Genetics Worksheet Bi Chapter 9

 Fundamentals of Genetics

Section 9-1 Mendel’s Legacy

1. What scientist is responsible for our study of heredity?

2. Define heredity.

3. What plant did Mendel use for his hereditary experiments?

4. Name the 7 characteristics, giving both dominant and recessive forms of the pea plants, in Mendel’s experiments.

5. In order to study pea plant traits, Mendel had to control __________________ among the plants.

6. Define pollination & name 2 types.

7. How do pea plants normally pollinate?

8. How can cross-pollination of pea plants be done?

9. How did Mendel obtain pure pea plants?

10. What is the P1 generation? How is it obtained?

11. What is the F1 generation &how is it obtained?

12. How did Mendel obtain his F2 generation?

13. When Mendel crossed his P1 plants to get the F1 generation, what ratio did he get?

14. What is the difference between dominant & recessive genes?

15. State Mendel’s law of segregation.

16. What are alleles?

Section 9-2 Genetic Crosses

17 What is the difference between genotypes & phenotypes?

18. Write the 2 genotypes for a purple flower.

19. Write the genotype for a white flower.

20. What is the difference in a homozygous and a heterozygous genotype?

21. What is  probability & tell 3 ways they can be expressed.

22. What is the probability that you will get “heads” each time you flip a coin?

23. What is a monohybrid cross?

24. Give an example of a monohybrid cross.

25. What is a Punnett Square used for?

26. Sketch the Punnett Square for crossing a pure purple flower with a white flower.

27. Use a Punnett Square to solve this cross — PP x pp.

28. What percentage of the offspring from this cross are purple? White?

29. Use a Punnett Square to solve this cross in guinea pigs — BB x Bb. Hint: See page 174.

30. In the above cross, what coat colors & percents did you get?

31. What phenotype (coat color) would each of these guinea pig genotypes result in:

        a. Bb?

        b. BB?

        c. bb?

32. Use a Punnett Square to solve this cross for coat color in rabbits: Bb x Bb?

33. What percent of the rabbits will have black fur? Brown fur? What ratio does this give for coat color?

34. Define genotypic ratio.

35. What is the genotypic ratio for all F1 crosses (bb x Bb)?

36. Define phenotypic ratio.

37. What is the phenotypic ratio for all F1 crosses?

38. What is a testcross?

39. A testcross can determine which individual’s phenotype is ________________________.

40. Use a Punnett Square to solve the following 2 testcrosses:

        a. BB x Bb

        b. bb x Bb

41. In each of the above testcrosses, tell how many offspring have black coats (dominant) and how many will have brown (recessive) coats?

42. What does complete dominance mean?

43. Give an example of complete dominance in pea plants.

44. What is incomplete dominance?

45. How many alleles influence the phenotype in:

        a. complete dominance?

        b. incomplete dominance?

46. Using four-o-clocks, give an example of how incomplete dominance occurs. Be sure to tell all possible genotypes & phenotypes.

47. Give the following ratios for crossing 2 pink four-o-clocks (Rr x Rr):

        a. Genotypic ratio?

        b. Phenotypic ratio?

48. Define codominance.

49. In what genotype does codominance appear?

50. In horses, _________________ coat color is a result of codominance.

51. Write the genotype for roan coat color & tell the color of each allele in the genotype.

52. What is a dihybrid cross?

53. How many different genotypes will result in a dihybrid cross when 2 homozygous organisms are crossed?

54. The offspring from a dihybrid cross of 2 homozygous organisms will all be __________________________.

55. Use a Punnett Square to show the results of the following cross: RrYy x RrYy

56. How many different genotypes resulted from this cross?

57. How many different phenotypes resulted from this cross?

58. Write the genotypes for each of these phenotypes:

        a. Round, green seeds

        b. Wrinkled, yellow seeds

        c. Wrinkled, green seeds

Extracting DNA


Extract DNA from Anything Living



Since DNA is the blueprint for life, everything living contains DNA. DNA isolation is one of the most basic and essential techniques in the study of DNA. The extraction of DNA from cells and its purification are of primary importance to the field of biotechnology and forensics. Extraction and purification of DNA are the first steps in the analysis and manipulation of DNA that allow scientists to detect genetic disorders, produce DNA fingerprints of individuals, and even create genetically engineered organisms that can produce beneficial products such as insulin, antibiotics, and hormones.

DNA can be extracted from many types of cells. The first step is to lyse or break open the cell. This can be done by grinding a piece of tissue in a blender. After the cells have broken open, a salt solution such as NaCl and a detergent solution containing the compound SDS (sodiumdodecyl sulfate) is added. These solutions break down and emulsify the fat & proteins that make up a cell membrane. Finally, ethanol is added because DNA is soluble in water. The alcohol causes DNA to precipitate, or settle out of the solution, leaving behind all the cellular components that aren’t soluble in alcohol. The DNA can be spooled (wound) on a stirring rod and pulled from the solution at this point.


Just follow these 3 easy steps:

Detergent, eNzymes (meat tenderizer), Alcohol




To extract DNA from cells.


Blender, split peas, salt, detergent, water, measuring cup and spoons, strainer, meat tenderizer, alcohol, test tube, glass stirring rod


  1. First, you need to find something that contains DNA such as split peas, fresh spinach, chicken liver, onion, or broccoli.

  1. Measure about 100 ml or 1/2 cup of split peas and place them in a blender.
  2. Add a large pinch of salt (less than 1 ml or about 1/8 teaspoon) to the blender.
  3. Add about twice as much cold water as the DNA source (about 200 ml or 1 cup) to the peas in the blender.
  4. Blend on high (lid on) for about 15 seconds.

  1. The blender separates the pea cells from each other, so you now have a really thin pea-cell soup.

And now, those 3 easy steps:

  1. Pour your thin pea-cell soup through a strainer into another container like a measuring cup or beaker.

  1. Estimate how much pea soup  you have and add about 1/6 of that amount of liquid detergent (about 30ml or 2 tablespoons). Swirl to mix.

  1. Let the mixture sit for 5-10 minutes.

The detergent captures the proteins & lipids of the cell membrane.

  1. Pour the mixture into test tubes or other small glass containers, each about 1/3 full.
  2. Add a pinch of enzymes to each test tube and stir gently. Be careful! If you stir too hard, you’ll break up the DNA, making it harder to see. (Use meat tenderizer for enzymes. If you can’t find tenderizer, try using pineapple juice or contact lens cleaning solution.)

The DNA in the nucleus of the cell is molded, folded, and protected by proteins. The meat tenderizer cuts the proteins away from the DNA.

  1. Tilt your test tube and slowly pour rubbing alcohol (70-95% isopropyl or ethyl alcohol) into the tube down the side so that it forms a layer on top of the pea mixture. Pour until you have about the same amount of alcohol in the tube as pea mixture.

  1. Alcohol is less dense than water, so it floats on top forming two separate layers.
  2. All of the grease and the protein that we broke up in the first two steps move to the bottom, watery layer.
  3. DNA will rise into the alcohol layer from the pea layer. You can use a glass stirring rod or a wooden stick to draw the DNA into the alcohol.
  4. Slowly turning the stirring rod will spool (wrap) the DNA around the rod so it can be removed from the liquid.


1. Does the DNA have any color?

2. Describe the appearance of the DNA.

3. Do only living things contain DNA? Explain.

Frequently Asked Questions: 1. I’m pretty sure I’m not seeing DNA. What did I do wrong?

First, check one more time for DNA. Look very closely at the alcohol layer for tiny bubbles. Often, clumps of DNA are loosely attached to the bubbles.

If you are sure you don’t see DNA, then the next step is to make sure that you started with enough DNA in the first place. Many food sources of DNA, such as grapes, also contain a lot of water. If the blended cell soup is too watery, there won’t be enough DNA to see. To fix this, go back to the first step and add less water. The cell soup should be opaque, meaning that you can’t see through it. Another possible reason for not seeing any DNA is not allowing enough time for each step to complete. Make sure to stir in the detergent for at least five minutes. If the cell and nuclear membranes are still intact, the DNA will be stuck in the bottom layer. Often, if you let the test tube of pea mixture and alcohol sit for 30-60 minutes, DNA will precipitate into the alcohol layer.

2. Why does the DNA clump together?

Single molecules of DNA are long and stringy. Each cell of your body contains six feet of DNA, but it’s only one-millionth of an inch wide. To fit all of this DNA into your cells, it needs to be packed efficiently. To solve this problem, DNA twists tightly and clumps together inside cells. Even when you extract DNA from cells, it still clumps together, though not as much as it would inside the cell.

Imagine this: the human body contains about 100 trillion cells, each of which contains six feet of DNA. If you do the math, you’ll find that our bodies contain more than a billion miles of DNA!

3. Can I use this DNA as a sample for gel electrophoresis?

Yes, but all you will see is a smear. The DNA you have extracted is genomic, meaning that you have the entire collection of DNA from each cell. Unless you cut the DNA with restriction enzymes, it is too long and stringy to move through the pores of the gel; instead, all you will end up seeing is a smear.

4. Isn’t the white, stringy stuff actually a mix of DNA and RNA?

That’s exactly right! The procedure for DNA extraction is really a procedure for nucleic acid extraction. However, much of the RNA is cut by ribonucleases (enzymes that cut RNA) that are released when the cells are broken open.


Fermentation Rootbeer


David Fankhauser’s Main Page



Fermentation has been used by mankind for thousands of years for raising bread, fermenting wine and brewing beer. The products of the fermentation of sugar by baker’s yeast Saccharomyces cerevisiae (a fungus) are ethyl alcohol and carbon dioxide. Carbon dioxide causes bread to rise and gives effervescent drinks their bubbles. This action of yeast on sugar is used to ‘carbonate’ beverages, as in the addition of bubbles to champagne).

We will set up a fermentation in a closed system and capture the generated carbon dioxide to carbonate root beer. You may of course adjust the quantities of sugar and/or extract  (Zatarain’s) to taste. 

  • clean 2 liter plastic soft drink bottle with cap
  • funnel
  • 1 cup measuring cup
  • 1/4 tsp measuring spoon
  • 1 Tbl measuring spoon
  • Cane (table) sugar [sucrose] (1 cup)
  • Zatarain’s Root Beer Extract (1 tablespoon)
  • (When I could not find it locally, I ordered a case of 12 bottles for $18 from Zatarain’s, New Orleans, LA 70114
  • powdered baker’s yeast (1/4 teaspoon)  (Yeast for brewing would certainly work at least as well as baking yeast.)
  • cold fresh water




1) Assemble the necessary equipment and supplies
2) With a dry funnel, add in sequence:

1 level cup of table sugar (cane sugar) (You can adjust the amount to achieve the desired sweetness.)

3) Add: 1/4 teaspoon powdered baker’s yeast ( fresh and active)

(Fleischmann’s or other brand)

4) You can see the yeast granules on top of the sugar.
5) Shake to distribute the yeast grains into the sugar.
6) Swirl the sugar/yeast mixture in the bottom to make it concave (to catch the extract).
7) Add with funnel:

1 Tbl of root beer extract (I prefer Zatarain’s, but Hires, etc. will work.)

on top of the dry sugar

8) The extract sticks to the sugar which will help dissolve the extract in the next steps.
9) Half fill the bottle with fresh cool tap water (the less chlorine, the better).

Rinse in the extract which sticks to the tablespoon and funnel. Swirl to dissolve the ingredients.

10) Q.s. [fill up] to the neck of the bottle with fresh cool tap water, leaving about an inch of head space, securely screw cap down to seal. Invert repeatedly to thoroughly dissolve.

If you leave it in a warm temperature longer than two weeks, you risk an explosion…

11) Place at room temperature about three to four days until the bottle feels hard to a forceful squeeze. Move to a cool place (below 65 F). refrigerate overnight to thoroughly chill before serving. Crack the lid of the thoroughly chilled root beer just a little to release the pressure slowly.

NOTE: Do not leave the finished root beer in a warm place once the bottle feels hard. After a couple weeks or so at room temperature, especially in the summer when the temperature is high, enough pressure may build up to explode the bottle! There is no danger of this if the finished root beer is refrigerated.

12) Move to a refrigerator overnight before opening.


NOTE: There will be a sediment of yeast at the bottom of the bottle, so that the last bit of root beer will be turbid. Decant carefully if you wish to avoid this sediment.

A WORD ABOUT THE ALCOHOL IN HOME MADE ROOT BEER: The alcoholic content which results from the fermentation of this root beer and found it to be between 0.35 and 0.5 %. Comparing this to the 6% in many beers, it would require a person to drink about a gallon and a half of this root beer to be equivalent to one 12 ounce beer. I would call this amount of alcohol negligible, but for persons with metabolic problems who cannot metabolize alcohol properly, or religious prohibition against any alcohol,  consumption should be limited or avoided.


DNA Code for Insulin


DNA’s Instructions for Insulin  



Below are two partial sequences of DNA bases (shown for only one strand of DNA)  Sequence 1 is from a human and sequence 2 is from a cow.  In both humans and cows, this sequence is part of a set of instructions for controlling the production of a protein.  In this case, the sequence contains the gene to make the protein insulin.  Insulin is necessary for the uptake of sugar from the blood.  Without insulin, a person cannot use digest sugars the same way others can, and they have a disease called diabetes.


paper, pencil, codon table


  1. Using the DNA sequence given in table 1, make a complimentary RNA strand for  the human.  Write the RNA directly below the DNA strand (remember to substitute U’s for T’s in RNA).
  2. Repeat step 1 for the cow.  Write the RNA directly below the DNA strand in table 2.
  3. Use the codon table in your book to determine what amino acids are assembled to make the insulin protein in both the cow and the human.   Write your amino acid chain directly below the RNA sequence.

Table 1 


Sequence 1 ­ Human
Amino Acids


Table 2

Sequence 1 ­ Cow
Amino Acids


1. The DNA sequence is different for the cow and the human, but the amino acid chain produced by the sequence is almost the same.  How can this happen?



2. Diabetes is a disease characterized by the inability to break down sugars. Often a person with diabetes has a defective DNA sequence that codes for the making of the insulin protein. Suppose a person has a mutation in their DNA, and the first triplet for the gene coding for insulin is C C C  (instead of C C A).   Determine what amino acid the new DNA triplet codes for.    Will this person be diabetic?


3. What if the first triplet was C A A ?


4. How is it that a code consisting of only four letters, as in DNA ( A, T, G, C ) can specify all the different parts of an organism and account for all the diversity of organisms on this planet?



DNA sequences are often used to determine relationships between organisms.  DNA sequences that code for a particular gene can vary widely.  Organisms that are closely related will have sequences that are similar. Below is a list of sequences for a few organisms:


HumanCCA   TAG   CAC   CTA
ChimpanzeeCCA   TAA   CAC   CTA
CricketCCT   AAA   GGG   ACG


5. Based on the sequences, which two organisms are most  closely related?


6. An unknown organism is found in the forest, and the gene is sequenced, and found to be   C C A  T G G  A A T  C G A  ,  what kind of animal do you think this is?



DNA Replication Lab

Modeling DNA Replication



Within the nucleus of every cell are long strings of DNA, the code that holds all the information needed to make and control every cell within a living organism. DNA, which stands for deoxyribonucleic acid, resembles a long, spiraling ladder. It consists of just a few kinds of atoms: carbon, hydrogen, oxygen, nitrogen, and phosphorus. Combinations of these atoms form the sugar-phosphate backbone of the DNA — the sides of the ladder, in other words.

Other combinations of the atoms form the four bases: thymine (T), adenine (A), cytosine (C), and guanine (G). These bases are the rungs of the DNA ladder. (It takes two bases to form a rung — one for each side of the ladder.) A sugar molecule, a base, and a phosphate molecule group together to make up a nucleotide. Nucleotides are abundant in the cell’s nucleus. Nucleotides are the units which, when linked sugar to phosphate, make up one side of a DNA ladder.

During DNA replication, special enzymes move up along the DNA ladder, unzipping the molecule as it moves along. New nucleotides move in to each side of the unzipped ladder. The bases on these nucleotides are very particular about what they connect to. When the enzyme has passed the end of the DNA, two identical molecules of DNA are left behind. Cytosine (C) will “pair” to guanine (G), and adenine (A) will “pair” to thymine (T). How the bases are arranged in the DNA is what determines the genetic code.


When the enzyme has passed the end of the DNA, two identical molecules of DNA are left behind. Each contains one side of the original DNA and one side made of “new” nucleotides. It is possible that mistakes were made along the way — in other words, that a base pair in one DNA molecule doesn’t match the corresponding pair in the other molecule. On average, one mistake may exist in every billion base pairs. That’s the same as typing out the entire Encyclopedia Britannica five times and typing in a wrong letter only once!


The replication of DNA before cell division can be shown using paper templates for the components of DNA nucleotides.


  • Cut Outs of basic subunits of DNA
  • Colors or markers
  • Scissors
  • Tape or glue
  • Paper & pencil


  1. Cut out all of the units needed to make the nucleotides from the handout provided.
  2. Color code the Nitrogenous bases, phosphorus, and deoxyribose sugar as follows —
    Adenine = red, Guanine = green, Thymine = yellow, Cytosine = blue, Phosphate = brown, and Deoxyribose = purple.
  3. Using the small squares and stars as guides, line up the bases, phosphates and sugars.
  4. Now glue the appropriate parts together forming nucleotides.
  5. Construct DNA model using the following sequence to form a row from top to bottom – cytosine (topmost), thymine, guanine, and adenine (bottommost).
  6. Let this arrangement represent the left half of your DNA molecule.
  7. Complete the right side of the ladder by adding the complementary bases. You will have to turn them upside down in order to make them fit.
  8. Your finished model should look like a ladder.
  9. To show replication, separate the left side from the right side, leaving a space of about 6-8 inches.
  10. Use the remaining nucleotides to complete the molecule using the left side as the base.
  11. Build a second DNA model by adding new nucleotides to the right half of the original piece of the molecule.
  12. Tape the nucleotides together to form 2 complete DNA ladders.


1. Of the 4 bases, which other base does adenine most closely resemble?

2. List the 4 different nucleotides.

3. Which 2 molecules of a nucleotide form the sides of a DNA ladder?

4. If 30% of a DNA molecule is Adenine, what percent is Cytosine?

5. What does the term replication mean?

6. What is another name for adenine and three phosphate molecules attached to it?