ by degree
i.e.height/skin color
-when different values are plotted on a histogram (frequency distribution), they form a bell-shaped curve (normal curve)

Front 30

polygenic inheritance

Back 30

-results in the transmission of quantitative traits
-each gene adds a small amount to the value of the phenotype