Family Pedigree

Thursday February 7, 2019

A pedigree analysis chart, usually used for families, allow us to visualize the inheritance of genotypes and phenotypes (traits). In this chart, the P, F1, and F2 generation are represented by the numerals I, II, and III respectively. Notice that those carrying the trait are colored red, and those not carrying the trait (the normal-looking ones) are in blue. The normal, non-trait carrying organisms on the chart are called the wild-type.


The term wild-type is used in genetics often to refer to organisms not carrying the trait being studied. For example, if we were studying a gene that turns house-flies orange, we would call the normal-looking ones the wild-type.


Let’s make a pedigree for your family. Here’s what you need:


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Materials:
• Paper
• Pen
• Access to a photocopier (optional)


Before starting this science project, you should go through your reference material and familiarize yourself with the proper way to draw a human pedigree (shown below)



To start this project, draw a pedigree showing the different members of your family.


a. Include as many family members as you can get data from. The more people and generations you include, the more likely it is that you’ll have enough information to determine the mode of inheritance.


b. You might need help from your parents to figure out all the relationships.


2. If you have access to a photocopier, make four copies of the pedigree—one for each trait you are going to evaluate. If photocopying isn’t an option, manually copy the pedigree.


3. Determine the phenotype of each person on your pedigree for each of the four traits. Use a separate pedigree for each trait. Examples are: eye-color, hair color, widow’s peak, height. Note: Widow’s peak can vary considerably; score any sort of V-shaped hairline as positive.


4. From your pedigrees, can you deduce the mode of inheritance for each trait? For which traits is your pedigree informative? If you don’t have enough information to determine the mode of inheritance of a particular trait, try making a pedigree for another family.




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Extracting DNA in your Kitchen

Monday May 2, 2011

If the cell has a nucleus, the DNA is located in the nucleus.  If not, it is found in the cytoplasm.  DNA is the genetic material that has all the information about a cell.


DNA is a long molecule found in the formed by of two strands of genes. DNA carries two copies—two “alleles”—of each gene. Those alleles can either be similar to each other (homozygous), or dissimilar (heterozygous).


We’re going to learn how to extract DNA from any fruit or vegetable you have lying around the fridge. Are you ready?


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Materials:


  • pumpkin OR apple OR squash OR bananas OR carrots OR anything else you might have in the fridge
  • dishwashing detergent
  • 91% isopropyl alcohol
  • coffee filter and a funnel (or use paper towels folded into quarters)
  • water
  • blender
  • clear glass cup


Download Student Worksheet & Exercises


Procedure:


Step 1: First, grab your fruit or vegetable and stick it in your blender with enough water to cover. Add a tablespoon of salt and blend until it looks well-mixed and like applesauce. Don’t over-blend, or you’ll also shred the DNA strands!


Step 2: Pour this into a bowl and mix in the detergent. Don’t add this in your mixer and blend or you’ll get a foamy surprise that’s a big mess. You’ll find that the dishwashing detergent and the salt help the process of breaking down the cell walls and dissolving the cell membranes so you can get at the DNA.


Step 3: Place a coffee filter cone into a funnel (or use a paper towel folded into quarters) and place this over a cup. Filter the mixture into the cup. When you’re done, simply throw away the coffee filter. Note: Keep the contents in the cup!


Step 4: Be careful with this step! You’ll very gently (no splashing!) pour a very small about of alcohol into the cup (like a tablespoon) so that the alcohol forms a layer above the puree.


Step 5: Observe! Grab your compound microscope and take a sample from the top. You’ll want a piece from the ghostly layer between the puree and the alcohol – this is your DNA.


What’s going on?


Veggies and fruits are made of water, cellulose, sugars, proteins, salts, and DNA. To get at the DNA, you first need to get inside the cells and separate it out from the other parts. The blender breaks up the fibers that hold the cells together.


The salt and detergent are added next so they can break down the cell walls. Cell walls of plants are made of cellulose. Inside that cellulose is another cell wall (cell membrane). This membrane has an outer later of sugar and an inner layer of fat.


The detergent is a special molecule that has an attraction to water and fats (which is why it works to get your dishes clean). The end of the molecule that is attracted to fat attaches to the fat part of the cell membrane. When you stir up the mixture, it breaks up the membrane (since the other end likes water). It wedges itself inside and  opens the cell up… which causes the DNA to flow out.


Since DNA dissolves in water, it stays in the vegetable juice. When alcohols is added, the DNA “comes out” of solution as the ghostly white strands seen at the bottom of the alcohol layer.


For Advanced Students:


For advanced students, here’s a set of videos that detail the cell walls, the basic biological molecules, DNA and RNA and how everything works together.


First watch this video below to see how we broke down the cell walls in the DNA extraction experiment:



Here’s a video on how DNA and RNA work:



Here’s a video that describes how the four biological molecules (proteins, lipids, carbohydrates, and nucleic acids) work:



Exercises


  1. What are fruits and veggies made of?
  2.  What does DNA stand for?
  3.  What is DNA?
  4.  What is a gene?
  5.  Describe the structure of DNA.

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Tracking Traits

Monday May 2, 2011

Why do families share similar features like eye and hair color? Why aren’t they exact clones of each other? These questions and many more will be answered as well look into the fascinating world of genetics!


Genetics asks which features are passed on from generation to generation in living things. It also tries to explain how those features are passed on (or not passed on). Which features are stay and leave depend on the genes of the organism and the environment the organism lives in. Genes are the “inheritance factors “described in Mendel’s laws. The genes are passed on from generation to generation and instruct the cell how to make proteins. A genotype refers to the genetic make-up of a trait, while phenotype refers to the physical manifestation of the trait.


We’re going to create a family using genetics!


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Materials
• Paper or use this Genetics Table
• Two different coins
• Scissors
• Glue or Tape



Download Student Worksheet & Exercises


Step one: Creating the Parent Generation

  1. First you’re going to create the genetic make-up of the parents. Here’s how:
  2. Take out the Genetics Data Table, and flip the first coin to create the genetic profile for the mother.
  3. Flip the coin and in the Mother’s Hair trait column, write D for dominant if the coin reads heads, and R for recessive if tails in the table.
  4. Flip the coin again. In the Mother’s Hair trait column right after the first trait, write D for dominant if the coin reads heads, and R for recessive if tails in the table.
  5. If you flipped heads the first time and tails the second, you’d write “DR” in the Mother’s Hair box.
  6. Continue this process for all of Mother’s traits. You should have two letters in each box for the entire column.
  7. Repeat steps 3-6 for Father. When you’ve completely filled out Mother’s and Father’s columns, you’ve completed the paternal genetic profile. Now you’re ready for the next part:

Step two: The Child

  1. Will the child be a boy or a girl? To determine this, flip the second coin. Heads for a boy, tails for a girl. After this is decided, circle boy or girl under “child 1” on the Genetics Data Table.
  2. Now the first coin will represent the gene from the mother and the second coin will represent the gene from the father.
  3. Start with the Hair trait: Flip both coins. If the first coin is tails, take the first trait from the mother. If the first coin is heads, take the second trait.
    1. For example, if the first coin is tails, and the mother’s code is DR, then write “D” in the child one column for hair.
    2. Do the same thing for the father’s traits with the second coin. For example, if the second coin is heads, and the father’s code is DR, then write “R” in the Hair Trait column of child 1.
    3. By the end of this step, child 1 should have one letter from the mother, and one letter for the father in child 1’s hair trait column.
  4. Use the same steps used to find the genetic code for the hair trait to find the code for the rest of the traits. By the end all the traits should have one letter from the mother’s genetic code and one letter from the father’s genetic code.

Step 3: What the Child Looks Like

Grab a sheet of paper and start drawing the child. If the genetic code for a trait has a “D” in it, then the dominant trait is used.


For example, if the hair color is DD, DR, or RD then the hair color is dark. If the hair color code is RR, then the hair color is light. Draw the traits on your paper!


You can repeat this for as many children as you would like in your family.


Step 4: Make another family and compare!

Are all families alike? What if you try this process again for another family? Do you see any similarities or differences? Do similar features come from dominant genes? Do differences come from recessive genes? What other traits would you include? Write this in your science journal!


Conclusions:

In fact, most similarities should come from the dominant genes because they are expressed more often. The recessive genes are expressed less often, so the create the differences.


Extra credit:

What percent of the children expressed the dominant allele of each trait? Did you get Mendel’s results? Do the calculations and check it out!


Exercises


  1. What is the difference between a genotype and a phenotype?
  2. What is a dominant trait?
  3. What is a recessive trait?
  4. Assume B=Black hair and b=blond hair.  Make a Punnet square to cross Bb with bb. Tell what the possibilities are for offspring hair color.
  5. Why don’t traits simply average out in offspring.  For example, why does a tall plant crossed with a short plant not yield a bunch of average-sized plants?
  6. In your activity, what percent of the children expressed the dominant allele of each trait? Did you get Mendel’s results? Do the calculations and check it out!

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Family Pedigree

Monday May 2, 2011

A pedigree analysis chart, usually used for families, allow us to visualize the inheritance of genotypes and phenotypes (traits). In this chart, the P, F1, and F2 generation are represented by the numerals I, II, and III respectively. Notice that those carrying the trait are colored red, and those not carrying the trait (the normal-looking ones) are in blue. The normal, non-trait carrying organisms on the chart are called the wild-type.


The term wild-type is used in genetics often to refer to organisms not carrying the trait being studied. For example, if we were studying a gene that turns house-flies orange, we would call the normal-looking ones the wild-type.


Let’s make a pedigree for your family. Here’s what you need:


[am4show have=’p8;p9;p26;p53;p65;p69;p87;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Materials:
• Paper
• Pen
• Access to a photocopier (optional)


To start this project, draw a pedigree showing the different members of your family.


a. Include as many family members as you can get data from. The more people and generations you include, the more likely it is that you’ll have enough information to determine the mode of inheritance.


b. You might need help from your parents to figure out all the relationships.


2. If you have access to a photocopier, make four copies of the pedigree—one for each trait you are going to evaluate. If photocopying isn’t an option, manually copy the pedigree.


3. Determine the phenotype of each person on your pedigree for each of the four traits. Use a separate pedigree for each trait. Examples are: eye-color, hair color, widow’s peak, height. Note: Widow’s peak can vary considerably; score any sort of V-shaped hairline as positive.


4. From your pedigrees, can you deduce the mode of inheritance for each trait? For which traits is your pedigree informative? If you don’t have enough information to determine the mode of inheritance of a particular trait, try making a pedigree for another family.



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Genetics Exercises

Monday May 2, 2011

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.


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1. Define “genetics” in your own words.
2. Describe Mendel’s experiments with peas.
3. What do P, F1, and F2 represent?
4. What were Mendel’s findings regarding tall vs short crosses?
5. According to Mendel’s law of segregation, what are dominant and recessive traits?
6. What is a Punnett Square?
7. An orange amoeba and a red amoeba walk into a bar. Several years later they get married and have a batch of beautiful, red kids. The kids then marry each other and have kids. 75% of that last generation is red, and 25% is orange. According to Mendel’s theories, which color is dominant? Which is recessive? How do we know?
8. What are genes?
9. What is the difference between phenotypes and genotypes?
10. What is the difference between incomplete dominance and codominance?
11. What are genetic disorders?
12. If a gene is sex-linked, which chromosomes could it be found on?
13. In a study on the gene that gives flies wings, 30 of the F1 generation were wingless, and 100 looked like normal flies. How many were wild-type?
14. What are restriction enzymes?
15. What did the Human Genome Project accomplish?
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Answers to Genetics Exercises

Monday May 2, 2011

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!


Simply click here for printable questions and answers.


Answers:
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1. Something close to: the science of heredity, dealing with resemblances and differences of related organisms resulting from the interactions of their genes and the environment.
2. Mendel observed traits in pea plants over many generations. He kept careful note of which traits appeared in each generation.
3. P represents the parental generation, F1 represents the generation of the offspring of P, and F2 represents the generation of the offspring of F1.
4. In the F1 generation was 100% tall, and the F2 generation was 75% tall and 25% short.
5. Dominant traits are always expressed when present, recessive traits are only expressed when they both alleles are recessive.
6. A table used for keeping track of the inheritance of genes.
7. Red. Orange. Mendel’s law of segregation predicts that dominant genes when crossed with the recessive allele will only express the dominant genes in the F1 generation, then express the dominant gene 75% of the time in the F2.
8. The individual codes for making proteins located in the DNA.
9. Phenotypes are the appearance of the organism—the physical traits. Genotypes are the genes that produce the trait.
10. Incomplete dominance is a shared expression of two traits. Codominance is the duel expression of two dominant traits.
11. Inherited genetic disorders—defective genes or chromosomes.
12. X or Y.
13. 100.
14. Enzymes used to cut specific sequences of DNA.
15. The Human Genome Project successfully sequenced over 20,000 human genes and mapped them on the 23 human chromosomes.


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