BIOLOGY EXAM 3

The breeder's equation predicts no response to artificial selection if:

- heritability is zero - the strength of selection is zero - the genetic contribution to the phenotype is zero

If DNA polymerase makes a mistake during DNA replication, it can affect:

- proteins translated from the mutated DNA - RNA transcribed from the mutated DNA - DNA in cells that descend from this cell will inherit the mutation

Consider a trait caused by a single gene with only two alleles: S and s, and S is the dominant alelle. If you cross one individual who is SS with an individual who is ss, how many different phenotypes will you see in the offspring?

1

What are the four necessary conditions for selection to take place? Provide an example of a plant trait that satisfies each of these necessary conditions and explain why the conditions are met.

1. Traits are variable: pink perry paintbrush flower, there is a lot of variation in one species 2. Traits are heritable: common garden experiments show that populations have adapted to different environments based on altitudes 3. A struggle for existence: a population cannot keep growing exponentially, resources run out, it reaches carrying capacity 4. Traits determine survival: copper tolerance in monkey flowers, if the plants inherits the copper tolerance it determines if the species with survive

If a plant that is homozygous resistant (RR) is mated with a plant that is heterozygous (RS), what proportion of offspring will be heterozygous?

50%

You are at a party and are explaining with excitement that you learned broccoli (and kale and cauliflower and brussels sprouts) evolved from wild mustard. Another person at the party is skeptical and asks, "If broccoli evolved from wild mustard, why is there still wild mustard?" How would you explain this common misconception about evolution?

As evolution happens there are reproductive barriers that cause different variations of the plant to occur. As this happens there becomes a phylogeny of many plants all related over time. The cultivated species share a common ancestor with wild species that have evolved since that common ancestor

A quantitative trait is likely to:

Be caused by many genes, each with small effect

If broccoli evolved from wild mustard, why is there still wild mustard?

Broccoli did not evolve from modern wild mustard, they share a common ancestor.

If a population has 50% of individuals with red flowers and 50% of individuals with blue flowers, and a new pollinator makes it so that red flowers are more fit, natural selection will tend to:

Decrease genetic diversity

Which of the following is the most appropriate definition of "evolution"

Evolution happens in populations over generations

What are two examples of reproductive barriers between populations? Why are reproductive barriers important for the evolution of new species?

Geographic Isolation: New mountain range, new river, isolated on an island Ecological Isolation: Different flowering time, different pollinators, different habitats

A gene that is associated with floral scent production would have:

High RNA in style, low RNA in leaves

Imagine you are trying to create a variety of broccoli that is tastier for children by genetically engineering broccoli to produce linalool— the compound that gives Fruit Loops their fruity taste. Broccoli does not naturally produce linalool, but it is produced by other plant species. Using what you know about modern crop improvement techniques, describe the steps you would take to make broccoli produce linalool and taste fruity.

I would use transformation to try to put the linalool into the broccoli cells. Traditional breeding and mutagenesis are far more unsure than transformation. The transformation steps I would take: 1. identify the gene to add to the crop species 2. insert gene into a vector 3. infect crop with vector 4. test for signs of new genes in the crop 5. breed the plants that have the new gene

Using what you know about the central dogma of molecular genetics, explain how changing the sequence of DNA can affect the function of proteins.

If there's a change in the DNA from a mutation or random assortment it will change the process of constructing the protein.

Individual Pokemon are often shown to "evolve" by changing their characteristics. For example, Caterpie evolves into Metapod by growing legume arms. She then evolves into Butterfree by growing wings. Why is this not an appropriate use of the term "evolution"?

Instead of referring to these changes as evolution, it would be more accurate to say these characters are acclimating to their environment. Evolution refers to changes that occur over many generations.

allele

One of two or more versions of a genetic sequence at a particular region on a chromosome

Which of the following a difference between meiosis and mitosis?

Meiosis results in four cells with reduced ploidy, mitosis results in two cells with the same ploidy

In land plants, gametes (sperm and egg) are produced by:

Mitosis

In plants, how do the cells that result from mitosis differ from cells that result from meiosis?

Mitosis cells are diploid having two sets of chromosomes, meiosis cells are haploid with one set of each chromosome.

What are two primary sources of genetic variation in natural populations? Why does natural selection tend to decrease genetic variation in populations?

Mutation and migration are two primary sources of genetic variation. Natural selection decreases genetic variation because the more fittest of the plant species reproduce and the less fit die off the less variation remaining.

When plant gametophytes make gametes, which kind of gene shuffling occurs?

None of the above: - Fertilization - crossing over - independent assortment

Which enzyme is responsible for gene expression using DNA as a blueprint?

RNA polymerase

Imagine a population of monkeyflowers is growing near a copper mine. A new mutation arises in the population that allows the monkeyflowers to tolerate higher concentrations of copper. What will is a likely outcome for this mutation?

The copper tolerance allele will increase in the population because copper tolerant plants will leave more offspring

Which of the following is true of flowering plants?

The dominant phase of the life cycle in flowering plants is the sporophyte

what determines the relationship between the selection and the response to selection?

heritability

A plant breeder is attempting to increase the height of a plant species by only selecting the 100 tallest plants to breed each generation. The breeder then takes the 100 tallest plants from that population and breeds them. However, after several generations of this process, the breeder does not see any increase in height. Using the breeder's equation, provide an explanation to why there is no change in phenotype.

The plant breeder is not seeing any change since there is no heritability. The breeders equation is R(response)=H(heritability)xS(selection), so even if the selection differential is high if there is zero heritability there will be no response. A trait is only heritable if it is constant throughout a population and if it can be passed onto the next generation.

Which of the following could be a pre-zygotic isolating barrier between two populations The in plants?

The populations have different flowering times

Which of the following is NOT a necessary condition for evolution of a trait to occur by natural selection?

The trait is determined only by environmental variation

What is the most likely explanation for a dihybrid cross to deviate from the 9:3:3:1 ratio of phenotypes - for example a ratio of 15:1:1:5?

The two traits are caused by two genes located on the same chromosome

A plant geneticist is studying two traits— flower color and pollen size. In a lucky break, each trait is controlled by a single gene. The geneticist breeds two plants together— one with purple flowers and big pollen, and one with red flowers and small pollen. In the second generation, the geneticist expects to find a 9:3:3:1 ratio of phenotypes, but instead observes a ratio of 15:1:1:5. What is the most likely explanation for the difference?

The two traits are caused by two genes located on the same chromosome, as an effect of recombination. Had the genes been shuffled by independent assortment on separate chromosomes, it would have resulted in the 9:3:3:1.

Using what you know about the central dogma of molecular genetics, explain how it is possible for a plant to have different types of cells and tissues, even though every cell contains the same DNA in its genome.

The way the DNA is read based on which part is transcribed determines the expression of the cell. Based on what is expressed, it can be things such as roots cells, stem cells, or leaf cells from cell differentiation.

Why are reproductive barriers important for the evolution of new species?

These are important because it allows for the formation of new isolated species. This is called speciation, when populations develop incompatibilities with other populations and can no longer breed together due to reproductive barriers they become an entirely separate species.

homologous chromosome pairs

Two chromosomes in a pair, normally one inherited from the mother and one from the father

in general, natural selection will

decrease genetic diversity

Consider these different types of plant cells. If a mutation were to arise in the cell during DNA replication, which cell would be most likely to pass the mutation to the next generation via sexual reproduction?

flower bud cell

Which of the following describe a cell or tissue that is haploid?

gamete

The part of the genome that encodes for proteins is referred to as:

gene

if the red allele gives individuals more fitness than the blue allele, then over time

genetic diversity will decrease

The spores being ejected in this image are the products of meiosis. That means the spores are most likely?

haploid

Which method of generating new plant varieties involves bombarding plants with radiation or chemicals?

mutagenesis

Which of the following is a source of genetic variation in natural populations?

mutation

Which of the following is true for meiosis and NOT true of mitosis?

pairing up of chromosomes

Which type of cell cannot be heterozygous?

pollen

Which stage of meiosis is responsible for recombination of gene variants on the same chromosome?

prophase

If the heritability of a trait is zero, which of these is true?

selection on the trait will be ineffective

if the heritability of a trait is zero, which of these is true

selection on the trait will be ineffective

The products of meiosis in land plants are:

spores

Which type of cell can be heterozygous?

sporocyte

Consider a gene that has only two alleles: R and r, and the r allele is recessive. If an individual is heterozygous at this gene, they will have:

the dominant phenotype

Which part of the life cycle is most unique to plants, and does not occur in animals?

the entire sporophyte to sporocyte part is unique to plants

locus

the position of a gene on a chromosome

homozygote

the two alleles being the same (RR)

Which method of genetic engineering would be most effective at giving a plant a new function with a new gene it does not normally have?

transformation

Which of these genetic engineering methods is currently classified as producing "Genetically Modified Organisms" by the USDA?

transformation

which genetic engineering method would be most effective for adding a new functioning gene in a plant

transformation

heterozygote

two alleles that are different (RS)

Speciation can occur when

two populations have not interbred for many generations, hybrids between two populations are not reproductively compatible, two populations have different numbers of chromosomes