BIO Buskirk 311D exam 1 learning outcomes

1-1 Compare and contrast mitosis and meiosis in terms of their function and the chromosome number in daughter cells as compared to the original cell.

mitosis: cell replication in the body

meiosis: transmission of genetics to gametes/sex cells

if we have 1 cell with 23 pairs of chromosomes: 2n=46

mitosis: 2 cells with 46 chromosomes

meiosis: 4 cells with 23 chromosomes

1-2. Know what these terms mean and be able to relate them: DNA molecule, chromosome, gene, allele

1 chromosomes consists of 1 wound up DNA molecule. A gene is a set of nucleotide bases that code for a set of traits. An allele is a specific trait and is apart of that gene

1-3. If the diploid number (2n) for a species is 50, how many homologous pairs are in that species’ genome, and how many chromosomes are in a sperm cell of that species?

25 homologous pairs (n) and 25 chromosomes in a sperm cells

1-4. For the following pairs of terms, define and distinguish between them: gene & allele; genotype & phenotype; homozygous & heterozygous; dominant & recessive alleles.

gene vs allele: gene: selection of DNA that codes for a specific set of traits (hair color). allele: variant of that gene (blonde)

genotype vs phenotype: genotype: the alleles in the chromosomes (hetero, homo). phenotype: what shows, (Dominant or homo recessive).

1-5. Tell how the Punnett square is related to meiosis and fertilization.

The 2 parents gametes (created from meiosis) are on the sides of the punnett square, and inside is the predicted fertilzed zygotes.

1-7. Distinguish these forms of allele dominance: simple (=complete), incomplete dominance, co-dominance

simple (=complete), whatever is dominant show in phenotype and only that. (Cystic Fibrosis)

incomplete: Can mix dominant (red + white flower = pink)

co-dominant: both show in phenotype. MN blood types

1-10. Use the multiplication rule to determine the probability of a certain combination of two independent events. (e.g.,2 sons)

probability of 1st event x probability of 2nd event.

2 sons: .5 x .5 = .25

1-11. How do single-locus genes with pleiotropy affect the phenotype of an individual?

There are multiple symptoms and impact multiple parts of a persons body. A single gene mutation that impacts multiple traits. Example Cystic fibrosis. Impacts lungs, reproductive system, pancreas

1-12. How could the offspring phenotype ratio from a heterozygote mating be different if one offspring genotype is embryonic-lethal?

This will cause the homo dominant to be lethal in the embryonic stage and we know that will not be a phenotype. leaving 3 options left

1-13. Name an example where some aspect of the environment affects gene expression so that the phenotype might differ.

Hydrangeas are pH and temperature dependent changing petal color in response

1-14. Review chromosome changes during meiosis, and briefly define or describe two processes in normal meiosis that lead to greater genetic variation among gametes.

homologous pairs separate first and then sister chromatids.

Crossing over: alleles get so close to one another that some parts flip at chiasma and exchange segments. Occurs early in meiosis

Independent assortment: produces 2^n combinations based on which sister chromatids end up in which cell.

1-15. In normal meiosis, different homologous pairs assort independently, creating different random combinations. What if two genes are on the same chromosome—will they assort independently or will they go together into the same gamete?

If 2 genes are on the same chromosome, they will most likely go into the same gamete unless crossing over occurs. If they are linked, they likelihood is even less.

1-16. What is aneuploidy? What is trisomy 21?

aneuploidy: not good ploidy = abnormal chromosome #

trisomy 21: 3 chromosomes at 21, causes down syndrome.

1-17. What is the genetic (chromosomal) basis of sex determination (male or female) in placental mammals?

X or Y

male if they have the SRY gene on the Y chromosome

1-18. Given information about parental phenotypes for an X-linked recessive trait, draw a Punnett Square (including X and Y chromosomes) and predict the percentage or fraction of (a) their offspring and (b) their sons that would express the recessive trait in their phenotype.

1/4 will be affected

1/2 of the sons

1-19. How can XX females, heterozygous for X-linked traits, express different phenotypes, even though genetically identical?

Only one of the Xs is activated. Random

1-20. Distinguish these underlined terms; what do they mean? (recall: allele vs genotype vs phenotype) allele frequency vs genotype frequency

allele frequency: the portion of the population with a certain allele at a given gene locus

genotype frequency: the portion of a given genotype within a population

1-21. Describe a gene pool quantitatively in terms of allele frequencies and genotype frequencies.

all the alleles and genotypes in a population. Gene pool: double the amount of alleles. Allele Frequency: Number of copies of a specific allele/ total number of all alleles for that gene in the population. Genotype frequency: Number of individuals with specific genotype/Total number of individuals in the population.

1-22. Calculate allele frequency (p, q) and genotype frequencies (p2, 2pq, q2) using the two Hardy-Weinberg equilibrium equations.

p + q = 1

p^2 + 2pq + q^2 = 1

Butterflies Black vs Brown

1-23. Name the main assumptions of Hardy-Weinberg equilibrium. Tell how violating any one of those assumptions would cause the population (gene pool) to evolve and not stay in equilibrium.

no mutations: gene pool will change with different genes

random mating: no inbreeding, if random mixing occurs genotype frequencies change

no natural selection: gene pool will change because some alleles will be favored in survival and reproductive success.

large population size: small makes it too easy for one to die out. Genetic drift

no gene flow: no new alleles introduced or more of a certain type

when not met: microevolution. By moving alleles into or out of populations it can alter allele frequencies.

1-24. Describe the effect of small population size on allele frequencies in a population over time.

Can lead to genetic drift, which is a change in the allele frequency in a population due to random event

Alleles are more likely to become completely extinct or fixed in a smaller population

class simulation (it increases the frequency of an allele to 100 or 0)

1-25. Tell how positive selection and negative selection, respectively, affect allele frequencies.

positive: it increases freqency over time because they have higher reproductive fitness

negative, decreases over time

1-26. Using a specific example, explain the process (sequence of changes) of evolution by natural selection for a given trait in a population in a specific environment.

pepper moths during the industrial revolution

when tree bark got darker: the favorable allele was for a darker phenotype. This was due to selection by predators and white moths became favorable

shifted back after industrial revolution

1-27. Why don't all unfavorable alleles disappear immediately from a population?

They remain in heterozygotes

1-28. What is the selection effect of heterozygote advantage on allele frequencies in a population?

heterozygotes have a higher reproductive fitness. advantage in malaria areas because they dont have sickle cell and are still protected against malaria

1-29. Provide examples of different selective pressures (e.g., predator, sexual) and how they affect evolutionary fitness. (despite reducing individual survivability in some cases).

predator: pepper moths

sexual: bird of paradise: bigger brighter feathers and mating dances for female selection but predators can spot them easier

1-30. Describe anisogamy and analyze how differences in gamete size create distinct selective pressures on males and females, shaping their reproductive strategies and behaviors.

anisogamy: females have a small amount of large gametes. Males have a large amount of small gametes

Male competition, female choice.

1-31. Explain how allele frequencies in a small population can evolve by some type of genetic drift. How does "genetic drift" differ from "gene flow"?

genetic drift: bottleneck and founders

gene flow: members of 1 population go to another.

if there is an allele frequency change by random chance it is more likely to make a bigger impact in small populations

1-32. What is the Biological Species Concept/Definition? Name an example of how it is used to distinguish two species.

If they can mat and produce fertile offspring, they are the same species

mules: horses and donkeys can mate but cannot produce fertile offspring

1-33. Name two examples of pre-zygotic barriers, i.e., reproductive isolating mechanisms, and tell how each can help keep two distinct species from inter-breeding, that is: how are they barriers?

habitat isolation: in different locations and cannot mate

behavioral isolation: mating behaviors are different. Females will not select the male

1-34. Describe a scenario when new species could arise by allopatric speciation. What genetic changes would be involved? How would we know the results are two different species?

1 population is split and is allopatriclly apart.

a species of bird (galapagos finches) are swept away to a different island. A mutation occurs that changes their size or sex organs or they have different mating behaviors. When the populations meet again, they cannot breed.

1-35. A geographic barrier alone is NOT an evolved reproductive isolating mechanism. Why not?

They may still be able to breed when brought back together

there must be a genetic mutation or changing in mating behaviors to the point they will not breed.