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Genetics
Study Tools
Vocabulary Help
Prefix or suffix
adi-genheterohomomonopolyphenozyg-
Meaning
not, without
two, twice
to produce, to begin
different, other
alike, same
one
many
appear
joined together
Examples
asexual
dihybrid
genetics
heterozygous
homozygous
monohybrid
polyhybrid
phenotype
zygote
WARM-UP SHEET
Directions: Write down the question and answer in complete sentences. If absent, you must get the warm-up from someone else.
Date:___________________
Date:___________________
Date:___________________
Date:___________________
Date:___________________
WARM-UP SHEET
Directions: Write down the question and answer in complete sentences. If absent, you must get the warm-up from someone else.
Date:___________________
Date:___________________
Date:___________________
Date:___________________
Date:___________________
GENETICS VOCABULARY
Definition
Word
Genetics
Fertilization
True-breeding
Trait
Hybrid
Gene
Allele
Segregation
Gamete
Probability
Punnett square
Example or Illustration
Word
Dominant
Recessive
Homozygous
Heterozygous
Phenotype
Genotype
Test Cross
Independent
assortment
Incomplete
dominance
Codominance
Multiple alleles
Polygenic traits
Definition
Example or Illustration
Reproduction
A. There are 2 main types of reproduction:
1) Asexual reproduction
2) Sexual reproduction
B. Differences between 2 main types of reproduction:
Asexual Reproduction
Sexual Reproduction
Involves….
Results in…
Examples…
Advantage
Disadvantage
C. Pollination: ____________________________________________________________________________________
Note: sperm cells are _____________________ and egg cells are __________________
1) Self-pollination: ____________________________________________________________________________
2) Cross-pollination: __________________________________________________________________________
Mendel’s Genetics
A.
B.
C.
Gregor Mendel is called the _________________________. He discovered the basic
_______________________ by breeding peas in carefully planned experiments.
Mendel’s experiments involved ______________________________ of pea plants with contrasting forms of
7 different traits.
Mendel’s conclusions:
1. Inheritance is determined by factors (_______) that are passed from one generation to the next.
 These factors (_________) have different forms, or ________________.
2. The principle of dominance: some alleles are ___________________ and others are ___________________.
3. The law of segregation: the two alleles for a trait ______________ when ____________ are formed.
 Each gamete carries only a __________________ of gene, or an ____________
 Alleles are paired again when _________________________________________________________
4. The law of independent assortment: the alleles of different ____________ separate __________________
of one another during __________ formation.
Probability & Punnett Squares
A. The principles of ____________________ can be used to predict the outcomes of ________________________.
1. Probability = the _______________________ that a particular event will occur.
2. Alleles segregate __________________, just like a coin flip= ___________ for each allele.
3. Probability is often expressed in ____________________ or _________________.
B. Punnett Squares are used to predict the outcome of a genetic cross
1. Gametes produced by each parent are indicated at the ________ and the _________________ of the square.
2. Possible gene combinations for ________________ appear in the _________________________ the square.
C. Observed ratio versus expected ratio
 The ________________________the ____________________________ are to the expected ratio.
D. Mendel used the following crosses:
1. Monohybrid cross - cross involving a ___________________ (such as flower color)
2. Dihybrid cross - cross involving _______________________ (such as seed color & seed shape)
3. Test cross - a ______________between an individual of _____________________________________ and a
_________________________________________ individual.
 If test cross results in _________________ trait only, then the unknown was
_____________________
 If test cross results in ___________________&___________________ traits, then the unknown
genotype was _____________________________________.
Punnett Squares: Step-by-Step
A Punnett square is a diagram you can use to show how likely each outcome of a breeding experiment is. It is used
when each parent’s traits are known. By filling in the squares, you can find the possible combinations of genes in the
offspring of the two parents. You can also predict the chances that each kind of offspring will occur.
Step 1: Determine the genotypes of the parents.
Reminders:
-sometimes this is already done in the question for you.
-homozygous has two of the same alleles (TT or tt)
-heterozygous means the organism has two different alleles (Tt)
-sometimes you will be given clues about the genotype based on descriptions of other family members
Step 2: Write down your “cross” (the genotypes of the organisms who will mate).
Write the genotypes of the parents in the forms of letters. For example, Tt x tt
Step 3: Draw a Punnett Square.
Step 4: Fill the parents’ genotypes on the square.
a. Split the alleles from one parent (the letters in the genotype) and place them along the left of the rows in the
square.
b. Split the letters from the other parents and place them
along the top of the columns in the square.
Step 5: Determine the possible genotypes of the offspring.
Now all we need to do is fill in the boxes by matching the letters from the sides with the letters from the top. If there is
a capital letter, write it first. Like this:
The top left box:
The bottom left box:
The top right box:
The bottom right box:
Step 6: Summarize your results
The Punnett square gives you valuable information about the possible genotypes of the offspring and of the
probability that each will exist. You can use the genotype information to also describe the possible phenotypes of the
offspring.
Your summary should include the probability that each genotype and each phenotype will appear in the offspring, or
ratio. Remember that probability can be given in percentages or fractions. For example, if T is the allele for a tall pea
plant and t is the allele for short pea plants, your summary would look like this:
Genotypes:
50% Tt
50% tt
Phenotypes:
50% tall
50% short
Genotypes:
½ Tt
½ tt
Phenotypes:
½ tall
½ short
Genotypic ratio: 1:1
Phenotypic ratio: 1:1
Punnett Squares
Directions: For each phenotype, indicate whether it is HETEROZYGOUS (HE) or HOMOZYGOUS (HO):
TT _______
Gg _______
Bb______
dd______
FF_______
Jj _______
hh ________
EE________
Directions: Complete the following Punnett Squares and provide answers as directed.
1. B= Brown eyes b= blue eyes Both parents have brown eyes, but mom is heterozygous while dad is
homozygous for brown eyes. What are the eye color possibilities if they chose to have children?
Cross: Mom’s genotype__________________ X Dad’s genotype _____________________
Genotypes:
Genotypic ratio:
Phenotypes:
Phenotypic ratio:
2. Hairy tail (H) is dominant, and no hair on tail is (h) is recessive. A hairy-tailed homozygous mouse
has offspring with a hairless tail mouse. Predict the outcomes for their offspring.
Cross: ______________ X ________________
Genotypes:
Phenotypes:
Genotypic ratio:
Phenotypic ratio:
3. Brown fur (B) is dominant in mice. White fur (b) is recessive. A mouse that is heterozygous for
brown fur is crossed with a white mouse. What are the possible outcomes for their offspring?
Genotypes
Phenotypes
Genotypic ratio:
Phenotypic ratio:
4. In humans, straight toes are dominant over curled toes. A cross is between a recessive male and a
heterozygous female.
Probabilities of genotypes:
Probabilities of phenotypes:
5. In humans, attached earlobes are dominant over free hanging earlobes.
A cross is between a homozygous dominant male and a recessive female.
Probabilities of genotypes:
Probabilities of phenotypes:
6. Freckles are recessive. No freckles are dominant.
A man and his wife both have freckles.
Possible Genotypes:
Possible Phenotypes:
Genotypic ratio:
Phenotypic ratio:
7. In cats, long hair is dominant over short hair. One cat carries heterozygous, long-haired traits, and its
mate carries homozygous short-haired traits.
Possible Genotypes:
Possible Phenotypes:
Probability of long-haired offspring _____________
8. In flowers, red is dominant over white color. Both flowers are heterozygous red.
Possible Genotypes:
Possible Phenotypes:
Genotypic ratio:
Phenotypic ratio:
A Summary of Mendel’s Principles




Genes are passed from parents to their _____________.
If two or more forms (alleles) of the gene for a single trait exist, some forms of the gene may be
_______________ and others may be _____________________.
In most sexually reproducing organisms, each adult has ___________ of each gene. These genes are segregated
from each other when ____________ are formed.
The alleles for ________________________________ usually segregate _________________ of one another.
Complex Patterns of Inheritance
1. Incomplete dominance = when one allele is ___________________________________________ over another
 an _____________________ phenotype in ______________________ individuals
 trait that is ____________________between two _________________________
phenotypes
 Examples:
2. Codominance = when _____________________ contribute to the phenotype and are
______________________ at the same time.
 Example: Roan cattle is heterozygous for coat color
3. Multiple alleles = traits determined by genes that are controlled by ______________________________
 An individual can have only __________________. However, more than two
alleles can exist in a _______________.
 Examples: ABO blood groups and rabbit’s coat color
4. Polygenic traits = traits controlled by _______________________________
 Examples: skin color, eye color and hair color in humans.
5. Traits influenced by environment = traits controlled by the _____________________ between __________ and the
________________________.
 Example: hydrangeas color based on soil pH
6. Traits caused by mutations are due to ___________________________.
 Examples: sickle-cell anemia, cystic fibrosis, hemophilia, etc.
Complex Patterns of Heredity
CODOMINANT TRAITS
1. In crocus flowers, white (W) and purple (P) colors are co-dominant, and result in a purple and white striped flower
when both genes are present. What is the probability for each possible genotype and phenotype from the crosspollination of a striped crocus with a white crocus?
Probabilities of genotypes: _________________________________
Probabilities of phenotypes: ________________________________
2. Cattle can be red (RR = all red hairs), white (WW = all white hairs), or roan (RW = red & white hairs together). Predict
the genotypic and phenotypic probabilites of the offspring when a homozygous white cow is crossed with a roan bull.
Probabilities of genotypes: _________________________________
Probabilities of phenotypes: ________________________________
INCOMPLETE DOMINANCE
3. A cross between a blue blahblah bird (I made this bird up) & a white blahblah bird produces offspring that are
silver. The color of blahblah birds is determined by just two alleles.
a. What are the genotypes of the parent blahblah birds in the original cross? _________and ___________
b. What is the genotype of the silver offspring? _________
c. What would be the phenotypic probability of offspring produced by two silver blahblah birds?
4. In a species of chickens, incomplete dominance between alleles for black (B) and white(w) feathers is observed.
Heterozygotes are blue. If two blue chickens are crossed, what is the probability that the offspring will be blue?
Probability of blue offspring? _________
Genetics Vocabulary Review
Matching: Correctly match each statement with a correct term.
Trait
Probability
Hybrid
Dominant
Homozygous
Heterozygous
Allele
Fertilization
Punnett square
Recessive
Incomplete dominance
Codominance
Gene
Polygenic
True-breeding
Test cross
Phenotype
Genetics
Gamete
Multiple alleles
Segregation
Independent assortment
Genotype
Mutation
______________________________
1. likelihood that something will happen
______________________________
2. specific characteristic that varies from one individual to another
______________________________
3. offspring of crosses between parents with different traits
______________________________
4. allele that is always expressed if present
______________________________
5. factor or a sequence of DNA that determines traits
______________________________
6. diagram showing possible gene combinations
______________________________
7. scientific study of heredity
______________________________
8. having two different alleles for a trait
______________________________
9. organisms that produce offspring identical to themselves
______________________________
______________________________
10. genes that segregate independently do not influence each other’s
inheritance
11. genetic makeup, or a set of alleles that determines the trait
______________________________
12. process during which male and female reproductive cells join together
______________________________
13. physical trait that appears in an individual
______________________________
14. separation of alleles during gamete formation
______________________________
15. allele that is not expressed when a dominant allele is present
______________________________
16. three or more alleles of the same gene
______________________________
17. form of a gene
______________________________
18. sex cell
______________________________
19. trait controlled by 2 or more genes
______________________________
20. when both alleles of a gene contribute to the phenotype of the organism
______________________________
21. having two identical alleles for a trait
______________________________
22. when one allele is not completely dominant over another
______________________________
23. change in genetic material that may be beneficial or harmful
______________________________
23. cross between an organism of unknown genotype and an organism that is
homozygous recessive for a particular trait