BIOL 1406 ch.11

How could the botanist best determine whether the genotype of the green-pod plant is homozygous or heterozygous? green = dominant

Cross the green-pod plant with a yellow-pod plant.

Quantitative characters vary in a population along a continuum. How do such characters differ from the characters investigated by Mendel in his experiments on peas?

Quantitative characters are due to polygenic inheritance, the additive effects of two or more genes on a single phenotypic character. A single gene affected all but one of the pea characters studied by Mendel.

Each chromosome in this homologous pair possesses a different allele for flower color. Which statement about this homologous pair of chromosomes is correct?

These homologous chromosomes represent a maternal and a paternal chromosome.

When a dominant allele coexists with a recessive allele in a heterozygote individual, how do they interact with each other?

They do not interact at all.

pedigree

a diagram of a family tree with conventional symbols, showing the occurrence of heritable characters in parents and offspring over multiple generations

dominant allele

an allele that is fully expressed in the phenotype of a heterozygote

recessive allele

an allele whose phenotypic effect is not observed in a heterozygote

homozygotes

an organism that has a pair of identical alleles for a gene

heterozygotes

an organism that has two different alleles for a gene

dihybrid

an organism that is heterozygous with respect to two genes of interest

lethal dominant alleles

are eliminated from the population if affected people die before reproducing. Nonlethal dominant alleles and lethal alleles that are expressed relatively late in life are inherited in a mendelian way

codominance

both phenotypes expressed in heterozygotes

sickle-cell

has probably persisted for evolutionary reasons: heterozygotes have an advantage because one copy of the sickle-cell allele reduces both the frequency and severity of malaria attacks

genetic counselors

help couples determine the probability of their children having genetic disorders

incomplete dominance of either allele

heterozygous phenotype intermediate between the two homozygous phenotypes

complete dominance of one allele

heterozygous phenotype same as that of homozygous dominant

autosomal inheritance patterns

if no evidence of sex-linkage

carrier

in genetics, an individual who is heterozygous at a given genetic locus for a recessively inherited disorder. The heterozygote is generally phenotypically normal for the disorder but can pass on the recessive allele to offspring

multiple alleles

in the population, some genes have more than two alleles

Suppose that the botanist carried out the test cross described in Parts A and B and determined that the original green-pod plant was heterozygous (Gg). Which of Mendel's findings does her test cross illustrate?

law of segregation

During which part of meiosis (meiosis I or meiosis II) do the two alleles of a gene separate? During which phase does the separation occur?

meiosis I, anaphase

pleiotropy

one gene affects multiple phenotypic characters

multifactorial

referring to a phenotypic character that is influenced by multiple genes and environmental factors

true-breeding

referring to organisms that produce offspring of the same variety over many generations of self-pollination

law of segregation

states that genes have alternative forms, alleles. In a diploid organism, the two alleles of a gene segregate during meiosis and gamete formation; each sperm or egg carries only one allele of each pair. This law explains the 3:1 ratio of F2 phenotypes observed when monohybrids self-pollinate.

law of independent assortment

states that the pair of alleles for a given gene segregates into gametes independently of the pair of alleles for any other gene

sex-linked inheritance patterns

tend to be seen more in males

in a cross between dihybrids

the offspring have four phenotypes in a 9:3:3:1 ratio

addition rule

the probability of an event that can occur in two or more independent, mutually exclusive ways is the sum of the individual probabilities

multiplication rule

the probability of two or more events occurring together is equal to the product of the individual probabilities of the independent single events

many human diseases are multifactorial

they have both genetic and environmental components and do not follow simple mendelian inheritance patterns