Teacher Presentation: Genetics

Introduction to

Genetics

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Rabbits, just like people, can look very different from each other.

Click on the rabbit who has floppy ears.

Yes! This rabbit has floppy ears!

Why does this rabbit have floppy ears while other rabbits have straight ears?

Click on one of the floppy ears to continue.

Each cell of the rabbit contains inherited information that determines its traits.

Where did the rabbit get its inherited information that determines its traits?

From its parents

From its brothers and sisters

From its aunts and uncles

Inherited information is inside the nucleus of each cell that makes up my body.

Click on the cell's nucleus to zoom in.

The inherited information is inside my 22 pairs of chromosomes.

22 pairs of chromosomes (1 set from each parent)

Click on the chromosomes.

The male Jack Jumper ant has only 1 chromosome!

Koalas have 16 chromosomes (8 pairs).

Tomato plants have 24 chromosomes (12 pairs).

Female Jack Jumper ants have 2 chromosomes.

The many species of the world have different numbers of chromosomes in their cells!Us rabbits have 44 chromosomes (22 pairs).

Some species of fern have over 1200 chromosomes!

Humans have 46 chromosomes (23 pairs).

Click on the organism with the least number of chromosomes.

The rabbit inherits one set of 22 chromomes from her mother....

I have 22 pairs of chromosomes (44 total). One set of 22 is from my mother and the other set is from my father.

10

11

18

17

14

15

16

19

20

21

12

13

22

Click on chromosome 22 to continue.

Rabbits _____ a set of 22 chromosomes from each parent.

inherit

purchase

subtract

The rabbit inherits one set of 22 chromomes from her mother....

I have 22 pairs of chromosomes (44 total). One set of 22 is from my mother and the other set is from my father.

10

11

18

17

14

15

16

19

20

21

12

13

22

...and a matching set from her father.

Rabbits _____ a set of 22 chromosomes from each parent.

inherit

purchase

subtract

Rabbits _____ a set of 22 chromosomes from each parent.

inherit

purchase

subtract

22 chromosomes from each parent = 44 chromosomes

Non-reproductive cells (somatic cells) contain 2 copies of each chromosome.

Mother

Father

Somatic Cell Nucleus

Somatic Cell Nucleus

Rabbits have ____ of 22 chromosomes in the nucleus of almost every cell.

2 copies

1 copy

22 copies

44 copies

Meet my parents. Like me, they have 2 copies of chromosomes in each of their somatic cells.

Note: A somatic cell is any cell of the body except sperm and egg cells

22 chromosomes from each parent = 44 chromosomes

Non-reproductive cells (somatic cells) contain 2 copies of each chromosome.

Mother

Father

Gamete (sperm) Cell Nucleus

Somatic Cell Nucleus

Gamete (egg) Cell Nucleus

Somatic Cell Nucleus

Rabbits have ____ of 22 chromosomes in the nucleus of each of their reproductive (gamete) cells.

2 copies

1 copy

44 copies

100 copies

But...they only have 1 copy of chromosomes in their reproductive (gamete) cells.

22 chromosomes from each parent = 44 chromosomes

Non-reproductive cells (somatic cells) contain 2 copies of each chromosome.

When the rabbits reproduce, the chromosomes from the egg cell and sperm cell combine, giving the offspring 2 sets of chromosomes that contain genetic information from each parent.

Father

Mother

Gamete (sperm) Cell Nucleus

Gamete (egg) Cell Nucleus

Click on the heart to combine the 2 sets of chromosomes.

She got my charming personality!

AWW! She got my ears!

Offspring

Father

Mother

Click on the offspring bunny to continue.

Now let's explore why this bunny offspring has ears like her father and not ears like her mother.

22 pairs of chromosomes (1 set from each parent)

Each chromosome is made up of very very long strands of DNA.

DNA is like an instruction manual for making all the different parts of the rabbit.

Click on the DNA.

Note: The floppy ear trait is controlled by multiple genes. For simplicity, this introcution to genetics focuses on just one of the genes that contributes to ear floppiness.

Each distinct gene controls the production of a specific protein, which in turn affects the traits of the individual

Gene- a section of DNA that contains instructions for making a specific protein

Sections of DNA that control the production of proteins are called genes.

Click on the gene in the image above.

22 pairs of chromosomes (1 set from each parent)

Genes contain instructions for building proteins. The proteins determine traits!

gene

Genes are sections of DNA that control the production of specific proteins, which determine _____ such as fur color, tooth length, and ear floppiness.

traits

enchantments

the weather

Ear floppiness in rabbits is affected by many genes and sometimes environmental factors as well. Since this is an introduction to genetics, we will focus only on one gene as a simplified model for how organisms inherit traits.

Mother

Genes are represented by either a capital or lowercase letter.

Let's say that the two copies of the gene above (labeled "e" and "E") code for a protein that affects the trait of ear floppiness in a rabbit.

Click on one of the copies of the "ear floppiness" gene.

Oftentimes, people show the approximate location of a gene in diagrams by drawing a band on the chromosome that the gene is located within.

E e

Click on one of the bands that represents the section a gene can be found within a chromosome.

Each parent has two copies of most every gene that can be passed down to their offspring. But these copies are not always EXACTLY the same! Alleles are two or more forms of the SAME gene.

Mother

Father

Offspring

The father has two matching alleles (ee) of the gene for ear floppiness. The mother's alleles (Ee) are not the same.

Click on the allele that is different from the others.

Individuals carrying two identical alleles (EE or ee) are homozygous for a trait. Individuals carrying different alleles (Ee) are heterozygous for a trait.

Mother

Father

Offspring

The father rabbit is __________ for ear floppiness and the mother is _________.

homozygous, heterozygous

heterozygous, homozygous

Alleles of a gene can be dominant (represented with a capital letter) or recessive (respresented with a lowercase letter). In the case of ear floppiness, the straight ears allele is dominant (E). The dominant trait will be expressed as long as at least one of the two alleles is dominant.

Mother

Father

Very Important!

Offspring

The mother rabbit has ____ dominant (straight ear) allele(s) for ear floppiness.

zero

one

two

over 1,000

The floppy ears allele is recessive (e). The recessive trait (written as a lowercase letter) will be expressed only if both alleles are recessive.

Mother

Father

Very Important!

Offspring

The father rabbit has ____ recessive allele(s) for ear floppiness.

zero

one

two

over 1,000

Sort the cards into the correct categories. Then, click on the blue checkbox (lower right corner) to receive the code.

Scroll over me for a reminder about the terms homozygous, heterozygous, recessive, and dominant.

Click here when you know the code.

Get Code

Enter the code below.

Enter the code here.

The genotype of an organism is its genetic code, such as EE, ee, or Ee. The phenotype is its expressed traits, such as straight of floppy ears.

Mother

Father

Offspring

What is another way to describe the father's genotype for ear floppiness?

Homozygous Dominant

Homozygous Recessive

Heterozygous

The genotype of an organism is its genetic code, such as EE, ee, or Ee. The phenotype is its expressed traits, such as straight of floppy ears.

Mother

Father

Offspring

What is the mother's genotype for ear floppiness?

floppy ears

ee

straight ears

EE

Ee

The genotype of an organism is its genetic code, such as EE, ee, or Ee. The phenotype is its expressed traits, such as straight of floppy ears.

Mother

Father

Offspring

What is the father's phenotype for ear floppiness?

floppy ears

ee

straight ears

EE

Ee

The genotype of an organism is its genetic code, such as EE, ee, or Ee. The phenotype is its expressed traits, such as straight of floppy ears.

Mother

Father

Offspring

What is the mother's phenotype for ear floppiness?

floppy ears

ee

straight ears

EE

Ee

Sort each genotype card into the corresponding phenotype category. Then, click on the blue checkbox (lower right corner) and follow the provided directions.

Remember, the allele for straight ears (E) is dominant and the allele for floppy ears (e) is recessive.

Each parent randomly passes on ONE of its two copies of each chromosome to offspring. This causes the offspring to have a unique genetic code!

Father

Mother

Offspring

What is the phenotype for ear floppiness of the offspring above?

floppy ears

ee

straight ears

EE

Ee

Each parent randomly passes on ONE of each chromosome (remember- there are 22 pairs for rabbits!) to offspring. This causes the offspring to have a unique genetic code!

Each parent randomly passes on ONE of its two copies of each chromosome to offspring.

Mother

Father

Offspring

What must be the genotype for ear floppiness of the offspring above?

floppy ears

ee

straight ears

Ee

EE

That's right! The offspring must have two recessive alleles (ee) for ear floppiness. If she had even just one dominant allele (E), she would have a phenotype of straight ears!

Mother

Father

Offspring

How can you describe the genotype of the offspring above?

Homozygous Dominant

Heterozygous

Homozygous Recessive

The two parents can pass on different combinations of alleles of a gene, resulting in different _________ (genetic combinations) and __________ (expressed traits).

phenotypes, genotypes

genotypes, phenotypes

Why do some of my brothers and sisters have straight ears and some have floppy ears?

Honey

Roger

Bugs

Velvetine

Easter

Peter

Thumper

Energizer

Father

Click on Father Rabbit to place his alleles for ear floppiness on the Punnet square.

Mother

We can use Punnet squares to determine the expected percentages of different genotypes in the offspring of two parents.

Father

Click onMother Rabbit to place her alleles for ear floppiness on the Punnet square.

Mother

Father

Mother

Click on the first Punnett square cell.

We can use Punnet Squares to determine the determine the expected percentages of different genotypes in the offspring of two parents.

Father

Mother

Click on the second Punnett square cell.

We can use Punnet Squares to determine the determine the expected percentages of different genotypes in the offspring of two parents.

Father

Mother

Click on the third Punnett square cell.

We can use Punnet Squares to determine the determine the expected percentages of different genotypes in the offspring of two parents.

Father

Click on the fourth Punnett square cell.

Mother

We can use Punnet Squares to determine the determine the expected percentages of different genotypes in the offspring of two parents.

Father

Of the four cells, how many show a genotype that would result in a phenotype of floppy ears?

1 cell

2 cells

3 cells

4 cells

Mother

Now that the Punnet square is filled in, we can determine the probability that the offspring will have floppy ears.

Father

Of the four cells, how many show a genotype that would result in a phenotype of straight ears?

1 cell

2 cells

3 cells

4 cells

Mother

That's right! 2 Punnett square cells show the homozygous recessive genotype (ee) that results in floppy ears!

Two of four squares show a genotype that results in a phenotype of floppy ears.

Father

What percentage of offspring would you expect to have straight ears?

50%

75%

2%

25%

Mother

That's right! 2 Punnett square cells show the heterozygous genotype (Ee) that results in straight ears!

Father

What percentage of offspring would you expect to have floppy ears?

50%

75%

2%

25%

Mother

Yes! Two of four cells (50%) show a genotype (Ee) that results in straight ears. Therefore, chances are that 50% of offspring would have straight ears.

Father

Click anywhere to continue.

Mother

Yes! Two of four cells (50%) show a genotype (ee) that results in floppy ears. Therefore, chances are that 50% of offspring would have floppy ears.

Click on each box below to choose the correct words. Then, click on the blue checkbox and follow the provided directions.

Father

Mother

Honey

Roger

Bugs

Velvetine

Easter

Peter

Thumper

Energizer

How would the expected percentage offspring having floppy ears change if the mother was homozygous dominant (EE) instead?

Father

Mother

E e

E e

Click on the mother to change her genotype to EE.

Father

Mother

E e

E e

What percentage of offspring would have floppy ears if the mother was homozygous dominant (EE) and the father was homozygous recessive (ee) as shown above?

50%

100%

0%

25%

How would the liklihood of floppy ears chance if the father was homozygous dominant (EE) instead?

That's right! All offspring would have the genotype Ee, which results in the phenotype of straight ears.

Father

Mother

E e

E e

Click anywhere to complete one last activity!

Click on each box and choose the best word. Then click on the blue checkbox and follow the provided instructions.

Honey

Roger

Bugs

Velvetine

Easter

Peter

Energizer

Thumper

Honey

Great work! You've completed this introduction to genetics!

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