ch14 mendel

what is the “blending” hypothesis

the idea that genetic materia lfrom the two parents blends together. definition of heredity from the mid-19th century

what was the alternative to the blending model, and what was this called?

the gene idea: parents pass on discrete heritable units, genes

what are some traits of the pea plants mendel used to his advantage

their distinct heritable features (characters), like their color or their character variants like the two colors

what is the parental generation called

P generation

what are the hybrid offspring of the P generation referred to as

F_{1} generation

what happens when the F_{1} generation self-pollinates?

F_{2} generation is made

what does monohybrid cross do for inheritance

tracks the inheritance of a single character

what is true-breeding?

plants that produce offspring of the same variety when they self-pollinate

the law of segregation

by mendel, it reveals the F_{1} generation of cross-breeding between pure-breeding plants. this led to his naming of dominant and recessive traits based on their frequency of appearance.

what do we call a “heritable factor”

a gene

what was mendel’s model to explain the F_{2} offspring

3:1 inheritance pattern. made of four related concepts, these being: alleles, genetic locus per homologous chromosome, dominant/recessive alleles, alleles for a heritable character segregate during gamete formation and end up in different gametes

what is an allele in the context of mendel’s work

alternative versions of genes that account for variations in inherited characters

describe the second part of mendel’s segregation model

for each character an organism inherits two alleles, one from each parent. a genetic locus is actually represented twice (one per homologous chromosome)

describe the third part of mendel’s law of segregation

the two alleles at a locus differ: the dominant allele determines the organism’s appearance, the recessive allele has no noticeable effect on the organism’s appearance

what’s the difference between mendel’s laws of segregation and independent assortment

genes segregating

what is the final part of mendel’s theory of segregation

the two alleles for heritable character segregate during gamete formation and end up in different gametes

how should you define an organism that is homozygous for a particular gene

• has a pair of identical alleles for that gene

• exhibits true-breeding

how would you define an organism that’s heterozygous for a particular gene

• has a pair of alleles that are different for that gene

• doesn’t exhibit true breeding

what is a testcross and what is it used for

an individual with an unknown genotype is crossed with a homozygous individual expressing the recessive trait

describe mendel’s law of independent assortment

states that each pair of alleles segregates independently from each other’s alleles during gamete formation. rumored to be only those who are located near each other.

how did mendel create his law of independent assortment

he followed two characters at once instead of one. by producing dihybrids who are heterozygous, the dihybrid cross determines whether two characters are transmitted to offspring as a package or independently

what does mendel’s law of independent assortment apply to

different nonhomologous chromosomes

what is the multiplication rule of probability

the probability that two or more independent events will occur together is the product of their individual proabilities

what rule do you use to determine the probability of an F_{1} monohybrid cross

multiplication rule

probability rule of addition

the probability that any one of two or more exclusive events will occur is calculated by adding together their individual probabilities

what can the rule of addition be used for

ex. the probability that an F_{2} plant from a monohybrid cross will be heterozygous rather than homozygous

what rule is used for the following probability equation:

probability of YYRR x yyrr → YyRr

the probability of Yy ___ Rr is ___

the probability of Y ___ or y is ____

Yy and Rr is multiplied, Y or y is added

describe the probability in a dihybrid cross

probability of one trait times the probability of the second trait

ex.

what is the only thing you can use a punnett square for

monohybrid cross

what are the degrees of dominance

complete: when phenotypes of the heterozygote and dominant homozygote are identical

incomplete: phenotype of F_{1} hybrids is somewhere between the phenotypes of two parental varieties

codominance: two dominant alleles affect the phenotype in separate, distinguishable ways

what are alleles

variations in a gene’s nucleotide sequence

are dominant alleles the most common in a population?

not necessarily

what is pleiotropy

when genes have multiple phenotypic effects

what is polygenic inheritance

some traits may be determined by two or more genes. for example, many human characters vary in the population along a continuum and are called quantitative characters

what is epistasis

a gene at one locus alters the phenotypic expression of a gene at a second locus. example, in mice their coat color depends on two genes: one for pigment and one for whether the pigment will be deposited in the hair.

quantitative variation indicated what type of inheritance

polygenic, an additive effect of two or more genes on a single phenotype

an organism’s phenotype includes what information

physical appearance, internal anatomy, physiology, behavior, and reflects the overall genotype and unique environmental history

why are humans bad subjects for genetic research?

generational period lasts too long, parents produce relatively few offspring, and breeding experiments are unacceptable

pedigrees do what for us

can be used to trace inheritance patterns of specific traits