Genetics: S7L3.A
Name:
How do we know about heredity?
1. ______________________ used pea plants to study the way traits are
passed from parents to offspring.
2. He discovered that some traits were ______________ and others
_______________.
3. He also discovered that each plant had two sets of instructions for each
characteristic
4. Gregor Mendel is called the “_____________________”
5. genetics:
____________________________________________________________
The Cell and Inheritance
Genetics, Let’s Break it down
1. The human body is made-up of trillions of cells
2. Each cell contains a _____________________
3. Each cell nucleus contains _____ pairs of chromosomes or 46 total
(depending on the type of organism)
4. ______________________ are rod shaped structures that carry
inheritance material
5. Each of the 46 chromosomes contain _________ for thousands of genes
What are genes?
1. ___________ are segments of DNA, found on a chromosome, and
determines the inheritance of a trait
2. Different genes determine the different characteristics, or _______, of an
organism
3. One gene might determine the color of a bird's feathers, while another
gene would determine the shape of its beak
4. The number of genes varies from species to species
5. We have around _____________ genes
What is DNA?
1. a very large _____________, made up of smaller units called nucleotides
2. It acts like the blueprint for cells of an organism, telling them how to put
together materials to produce certain traits
3. Everyone’s _____________ is different (unless you are an identical twin)
4. Identical twins come from one egg fertilized by one sperm
5. They have exactly the same ___________________
Heredity
1. When organisms ________________, genetic information from each
parent is passed to the next generation.
2. Some are easy to see, like hair and eye color, skin type and height
Genetics: S7L3.A
Name:
3.
4.
5.
6.
Some traits cannot be seen, such as traits for ______________________.
Hemophilia (blood clotting disorder)
Color-blindness
Some traits we ______________are also affected by our
_________________ such as: our height, weight, and the shape of our
bodies
Can you think of other environmental factors?
What are dominant and recessive alleles?
1. As we said earlier, every organism has a set of ________ that determines
traits.
2. Each pair of genes are called _____________
3. Offspring inherit one allele from each parent.
4. Sometimes one allele will hide the affects of another. When this happens
we call it a ____________________ allele.
5. The allele that is hidden or blocked is called a
_______________________ allele.
6. Alleles are written using letters.
7. A dominant allele is represented by a __________________ letter, X
8. A recessive allele is represented by a _______________________letter, x
Alleles may be written like this:
XX
Xx
xx
Example: Color of seeds
Yellow: YY
Green: yy
Yellow: Yy
Which allele is dominant? Recessive?
1. Offspring inherit ___________ allele from each parent.
2. The offspring may get two dominant alleles (TT) or two recessive alleles
(tt)
3. When an organism has two alleles that are the same the alleles are called
______________________________ (remember “homo” means the
same)
4. Example: Tall (TT) Short (tt)
5. Offspring that inherit two of the same alleles for a trait are said to be
______________ for that trait
Genetics: S7L3.A
Name:
6. The offspring may inherit one dominant allele and one recessive allele.
( Tt )
7. When an organism has two alleles that are different, the alleles are called
____________________________(remember “hetero” means different)
8. The organism that carries both the dominant allele and the recessive allele
for the trait is called a ________________________.
How do I identify dominant and recessive alleles?
TT will produce a tall plant
Tt will produce a tall plant (the dominant trait blocks out the recessive trait)
tt will produce a short plant
How do I use a Punnett Square to predict results of genetic crosses?
The ______________________________ is a table that can be used to predict
what traits offspring will inherit.
The top part of the table shows the alleles of the ________________parent.
On the side are the two alleles from the ______________________ parent.
Draw example:
Each of the squares shows a possible outcome for the offspring.
Draw Example:
The possible outcomes are called ___________________.
GG, Gg, gg are genotypes.
The actual physical appearance of the trait is the _______________________.
A green pod would be a phenotype.
Draw Punnett Square
What is the dominant trait?
What is the recessive trait?
Genetics: S7L3.A
Name:
What are the possible genotypes?
What are the possible phenotypes?
What are the chances?
1. Offspring are _______________ likely to inherit either allele from either
parent.
2. The mathematical chance that an event will happen is called
_______________.
3. Probability is shown as a __________________ or as a percent.
4. We can compute the probability that an offspring will inherit a certain trait
using the Punnett square.
What is the probability that the puppies will have black fur?
1. There are __________________ possibilities.
2. Two squares have ______. The other two squares have
_____________.
3. So, there are two genotypes for ______________ fur.
4. What is the probability that the puppies will have black fur?
5. 2/4 = ½ = ________________%
6. There is a 50% chance the puppies will have black fur.