BIOLOGY

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BIOLOGY Worksheet Unit 3 Review
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• Define the following terms
• Homozygous-
• heterozygous -
• true breeding-
• genotype-
• phenotype-
• non-disjunction-
• co-dominance-
• incomplete dominance-
• linked genes-
• genetic engineering-
• cloning-

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Homozygous- two of the same allele (i.e. EE or ee)
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Heterozygous- Two different alleles (i.e. Ee or
Ss)
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True-breeding- Means the same thing as pure-bred.
Will always produce the same offspring.
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Genotype- The letter combination. Describes the
two alleles an organism has (i.e. EE, Ee, ee)
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Phenotype- The physical characteristic that
results from a gene (i.e. Tall or short, Red or
white)
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Non-disjunction- When chromosomes do not separate
during meiosis. Results in gametes with extra or
too few chromosomes Example would result in
Down Syndrome, Klinefelters Syndrome, Turners
Syndrome)
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Co-dominance- Both alleles are dominant and both
expressed in offspring. (i.e. Red and White
hair are dominant in cattle. A purebred red is
crossed with a purebred white cow and results in
a cow that is roan in color- has both red and
white hair)
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Incomplete dominance- Neither allele is dominant.
red flower crossed with white flower and
produces pink flowers in offspring
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Linked genes- Genes that are located on the same
chromsome. Usually inherited together- theyre
linked
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Genetic engineering- changing of an organisms DNA
to give new trait
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Cloning- creating a genetically identical copy of
gene or of an organism
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• What do you call the process where two gametes
  fuse?
• Fertilization

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3. What is the name of the cell that is formed as
a result of this fusion? Zygote
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• What is crossing-over (what process does it occur
  in, and what is the result of this process)?
• When chromosomes cross over each other during
  meiosis and exchange bits and pieces of themselves

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5. Describe the process of DNA replication.
(where does it occur and what is the result) DNA
making copy of DNA. Occurs in nucleus of cell.
Requires certain enzymes to catalyze reaction.
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6. Complete the chart below comparing DNA and
RNA
DNA RNA
Type of sugar Deoxyribose Ribose
Nitrogen base A,T,C,G A,U,C,G
Complimentary bases A-T C-G A-U C-G
Double or Single stranded? Double Single
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7. Blood type is determined by multiple alleles.
Complete the chart below showing possible
genotypes and phenotypes of blood type (page 205)
Phenotype Genotype
Type A IAIA, IAi
Type B IBIB, IBi
Type AB IAIB
Type O ii
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8. A human karotype shows 22 pairs of autosomes,
and one pair of sex chromosomes.
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9. A male has the genotype XY and a female has
the genotype XX
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10.In the process of transcription a DNA sequence
reads CATTGA, what would the complementary mRNA
strand that would read? CATTGA GUAACU
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11. The genes on DNA contain instructions to
assemble proteins
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12.The monomers of proteins are amino acids
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13. Three nitrogen bases make up a codon for an
amino acid.
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14.State Mendels principles of genetics.
a. What is the Principle of Dominance? Some
alleles are dominant and some are recessive
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b. What is the Law of Independence
Assortment? allele pairs separate independently
of each other during meiosis
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15.Be able to use the genetic code chart. What
are the amino acids coded for with the following
codons? a. UUU- b. UUC- c. ACG- d. CCU- e. AUU- f.
AAA- g. GUC- h. GCC-
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15.Be able to use the genetic code chart. What
are the amino acids coded for with the following
codons? a. UUU- Phe b. UUC- Phe c. ACG-
Thr d. CCU- Pro e. AUU- Ile f. AAA- Lys g. GUC-
Val h. GCC- Ala
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16.Summarize the process of translation (where
does it occur and what is the result. Include the
three types of RNA involved) RNA making Proteins.
Occurs in the cytoplasm on the ribosomes.
Involves all three types of RNA (mRNA, tRNA, and
rRNA)
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17. What did Mendel call the factors that
determine traits? Genes
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18.What organisms do Mendels principles apply
to? All living things
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19.What causes mutations in DNA? a. Are all
genetic mutations expressed? Explain No. May not
affect phenotype. May not change protein
produced. May occur in non-coding part of DNA
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b. What created oil-eating bacteria? Induced
mutations (radiation)
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20.What is the purpose of Punnett squares? A tool
to predict the possible offspring of a genetic
cross
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• State the phenotypic ratio of a heterozygous
  dihybrid cross?
• 9331

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22. Why would a scientist or breeder use
selective breeding? To try and combine certain
traits in offspring to produce desired results
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23. What is inbreeding and how does it
occur? Inbreeding is when two closely related
organisms are crossed. Increases the chances
that recessive alleles will combine in offspring
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24. Skin color in humans is a result of Polygenic
inheritance.
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25. What are the possible gametes produced by the
parent genotypes below? a. RrYy- RY, Ry, rY,
ry b. rrYY- rY only c. SSDD- SD only
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26. Colorblindness is a sex-linked trait. Why do
males exhibit colorblindness more than
females? Because the genes are carried on the X
chromosome and males only have one X chromosome.
If they have the recessive allele they will have
the disorder
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27. Complete the following table comparing
Mitosis to Meiosis
MITOSIS MEIOSIS
Number of cells produced 2 4
Haploid or diploid cells produced Diploid Haploid
Involved in asexual or sexual reproduction Asexual Sexual
Results in body cells or sex cells Body cells Sex cells
Number of divisions involved (one or two) One Two
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28. Complete the chart below comparing the
process of Replication, Transcription and
Translation.
Replication Transcription Translation
Where does it occur? Nucleus Nucleus Cytoplasm
___ making ___ DNA making DNA DNA making RNA RNA making Proteins
What molecules are involved in the process? (DNA, mRNA, tRNA, rRNA) DNA DNA and RNA (mRNA, tRNA, rRNA) RNA (mRNA, tRNA, rRNA)