Genetics Chapter 3: Basic Principles of Heredity

the pea plant

what was Mendel's experimental subject?

an inherited factor (encoded in DNA) that helps determine a characteristic

what is a gene?

one of two or more alternative forms of a gene

what is an allele?

a specific place on a chromosome occupied by an allele

what is a locus?

a set of alleles possessed by an individual organism

what is a genotype?

an individual organism possessing two of the same alleles at a locus

what is a homozygote?

an individual organism possessing two different alleles at a locus

what is a heterozygote?

an attribute or feature possessed by an organism

what is a characteristic/character?

the appearance or manifestation of a characteristic

what is a phenotype/trait?

crosses between parents that differed in a single characteristic

what are monohybrid crosses?

parental generation, first generation of a cross

what is the P generation?

first filial generation, the offspring of the parents in the P generation

what is the F1 generation?

a cross between an F1 genotype and either of the parental genotypes

what is a backcross?

F1 expressed only one of the phenotypes found in the P generation, while both traits appeared in the F2 generation

what did Mendel find about the F1 vs F2 generation?

offspring must inherit genetic factors from both parents, two alleles in each parents separate and go into gametes, concept of dominance, two alleles of an individual separate with equal probability into the gametes

what conclusions did Mendel draw from his monohybrid crosses?

that each individual diploid organism possesses two alleles for any particular characteristic, one inherited from the maternal parent and one from the paternal parent

what does the principle of segregation state?

that when two different alleles are present in a genotypes, only the trait encoded by one of them - the dominant allele - is observed in the phenotype

what does the concept of dominance state?

specific DNA sequences

what do alleles usually represent?

7

how many traits did Mendel test?

a 3:1 phenotypic ratio

what did self-fertilization of the F1 generation in Mendel's experiments produce?

Mendel's first law

what is another term for the principle of segregation?

the theory that genes are located on chromosomes

what is the chromosome theory of heredity?

the likelihood of the occurrence of a particular event

what is probability?

states that the probability of two or more independent events taking place together is calculated by multiplying their independent probabilities

what is the multiplication rule?

and

what key word should you look for when using the multiplication rule for probability?

states that the probability of any two or more mutually exclusive events is calculated by adding the probabilities of the events

what is the addition rule?

either/or

what key word should you look for when using the addition rule for probability?

a tool in which one individual of unknown genotype is crossed with another individual with a homozygous recessive genotype for the trait in question

what is a testcross?

+

what symbol usually symbolizes a wild type?

3:1

what is the phenotypic ratio of a cross between two heterozygous parents?

1:1

what is the phenotypic ratio of a cross between a heterozygote and homozygous recessive individual?

1:2:1

what is the genotypic ratio of a cross between two heterozygous parents?

1:1

what is the genotypic ratio of a cross between a heterozygote and homozygous recessive individual?

1:1

what is the genotypic ratio of a cross between a heterozygote and homozygous dominant individual?

that alleles at different loci separate independently of each other

what does the principle of independent assortment state?

Mendel's Second Law

what is another name for the principle of independent assortment?

the principle of independent assortment is an extension of the principle of segregation, refer to the same process

how are the principle of segregation and principle of independent assortment related?

9:3:3:1

what phenotypic ratio results from a dihybrid cross?

applies to characteristics encoded by loci located on different chromosomes

what is an important qualification of the principle of independent assortment?

a statistical test that provides information about how well observed values fit expected values

what is the chi-squared goodness-of-fit test?

anaphase I

when does segregation of alleles and independent assortment take place?

chance alone is responsible for a deviation between observed and expected values

what is the null hypothesis in the chi-squared goodness-of-fit test?

0.05

what is the threshold for the p-value in the chi-squared goodness-of-fit test?

n-1, n = number of different expected phenotypes

what are the degrees of freedom in the chi-squared goodness-of-fit test?

reject the null hypothesis, the outcome did not occur by chance (if the p is low, the null must go)

what does it mean if the p-value is below 0.05?

fail to reject the null hypothesis, the outcome likely occurred by chance (if the p is high, the null will fly)

what does it mean if the p-value is above 0.05?