TEST REVIEW FILL-IN -
Genetics
Name _______________________
Class 2
3
4

Trait -

phenotype

Carrier

Heredity

genotype

Pedigree

Genetics
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codominance

Genetic disorder
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Purebred

sperm

Selective breeding
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Gene

egg

Inbreeding
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allele
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meiosis
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hybridization
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dominant allele / recessive
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mitosis
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Clone
allele
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messenger RNA
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Genetic engineering
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hybrid
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transfer RNA
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Gene therapy
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probability
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mutation
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Punnett square
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Multiple alleles (in blood)

Use the following words to explain Mendel’s experiments and how they contributed to our
understanding of genetics, especially how traits can disappear for a generation and then reappear.
-dominant & recessive alleles
- Punnett squares
-purebred
-hybrid
Mendel crossed purebred tall pea plants with purebred short pea plants. All of the offspring were tall (they were all
hybrid). He then crossed these hybrid offspring, and ¼ of them were short. Today, we can see what happened by using a
Punnett Square. Mendel learned that some traits are dominant, and some are recessive. The dominant allele will always
show up if it is present. The recessive allele will only show up in a purebred (homozygous) organism.
First cross
Second cross
T
T
t
Tt
Tt
t
Tt
Tt
All hybrid (heterozygous) offspring

T
t
T
TT
Tt
t
Tt
tt
25% are short
What do the top and side letter combinations on Punnett squares represent?
The parents’ alleles

Why do you move one letter from each parent on the Punnett squares to the boxes on the
inside? What does this represent?
Moving one letter from each parent on the Punnett squares to the boxes on the inside represents the
separation of alleles during meiosis and the movement of those alleles to offspring.

Use a Punnett square to cross a hybrid tall pea plant with a purebred short pea plant. What is
the probability of having a tall offspring? A short offspring?
The probability of having a tall offspring is 50%
The probability of having a short offspring is 50%

T
t
t
Tt
tt
t
Tt
tt
What is a pedigree? Draw one showing a married couple with the male having a genetic
disease. They have two boys and two girls. One girl is a carrier, and one boy has the disease.
A pedigree is a map that tracks which members of a family have a particular trait.

Show how gender is determined using a Punnett Square.
X
Y
X
XX
XY
X
XX
XY

What is the male sex cell called?
Sperm

The female sex cell called?
Egg

Some human genes are controlled by a single gene that has multiple alleles – three or more
forms (like in blood) What are the four types of blood, and the allele combinations that create
the blood types? (Use your book)

Blood types
Allele combinations
A
IA IA , IA i
B
IB IB , IB i
AB
IA IB
O
ii
What is a carrier of a genetic disease?
A carrier of a genetic disease is someone who has the recessive allele for a disease but who does not
have the disease.

How are MEIOSIS and MITOSIS different, regarding the number of chromosomes
passed on to the “daughter” cells? Make a sketch of each using a cell with 4 chromosomes.
(Remember, the first step is that the chromosomes double.)

How are a chromosome, a gene, and DNA related? Draw a sketch to show.

In DNA, what nitrogen bases line-up with each other? Draw line connecting the words.

Adenine
Guanine
Cytosine
Thiamine
What is a recessive sex-linked trait? What chromosome is it on? Why are males more
likely to acquire them?
A recessive sex-linked trait is found on an allele of the X chromosome. Males are more likely
to get it because they have only one X chromosome, so it can not be “covered-up” by a
dominant allele.

Use a Punnett square to cross a colorblind male (lowercase c ) with a carrier female.
Xc
Y
XC
XCXc XCY
Xc
X cX c X cY

What is the percentage of male offspring with colorblindness?
50%

What is the percentage of female offspring with colorblindness?
50%

Use the following words in order to describe how a protein is made.
Nucleus, chromosome, DNA, gene, mRNA, cytoplasm, ribosome, tRNA, amino acid, protein
In the nucleus, cells have chromosomes, which are made of DNA. A section of the
chromosome that codes for a trait is called a gene. A gene is copied and carried to the cytoplasm by
mRNA. There in the cytoplasm a ribosome reads the mRNA, and tRNA carries over an aminio acid,
which is put together with other amino acids to create a protein.
FILL-IN THE BLANKS
-
Mendel’s work was the foundation for understanding how traits are passed from parents to
offspring.

Traits are controlled by alleles of genes.

Organisms inherit one allele from each parent.

Some alleles are dominant and some are recessive

Probability is the likelihood that an event will occur.

Geneticists use Punnett Squares to determine the possible outcomes of a genetic cross.

Genes are carried from parents to their offspring on chromosomes.

During MEIOSIS, chromosome pairs separate to form sex cells. Only one chromosome from
each pair ends up in each sex cell. The sex cells have half the number of chromosomes as the body
cells.

A mutation is a change in a gene or chromosome. Some are helpful, some are harmful, and
some are neutral.

Some human traits show a wide range of phenotypes because these traits are controlled by
many genes that act as one.

Males = XY

Males are more likely than females to have a sex-linked trait controlled by a recessive allele.

Genticists use pedigrees to trace the inheritance patterns of a trait through a number of
Females = XX
generations of a family.

Genetic disorders are abnormal conditions that are caused by mutations, or DNA changes, in
genes or chromosomes.

Common genetic disorders include (four from book, no words in word bank) 1.
HEMOPHILIA, DOWN’S SYNDROME, SICKLE-CELL DISEASE, HUNTINGTON’S
DISEASE, AND CYSTIC FIBROSIS

Amniocentesis and karyotypes are tools used to diagnose genetic disorders.

Genetic counselors help couples understand their chances of having a child with a genetic
disorder.

Selective breeding is the process of selecting a few organisms with desired traits to serve as
parents for the next generation.

Cloning is a technique used to create genetically identical organisms.

Genetic engineering can be used to produce medicines and to improve food crops.
Researchers are also trying to use Genetic engineering to help cure genetic disorders.

DNA fingerprinting can be used to help determine whether material found at a crime scene
came from a particular suspect.
ALSO:
1. Study chapter 3 and 4 of your textbook.
2. Review all the pictures and graphics from these chapters of your book.
3. Look at and understand the HW you have completed and had returned.
4. Check out the websites we have studied. They are all still linked on my website.