Chapter 5
5.1 DNA and RNA are required to make proteins
►DNA
contains a code – a set of
rules or symbols used to carry out
the information
 Stores information that
allows a cell to put
together the right
sequences of amino
acids needed to produce
specific proteins
5.1 DNA and RNA are required to make proteins
► DNA
Structure
 Shape – double helix
 Strands – made of
alternating sugars and
phosphates
 Rungs – made of
nucleotide bases
5.1 DNA and RNA are required to make proteins
► Two
bases come together
to form a rung
► Adenine
pairs with Thymine
► Cytosine
pairs with Guanine
► The
bases fit together like
puzzle pieces
► The
order of the bases forms a code for
making proteins
5.1 DNA and RNA are required to make proteins
► Replication
–
 Process by which DNA is copied before it
condenses into chromosomes
 Happens before a cell divides
5.1 DNA and RNA are required to make proteins
► Replication
–
5.1 DNA and RNA are required to make proteins
► Replication
–
 Process –
►1.
two strands of DNA separate, forming a
template
►2.
nucleotide bases match up and join the
open DNA strands
►3.
When all open bases are matched up, two
new molecules have formed
5.1 DNA and RNA are required to make proteins
► Transcription
–
 Process of transferring DNA to RNA
 RNA bases pair like puzzle pieces too
►Cytosine
►Adenine
pairs with guanine
pairs with uracil
5.1 DNA and RNA are required to make proteins
► Transcription
–
5.1 DNA and RNA are required to make proteins
► Transcription
–
 DNA is used as a template for RNA
►1.
A section of the DNA molecule opens up
►2.
Nucleotides of RNA match up and join to
the open DNA section
►3. The completed RNA strand is released and
moves into the cytoplasm to be translated
 DNA closes at the end of transcription
 One strand of RNA is produced
5.1 DNA and RNA are required to make proteins
► Translation
–
 Assembly of
amino acids in
their proper
sequence
5.1 DNA and RNA are required to make proteins
► Translation –
►1. the ribosome attaches to the beginning of a
messenger RNA molecule
►2.
tRNA molecules carrying an amino acid matches
up to a complementary mRNA at the ribosome
►3.
ribosome attaches one amino acid to another as
it moves along the mRNA molecule
►4.
once the amino acids they carry are attached to
the chain of amino acids, the tRNA molecules are
released
►5.
ribosome completes the translation when it
reaches the end of the mRNA strand
5.1 DNA and RNA are required to make proteins
DNA
Is transcribed to make
RNA
Is translated to form
proteins
Changes in DNA can produce
variation
5.2
• Each human cell and 6 billion base
pairs in its DNA
►With such a large number of base
pairs, errors can occur
►Errors
occur when:
• DNA is copied
• the environment
has an effect
►Mutation
►any change in DNA
• Three possible outcomes of a mutation
►Mutation
causes no effect
►This
is possible because only 5% of
the 6 billion base pairs are code for
RNA
• If the mutation occurs in a
non-coding region of DNA,
the mutation will most
likely not have an effect
►The
effect of the mutation is minor
►Example: mutation causes a
change in appearance
A white American
alligator shows a
genetic mutation
know as leucism.
This allele controls
migration of pigment
cells during
development;
absence in cells
leads to white
patches on the skin.
►The
effect of the mutation is great
►example: mutation causes a
genetic disorder
►Genetic
Disorders -
►Disease
or condition that results
from a mutation
• Can
• be inherited
• Occur during a person’s life
►Example
of a genetic disorder
• Sickle cell disease
►A
recessive
genetic disorder
which means the
person must
have two alleles
for sickle cell in
order to have the
disease
►A
pedigree is a diagram that shows
family relationships including two or
more generations
5.3
Modern Genetics Uses
DNA Technology
►Changes
in organism occur over time
because of mutations in DNA
►Random
changes may introduce new
traits which may become more
common over time
• This depends on interactions with the
environment and each other
• Humans also have some control over
changes in groups of organisms
►Selective
Breeding
►Process
of selecting and breeding
parent organisms to pass on
particular traits to the offspring
• In selective breeding,
humans are actually
taking genes that
were already present
and making them
more common
►Examples
►Horses
have become faster
• Pigs have gotten
leaner
• Corn has
become
sweeter
►In
the past 50 years, it has become
possible to directly change the DNA of
an organism
►Genetic
engineering
• Process in which a sequence of
DNA from an organism is altered
• The DNA is isolated, changed,
and then returned to the
organism or to another organism
• Engineered DNA usually codes for a
desired trait
►Example:
►Plants
being more insect repellent
►Possible
Benefits:
►Having
more resistant
plants increases the
food production while
decreasing the
amount of pesticides
needed
• Having less chemical pesticides on
the ground reduces the risk of
environmental pollution
►Possible
Risks:
►Affecting natural populations
• Scientists
genetically
modify salmon
to grow more
quickly
• If the genetically modified fish breed
with fish from the natural population,
the natural population will be
►DNA
Technology
►To add nutrients to food
• Produce new and better
drugs for treating disease
• Predict if a drug will have a side
effect in an individual
• Screen for/treat genetic disorders
• Law enforcement such as DNA
fingerprinting
• Cloning
►Cloning-
technique that uses
technology to make copies of DNA
►Can
be applied to a
segment of DNA or a
whole organism
• Has been used for bacteria
to produce proteins and
drugs that help fight
diseases
• Example – insulin is produced in
large quantities as a result of cloning
techniques