Category: 1st Semester

Ink Chromatography

Chromatography of Inks

Introduction:

One of the main jobs of biochemists is to unravel the complexities of chemical compounds and reduce them to their individual components.  The term chromatography comes from two Greek words, “chromat” meaning color and the word “graphon” meaning to write.  Separation of the components of chemical compounds can be done by using several methods. Liquids can be separate by High Performance liquid Chromatography (HPLC), while the components of gases are separated by Gas Chromatography.  Chromatography is a method for analyzing complex mixtures (such as ink) by separating them into the chemicals from which they are made. Chromatography is used to separate and identify all sorts of substances in police work. Drugs from narcotics to aspirin can be identified in urine and blood samples, often with the aid of chromatography.

Chromatography was first used to separate pigments (colors) in leaves, berries, and natural dyes. Paper chromatography is a technique used to separate, isolate, and identify chemical components of a compound. In paper chromatography, the solid surface is the cellulose fibers in the chromatography paper.  A solvent or developer (water, alcohol, or acetone) is placed in the bottom of the chromatography chamber. The paper acts as a wick to pull the solvent up the paper. The solvent front will “wick” up the chromatography paper by capillary action.  A minute drop of the ink or chemical mixture to be separated is placed near the bottom of the strip of chromatography paper, but slightly above the level of the solvent in the chamber.  As the solvent passes over the drop of ink, the components of the ink dissolve in the solvent. Because the components of the ink do not all dissolve at the same rate, as the components of the mixture move upward, they show up as colored streaks.  The separated substances on the chromatography paper form a color pattern called a chromatogram.

To determine the rate of migration for each pigment or component of the ink, the Rf value for each pigment must be calculated. The Rf value represents the ratio of the distance a pigment moved on the chromatogram relative to the  distance the solvent front moved. Each pigment or compound will have a unique Rf value that scientists can use to identify the substance. The Rf value is calculated using the following formula:

Rf = distance traveled by the compound / distance traveled by the solvent

Objective:

Use the process of paper chromatography to separate the pigments in various markers and then determine the Rf value for each color on your chromatogram.

Materials:

Plastic vials, paper clips, markers in assorted colors, chromatography paper, scissors, pencil

Procedure:

  1. Obtain chromatography vials and chromatography strips, and different color markers so that each person in the group will have two chromatograms.
  2. Cut one end of the chromatography strip to a point. The bottom of the point will mark the starting point for movement of the solvent (H2O).
  3. About 2.0 centimeters from the bottom of the strip, draw a faint horizontal line with pencil. This will mark the starting point for measuring the migration distance of each color.
  4. Using a different color marker for each strip, drop a dot of ink on the center of the horizontal pencil line.  Let this dry a moment & then add more ink to the dot.
  5. Add a small amount of water to the bottom of the chromatography chamber. (The ink dot should be ABOVE the surface of the water.)
  6. Straighten a paper clip and poke a hole through the top of your chromatography strip
  7. Use the paper clip to hang the strip in your chamber. (The straighten paper clip will lay across the top of the chamber.)
  8. MAKE SURE THE TIP OF THE STRIP BUT NOT THE INK IS IMMERSED IN THE WATER!
  9. Notice the separation of the ink as both the solvent and ink travel up the chromatography strip.
  10. Once the solvent front has neared the top of the strip, remove the strip from the chamber and lay it on a piece of paper towel.
  11. Immediately mark the solvent front with a faint pencil line.
  12. Immediately mark the leading edge of each color with an “x”.
  13. Measure, in millimeters, the distance the solvent migrated from the tip of the strip to your solvent front pencil line.
  14. Measure, in millimeters, the distance each color migrated from the point of origin (pencil line where the ink dot was placed) to the leading edge of the color (marked with an “x”.
  15. Record all data in Data table 1.
  16. Calculate and record the Rf value for each color using the formula below.

Rf = distance traveled by the compound / distance traveled by the solvent

Data Table 1

 

Color pen/marker used:

Separated colors
(list top of strip to bottom) 		Distance each color traveled

(mm)

Distance solvent (H2O)
(mm) 		Rf Value for each color

(Distance color traveled / Distance solvent traveled)

       
       
       
       
       
       
       
       

 

 

 

Color pen/marker used:

Separated colors
(list top of strip to bottom) 		Distance each color traveled

(mm)

Distance solvent (H2O)
(mm) 		Rf Value for each color

(Distance color traveled / Distance solvent traveled)

       
       
       
       
       
       
       
       

 

 

Questions:

1. Which color of marker did you use?

2. which color separated out first from your ink dot?

3. Why did the inks separate?

 

4. What was your solvent?

5. If you had used markers that weren’t water-soluble, how would you have had to change this lab?

 

6. Why did some inks move a greater distance than others?

 

7. How do scientists use paper chromatography in their investigations?

 

 

Homeostasis & Transport

 

HOMEOSTASIS AND TRANSPORT
All Materials © Cmassengale

 

I. Cell Membranes

 

A. Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells

B. Some substances can cross the cell membrane without any input of energy by the cell

C. The movement of such substances across the membrane is known as passive transport

 

D. To stay alive, a cell must exchange materials such as food, water, & wastes with its environment

E. These materials must cross the cell or plasma membrane

F. Small molecules like water, oxygen, & carbon dioxide can move in and out freely

G. Large molecules like proteins & carbohydrates cannot move easily across the plasma membrane

H. The Cell Membrane is semipermeable or selectively permeable only allowing certain molecules to pass through

 

II. Diffusion

 

A. Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration

B. Small molecules can pass through the cell membrane by a process called diffusion

 

C. Diffusion across a membrane is a type of passive transport because it does not require energy

D. This difference in the concentration of molecules across a membrane is called a concentration gradient

 

E. Diffusion is driven by the kinetic energy of the molecules

F. Kinetic energy keeps molecules in constant motion causing the molecules to move randomly away from each other in a liquid or a gas

G. The rate of diffusion depends on temperature, size of the molecules, & type of molecules diffusing

 

H. Molecules diffuse faster at higher temperatures than at lower temperatures

I. Smaller molecules diffuse faster than larger molecules

J. Most short-distance transport of materials into & out of cells occurs by diffusion

K. Solutions have two parts — the solute which is being dissolved in the solvent

 

L. Water serves as the main solvent in living things

M. Diffusion always occurs down a concentration gradient (water moves from an area where it is more concentrated to an area where it is less concentrated)

N. Diffusion continues until the concentration of the molecules is the same on both sides of a membrane

 

O. When a concentration gradient no longer exists, equilibrium has been reached but molecules will continue to move equally back & forth across a membrane

 

III. Osmosis

 

A. The diffusion of water across a semipermeable membrane is called osmosis

B. Diffusion occurs from an area of high water concentration (less solute) to an area of lower water concentration (more solute)

 

C. Movement of water is down its concentration gradient & doesn’t require extra energy

D. Cytoplasm is mostly water containing dissolved solutes

E. Concentrated solutions have many solute molecules & fewer water molecules

F. Water moves from areas of low solute concentration to areas of high solute concentration

G. Water molecules will cross membranes until the concentrations of water & solutes is equal on both sides of the membrane; called equilibrium

 

H. At equilibrium, molecules continue to move across membranes evenly so there is no net movement

I. Hypertonic Solution
1. Solute concentration outside the cell is higher (less water)
2. Water diffuses out of the cell until equilibrium is reached
3. Cells will shrink & die if too much water is lost
4. Plant cells become flaccid (wilt); called plasmolysis

J. Hypotonic Solution
1. Solute concentration greater inside the cell (less water)
2. Water moves into the cell until equilibrium is reached
3. Animal cells swell & burst (lyse) if they take in too much water
4. Cytolysis is the bursting of cells
5. Plant cells become turgid due to water pressing outward against cell wall
6. Turgor pressure in plant cells helps them keep their shape
7. Plant cells do best in hypotonic solutions

K. Isotonic Solutions
1. Concentration of solutes same inside & outside the cell
2. Water moves into & out of cell at an equal rate so there is no net movement of water
3. Animal cells do best in isotonic solutions

 

IV. How Cells Deal With Osmosis

 

A. The cells of animals on land are usually in isotonic environment (equilibrium)

B. Freshwater organisms live in hypotonic environments so water constantly moves into their cells

C. Unicellular freshwater organisms use energy to pump out excess water by contractile vacuoles

D. Plant cell walls prevent plant cells from bursting in hypotonic environments

E. Some marine organisms can pump out excess salt

 

V. Facilitated Diffusion

 

A. Faster than simple diffusion

B. Considered passive transport because extra energy not used

C. Occurs down a concentration gradient

D. Involves carrier proteins embedded in a cell’s membrane to help move across certain solutes such as glucose

 

E. Carrier molecules change shape when solute attaches to them

F. Change in carrier protein shape helps move solute across the membrane

G. Channel proteins in the cell membrane form tunnels across the membrane to move materials

H. Channel proteins may always be open or have gates that open & close to control the movement of materials; called gated channels

 

I. Gates open & close in response to concentration inside & outside the cell

 

VI. Active Transport

 

A. Requires the use of ATP or energy

B. Moves materials against their concentration gradient from an area of lower to higher concentration

C. May also involve membrane proteins

D. Used to move ions such as Na+, Ca+, and K+ across the cell membrane

E. Sodium-Potassium pump moves 3 Na+ out for every 2 K+ into the cell
1. Causes a difference in charge inside and outside the cell
2. Difference in charge is called membrane potential

 

F. Ion pumps help muscle & nerve cells work

 

G. Plants use active transport to help roots absorb nutrients from the soil (plant nutrients are more concentrated inside the root than outside)

 

VII. Bulk Transport

 

A. Moves large, complex molecules such as proteins across the cell membrane

B. Large molecules, food, or fluid droplets are packaged in membrane-bound sacs called vesicles

 

C. Endocytosis moves large particles into a cell

D. Phagocytosis is one type of endocytosis
1. Cell membrane extends out forming pseudopods (fingerlike projections) that surround the particle
2. Membrane pouch encloses the material & pinches off inside the cell making a vesicle
3. Vesicle can fuse with lysosomes (digestive organelles) or release their contents in the cytoplasm
4. Used by ameba to feed & white blood cells to kill bacteria
5. Known as “cell eating”

 

E. Pinocytosis is another type of endocytosis
1. Cell membrane surrounds fluid droplets
2. Fluids taken into membrane-bound vesicle
3. Known as “cell drinking”

 

F. Exocytosis is used to remove large products from the cell such as wastes, mucus, & cell products

G. Proteins made by ribosomes in a cell are packaged into transport vesicles by the Golgi Apparatus

H. Transport vesicles fuse with the cell membrane and then the proteins are secreted out of the cell (e.g. insulin)

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Genetics Study Guide

Genetics Study Guide 

The two genes or alleles that combine to determine a trait would be the organism’s _______________.
Type AB blood, having two genes dominant for a trait, is an example of ________.
State Mendel’s law of segregation.
Rr x Rr is an example of what type of cross —– P1, F1, or F2?
If both alleles are the same in a genotype, is the genotype homozygous or heterozygous?
Which cross is a cross between two hybrids —– P1, F1, or F2?
__________ dominance results in the blending of genes in the hybrid. Give an example using flower color.
What is another term for a heterozygous genotype?
The _____________ is the physical feature such as round peas that results from a genotype.
How many traits are involved in a monohybrid cross?
What type of organism was used in the first genetic studies done by Gregor Mendel?
What is a karyotype?
The two genes for a trait represented by capital & lower case letters are called __________.
How many traits are involved in a dihybrid cross?
Which of Mendel’s laws states that the dominant gene in a pair will be expressed?
If both alleles are the same, is the genotype homozygous or heterozygous? Write an example.
Write an example of a hybrid or heterozygous genotype.
The genes for sex-linked traits are only carried on which chromosome?
Who is considered to be the “father of genetics”?
A second filial or F2 cross is also called a ____________ cross.
The failure of chromosomes to separate during meiosis (egg & sperm formation) is known as _________________.
A cross between two pure or homozygous organisms is called what type of cross —– P1, F1, or F2?
What genetic disorder results from a sex-linked trait that affects color vision?
The genetic disorder called _______________ is known as the “free bleeders” disease.
Having three 21st chromosomes causes the genetic disorder known as _________.
A person suffering from the genetic disorder called ______________ can not digest fats.
_____________________ disease is a genetic disorder where red blood cells carry less oxygen.
Work a P1 cross for plant height in peas.
Work an F1 cross for plant height in peas.
BACK

 

Hardy-Weinberg Problems

 

POPULATION GENETICS AND THE HARDY-WEINBERG LAW

 

The Hardy-Weinberg formulas allow scientists to determine whether evolution has occurred. Any changes in the gene frequencies in the population over time can be detected. The law essentially states that if no evolution is occurring, then an equilibrium of allele frequencies will remain in effect in each succeeding generation of sexually reproducing individuals. In order for equilibrium to remain in effect (i.e. that no evolution is occurring) then the following five conditions must be met:

  1. No mutations must occur so that new alleles do not enter the population.
  2. No gene flow can occur (i.e. no migration of individuals into, or out of, the population).
  3. Random mating must occur (i.e. individuals must pair by chance)
  4. The population must be large so that no genetic drift (random chance) can cause the allele frequencies to change.
  5. No selection can occur so that certain alleles are not selected for, or against.

Obviously, the Hardy-Weinberg equilibrium cannot exist in real life. Some or all of these types of forces all act on living populations at various times and evolution at some level occurs in all living organisms. The Hardy-Weinberg formulas allow us to detect some allele frequencies that change from generation to generation, thus allowing a simplified method of determining that evolution is occurring. There are two formulas that must be memorized:

 

p2 + 2pq + q2 = 1 and p + q = 1

 

p = frequency of the dominant allele in the population
q = frequency of the recessive allele in the population
p2 = percentage of homozygous dominant individuals
q2 = percentage of homozygous recessive individuals
2pq = percentage of heterozygous individuals

Individuals that have aptitude for math find that working with the above formulas is ridiculously easy. However, for individuals who are unfamiliar with algebra, it takes some practice working problems before you get the hang of it. Below I have provided a series of practice problems that you may wish to try out. Note that I have rounded off some of the numbers in some problems to the second decimal place.

PROBLEM #1    You have sampled a population in which you know that the percentage of the homozygous recessive genotype (aa) is 36%. Using that 36%, calculate the following:

  1. The frequency of the “aa” genotype.
  2. The frequency of the “a” allele.
  3. The frequency of the “A” allele.
  4. The frequencies of the genotypes “AA” and “Aa.”
  5. The frequencies of the two possible phenotypes if “A” is completely dominant over “a.”

PROBLEM #2.    Sickle-cell anemia is an interesting genetic disease. Normal homozygous individuals (SS) have normal blood cells that are easily infected with the malarial parasite. Thus, many of these individuals become very ill from the parasite and many die. Individuals homozygous for the sickle-cell trait (ss) have red blood cells that readily collapse when deoxygenated. Although malaria cannot grow in these red blood cells, individuals often die because of the genetic defect. However, individuals with the heterozygous condition (Ss) have some sickling of red blood cells, but generally not enough to cause mortality. In addition, malaria cannot survive well within these “partially defective” red blood cells. Thus, heterozygotes tend to survive better than either of the homozygous conditions. If 9% of an African population is born with a severe form of sickle-cell anemia (ss), what percentage of the population will be more resistant to malaria because they are heterozygous (Ss) for the sickle-cell gene?

PROBLEM #3.    There are 100 students in a class. Ninety-six did well in the course whereas four blew it totally and received a grade of F. Sorry. In the highly unlikely event that these traits are genetic rather than environmental, if these traits involve dominant and recessive alleles, and if the four (4%) represent the frequency of the homozygous recessive condition, please calculate the following:

  1. The frequency of the recessive allele.
  2. The frequency of the dominant allele.
  3. The frequency of heterozygous individuals.

PROBLEM #4.    Within a population of butterflies, the color brown (B) is dominant over the color white (b). And, 40% of all butterflies are white. Given this simple information, which is something that is very likely to be on an exam, calculate the following:

  1. The percentage of butterflies in the population that are heterozygous.
  2. The frequency of homozygous dominant individuals.

PROBLEM #5.     A rather large population of Biology instructors have 396 red-sided individuals and 557 tan-sided individuals. Assume that red is totally recessive. Please calculate the following:

  1. The allele frequencies of each allele.
  2. The expected genotype frequencies.
  3. The number of heterozygous individuals that you would predict to be in this population.
  4. The expected phenotype frequencies.
  5. Conditions happen to be really good this year for breeding and next year there are 1,245 young “potential” Biology instructors. Assuming that all of the Hardy-Weinberg conditions are met, how many of these would you expect to be red-sided and how many tan-sided?

PROBLEM #6.    A very large population of randomly-mating laboratory mice contains 35% white mice. White coloring is caused by the double recessive genotype, “aa”. Calculate allelic and genotypic frequencies for this population.

PROBLEM #7.    After graduation, you and 19 of your closest friends (lets say 10 males and 10 females) charter a plane to go on a round-the-world tour. Unfortunately, you all crash land (safely) on a deserted island. No one finds you and you start a new population totally isolated from the rest of the world. Two of your friends carry (i.e. are heterozygous for) the recessive cystic fibrosis allele (c). Assuming that the frequency of this allele does not change as the population grows, what will be the incidence of cystic fibrosis on your island?

PROBLEM #8.    You sample 1,000 individuals from a large population for the MN blood group, which can easily be measured since co-dominance is involved (i.e., you can detect the heterozygotes). They are typed accordingly:

 

BLOOD TYPE GENOTYPE NUMBER OF INDIVIDUALS RESULTING FREQUENCY
M MM 490 0.49
MN MN 420 0.42
N NN 90 0.09

 

Using the data provide above, calculate the following:

  1. The frequency of each allele in the population.
  2. Supposing the matings are random, the frequencies of the matings.
  3. The probability of each genotype resulting from each potential cross.

PROBLEM #9.    Cystic fibrosis is a recessive condition that affects about 1 in 2,500 babies in the Caucasian population of the United States. Please calculate the following:

  1. The frequency of the recessive allele in the population.
  2. The frequency of the dominant allele in the population.
  3. The percentage of heterozygous individuals (carriers) in the population.

PROBLEM #10.    In a given population, only the “A” and “B” alleles are present in the ABO system; there are no individuals with type “O” blood or with O alleles in this particular population. If 200 people have type A blood, 75 have type AB blood, and 25 have type B blood, what are the allelic frequencies of this population (i.e., what are p and q)?

PROBLEM #11.    The ability to taste PTC is due to a single dominate allele “T”. You sampled 215 individuals in biology, and determined that 150 could detect the bitter taste of PTC and 65 could not. Calculate all of the potential frequencies.

ANSWERS

Genetic Traits Activity

 

Finding Your Genetic Match

Introduction:

Have you ever noticed that brothers or sisters often look alike?  Their inherited traits are what make their physical appearance so similar. An inherited trait is a particular genetically determined characteristic that distinguishes a person. The traits of children are determined by the traits that  are passed on from their parents. Some traits are obvious in a family — a child’s nose is shaped like their mother’s nose, but some traits are less obvious. You may have similar traits to many of your classmates even though you are not related to them. Some examples of often un-noticed human traits are the ability or not to roll your tongue, attached or unattached earlobes, dimples or freckles, naturally curly or straight hair, hitchhiker’s or straight thumb, straight or widow’s peak hairline, smooth or cleft chin, or colorblindness or normal vision.

There are numerous traits in humans, but some traits occur more frequently than others.  Between 70-90% of the human population have free-hanging earlobes, can roll their tongue,  are right-handed, and can taste a chemical called PTC.  These traits are called high frequency traits.

Objective:

Students will determine the presence of certain high frequency traits in themselves & their classmates.

Materials:

Genetic Inventory sheet with pictures, paper, pencil, PTC taste strips.

Procedure:

  1. Identify which of the following 10 human traits you have by placing a check mark beside that trait.
  2. Compare the traits you have with other students in the classroom and find the student you most closely match.

 

 

Human Trait Inventory
Student:
Tongue Roller
Non-Tongue Roller
Attached Earlobes
Unattached earlobes
Dimples
No Dimples
Right-handed
Left-Handed
Widow’s Peak
Straight Hairline
Left Thumb on top when Hands Crossed
Right Thumb on top when Hands Crossed
Hair on mid-digit of hand
No hair on mid-digit of hand
Bent little finger
Straight little finger
Second toe longer than big toe
Second toe not longer than big toe
Can Taste PTC
Can Not Taste PTC
Vulcan (Fingers spread 2 by 2)
None Vulcan
Class Match:

 

 

 

Tongue Roller Non Roller Dimples No Dimples
Attached Earlobes Unattached Earlobes Widow’s Peak Straight Hairline
Longer Second Toe Short Second Toe Bent Little finger Hitchhiker’s Thumb
Attached Ear lobes (left)
Unattached ear Lobes (right)		 “VULCAN” or No “VULCAN” Dimples Right/Left Thumb on top