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Study Guide for Genes and Gene Technology
Test Date______
DNA:
- In a DNA strand, the rungs (the part you step on) of the “ladder” are made of nitrogen bases.
- In a DNA strand, the sides of the “ladder” are made of alternating sugar and phosphate
molecules.
- Rosalind Franklin was able to create images of DNA molecules and discover that DNA was
spiral shaped.
- Genes are found on chromosomes.
- The passing of traits from parents to offspring is heredity.
- Watson and Crick made models to determine DNA’s “twisted ladder” structure.
- A nucleotide in a DNA molecule is made up of a sugar, a phosphate, and a base.
- In DNA there are four different bases: Adenine, Thymine, Cytosine, and Guanine.
- According to Chargaff’s rules Adenine always pairs with Thymine and Cytosine always pairs
with Guanine. A-T and C-G
- Understand what a complementary strand of DNA is. Example: The complementary strand of
ATTGCCG is TAACGGC because A goes to T and G always goes to C.
Mutations:
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a change in the order of bases in DNA is called a mutation.
There are three types of mutations: insertion, deletion, and substitution.
 Insertion is when an extra base is added into the sequence.
 Deletion is when a base is deleted from the sequence.
 Substitution is when one base is substituted for another.
A mutation in DNA could result in no change, death or a genetic disorder.
A mutagen is something that causes mutations. (Ex: X-rays, U.V. light, radioactivity)
Ultraviolet radiation from the sun is known to cause mutations in skin cells that can lead to
cancer, which is why you should wear sunscreen in the summertime.
A disease that occurs when a child inherits a mutated gene from parents who do not have the
disease is a recessive disorder.
- Sickle cell anemia could be caused by a change in the order of the bases in a person’s DNA.
Know how to read a Pedigree Chart:
- In a pedigree, squares represent males and circles represent females.
- a solid black square or circle indicates that the person has a certain trait.
- a half-filled square or circle indicates that the person is a carrier of a certain trait but does
not show the trait.
- Most genetic disorders, such as Cystic Fibrosis, are due to a recessive gene.
Other important facts:
● Dolly, the sheep, is the first successfully cloned mammal because of genetic engineering.
● A red snapdragon flower crossing with a white snapdragon flower and producing a pink
snapdragon flower is an example of incomplete dominance.
● In incomplete dominance, each allele for a trait has its own degree of influence.
● The picture above is the basic structure of DNA and it is made of nucleotides.