DNA Structure and Technology

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14 Δεκ 2012 (πριν από 4 χρόνια και 7 μήνες)

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DNA Structure and
Technology

By: Amber Tharpe

DNA Structure


Monomers are nucleotides


3 parts of a nucleotide


Phosphate group


Deoxyribose sugar


Nitrogen base


4 different bases


Cytosine (C)

-

thymine (T)


Adenine (A)

-

Guanine (G)


DNA Structure


Double helix
-

shape of 2
chains of DNA in a twisted
spiral


2 chains held together by H
-
bonds between the bases


DNA


Nucleic acid that serves as the
“blueprints of life”


Housed in the nucleus


Determines what traits are inherited
from one generation to the next


Leads to the variation in all living
things

Base Pairing Rules



A always bonds with T


C always bonds with G


Base Pairing Practice


If one strand of DNA is ACACAC,
what is the other strand?


If one strand of DNA is TGAC, what
is the other strand?


If one strand of DNA is CTGCTA,
what is the other strand?

Replication


DNA has the ability copy itself


An enzyme “unzips” the 2 strands


A single DNA strand serves a template
or pattern for making a new strand


Free bases bind based on the base
pairing rules


2 identical strands are formed


Replication Terms


Template strand


DNA strand that is being copied


Complimentary strand


New DNA strand that is formed by pairing
nucleotides to the template strand


DNA polymerases


Enzymes that bond nucleotides together to
form complimentary strands

Central Dogma


DNA→ RNA→ Protein


DNA
-

RNA is transcription


RNA
-

Protein is translation


In eukaryotes, replication and
transcription occurs in the
nucleus, while translation occurs
in the cytoplasm

RNA


Single
-
stranded nucleotides with
U’s bonding to A’s


DNA

RNA

sugar

deoxyribose

ribose

bases

T bonds
with A

U bonds with
A

strands

Double
-
stranded

Single
-
stranded

Transcription


Process of using a strand of
template DNA to make a
complimentary strand of RNA


RNA polymerases


Enzymes that bond nucleotides
together to make a new RNA
molecule

Transcription Practice


Transcribe a strand of DNA that is
ACACAC.


If a strand of DNA is TGAC, what
strand of RNA will it make?


Convert a strand of DNA that is
CTGCTA to RNA.

3 Types of RNA


Messenger RNA (mRNA)


Code translated to form a protein


Ribosomal RNA (rRNA)


Forms part of ribosomes to make protiens


Transfer RNA (tRNA)


Brings amino acids from the cytoplasm to
make proteins


Has an anticodon on one end

Transcription


Does not transcribe the
whole DNA molecule


Only transcribes the
portions of DNA (gene)
needed for cell function at
that specific time

Translation


The process that converts mRNA into a
polypeptide (or protein)


The code for nucleic acids is 4 nucleotides:


A,G,C, and T or U


The code for proteins 20 different amino
acids


Nucleotides are like letters, while amino
acids are like words



Codons


3 nucleotide sequence that codes for a particular
amino acid


Considered a triplet code, since 3 nucleotides are
used to make each amino acid


Many amino acids are coded for by more than 1
codon


Anticodon


Set of 3 nucleotides found on tRNA that is
complimentary to an mRNA codon


Translation


Occurs in the cytoplasm

1.
mRNA is pulled through the ribosome
exposing one codon at a time to pair with the
complimentary tRNA

2.
The ribosome forms a peptide bond between
the amino acids brought in by the tRNA

3.
This process continues as the polypeptide
grows and eventually a stop codon is reached


Translation Practice p. 244


If a strand of RNA is ACACAC, what
amino acids does this make?


Translate a strand of RNA is
UGACUC.


If a strand of DNA is CUGCUA, what
amino acids does this make?

Mutation


Change in an organism’s DNA


Can occur in DNA replication or in
meiosis


Substitution (point mutation)


One nucleotide is substituted for an
incorrect one


May alter an amino acid in a protein


Ex: sickle cell anemia



Frameshift Mutation


Frameshift mutation


Insertion or deletion of a nucleotide in DNA


Makes an abnormal protein


Reading frame is shifted because DNA is read
in a triplet code


THE CAT ATE THE RAT


Remove the first E


What does the sentence say?

Nondisjunction



When chromosomes fail
to separate properly in
meiosis


Ex. Down Syndrome
-

3
copies of chromosome 21


Mutagens


Agents in the environment
that can change DNA


Ex: UV light, radiation,
chemicals in tobacco
products


Often lead to cancer

Biotechnology


The use of organisms or their products
to improve human health or food
production


Types



DNA Fingerprinting


Genetic Engineering


Genetic Screening

DNA Fingerprinting


Gel electrophoresis


Used for comparing DNA samples


DNA is cut and run through the gel
based on electric charge


Smaller fragments move farther than
large fragments


The different size fragments make bands
on the gel that can be compared

DNA Fingerprinting


Uses


Paternity testing


Forensics


Identifying dead bodies


Solving crimes


Compare DNA left at crime scene
to suspects’ DNA

Genetic Engineering


Genes are transferred from 1 organism to
another


Recombinant DNA


When DNA from 2 different sources are
combined


Used in medicine (gene therapy) and agriculture


Modify plants to grow larger, faster, and more
disease resistant


Use the gene for making insulin to treat
diabetes


Cloning


A normal cell is taken from the
organism that is being cloned


An egg cell from an organism of the
same species is taken and the nucleus
removed


The 2 cells are fused and the embryo is
placed in the uterus of a female to
develop and be born