Download Genetic Code

Chapter 5 Lesson 3
DNA and Genetics
The Discovery of the Structure of DNA
James Watson and Fransis Crick
Rosalind Franklin
DNA Structure
•
DNA looks like a twisted ladder and is
double helix
often called a ________________.
DNA Structure
a. The sides of the ladder are made up of molecules
sugar
deoxyribose
of ______________
called ______________
that
are alternating with molecules of phosphate.
DNA Structure
•
Ladder rungs are made up of a pair of
molecules called nitrogen bases
(containing nitrogen and other elements).
The four nitrogen bases are:
o
o
o
o
Adenine
____________________(A)
Thymine
____________________(T)
Guanine
____________________(G)
Cytosine
____________________(C)
DNA Structure
•
How do the nitrogen bases pair up to make the
rungs of the DNA ladder?
Adenine
Thymine
o ______________
pairs only with _______________
Cytosine
Guanine
o ______________ pairs only with _______________
Nitrogen Base Pairing
What is DNA Replication?

The process of copying a DNA molecule to
make another DNA molecule that is an
exact copy.
DNA Replication
•
•
•
•
DNA molecule unwinds and separates
between the nitrogen bases on each rung.
Nucleotides
____________________
that are floating
in the nucleus pair up with each half (A
with T and G with C)
Two identical DNA molecules are formed
The order of nitrogen bases in each new
DNA molecule will exactly match the order
in the original DNA molecule.
DNA Replication
• DNA replication ensures that:
• each new daughter cell will have a complete
set of DNA which it needs to carry out all the
cell’s activities.
DNA Replication
http://www.youtube.com/watch?v=hfZ8o9D1tus
Let’s Review DNA

What are the 4 different nitrogen bases in
a DNA molecule? How do they pair?


Adenine pairs with Thymine
Cytosine pairs with Guanine
Base Pairing – The secret to the code!!
Adenine pairs with Thymine
Guanine pairs with Cytosine
Introducing a New Player



This structure, along with DNA, is critical
in the construction of YOU!
This structure comes in three different
forms with different functions.
What is the name of this “New Player”?
RNA
DNA vs. RNA –
How are they different?
DNA vs. mRNA

How many strands in each?


DNA – Double strand
RNA – Single strand
(ex. How many sides?)
DNA vs. mRNA

What are the nitrogen bases in each?


DNA – has A, T, C, G
RNA – has A, U, C, G
DNA vs. mRNA

What is the sugar in each backbone?


DNA – has deoxyribose
RNA – has ribose
Three types of RNA

mRNA (messenger RNA)

tRNA (transfer RNA)

rRNA (ribosomal RNA)
The Genetic Code
ATTCGGTG
Genes make proteins
Proteins make YOU!!
Protein Structure
unwind
Your DNA determines the proteins that are
produced. These proteins give you your traits
such as hair color, eye color, and skin color.
The Genetic Code (cont.)



What are the building blocks of
protein?
A group of three nitrogen bases
codes for a specific amino acid.
The production of proteins is
called protein synthesis.

Two steps – Transcription and
Translation
The Genetic Code





The order of nitrogen bases along a gene
forms a Genetic Code that specifies what
type of protein will be produced.
The type of protein produced determines
the trait!
Are you ready to see the code that
unlocks the mystery of life????
Are you sure?????
Are you really sure????
The Genetic Code
Protein synthesis takes place on the ribosome.
Two types of RNA
A Look at Protein Synthesis:
Protein Synthesis
http://highered.mcgrawhill.com/sites/0072943696/student_view0/chapter3/
animation__how_translation_works.html
Steps of Protein Synthesis
Fig. 15 – pg. 173



DNA “unzips” between the Nitrogen Base
pairs
mRNA nucleotides pair up with DNA
nucleotides
Completed mRNA moves into the
cytoplasm
This process is called TRANSCRIPTION
Steps of Protein Synthesis (cont.)
Fig. 15 – pg. 173



The genetic messenger is called
messenger RNA (or mRNA).
mRNA carries the DNA code from the
nucleus out into the cell’s cytoplasm to the
ribosomes where proteins are produced.
Why can’t DNA deliver the code to the
ribosomes?

DNA is too large to fit through the nuclear pores.
Steps of Protein Synthesis (cont.)
Fig. 16 – pg. 174



Transfer RNA (tRNA) carries amino acids
to the ribosome.
tRNA matches up to mRNA using base
pairing rules: A-U and C-G
Each tRNA molecule attaches the amino
acid to the growing protein chain.
This process is called TRANSLATION
(nucleic acid language is “translated” to amino
acid language – a protein is made from mRNA)
A review of your notes:

What is a codon?


How many codons are possible?


Series of three nitrogen bases on mRNA
64 codons
How many different amino acids are there?

20 different amino acids to form proteins
Let’s Review Protein Synthesis:
Mutation

Definition – a change in the nucleotide
sequence of a gene. This causes the cell
to produce an incorrect protein which
results in a different physical trait or
phenotype.
Mutations
(pg. 175, Figure 17)
The mice ran away.
Substitution Mutation
Deletion Mutation
Insertion Mutation
The rice ran away.
Thei cera naway.
The migukce ran away.
Mutations

Mutations are usually random and can be:




Harmful – causes harm to the organism
Helpful – helps the organism to survive
Neither harmful or helpful.
Mutations can also be caused by
environmental hazards.

These are usually harmful
Cancer
•
Cancer is a disease in which:
•
•
Cells grow and divide uncontrollably,
damaging the parts of the body around them.
Cancer can occur when something
damages a portion of DNA in a
chromosome. This damage causes a
mutation
change in DNA called _____________.
Cancer
•
•
Abnormal cells that develop uncontrollably
may form a mass of abnormal cells which
tumor
is called a _________________.
Treatment for cancer include
radiation
surgery
_____________,
________________
and
Drugs (chemotherapy)
or ____________________
Questions


Why can’t DNA leave the nucleus to
produce proteins?
Why is it important for meiosis to occur?
What would happen if human sex cells
had 46 chromosomes instead of 23?
Human Cells



Human body cells contain 46 chromosomes
(23 pairs)
Sex cells (egg and sperm) contain 23 chromosomes
The 23rd pair of chromosomes determines the sex of
an individual.



Female genotype – XX
Male genotype – XY
Design a Punnett Square to calculate the probability
of a man and woman having a baby girl of baby boy
Karyotype


Definition –
picture of all the
chromosomes in
a cell arranged
in pairs
Is this karyotype
from a male or
female?
Where is there a problem?