DNA and Genetic Engineering Notes - MrHaskellBiology

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Dec 11, 2012 (4 years and 6 months ago)

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DNA and
Genetic Engineering

Notes

1.
Genetic Code: a program written in a DNA code that runs the cell.


2.
DNA (Deoxyribonucleic Acid): Nucleic acid that stores and transmits the genetic information
from one generation to the next.

-

It is the master molec
ule found

in the nucleus of the cell. (It’s the king of the kingdom)

-

DNA looks like a twisted ladder, a spiral staircase
(a double helix)



3.
DNA is made into a double chain from molecules called
Nucleotides.

Nucleotide: the building block of DNA


4.
Nucleotides are made of 3 parts

1. Deoxyribose sugar


2. Phosphate group


3. Nitrogen base


5.
There are 4 different nitrogen bases. These nitrogen bases are what
create

the genetic code. So
our genetic is written with only 4 letters.



1. Thymine ( T

)

2. Adenine ( A )

3. Cytosine ( C )

4. Guanine ( G )



Adenine and Guanine are
Purines

(a Double Ring Base)



Cytosine and Thymine are
Pyrimidines

(a s
ingle Ringed Base)


6.
In the double helix model of DNA the nitrogen bases or nucleotide match up

Thymi
ne T with Adenine A

Cytosine C with Guanine G





7.
So if you know what one side of the ladder is or one side of the Helix you should know what
the other side is




A G T G C

C T A

l

l


l

l

l

l

l

l


DNA Replication / DNA Synthesis

8.
DNA Replication (DNA synthesis): Duplication of the DNA in the cell


9.
How does the cell make a copy of
the entire

DNA
molecule
in the cell
?


Step #1
-

a special enzyme

(DNA helicase)

is used to unzip, untwist and separate the two
sides of the double helix.

* Enzyme: (the chemist in the cell) A protein that tells the cel
l
how to make lipid, carbohydrates, nucleic acids and other proteins. It
builds the cell.

Step #2


Another enzyme (DNA Polymerases) takes n
itrogen bases
and

match

them

to
each side of a the double helix one nucleotide at a time ( A matches with T and C
matches with G) until two complete DNA strands are made.


Step #3
-

The nucleotides combine and the double helix twist back up

















RNA

10.
RNA
: (Ribonucleic Acid) Nucleic acid that act
s

as a messenger between DNA and ribosome
and helps make p
roteins and enzymes.


11.
3 main differences between RNA and DNA.

1. RNA has ribose sugar and DNA has deoxyribose sugar

2. RNA has a single nucleotide strand, DNA has double strand

3. RNA has the nitrogen base
Uricil

instead of Thymine

12.
3 types of RNA

1. Messenger RNA (mRNA): RNA strand that takes and
message from the DNA to the ribosome.


2. Transfer RNA (tRNA): type of RNA that carries amino
acids to the
ribosomes,

where the amino acids are joined
together to form polypeptides (
P
roteins

and Enzymes
).


3. Ribosomal RNA (rRNA): type of RNA
that
ribosomes

are
made of.


Gene Expression:

Gene
expression
: T
aking a gene (a section of DNA) and turn
ing

it in
to a trait
.

1
st

step in Gene expression is Transcription

13.
Transcription
: (RNA synthesis) The process
where a section of DNA

(a gene)

is copied into
messenger RNA .

*

-

RNA polymerase (an enzyme) finds the right starti
ng point on a DNA molecule and
copies it until it reaches the ending point.

Step 1
-

unzip DNA

Step 2
-

Copy one side of DNA


14.
Understan
ding the DNA
-

RNA code

-

It has a 4 letter alphabet, (the 1
st

letter of the 4 nucleotides)

-

It takes 3 letters to make one code word called a
Codon

Codon:

it is a 3 letter code or, 3 nucleotide
chains
, on the mRNA for a specific
amino acid, also there ar
e some starting and ending codons

64 different codons

Amino Acid
: (the building blocks of proteins); a molecule that makes proteins

20 different amino acids

-

see the chart on page 307

in the book to determine what amino acid goes with these
codons

AAA






GUC

UGA






AUG











methionine

the start codon



15.
2
nd

Step towards Gene expression.
-

After Transcription the mRNA moves out of the
Nucleus into the cytoplasm, finds ribosomes and does
T
ranslation


Translation
: decoding the mRNA and maki
ng a protein or a polypeptide

Step 1
-

mRNA comes from the nucleus goes to the ribosome
and the tRNA attaches at
the start codon

(
The start codon AUG codes for the amino acid methionine
.)



Step 2
-

The next

tRNA
with the right

anticodon
matches to the n
ext codon

on the
mRNA and
the amino acid that the tRNA is
carrying

attaches to the last amino acid
creating a chain of amino acid. The bond between the amino acids is called a peptide

bond
.

(a polypeptide chain)


Anticode: the three nucleotide bases on t
he tRNA that match the codon



Example: codon GUG
its

anti
-
codon is CAC


Step 3


The ribosome moves down the mRNA molecule one codon and step two is
repeated.


Step 4


The steps of 2 and 3 are repeated until a stop codon is reached.


Step 5


The ami
no acid chain, also known as a polypeptide chain, also known as a
protein is released, and the ribosome falls off.


*Ribosome: (site of protein synthesis
) organelle

that is made of rRNA that holds
the mRNA


*In most cases many ribosomes attach to a mRNA at

the same time and many
proteins can be made at the same time


16. Every gene makes one Protein or Enzyme. How these prot
eins affect us is complex. Most
often
several o
r even hundreds of proteins

must
work together in order to make a
single
visible
trait.


17. The human body is capable of producing around 100,000 different proteins. That means we
have around 100,000 gene
pairs. These 100,000 proteins are

what makes and creates a human
being.