Download DNA and Protein Synthesis

DNA and Protein Synthesis
A Brief Tutorial
Background

DNA is the genetic material.

Sometimes called “the blueprint of life.”

Used to help build everything the organism
needs to function.

Must remain in the nucleus.
Structure of DNA

Nucleotide

5 carbon sugar + phosphate group + nitrogenous base

DNA sugar = deoxyribose

Nitrogenous Bases = adenine, thymine, cytosine, guanine

Nucleotides are linked together into shape of
double-helix.

Twisted Ladder Analogy
A DNA Sequence
DNA is really a
pattern of
repeating
nucleotides.
LADDER
ANALOGY
Science Aid: DNA Structure and Replication
scienceaid.co.uk/biology/genetics2/dna.html
The DNA molecule needs to coil and foldup so that it can fit into the small nucleus.
The Double
Helix
The Ladder
Latest from the Labs: Cells and DNA
info.cancerresearchuk.org/.../cellsanddna/
Complementary Base-Pairing

DNA molecule is double-stranded and
“complementary”

Adenine always pairs with Thymine (A=T)

Cytosine always pairs with Guanine
(G =C)

Backbone/rails = alternating
sugar/phosphate molecules
Practice DNA Strands

ATCCGTGCT

GCGTAGCTGACCGCGATGACA
DNA Replication

How DNA makes a copy of itself

Semi-conservative Replication
2
New DNA molecules each with 1 old strand and
1 new strand
 DNA
Ladder unzips, enzymes come in and add
new base pairs…. 2 new molecules!
 ANIMATION!
DNA, RNA, and Protein
Main Idea: DNA codes for RNA,
which helps build proteins.
Central Dogma

How does the information stored in DNA get
expressed in genes?
DNA
 RNA
 RNA  Protein
is able to take the information
stored in DNA out of the nucleus and
go to the ribosome to help build
proteins!
RNA
5 carbon sugar = ribose
 Nitrogenous bases = adenine, uracil,
cytosine, and guanine
 Single (not double) stranded


3 different forms:
mRNA – messenger RNA
 tRNA- transfer RNA
 rRNA- ribosomal RNA

Transcription

DNA  mRNA

Information in DNA gets transcribed (or
rewritten) into RNA language.
C
pairs with G
 A pairs with U

Sample Transcription: AGCGTGAACGT

Next, mRNA shuttles its message to the
ribosome
Translation

mRNA  Protein

At the ribosome, information stored in
mRNA molecule gets translated into a
chain of amino acids (protein) with the
help of tRNA.
Steps

Break mRNA molecule into 3 bases =
codon

Use the codon chart to determine what
amino acid the tRNA molecule would bring
to the ribosome to help build the protein.
Protein Synthesis

DNA Strand: AGTACCGCGTCATT

Transcription Product:

Translation Product:

ANIMATE!
Mutations

A permanent change in the DNA of a cell

Missense mutation: change in DNA
results in wrong amino acid placed in
protein. (Might still be ok….)

Nonsense mutation: change in DNA
causes translation to stop early. (VERY
BAD)

Point mutation  base substitution (C
instead of G)

Addition/Deletion  “Frame shifts”…
cause change the multiple of three codons

Tandem Repeats  excessive repeating
of sequences.

Multiple Choice (Scantron) Analogy