Bio 182, M1/M2

Key words

Trait

Trait

A characteristic of an organism that varies genetically

phenotype

a description of an organism’s appearance or behavior.

mutation

an error in the sequence of nucleotides when copying DNA.

allele

a form of a gene that affects the way an organism looks or behaves

genotype

the set of alleles that determines how an organism looks or behaves.

gene

a linear sequence of DNA that codes for a certain protein

locus

a place on a chromosome where a certain gene occurs

meiosis

a process in which a diploid cell produces 2 haploid cells.

chromosome

a highly condensed molecule of DNA that codes for many proteins

gamete

a haploid cell that develops into a sperm or egg

zygote

the diploid cell that results from fertilization between sperm and egg

heritability

percentage of phenotypic variation determined by the additive effects of alleles

discrete traits

these are Medellin traits that are determined by one allele and can result in two or three phenotypes (wrinkled, smooth; red, pink, white)

continuous traits

these traits are determined by hundreds or thousands of alleles and are summed (additive) to express one phenotype (height, skin color)

chi-square model

mathematical model to find the probabilities of observations in experiments.

incomplete dominance

this occurs when two alleles blend instead of one expressing it’s phenotype over the other (white and red parents make pink offspring)

codominance

this occurs when two alleles both are expressed instead of one expressing it’s phenotype over the other (white and red parents make offspring with both white and red in their flowers)

homozygous

when an individual carries two identical alleles for a gene. (aa, AA)

heterozygous

when an individual carries two identical alleles for a gene (aA, Aa)

homologous

when two chromosomes contain the same genes

diploid

when a cell contains two copies of each chromosome

haploid

when a cell contains one copy of each chromosome

True or False? Scientists believe in evolution even though they currently lack evidence for the theory.

False. Scientists believe in evolution because there is ample evidence.

The scientific method relies on __.

models, observations, and experiments

A model is a formal description of a scientific hypothesis. Which type of model provides the most precise description of a hypothesis?

mathematical

True or False. An experiment enables one to demonstrate that a correlation between two variables results from cause and effect.

True

A well designed experiment ___________.

controls for environmental and genetic factors, involves the replication of experimental subjects, and randomizes experimental subjects among treatments.

True or False? Natural selection occurs whenever some individuals reproduce more than others.

false. natural selection occurs when heritable traits are passed to offspring.

True or False? Organisms evolve by natural selection.

false. Populations evolve by natural selection

True or False? Artificial selection requires heritable variation in a trait.

True

True or False? According to a model of blending inheritance, a mom with red eyes and a dad with white eyes would produce a mixture of offspring: some with red eyes and some with white eyes.

False. According to a model of blending inheritance, a mom with red eyes and a dad with white eyes would produce offspring with pink eyes.

True or False? According to a Lamarckian model of inheritance, a child would have opaque or cloudy eyes if its mother developed a cataract prior to pregnancy.

True. Lamarckian inheritance posits that changes that occur in the parents lifetime will affect the phenotypes of their offspring.

True or False? According to the theory of blending inheritance, a mating between a plant that produces round peas and a plant that produces wrinkled peas would result in offspring that produce slightly wrinkled peas.

True. The theory of blending inheritance supposes that traits of the parents are blended fully together in the offspring.

True or False? If some plants with round peas were heterozygotes, then these plants should produce offspring with wrinkled peas when mated to plants with wrinkled peas.

true. We learned that round peas are the dominant trait and when a heterozygous parent is mated with a homozygous recessive parent, their offspring may be either wrinkled (recessive homozygous) or round (dominant heterozygous)

True or False? If a heterozygote (Aa) makes enough enzymes to catalyze as many reactions as a homozygote (AA) can, these genotypes would have the same phenotype.

True. This is complete dominance.

True or False? If a heterozygote (Aa) makes some enzymes, but not enough to catalyze as many reactions as a homozygote (AA) can, all genotypes would have the same phenotype (AA = Aa = aa).

False. This would be incomplete dominance, where AA, Aa, and aa all have different phenotypes.

True or False? If two heterozygotes mate to produce two offspring, the chance that both offspring are homozygous equals 50%.

False. There is a 1/2 chance their offspring are AA or aa homozygous. Then we must multiply that by the chance the second offspring is homozygous AA or aa, which is another ½ chance. This makes a ¼ or 25% chance both offspring are homozygous.

True or False? Given a P value less than 0.01, our model of genetics probably fails to explain the observed phenotypes.

True. P Value is the probability of the observed deviation when the model is correct. If the P value is less than a 1% chance of observing these phenotypes, then it is wildly unlikely that the hypothesis of the parent genotypes is correct and we need to adjust our model. Perhaps you hypothesized the parents were both homozygous, when in fact one or both of them are heterozygous.

True or False? If a male fly carries a recessive allele for white eyes in the sex-linked chromosome, he could have either white eyes or red eyes.

False. Males only have 1 allele in their sex-linked chromosomes, so if the fly only has one allele and it’s recessive, then he can only have white eyes.

True or False? A mutation on a sex chromosome is more likely to create a novel phenotype in a male than in a female.

True. Because males only have one x chromosome, they are more likely to express the mutated allele.

True or False? Natural selection should minimize the chance of mutation.

True. Most mutations are deleterious and are naturally selected out of the population.

True or False? In a rapidly changing environment, a population would likely benefit from more frequent mutation.

True. The more mutations that occur in a rapidly changing environment increases the chance of a beneficial mutation to occur that will help the population survive in this new environment.

True or False? A point mutation in the third position of a codon is more likely to change the structure of the protein synthesized from the gene.

False. There is redundancy in protein coding that helps prevent a point mutation from making radical changes. For example: CUU, CUC, CUA, and CUG all code for the protein Leucine. If there is a point mutation in the third position, the protein does not change.