Genetics labs, youtubes, and information for biology students
Genetics, which is a branch of biology, is the study of genes and heredity. All living things, including plants, bacteria, and animals, have DNA which they get from their parents. Located on the DNA are genes. It is these genes which determine why various organisms inherit certain traits.
The youth in our homeschool co-op are taking a high school level biology class this year. We're using Holt Biology as our primary text, and adding labs, you-tubes, websites, and other activities to accompany it. On this page, you'll find the resources we'll be using for unit 2 on genetics. In addition to the youtubes, labs, and genetics related websites, I've also provided several free study guides on genetics to help you quickly review the material before your test.
Note: This webpage is in the process of moving... Please pardon any mess that may result. I'll get the page tidied back up again asap.
Gregor Mendel: The Father of Genetics
Gregor Mendel is often refereed to as the Father of Genetics. His pea plant experiments established many of the rules of heredity. Mendel experimented with seven characteristics of pea plants: pod shape and color, plant height, flower position and color, and seed shape and color. Mendel used the terms recessive and dominant to explain his results.
Holt Biology - This is the biology text we're using for our homeschool co-op.
This is the primary book we'll be using for our biology course. It comes as both a hardbound book, as well as a book on CD. By visiting the link, you'll be taken to a page which shows the various formats and their prices.
Chapter 7: on Meiosis
In chapter 6, we learned about mitosis, which is the way that cells divide into exact replicas of themselves.
A different type of cell division is used to create the egg and sperm cells that are used in sexual reproduction. It's called Meiosis and is the topic of chapter 7. There are a lot of similarities between mitosis and meiosis, but one big difference is that with meiosis, each new cell only contains half of the number of chromosomes of the parent cell.
Section 1 of Chapter 7 of Holt Biology
1. Watch this short animation of meiosis. To see the steps in meiosis clearly, watch the movie one step at a time. Then go back and "play" it to see all the steps happen quickly.
2. Read the chapter and answer the review questions.
3. Watch the youtube below on meiosis.
3. If you'd like, visit this website for a nice chart comparing Meiosis and Mitosis.
Meiosis - This is an excellent youtube on meiosis!
Reproduction - Section 2 of Chapter 7 of Holt Biology
Vocabulary reminder: Haploid cells are ones which have only one set of chromosomes. Diploid cells have 2 full sets of chromosomes (1 set from mom and 1 set from Dad.)
1. Watch the youtube belows on the Diploid cells and the moss life cycle.
2. Read section 2 of chapter 7. When you get to the part about the hydra budding, watch this hydra budding.
3. Watch this very short movie that shows spores being ejected out of fungi.
Labs and Activities On Meiosis
for Chapter 7 of Holt Biology
Observe yeast reproducing until a microscope. (page 151 in our textbook).
Model crossing over (page 147 in our textbook)
Do the meiosis modeling lab in the textbook (page 158).
Here's another way to model meiosis. This one uses balls of clay or playdough.
Study Guide: Important Info for Chapter 7
on Meiosis and Repoduction
There are two basic ways organisms can reproduce: sexually (with meiosis making gametes that unite to form a zygote), or asexually.
Asexual reproduction is the process of reproduction that involves only one parent. The offspring is genetically identical to the parent.
Binary Fission is one type of Asexual Reproduction
Binary fission is one type of asexual reproduction. Many prokaryotes (cells without a nucleus) reproduce by binary fission. They simply copy their own DNA and then divide in the middle by pinching into two (somewhat like squeezing a long skinny balloon in the middle.) Amoebas and e coli bacteria are two examples of organisms that reproduce by binary fission.
Budding is another type of asexual reproduction. A bud forms on the parent organism. It may, or may not, break off of the parent to form an independent organism. Hydra engage in budding. Just like with binary fission, organisms that reproduce by budding are genetically identical to their offspring.
Fragmentation is yet another type of asexual reproduction. In fragmentation, an organism "fragments" into many parts. Some of the pieces later grow into adults by regrowing any missing parts.
Sexual reproduction involves the joining of two reproductive cells. During meiosis, the parents form reproductive cells (gametes) that contain only 1 set of chromosomes. Because the gametes have only 1 set of chromosomes, they are haploid cells. When the gamete from the male combines with the gamete from the female (their joining is called fertilization), the new zygote that is formed will have 2 sets of chromosomes. Because the zygote has 2 sets of chromosomes, it's a diploid cell. The new zygote will have characteristics in common with both parents, but will not be genetically identical to either. It is this aspect about sexual reproduction - that the offspring are not genetically identical to their parents - that allows for evolution by creating genetic diversity. Genetic diversity means that the genes that are passed on from parent to offspring are not exactly identical.
In humans, each gamete has 23 chromosomes. Each zygote has 46 chromosomes because it received 23 from each of it's parents.
Basically, in meiosis, a diploid cell copies all it's chromosomes, mixes them up some in the crossing over stage, then turns them into 4 haploid cells. Each haploid cell will have half the chromosomes of a normal diploid cell. Although four usable sperm are made during spermatogenesis, only 1 usable egg is made during oogenesis.
Because only diploid cells can repair the own DNA, it is believed that sexual reproduction may have been an advantage to early protists (as they evolved) by allowing them to repair damage to their chromosomes.
Watch the youtube on meiosis again (you can just watch the second half that begins with meiosis) and then tell what happens in each stage as you look at the pictures in the textbook.
Types of Life Cycles
Eukaryotes that reproduce sexually can have one of three types of life cycles: The Haploid Life Cycle, the Diploid Life Cycle, and an Alternating Life Cycle.
Haploid Life Cycle - In this type of life cycle, most of the organism's cells are haploid. Two haploid cells combine to make a diploid zygote, but the zygote them immediately undergoes meiosis in order to create haploid cells again.
Diploid Life Cycle - This is the type of life cycle that humans and most other animals have. Most of the organism's cells are diploid. As with the Haploid Life Cycle, two haploid gamete cells combine to make a diploid zygote, but instead of then using meiosis to create haploid cells (as occurs in the Haploid Life Cycle), the cells use mitosis to create more diploid cells.
Alternating Life Cycle - This type of life cycle alternates between a haploid phase (the gametophyte) and a diploid phase (sporophyte).
This is the alternating generations life cycle. The Sporophyte (diploid) undergoes meiosis which produces haploid spores. The haploid spores divide repeatedly by mitosis in order to become multicelluar gametophytes. The gametophytes release haploid gametes (sperm and egg cells) which join to create a diploid zygote which divides repeatedly by mitosis to become the next multicellular sporophyte.
In essence, the gametes are made by mitosis, and spores are made by meiosis. Gametes come from the gametophytes, and spores come from the sporophytes.
Origins of Genetics
Gregory Mendel discovered patterns while doing breeding experiments with pea plants. Although a man named T.A. Knight had done similar experiments, what made Gregory Mendel's experiments unique was that he counted the number of offspring carrying particular traits that resulted from each experiment. For example, he discovered that when a yellow pea plant and a green pea plant were bred together, the resulting plants would all have yellow peas. Yet when he crossed those plants, 1 out of every 3 of the next generation would have green peas.
Heredity and Punnett Squares
Section 3 of Chapter 8
A Punnett square is a diagram that is used to predict an outcome of a breeding (or crossing) two particular organisms together. Punnett squares are named after Reginald C. Punnett, who came up with this method.
The punnett square above shows the combinations that could result from a yellow pea plant being crossed with a green pea plant. In peas, the color yellow (Y) is dominant and the color green (y) is recessive. That means that a pea plant only needs one yellow allele to produce a yellow plant. (It will be yellow if it has two yellow alleles too.) The only way for the pea plant to be green is for it to have two green alleles.
1. Watch the youtube below on Punnett Squares.
2. Look for the Punnet Squares worksheets in the "labs" section of this page (below) for this chapter.
Complex Patterns of Heredity - Section 4 of chapter 8
1. Watch the youtubes below.
Labs and Activities on Genetics
Here's an animation and activity about Mendel's Experiments.
Pass the Genes, Please - This is an online game where you select the genes (dominate and recessive) needed to create certain traits in "Baby Melonhead."
If red flower color is dominant over white, then:
Red flower color = R and white flower color = r
a flower that was RR would be red
a flower that was Rr would be red.
a flower that was rr would be white, because it doesn't have any Rs at all.
Study Guide: Important Info to Remember for Chapter 8
Genetics Vocabulary Words to Learn:
Alleles - Different forms of a gene. For example, for the gene for flower color, you could have 2 red alleles, 2 white alleles, 1 of each, etc.
Dominant - If an allele is dominant, that means it's the one that gets expressed in the individual organism. (It's the one that shows up.) It's usually represented by a capital letter. In Bb, the B would be the dominate allele.
Recessive - If an allele is recessive, it doesn't get expressed in the organism unless the organism receives two of them.
Homozygous / Heterozygous. Try remembering which is which this way: Homo means "same." Hetero means "different."
Genotype / Phenotype. To remember which is which, look at the beginning of each word. The first syllable in Genotype says, "gene." So genotype is the particular genes (alleles) an organism has. Phenotype starts with a "ph," just like "physical appearance" so phenotype refers to the physical appearance.
Homozygous means the organism received two of the same type of allele.
Example: RR or rr, but not Rr.
Heterozygous means the organism received two different alleles for a particular trait.
Example: Rr, but not RR or rr.
Genotype is the set of alleles that a particular organism has. For example, BB, Bb, or bb.
Phenotype is the physical appearance of the organism and it's based on the genes that are organism has. The genotype determines the phenotype. (In other words, the genes determine which traits the organism will actually have.)
Punnett Square - That's the square box that many genetics problems are worked in.
Autosomal traits - These are all the traits that are not sex-linked. These traits appear in males and females equally.
Sex-Linked traits - These are traits which are found on the X chromosome and which shows up more often in males than in females. Color-blindness is an example of a sex linked trait. Since the traits are recessive, in order for a female to actually show the trait, she'd have to receive the trait on BOTH of her X chromosomes. If she has the gene for the trait on one X, but still has one X without the trait, she won't show the trait herself. Females can be carriers of the trait though, meaning they can pass it on along to their children, even without having the trait themselves.
Since males only have one X (and one Y), they are affected with the particular sex-linked trait if they receive it on their one X. The reason for this is because they don't have an X without the trait to "dominate" over the recessive one.
Probability - this refers to the likelihood that something will happen. Flip a coin. What's the probability it will land heads-up? 50%. Roll a regular six sided die. What's the probability you'll roll a 6? 1 in 6.
Mutations - these are changes in the DNA of a gene
Gregor Mendel and His Laws on Heredity
Although Gregor Mendel was not the first person to engage in various breeding experiments, his work stands out because he used a quantitative approach (systemic approach) and also developed laws (rules) that accurately predicted the result of crossing one individual with another.
The Law of Segregation was one of the laws Mendel discovered. The law says that when gametes (reproductive cells) are being formed, the two alleles for a certain gene separate from each other, so that one gamete gets one and another gamete gets the other. (We learned this when studying meiosis. The chromosomes are separated into different cells.)
The Law of Independent Assortment was another of the laws Mendel observed. This law says that traits are not tied or linked together. For example, you can't accurately predict the color of a pea flower just by knowing the height of the same pea plant. Having white flowers does not mean a pea plant is more likely to be short or more likely to be tall. The genes that determine the color of the flower separate during gamete formation from the genes that determine the height of the plant. We now know that there are exceptions to this. If the two types of genes are spaced close together on the same chromosome, they are much less likely to separate during the stage of meiosis called crossing over. Therefore, Mendel's Law of Independent Assortment only applies if the genes are located on different chromosomes or else are located far apart on the same chromosome.
Example of Incomplete Dominance
Example of Codominance
Complex Heredity Patterns
There are some patterns of heredity that work differently.
Polygenic Inheritance - Sometimes multiple genes work together to determine a single trait. For example the height of a person is controlled by several genes. Skin color, eye color, and hair color are other examples of multiple genes working together. That's why there aren't just two or three colors of skin, for example, but many shades in between!
Incomplete dominance - This is where two genes blend together. For example, if you cross a white snapdragon plant with a red snapdragon, you'll get a pink snapdragon.
Codominance - This is where neither allele is dominate. Instead they share dominance, creating a speckled or spotted pattern on the organism.
Multiple Alleles - There are some genes that have three or more alleles, rather than only two. Blood is an example in humans, which is why we have so many different types of blood.
Traits Influenced By The Environment - Some traits are influenced not only by their corresponding genes, but also by the environment.
Although mutations (changes in genetic material) are rare, when they occur and then get passed down to future generations, they are called genetic disorders. Sickle Cell Anemia, Cystic Fibrosis, Hemophilia, and Huntington's Disease are some examples of genetic disorders. Genetic disorders are caused when the proteins (that are encoded by the genes) can't do their job properly because they are mutated.
Visit: How Do Mutations Cause Genetic Disorders? for more information about how mutations cause genetic disorders and the role that proteins play in that.
Treating Genetic Disorders
Some genetic disorders can be treated if caught soon enough. PKU is an example. People with PKU lack the enzyme needed to change phenylalanine into tryrosine. If the phenylalanine can't be converted to tryosine, it builds up in the blood and causes mental retardation. Fortunately, a test is available which can diagnose PKU in newborn babies. Babies found to have the disorder can be placed on a special diet to prevent them from becoming mentally retarded.
Gene Therapy is a treatment that is still in its infancy but looks promising for the future. During gene therapy, a doctor puts a healthy gene into the DNA of a person with the genetic disorder. Viruses are used to transport the healthy gene into the person.
Genetic Material: DNA
DNA stands for Deoxyribonucleic acid. DNA is the genetic material that is in the cells of almost all organisms. Almost every cell in your body carries the same DNA.
DNA is made up of two strands of nucleotides which are twisted into a double helix.
There are four nitrogen bases of DNA: adenine (A), guanine (G), cytosine (C), and thymine (T). Adenine always pairs with Thymine. Guanine always pairs with cytosine.
The order the bases are in determines the biological instructions that are contained in that DNA, so one order might give you blue eyes, and another order might give you brown eyes.
What is DNA? - Watch this Boseman Biology video to find out about DNA!
Structure of DNA - Section 2 of Chapter 9
DNA Replication - Section 3 of Chapter 9
DNA replication is the process a cell takes to copy its DNA before it divides.
Enzymes unwind and separate the two strands of DNA in the double helix. Next, the complementary nucleotides are added to each unwound strand. The end result is two exact copies of the DNA.
Just as a good author has a proofreader to catch any mistakes, the process of DNA replication has a proofreader called DNA polymerase. DNA polymerase helps the process of DNA replication be very accurate.
1. Watch the videos below on DNA replication.
2. Try this online activity: DNA Workshop
(To start the activity, click on "DNA Replication" and then click on unzip. After you finish the activity there, click on "Protein Synthesis," for the next part of the activity.)
DNA Replication - Another excellent video by Paul Anderson!
Labs and Activities on DNA and it's Replication
How To Extract DNA From Anything Living (We did this one in our homeschool co-op, and it was pretty amazing!)
Genes to Proteins
1. Watch: translation.
3. Watch this short animation of Translation. (I suggest using the step-through version, rather than the verbal narration.)
Gene Structure and Regulation - Section 2 of Chapter 10
Genetic Engineering - Section 1 of Chapter 11
Genetic engineering is the process of adding new DNA to an organism for the purpose of adding one or more new traits that were not already found in that organism. For example some plants have been genetically engineered to be resistance to certain insects. Some plants have been changed by the addition of DNA in order to be able to better tolerate herbicides.
Human Applications of Genetic Engineering - Section 2 of Chapter 11
Genetic Engineering in Agriculture - Section 3 of Chapter 11
Watch this video on Genetic Engineering: Genetic Modification- The Movie as well as the youtube below.
Unit 3 Of Holt Biology
This is the next unit in this biology series.
Unit 3 of Holt Biology is on The History of Life On Earth, including evolution and the classification of living things.
List of pages in this series
Homepage: Biology: Information, Videos, and Labs
Unit 1 on Cell Biology
Unit 2 on Genetics
Unit 3 on The History of Life on Earth
Unit 4 on Ecology
Unit 5 on Diversity
Unit 6 on All About Plants
Unit 7 on The Animal Kingdom: Invertebrates
Unit 8 on Vertebrates
Check back later for additional biology units!
What's your favorite subject in school?
What's your favorite topic in biology?
Did you find the genetics videos, study guides, links, or labs helpful?
Do you have any others to recommend?
© 2011 JanieceTobey
anonymous on July 19, 2012:
Thans the videos and classes help me to much.
Paperquest5 on June 18, 2012:
Janiece, I'll bet you're a good teacher. Maybe I would have learned some of this with you as a teacher.
andreaberrios lm on April 30, 2012:
Excellent!! This is very important, lots of great links and resources.
infiniti99 lm on March 15, 2012:
awesome lens thank you for sharing.
Frischy from Kentucky, USA on January 07, 2012:
This took me back to my college course on human heredity. Great collection of information here for anyone who needs to brush up on genetics!
anonymous on January 07, 2012:
I learned a lot here. thanks
JanieceTobey (author) on November 06, 2011:
@anonymous: Thank you, Tipi! Biology is a favorite of mine! I bet your were an excellent homeschooling mom!!
JanieceTobey (author) on November 06, 2011:
@ajgodinho: Yes, genetics is interesting! I agree! Thanks for writing!
anonymous on October 25, 2011:
This was a refresher for me, it took me back to my high school biology days. An excellent teaching resource for everyone. I sure wish you had been around with your lessons back when I was homeschooling my kids. Excellent, that's just what you do!
Anthony Godinho from Ontario, Canada on October 07, 2011:
Looking at many of these topics reminded me of my days in school. I enjoyed biology in school and the topic on genetics is definitely interesting. Great work on this lens and I can see this lens evolving as your homeschooling progresses.