DNA to Protein

How does the structure of DNA
determine the structure of
specialized cells in an organism?

DNA Structure

•

Nucleotides are made up of
phosphate, deoxyribose
sugar, and one nitrogenous
base (GATC).

•

Nucleotides are the
monomer building blocks of
nucleic acids (DNA & RNA)

Each nitrogenous base has a complementary pair

•Adenine (A) 🡪 Thymine (T)

•Guanine (G) 🡪 Cytosine (C)

DNA

Function

Replicates itself during

mitosis & meiosis

Controls cell activities by

transmitting instructions for making

proteins

Stores genetic information

(different for every individual).

This particular segment may contain a
gene, which would code for a protein that
determines a trait.

Ex: This segment may code for blue
eyes. If we changed some of the base
pairs (G,A,T,C) it may code for the protein
to make green eyes.

When

and why
does DNA
need to
replicate?

DNA replicates right
before a cell divides.

Cells divide for an organism to
grow or reproduce; every new
cell needs a copy of the DNA or
instructions to know “how to be
a cell.”

DNA replication is
semi-conservative. That
means that when it makes a
copy, one half of the old strand
is always kept in the new strand.

DNA replication occurs before a cell divides

Step 1:

Step 2:

Step 3:

Summary:
Steps to

DNA

Replication

DNA helicase breaks H bonds between
nitrogen bases causing complementary
strands to “unzip” and separate.

DNA polymerase adds free floating
nucleotides and forms Hydrogen bonds
between nitrogenous bases.

DNA polymerase “proofreads” the new
DNA for errors and performs an excision
repair if needed.

DNA ligase “seals” DNA fragments and
recoils the two new identical DNA
molecules

The main function of DNA is to carry the information to
create YOU. Yes, you. The question is HOW. How do we go
from a bunch of nucleotides, to all the specific proteins that
make you?

CENTRAL DOGMA OF BIOLOGY

How does the structure of DNA determine the structure of a protein?

TRANSCRIPTION

• DNA is copied into messenger RNA (mRNA)

by the enzyme RNA polymerase.

• Takes place in the nucleus

DNA
vs.
RNA

TRANSCRIPTION

DNA helicase
separates two
strands of DNA

1

RNA polymerase

adds

complimentary
RNA nucleotides
Uracil 🡪 Adenine

2

mRNA strand is

created and

ready to leave

nucleus

3

Process of Transcription

TRANSLATION

•

The process of translating the sequence of
a messenger RNA (mRNA) molecule to a
sequence of amino acids during protein
synthesis.

•

Amino acids don’t speak the same
language as mRNA, so tRNA needs to
“translate” the mRNA instructions.

•

Each tRNA molecule contains only 3 base
pairs and a corresponding amino acid

•

Occurs at the ribosome.

PROCESS OF TRANSLATION

Transfer RNA (tRNA) contains the matching code to attach the
corresponding amino acids.

They help TRANSFER the amino acid to the mRNA
strand.

The amino acids bond together using the code from the mRNA -
forming a PROTEIN chain.

tRNA’s break loose from amino acid, leave the ribosome, &
return to cytoplasm to pick up another amino acid

Process of
Translation

1.

Transfer RNA (tRNA) contains
the matching code to attach
the corresponding amino
acids.

2.

They help TRANSFER the
amino acid to the mRNA
strand.

3.

The amino acids bond
together using the code from
the mRNA - forming a
PROTEIN chain.

4.

tRNA’s break loose from
amino acid, leave the
ribosome, & return to
cytoplasm to pick up another
amino acid

Amino
Acids

20 main amino acids

8 are called essential – since your body cannot
synthesize these 8, you must eat them in your
diet

Amino acids are the monomers
(building blocks) of proteins

DNA contains the instructions for an amino acid
in a 3 base sequence called a triplet. This
information is carried to the ribosomes on a
mRNA codon.

GUA

VALINE

UUC

PHENYLALANINE

ACU

THREONINE

MUTATIONS

•Changes in genetic material
•Happens during DNA replication or
proteins synthesis.
•Mutations may be neutral, harmful, lethal, or
beneficial

PROTEINS

•The order of amino acids
determine how a protein
folds (it’s shape).
•A different amino acid, can
lead to a different shape.
•A different shape, will lead
to a different function!

Original Mutant

PROTEINS SUMMARY

ORDER OF

AMINO
ACIDS

DETERMINE

:

1

FOLDING

PROPERTIE

S

DETERMINE

:

2

SHAPE OF
PROTEIN

DETERMINE

S:

3

FUNCTION
OF PROTEIN

4

Substitution
(Point)
Mutation

•

Changes in one or a few
nucleotides

•

MAY have
consequences, or may
cause no change in the
protein

Original

Sickle Cell
Anemia

POINT MUTATION

DUPLICATION

A duplication consists of a piece of DNA that is abnormally
copied one or more times. This type of mutation may alter
the function of the resulting protein.

Original: TheBigCatAteTheRat

Mutant: TheBigCatCatCatCatCatCatAteTheRat

Duplication Mutation

FRAMESHIFT MUTATION

•

Insertions or Deletions are known as a “frameshift.”

•

May change every amino acid after the point of
mutation (they SHIFT everything forward or
backward)

•

The resulting protein is usually nonfunctional

• Original: TheCatAteTheBigRat
• Mutant: TheCtaTetHebIgrAt

TAY SACH’S DISEASE

•STARTS AROUND 6 MONTHS

•NERVES DETERIORATE

•CHILDREN BECOME BLIND AND DEAF

•MUSCLE LOSS

•USUALLY DIE BY AGE 4