Download Chapter 5: DNA

DNA and Modern
Genetics
Chapter 5C
DeoxyriboNucleic Acid
 DNA is a molecule that stores information that a cell needs
to function, grow, & divide.
 Proteins are large molecules that are made up of chains of
amino acids.
 Do most of the work of the cell and make up much of the structure of a
cell
 20 different amino acids combine to make up thousands of different
proteins.
 DNA provides the code, or set of rules, for making proteins.
**How do DNA and proteins work together??
Nucleotide Bases
 DNA is a double-stranded spiral, much like a twisted
ladder.
 It is made up of four nucleotides:
adenine (A),
thymine (T),
cytosine (C), and
guanine (G).
Adenine pairs with thymine & cytosine pairs with
guanine
 Genes are made up of a sequence of bases at
a particular location on the DNA
 All Tigers Can Growl 
DeoxyriboNucleic Acid
 Before a cell divides, its
entire DNA is copied in a
process call replication.
 DNA separates into 2
strands.
 Each strand is used as a
template to produce a
copy of the other strand
 Nucleotides in the area
match up with the bases
left & form 2 new strands
RiboNucleic Acid
 RNA, ribonucleic acid, is involved in making proteins.
 3 types of RNA
 Messenger RNA (mRNA): carries the
information from DNA to a ribosome.
 Ribosomal RNA (rRNA): forms the
ribosome with other proteins.
 Transfer RNA (tRNA): carries an
amino acid and matches up to a
complementary mRNA at the ribosome.
Transcription and Translation
 Transcription: the process of transferring
information from DNA to RNA.
 RNA base pairs: cytosine pairs with guanine & adenine
pairs with uracil.
 Transcription VS. Replication
 Only 1 strand of DNA is transcribed, producing a single
strand of RNA
 After transcription, RNA is released
 Many copies of RNA can be made from the same gene
 Translation: the assembly of amino acids in their
proper sequence according to the mRNA template.
DeoxyriboNucleic Acid
 46 chromosomes contain 6 billion base pairs
of DNA.
 99.9% of DNA in the cells of two different humans is the
same.
 0.1% variation in DNA makes a unique person.
 Errors can occur when DNA is copied.
Any change in DNA is called a mutation. This mutation
can have
 no effect: each cell has 2 sets of DNA, even if one is
mutated, the other may work fine
 minor effect: could affect physical appearance
 major effect: can cause genetic disorder
 A genetic disorder is a disease or condition that results
from mutations that affect the normal functioning of a
cell.
Pedigree: a diagram of family relationships that
shows two or more generations
What can we use DNA for?
 Selective breeding: process of selecting and breeding
parent organisms to pass on particular traits to the
offspring
 People are not changing DNA, but causing certain alleles to become more
common in a particular breed.

**How does selective breeding affect the
DNA of a species?
 Genetic Engineering: process in which a sequence of DNA of
another organism is first isolated, then inserted into the
DNA of another organism, changing that organisms DNA
 Example: plants, organic foods
**What is one major difference between changing offspring through
selective breeding and genetic engineering?
 DNA Technology: DNA identification helps
police establish if a criminal is guilty.
Specialists can compare DNA evidence from a
crime scene with DNA from a suspect to
determine if the person was at the scene.
 Cloning is a technique that uses technology to
make copies of DNA. Cloning has been used in
bacteria to make proteins and drugs to fight
disease.
In 1996, scientists successfully cloned the first
mammal, a sheep named Dolly. All of her DNA came
from a single body cell. Dolly lived for 6 years.
**Why might the practice of cloning raise concerns about its
future use?