lab # 4 anthropology
READ: Before attempting to complete this lab assignment, do this: (1) Read the directions on this Canvas Assignment, and (2) watch the Zoom pre-recorded and captioned video instructions on how to complete the online version of Ex. 4 “Population Genetics” in the Lab Manual for Anth 111, 7th Edition.
Melanic (black) cats have two copies of the recessive piebald
spotted “S” alleles–symbolized by lowercase “ss” as seen in
the LAVC Lab Manual for Human Biological Evolution.
Materials
Two coins
Heads = The front of the coin with a person’s head on it, stands for the dominant allele symbolized by the capital letter “S”
Tails = The back of the coin stands for the recessive allele symbolized by the lowercase letter “s”
Dark-colored or black 8″x11″ paper cut into 40 small squares (for this at-home online class instead of “black bingo disks” in the lab manual’s instructions)
White 8″x11″ paper cut into 40 small squares (for this at-home online class instead of “white bingo disks” in the lab manual’s instructions)
Permanent marker to write a “M” one one quarter and a “F” on the other quarter.
My Lab #4 supplies: 40 squares of white paper with
black Sharpie marks to symbolize the piebald spotted
dominant allele (“S”), 40 squares of black paper to
symbolize the piebald spotted recessive allele (“s”),
two quarters (one marked “M” for Male and the other
marked “F” for Female), and scratch paper. I used a
Sharpie marker to draw on the quarters and paper.
- Resources
Exercise 4 “Population Genetics” (pages 41-48) in the LAVC Lab Manual for Human Biological Evolution (PDF): Anth111Manual7Ex4PopGenetics.pdfDownload Anth111Manual7Ex4PopGenetics.pdf
Microsoft Word file of the LAVC Lab Manual for Human Biological Evolution (7th Edition): LAVCLabManual7thEditionc2019Word.doc Download LAVCLabManual7thEditionc2019Word.doc
In the Microsoft Word file above, you can use an audio screen reader and listen to the directions. You can also type your answers on its exercise questions. You can also copy-paste the questions and your typed answers onto a Google Doc or Microsoft Word doc and upload that file as your answers for this Canvas Assignment for Lab #1. ALWAYS read the directions on the lab’s Canvas Assignment page first. When the directions on a Canvas Assignment differ from the lab manual’s directions in the PDF or Word file, use the directions on the Canvas Assignment page. Some of the exercises have been modified from their original lab manual directions for this 100% online class.
- Pre-recorded and captioned video lecture: Zoom pre-recorded lecture: Lab #4 “Population Genetics”
- My lecture slides: 04_popgeneticsAnth1112024.pdf Download 04_popgeneticsAnth1112024.pdf
You don’t need these lecture slides. You can review these lecture slides if you think you need help answering some of the Study Questions based on what you were taught about genes, alleles, chromosomes, mitosis, and meiosis in Anth 101.
- Directions
Before beginning the lab exercises, you must follow the directions on this Assignment for the online version of this lab.
- Complete these exercises
Complete and answer the online versions of the following exercises/questions in the LAVC Anth 111 Lab Manual for Human Biological Evolution (7th Ed).
- The Hardy-Weinberg Equilibrium Law states that there will be no evolution (change in allele frequencies over multiple generations) if the following factors occur:
None of the four factors of evolution are occurring (no mutation, no genetic drift, no gene flow, and no natural selection)
No sexual selection (individuals mate at random)
Each individual has the same number of offspring
Large population (no genetic drift)
By the way, there is a typo on page 41: “Sexual reproduction” should say “sexual selection” (meaning the mating is completely random).
Review: Remember there are two alleles on every pair of homologous chromosomes. For most alleles, there is a dominant form that overrides a recessive form. It takes two copies of a recessive allele to produce a phenotypic trait.
It takes only one copy of a dominant trait to code for a phenotypic trait on a pair of homologous chromosomes.
Homologous chromosomes are the autosomal chromosomes 1-22, and the female (XX) sex chromosomes and they require two copies of a recessive allele to code for a trait.
[The male (XY) sex chromosomes are not homologous. They require only one copy of an x-linked or a y-linked recessive allele to code for a trait in a chromosomal male because there is no dominant version of the same allele on the other different (not homologous) chromosome to override that x-linked or y-linked recessive allele.]
If both alleles are dominant, then they are called “homozygous dominant.”
If both alleles are recessive, then they are called “homozygous recessive.”
If both alleles are different, one is dominant and the other is recessive, then they are called “heterozygous dominant.”
Exercise 4.1 demonstrates how to use an algebraic formula, the Hardy-Weinberg formula, to see if natural selection occurred over multiple generations. Evolution happens when the frequency of a gene’s alleles changes over time in the genome of a species. That algebraic formula is the Hardy-Weinberg formula: p2 + 2pq + q2 = 1. If there is no change in allele frequencies from one generation to the next, then the population is said to be in equilibrium or “Hardy-Weinberg Equilibrium”.
Exercise 4.1 “Hardy-Weinberg Equilibrium” (pages 41-45).
The Hardy-Weinberg formula:
p2 + 2pq + q2 = 1
p2 = the frequency of the homozygous dominant genotype or “ƒ(SS)“
2pq = the frequency of the heterozygous genotype or “ƒ(Ss)“
q2 = the frequency of the homozygous recessive genotype or “ƒ(ss)“
–>The frequencies (“ƒ”) of the three genotypes (p2, 2pq, and q2) added together always equal 1.0 (or 100% of the population’s genome).<– On page 42, you can see a pie chart that demonstrates this visually. The pieces of the pie, added together, create one pie (100% of the pie).
The Hardy -Weinberg formula is used to measure the change in allele frequencies in the genes of a population of organisms, called its “genome”. If there is no evolution, then there is no change in allele frequencies in the genome, and the population is, genetically speaking, unchanging–a state of “equilibrium.” The word equilibrium means that the state of something (in this case allele frequencies) is in balance/there is no change.
In the lab manual, on page 41, where it says “For this equation, p=ƒ(S) and q = ƒ(s),” It means that for this equation, the alleles for one trait are symbolized by the letter “S”. And, the following is true:
The lowercase letter “p” is equal to the frequency of one dominant allele, symbolized by the capital letter “S”.
The lowercase letter “q” is equal to the frequency of one recessive allele, symbolized by the lowercase letter “s”.
–> Skip the last question on the bottom of page 44 (“Compare your results to those of another lab group…”)
- Skip Exercise 4.2! You do not have to do this exercise and no points will be awarded for it.
Study Questions 1-5 (page 48).
Curious about cat genetics? I found a scientific article with an electron scanning microscope image of a cat’s entire genome (called a karyotype) of 19 pairs of chromosomes (38 chromosomes total)! In comparison, our human genome’s karyotype has more chromosomes: 23 pairs (46 chromosomes total). Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7152298/
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