A.
B.
True
False
1.
All of your cells have
different functions. If all of
your cells have the same
DNA, how do they
differentiate from each
other and become
different cells?
A.
B.
C.
D.
Through mutations during
development
Through skipping
checkpoints in the cell
cycle
By expressing certain
combinations of genes
and repressing others
Different cells have
different DNA
Central Dogma: Gene  _______  ___________
Gene - a segment of
DNA that codes for a
protein
 Humans have about
25,000 genes
 Each of your 46 DNA
molecules in every cell
contains a few hundred
–a few thousand genes




Protein synthesis is the process of making a protein
from a gene
Gene expression – when a gene is being used to make a
protein in a cell
In a multicellular organism, different cells express
different genes and at different times

Gene (segment of DNA)  RNA protein

In an organism, all cells
(except sperm and egg)
have the same DNA
molecules
 Due to DNA replication
and mitotic cell division

Cells can look and
behave different by using
different genes
 Some are expressed and
some are not
 Depends on hormones
environmental factors
In a simplified form,
protein synthesis is a 2
step process:
1. Transcription


mRNA is transcribed
from a gene
Translation
2.

A protein is
synthesized from the
mRNA codons

DNA
 Monomers=
nucleotides

RNA
 Monomers =
 Deoxyribose sugar
 Double stranded
 Cannot leave the



nucleus
 A- T
 C-G

nucleotides
Ribose sugar
Single Stranded
Can leave the
nucleus
A, U (Uracil),G,C

mRNA
 m = messenger
 Carries genetic code from the nucleus to a ribosome

rRNA
 R = ribosomal
 makes up ribosomes

tRNA
 t = transfer
 Connects amino acids to mRNA codons

1.
2.
3.
4.
Occurs in the nucleus in
eukaryotes and the cytoplasm
in prokaryotes
An enzyme unzips an area of a
DNA molecule exposing a
particular gene
RNA Polymerase makes a
strand of mRNA from the
DNA coding strand (A-U, C-G)
The newly made strand
separates and leaves the
nucleus through a nuclear
pore
DNA is zipped back by
another enzyme
Transcription
Protein Synthesis- Part 1
Transcription
From HHMI’s Biointeractive: DNA
Animations/Transcription (basic)
http://www.hhmi.org/biointeractive/dna/D
NAi_transcription_vo1.html
A.
B.
C.
D.
ACU
ACT
UGA
AGU
Occurs in a ribosome of
both prokaryotic and
eukaryotic cells
 The mRNA interacts with
the rRNA of the ribosome
to initiate translation at
the start codon
 The sequence of
nucleotides on the mRNA
is read in triplets called
codon
 Each codon encodes for a
specific amino acid, which
can be deduced by using
the genetic code chart

tRNA brings the correct AA to the correct place
on the mRNA
2. Peptide bonds form between the amino acids
3. A growing polypeptide chain forms
4. The process continues along the mRNA until a
stop codon is reached
5. The process terminates by release of the newly
synthesized polypeptide
6. It will then get folded into its specific shape and
be packaged and transported throughout the
cell
1.
From HHMI’s Biointeractive: DNA
Animations/Translation (basic)
http://www.hhmi.org/biointeractive/dna/DN
Ai_translation_vo1.html
A.
B.
C.
D.
Amino acids are assembled into protein on
the ribosomes
Messenger RNA is made from DNA
Ribosomal RNA and transfer RNA form base
pairs
Transfer RNA contains the genetic code
copied from DNA

Two ends:
 1. Amino Acid
 2. Anti Codon
The anti codons bond
to the mRNA codons
 mRNA codon = AGU
 Anti codon = UCA
Amino acid

Anti codon 

As the mRNA strand
moves through the
ribosome, tRNA brings
a specific amino acid to
each of the mRNA
codons
The amino acids bond
together (peptide
bonds) and break off
from the tRNA-mRNA
hold
 The newly formed
sequence of amino
acids will then be
folded into a protein
and go do its cellular
function.

SHAPE MATTERS
Structure of the Digestive Enzyme
Chymotripsin





The sequences of
amino acids make
different proteins
There are only 20
amino acids
The same 20 for all life
All species on Earth
use the same code to
build proteins
How do you get amino
acids in your body?
A.
B.
C.
Alanine
Arginine
Proline