1. Introduction to Genetics
Packet 11

2. Vocabulary Allele Genetics P1 Generation Crossing Genotype Phenotype
Dihybrid cross
Gregor Mendel
Probability
Dominant
Heterozygous
Punnett square
F1 Generation
Homozygous
Recessive
F2 Generation
Monohybrid cross
Test cross
Gene
Offspring
Trait

3. Notes: Introduction to Genetics pages 1-2

4. What is Genetics heredity 8 years Gregor Mendel Pea Plants
Genetics is the branch of biology that studies _____________ or the passing of traits from parent to offspring.
___________ ___________ ( ) was an Austrian monk that taught high school science and tended the garden of the monastery.
Gregor Mendel
8 years
It took approximately ___ __________ for Mendel to gather enough data to support his theories of heredity.
He bred ______ __________ to show how traits pass from parents to offspring. His experiments created more than 25,000 pea plants.
Pea Plants

5. Mendel looked at 7 traits in pea plants, he figured out that each trait had two different forms called _______________
Alleles.

6. Smooth (s) wrinkled (s)
Below is an example of when Mendel bred pea plants to study seed shape… the two different alleles were:
_______________ & ________________
Smooth (s) wrinkled (s)
Symbols he used:
_____ – Parental Generation
_____ – 1st generation of offspring
_____ – 2nd generation of offspring p1 F1 F2

7. What is Genetics
While he was not a considered a well known scientist of his time, today Gregor Mendel is considered to be the father of modern genetics
Two concepts that resulted from his experiments:
Inheritance is determined by traits that are passed from one
generation to the next.
2. Some forms of a trait are dominant and others are recessive.

8. In most cases, when both parents pass down different alleles for the same trait, one usually is expressed and the other one is hidden.
Dominant
The _______________ allele is the trait that shows up even when paired with a different allele.
The ________________ allele is a trait that can be hidden or masked when it is paired up with a dominant allele.
Recessive

9. Phenotype genotype Dominant Recessive Some other terms to know:
_______________ – the appearance of a trait (freckles or no freckles, brown hair or blond hair)
_____________ – the genetic makeup of a trait represented by a pair of letters (FF, Ff or ff; BB, Bb or bb). The 2 letters symbolize the alleles given by each parent.
A capital letter is used to represent a _____________________ allele.
A lower case letter is used to represent a __________________ allele.
Phenotype
genotype
Dominant
Recessive

10. zygote homozygous heterozygous
Since each gamete (egg or sperm) carries one set of instructions for each trait – when they combine to make a ___________ (fertilized egg), there are two sets of instructions for each trait (one from mom and one from dad).
zygote
homozygous
___________________ – when the pair of alleles are identical or the same form. Also known as pure or true breeding. Examples: TT or tt
_____________________ – a pair of alleles that are not the same form…one is dominant and the other is recessive. Also know as a hybrid. Example: Tt
heterozygous

11. In the two chromosomes , 1 trait has been identified in which the plant has received different ___________ (forms of the same gene) from its parents.
alleles
The different alleles are the result of slight differences in the order of G’s, C’s A’s & T’s in that part of its DNA. Genetic differences are the result of _______________.
mutations

12. Practice with Terms page 3

13. Round
Round
wrinkled

14. TT or Tt tt aa
AA or Aa
Gray

15. TT YY tt aa Rr yy RR AA rr Tt Aa Gg Yy
Because a heterozygous genotype will cover up the recessive allele NO
The genotype could be homozygous or heterozygous for a dominant characteristic

16. Notes: How likely is that trait passed to the offspring? page 4

17. Notes: Intro to Punnett Squares
PROBABILITY
_________________ is the likelihood that an event will occur.
So if we know the genetic makeup of the mom and dad, we should be able to figure out if it is probable (how likely) and/or possible (could it) for them to pass down certain traits.
We will use a box called a _____________ ___________ to determine the probability that specific traits will be passed down from parent to offspring.
This shows how a mom or dad’s alleles may separate during meiosis (making the egg or sperm).
Punnett Square

18. dad’s EE Ee Ee ee Monohybrid mom‘s
_________________ cross- a cross that involves ONE pair of contrasting traits (Ee x Ee).
Monohybrid
dad’s
mom‘s EE Ee Ee ee

19. _____________ cross– a cross that involves TWO pairs of contrasting traits (AaBb x aaBB).
Dihybrid

20. In some cases – genetics problems can be answered without using a Punnett square:
If dad has the genetic makeup (AAbbCCdd), he can produce the gametes with:________________________
If mom has the genetic makeup (AaBBccDD), she can produce gametes with:____________ ___________

21. Practice Problem: In pea plants, tall is dominant over short
Practice Problem: In pea plants, tall is dominant over short. (T = tall, t = short)
What letters will represent a heterozygous tall plant? _______
What letters will represent a homozygous short plant? _______
What type of offspring would result if we crossed a heterozygous tall plant with a short plant.? Complete the Punnett square below to find out.

22. The first thing we do is write out the genotypes of the parents: Parents (P) = Tt X tt

23. Guided Practice Problems page 5

27. Practice Problems (Independent work) page 6

31. Notes: Test Crosses page 7

32. NOTES: TEST CROSSES Test cross Dominant homozygous
A _______ _________ is an experimental breeding/mating used to determine the genotype of a parent.
A test cross would be used to determine if an organism with a _______________ trait is homozygous or heterozygous
when an individual shows a recessive trait, we always know that they are ____________________
Dominant
homozygous

33. dominant
In a test cross a parent with a _________________ trait is always mated with one showing the __________________.
By looking at the offspring we can usually determine the genotype the parent with the dominant trait.
Example: In carnations red flower color is dominant over white.
We have a plant that produces all red carnations, but we don’t know if it is homozygous red or heterozygous red. To find out the genotype, we can do a test cross.
recessive

34. We cross the red (dominant) with a plant that produces ___________ flowers (homozygous recessive).
White

35. Sample test cross: In dogs, there is a hereditary deafness caused by a recessive gene, “d.” A kennel owner has a male dog that she wants to use for breeding purposes if possible.
The dog can hear, so the owner knows his genotype is either DD or Dd.
If the dog’s genotype is Dd, the owner does not wish to spend the money to use him for breeding.
The only way to be certain is to breed the dog with a deaf female (dd) and observe the offspring that they produce.

37. SpongeBob Practice Problems (Independent work) worksheet

38. Long
Round
yellow
stubby
Square
round
Round
Blue bb
RR or Rr qq ll rr
QQ or Qq
LL or Ll
BB or Bb Rr LL QQ
n/a

42. Notes: Crosses Involving 2 Traits page 8 & 9

43. Sometimes instead of just comparing a single trait (like we have been with the four box punnett square) – we may want to see the results of two or more different traits, at the same time.
Example: AAbbCCdd x aaBBccDD … Can you tell what genotype their offspring would have?
AaBbCcDd

48. Gregor Mendel 23 46 Dominant recessive Homozygous
The father of genetics; studied heredity using pea plants. _________________________________
There should be ______ pairs of chromosomes or ______ total in each human cell (except for egg & sperm).
A/an ___________ is the different form that the gene may take. For each gene you inherit, you receive one of these from each parent.
According to Mendel’s experiments, if the two alleles are different from one another, the ______________ will be expressed. The ________________ has no noticeable affect on the organism.
___________________ - An organism that has a pair of identical alleles for a characteristic.
Gregor Mendel 23 46
Allele
Dominant
recessive
Homozygous

49. heterozygous Zygote 46 Genotype Phenotype Test
________________________ – An organism that has a pair of alleles for a characteristic that are not the same.
A ____________ is a fertilized egg, which contains ______(#) chromosomes.
_______________ is the genetic makeup of a trait that is represented by a pair of letters.
________________ is the appearance of a trait (what we actually see).
A ________ cross may be used to determine the (unknown) genotype of a parent that possesses a dominant trait (in this we breed an organism with a dominant trait with a homozygous recessive individual).
Zygote 46
Genotype
Phenotype
Test

50. Gametes 23 monohybrid dihybrid true True
Sperm and Eggs are also known as _______________ and only have a single copy of each gene. In humans, they only have _____ chromosomes.
A Punnett square that has 4 boxes is also known as a __________________cross and a 16-box punnett square is a _____________ cross.
True or false – It is not necessary to perform a test cross on an individual that expresses a recessive trait. _______
True or false – If a parent’s genotype is MM NN oo pp and the other parent’s is mm NN OO pp, then their child must have the genotype Mm NN Oo pp. __________ 23
monohybrid
dihybrid
true
True

51. Short Hair
Short Hair

52. Ll Ll
L l L l LL Ll Ll ll
1:2:1
3:1 ll
LL & Ll

53. Because it could be homozygous or heterozygous
A test cross BB
B B b Bb Bb Bb Bb

54. Normal skin & no dimples (25%) Normal skin & dimples (25%)
Albino with dimples
AaDd
Aadd
aadd
aadd
AaDd, Aadd, aadd, aadd
4 : 4 : 4 : 4
Albino & dimples (25%)
Normal skin & no dimples (25%)
Normal skin & dimples (25%)
Albino & No dimples (25%)

55. ` A a D d A AA Aa D DD Dd Dd dd a Aa aa d
¼ * ¼ = 1/16