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Bio-Genetics Ch. 11


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the scientific study of heredity
gregor mendel
austrian monk who was born in 1822 in what is now the czech republic-became a priest and spent several ears studying in vienna. worked at a moestry w/ plants
how do pea plants reproduce
plants that if they were allowed to self-pollinate, they would produce offspring identical to themselves. (the basis os mendels experiment)
gregor mendels experiment
he selected pea plants that he would mate with each other. he had to prevent the pea plants from self-pollinating and control their cross-pollination. he did this by cutting away the male parts of a flower. then he dusted that flower w/ the pollen from a secnod flower. the resulting seeds were crosses between two plants
a specific characteristic
parent generation
P-each original pair of plants
first fillial
F1-the offspring of the parent generation
the offspring of crosses between parents with different traits
what were mendel's two conclusions?
1)biological inheritance is determined by factors that are passed from one generation to the next.
2) the principle of dominance
the chemical facotrs that determine traits
different forms of a gene
ex. short plant and tall plant
principle of dominance
states that some alleles are dominant and others are recessive.
second fillial-offspring of F1
mendel's experiemnt outcomes
Tall plant x Short plant=100% tall
Tall Plant x Tall plant=25% short, 75% tall (SECOND FILLIAL GENERATION)
Mendels 7 f1 crosses on pea plants
seed shape, seed color (yellow-dominant, green-recessive), seed coat color, pod shape, pod color, flower position, plant height
the separation of alleles during the formation of the sex cells (gametes)-ex. when each F1 plant flowers, two alleles are segregated from each other so that each gamete carries only a single copy of each gene. therefore, each F1 plant produces two types of gametes-those with the allele for tallness and those with the allele for shortness.
the likelihood that a particular event will occur
Punnett Square
a diagram that shows the gene combinations that might result from a genetic cross
pure/true breeding
organisms that have two identical alleles for a particular trait
organisms that have two different alleles for the same trait.
the physical characteristics of an organism
the genetic makeup of an organism
describe mendels two-factor cross: F1
mendel crossed true-breeding plants that produced only round yellow peas (RRYY) with plants that produced wrinkled green peas (rryy). All of the F1 offspring produced round yellow peas, which shows that the alleles for round yellow peas are dominant over the alleles for green wrinkled peas.
describe the two-factor cross-F2
all the F1 plants had the genotype RrYy-were all heterozygous for both color and shape genes-in his experiment most were round and yellow, some were wrinkled an green, and some had combos of phenotypes, not found in either parent, which meant that the alleles for seed shape segregated separately from those of seed color.
independent assortment
genes that separate independently do not influence each other's inheritance.
principle of independent assortment
states that geners for different traits can segregate independently during the formation of gametes.
Mendel's 4 principles
1) the inheritance of biological characteristics is determined by genes. in organisms that reproduce sexually, genes are passed from parents to the offspring
2) in cases in which two or more forms of the gene for a single trait exist, some forms of the gene may be dominant and others may be recessive
3) In most sexually reproducing organisms, each adult has two copies of each gene--one from each parent. these genes are segregated from each other when gametes are formed.
4) the alleles for different genes usually segregate independly of one another
incomplete dominance and example
cases in which one allele is not completely dominant over another-the heterozygous phenotype is somewhere in between the two homozygous phentype
example: four o'clock plant-
red flowers (RR) x white flowers (WW)=pink flowers (RW)
codominance and example
both alleles contribute to the phenotype of the organism
example-cattle-each hair is a different color
multiple alleles and example
when genes have more than two alleles-means that the organism cannot have more than two alleles but that more than two possible alleles exist in a population-
ex. rabbit coats and human blood type
polygenic traits and example
traits produced by the interaction of several genes and are controlled by two or more genes-often show a wide range of phenotypes
example-different combos of alleles produce very different eye colors
thomas morgan
experimented w/ the fruit fly b/c it produced large #'s of offspring in a short amount of time, very small, and easy to keep in the lab-
how do mendel's principles also apply to humans?
the basic principles of mendelian genetics can be used to study the inheritance of human traits and to calculate the probability of certain traits appearing in the next generation.
archibald garrod
discovered the pattern of inheritance in a rare disorder known as alkaptonuria fit the mendalian pattern

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