Hardy-Weinberg Principle

Van Roekel IB BIO II4/14/14

Used to calculate frequencies of alleles, genotypes, or phenotypes within a population

Useful in determining how fast a population is changing or in predicting the outcomes of matings or crossings.

Based off of Punnett squares and probabilities to model allele and genotype frequencies

Hardy-Weinberg Equation

When looked at individually, the frequencies of alleles on chromosomes must add up to 1

p + q = 1 p = frequency of dominant allele q = frequency of recessive allele

p = 0.5 q = 0.5

Allele Frequency

T

T

t

t

TT

Tt

Tt

tt

We are interested in diploid organisms that carry two copies of any trait, so…

(p+q)2 = 1 p2 + 2pq + q2 = 1

p2 = frequency of homozygous dominant q2 = frequency of homozygous recessive 2pq = frequency of heterozygote

Genotype frequencies

TT = p2 = ¼ tt = q2 = ¼ Tt = 2pq = ½

p2 + 2pq + q2 = 1 ¼ + ½ +1/4 = 1

Genotype Frequencies

T

T

t

t

TT

Tt

Tt

tt

What is the Hardy-Weinberg Equation and what does each variable represent? What does this equation tell us?

(p+q)2 = 1, or p2 + 2pq + q2 = 1 p2 = homozygous dominant frequency q2 = homozygous recessive frequency

2pq = heterozygous frequency p = dominant allele frequency q = recessive allele frequency

Used to calculate frequencies of alleles, genotypes, or phenotypes within a population

Useful in determining how fast a population is changing or in predicting the outcomes of matings or crossings

BILL - Hardy-Weinberg Equation

Populations being studies must be a large population, ideally infinite

Random mating between individuals with the particular alleles being examined, aka the trait is autosomal

There must be a constant allele frequency over time There is no allele specific mortality (sickle cell

anemia) There are no mutations that could introduce new

alleles There is no emigration or immigration which would

alter allele frequency

Hardy-Weinberg Assumptions

Consider a disease caused by a recessive allele t. The predicted allele frequency in a population in 10%, what is the frequency of the healthy allele in the population?

Answer: 90% p + q = 1 1-q = p 1-.10 = .90

Practice Problems

A study examined 989 members of the previous population, it was found that 11 people had the disease. Calculate the allele frequency of the recessive allele t.

Answer: 10.5% 11/989 = .011 = q2 = genotype frequency Square root of .011 = 0.105 = 10.5% = q

Practice Problems

Calculate the allele frequencies and genotype frequencies of the population in example 1. Calculate the number of carriers in 500 members of the population

Allele Frequencies: q = 0.10 or 10%p= 0.90 or 90%

Genotype Frequencies: q2 = .01 or 1% 2pq= 0.18 or 18% p2 = 0.81 or 81%

Carriers = 90 people (500 x 18%)

Practice Problem

Using information from example 3, calculate the number of people in 500 members that do not suffer from the disease.

Answer: 495 people p2 + 2pq = 81% + 18% = 99% 99% x 500 = 495

Practice Problem

Use binomial nomenclature to name and classify organisms

1st word refers to the genus, 2nd word to the species, i.e. Homo Sapiens.

Carolus (Carl) Linnaeus consolidated and popularized binomial nomenclature

Reasons:◦ Make sense of biosphere◦ Identify unknown organisms ◦ Show evolutionary links ◦ Predict characteristics shared by members of a group

Classification

Five Kingdoms◦Kingdom Plantae (plants) ◦Kingdom Animalia (animals)◦Kingdom Fungi (fungi and molds)◦Kingdom Protoctista (protozoa and algae)◦Kingdom Prokaryote (bacteria)

Hierarchy of classification

Within each kingdom, there are several subdivisions, called taxa

Seven-level hierarchy of taxa:◦Kingdom◦Phylum◦Class◦Order◦Family◦Genus◦Species

King Phillip Came Over For Good Soup

Hierarchy of Classification

Taxa Human Garden Pea

Kingdom Animalia Plantae

Phylum Chordata Angiospermae

Class Mammalia Dicotyledoneae

Order Primate Rosales

Family Hominidae Papilionaceae

Genus Homo Pisum

Species sapiens sativum

Examples

Feeding Habits (carnivore/herbivore) Habitat (land dwelling/aquatic) Daily activity (nocturnal/diurnal) Risk (harmless/venomous) Anatomy (vertebrates/invertebrates)

System of classification must be clear, consistent, easily implemented and a general consensus to apply it.

Other Means of Classification

Four of the several types of plant phyla include:◦Bryophyta: short in stature such as moss◦Filicinophyta: ferns and horsetails◦Coniferophyta: coniferous, pine trees

cedar, juniper, fir◦Angiospermophyta: all plants that make

flowers and have seeds surrounded by fruit

Plant Phyla

Vegetative Characteristics such as leave types and stems◦Bryophytes: non-vascular, lack vascular

transport tissue such as xylem or phloem◦Filicinophyta: vascular plants, small

leaves◦Conifers: vascular, all produce woody

stems and leaves are needles or scales◦Angiosperms: vascular and have flowers

and fruit

Distinguish plant phylas

Reproductive characteristics◦Bryophytes: produce spores (microscopic

reproductive structures) transported by rain water

◦Filicinophytes: produce using spores in a similar manner

◦Conifer: use wind to help reproduce by pollination, produce seed cones with seed scales

◦Angiosperms: produce seeds, rely on birds, insects, and mammals to transport pollen. Sexual organ is flower, fruit is enlarged ovary

Distinguish plant phylas

Six of many animal phyla include: ◦Proifera: sponges◦Cnidaria: sea jellies (jellyfish), coral

polyps, and others◦Platyhelminthes: flatworms◦Annelida: segmented worms◦Mollusca: snails, clams, octopi, etc…◦Atrhtropoda: insects, spiders, crustaceans,

etc… All listed phyla are invertebrates

Animal Phyla

Porifera:◦ Simple marina animals that are sessile (stuck)◦ Feed by pumping water through tissues and

filtering out food◦ No muscle, nerve tissues, or internal organs

Cnidaria:◦ Very Diverse: Coaral, sea anamones, jellyfish,

hydra, Portuguese man-of-war ◦ All have stinging cells called nematocysts◦ Some sessile, some free swimming, some both◦ Gastric pouch for digestion

Details

Platyhelminthes:◦ Flatworms with one body cavity, gut with one

opening for food to enter and waste to leave◦ No heart, no lungs◦ Exchange gas by diffusion◦ Example: Tapeworms

Annelida:◦ Segmented worms such as earthworms, leeches,

and polychaetes◦ Bodies divided into sections separated by rings◦ Have gastric tracts, w/ mouth at one end and anus

at opposite

Details

Mollusca:◦ Aquatic animals, snails, clams, octopi◦ Shell produced with calcium◦ Non-segmented bodies

Arthropoda:◦ Hard exoskeleton made with chitin, segmented

bodies, and limbs (walking, swimming, eating)◦ Insects, spiders, scorpions, crustaceans such as

crab and shrimp◦ Live in most habitats throughout world◦ Vary in size

Details

Used to help identify which order, genus, and species an organism is by using observable characteristics

In General:◦ Look at first section of key which has a pair of sentences◦ Look at the organism to see if particular characteristics

are present◦ If answer is yes, to go end of line/next section that

contain a new pair of statements to examine◦ If answer is no, go to second statement just below it and

follow that one, should it be true◦ Continue this until the end of the line has a name, not a

number and if each question was answered correctly, should be your organism.

Example in book, pg. 149

Dichotomous Key

1. a. Organism is living........................................................go to 4. 1. b. Organism is nonliving..................................................go to 2. 2. a. Object is metallic........................................................go to 3. 2. b. Object is nonmetallic..................................................ROCK.

3. a. Object has wheels......................................................BICYCLE. 3. b. Object does not have wheels......................................TIN CAN. 4. a. Organism is microscopic...................................PARAMECIUM. 4. b. Organism is macroscopic............................................go to 5. 5. a. Organism is a plant.....................................................go to 6. 5. b. Organism is an animal.................................................go to 8. 6. a. Plant has a woody stem..............................................go to 7.

6. b. Plant has a herbaceous stem.................................DANDELION. 7. a. Tree has needle like leaves.....................................PINE TREE. 7. b. Tree has broad leaves............................................OAK TREE. 8. a. Organism lives on land................................................go to 9. 8. b. Organism lives in water...............................................CLAM.

9. a. Organism has 4 legs or fewer......................................go to 10. 9. b. Organism has more than 4 legs...................................ANT.

10 a. Organism has fur........................................................go to 11. 10 b. Organism has feathers................................................ROBIN. 11 a. Organism has hooves.................................................DEER.

11 b. Organism has no hooves............................................MOUSE.

Vocabulary can be challenging and technical

Make sure using the right key, no key can identify all the species

Making a Dichotomous Key◦ Start by putting things in groups by identical

characteristics◦ Invent statements that divide things into created

groups

Dichotomous Key