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Nucleic Acids: DNA and RNA

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Shiley Biology

on 21 October 2014

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Transcript of Nucleic Acids: DNA and RNA

Transcription: formation of mRNA from DNA
Genes are segments of chromosomes that code for proteins
One gene is transcribed & translated into One protein.
DNA is packaged into chromosomes
DNA Replication
two strands of nucleotides twisted into a double helix
THE BIG PICTURE:
DNA & RNA
DNA
RNA
PROTEIN
Steps
an enzyme unzips DNA at H bonds
a different enzyme adds
free nucleotides
that are 'complimentary' to each strand
Chromatin:
made of DNA + protein
long, thread-like
during interphase
tightly packed into chromosomes for mitosis
Chromosome
“colored bodies”
made of DNA + protein
chromatin that supercoils until it is short and thick
name used during mitosis
Non-replicated
Replicated
Centromere
Sister chromatids
chromosomes
ONE chromosome
Function
Produce a temporary RNA copy complimentary to part of 1 DNA strand
mRNA will be used to take DNA code to ribosome & make protein
http://acs.lbl.gov/ImgLib/COLLECTIONS/BERKELEY-LAB/RESEARCH-1991-PRESENT/LIFE-SCIENCES/images/96703355.lowres.jpeg
Steps (in Nucleus)
1. Initiation: large enzyme complex partially unzips DNA strands at start of gene
if DNA is… then add RNA
G
C
T
A
C
G
A
U!!!!!!
free nucleotides covalently bonded to form mRNA
3. Termination: mRNA detaches from DNA & leaves nucleus thru pores but DNA stays in nucleus & rezips!
Interpreting the codons
If 4 bases, 3 at a time, how many codons?
How many amino acids?
Each a.a. can be coded for by more than one codon
___ START codon; ___ STOP codons
Translation: formation of protein from code on mRNA
tRNA: Transfer RNA
the TRANSLATOR - knows
Amino acid language: Carries correct aa coded for by genetic code
Nucleotide language: 3 Bases = ANTICODON
Ribosome
Made of protein & rRNA (ribosomal RNA)
2 Subunits, large & small
Subunits produced in nucleolus, come together in cytoplasm
Anticodon & Codon
COMPLIMENTARY
if mRNA codon = CAU
then tRNA anticodon = GUA
and amino acid = His
Use chart, look up mRNA to find aa
1. Initiation
Ribosome & mRNA attach
tRNA complimentary to 1st codon brings 1st aa
2. Elongation
tRNA complimetary to next codon brings next aa
Amino acid chain moves over
Old tRNA leaves ribosome
http://www.lbl.gov/Science-Articles/Archive/ribosome-crystallography.html
REPEAT steps until stop codon is reached
3. Termination
Release factor attaches to stop codon.
Polypeptide released & ribosome falls apart & mRNA freed & reused
Steps
TINY!:
Change In A Single Gene
Mutagens:
examples: asbestos, dioxin, cyanide, formaldehyde, cosmic rays, X rays
Location of Mutation:
Body cells – can only cause damage in organism in which it occurs
Gametes (egg or sperm)– mutation will be part of every cell in resulting offspring
GINORMOUS!
Mutation in Chromosome Structure
Insertion
Mutation: any change in the DNA sequence
2. frameshift:
1. point mutation:
RNA polymerase adds RNA nucleotides complimentary to 1 DNA strand:
C
T
T
T
C
G
G
A
A
A
DNA is the blueprint for protein synthesis which provides genetic material
DNA makes us all different!
Importance of DNA:
purpose:
produce 2 identical DNA's
each distributed to 2 new cells
end result:
2 new DNA molecules each identical to the original
each new DNA has 1
original strand
& 1 new
complimentary strand
small subunit of ribosome holds mRNA
large subunit of ribosome holds protein
Peptide bond forms between 2 aa’s
DNA: GGG-GTT-TTA-AAA-CCC
mRNA: CCC-CAA-AAU-UUU-GGG
tRNA: GGG-GUU-UUA-AAA-CCC
AA order: pro-gln-asn-phe-gly
mRNA
carries code from DNA
3 bases = 1 codon
each codon codes for 1 aa
repeat steps until end of gene is reached
DNA code: A C T G G T C A A
mRNA code: U G A C C A G U U
base pair substitution results in
base pair insertion or deletion results in
watch 1st 3 minutes only
generally occur during meiosis
generally occur during DNA replication
Substances in environment that change the DNA
2. Elogation:
DNA Shape:
ladder-shaped that twists into double helix
2 polynucleotides arranged like a ladder:
sides are S-P (antiparallel)
rungs are bases
A with T
G with C
H bonds connect
a structure in the nucleus of a cell that is composed of ONE long strand tightly coiled of DNA
Chromosome
provides the blueprint for protein synthesis by the arrangement of nitrogenous bases
DNA
Gene
a specific location on a chromosome, consisting of a segment of the DNA, that codes for a specific protein
BACKGROUND KNOWLEDGE
DNA
Nucleotides:
DNA is a nucleic acid
C
G
A
T
(only in DNA)
Nucleotides that make up nucleic acids (DNA and RNA) have 3 parts:
Nitrogenous Bases
RNA
RNA is a nucleic acid
a single strand of nucleotides with nitrogenous bases exposed along the side
when the nitrogenous bases of RNA chemically bond to a strand of DNA, each RNA base bonds with one DNA base.
these are called
complementary bases
A
G
A
T
G
U
C
U
C
A
A
G
A
T
G
T
C
T
C
A
PENTOSE SUGAR
Phosphate
nitrogenous base, a simple sugar and a phosphate.
nucleotide
Nitrogenous Bases
A
G
C
T
when the nitrogenous bases of two DNA strands chemically bond to form the double helix, each base bonds with one other DNA base.
these are called:
complementary bases
DNA
RNA
Quick Review
DNA RNA


A-T
G-C
Types of
nitrogenous bases
Type of sugar used
molecule structure and shape
deoxyribose


double helix
G-C
A-U
ribose
nucleic acid
Genes continued
one gene codes for one protein

proteins coded by DNA on genes determine the characteristics of an organism.

Each chromosome consists of hundreds of genes determining the many proteins in an individual organism.


centromere
single chain
Decoding the DNA Code
DNA = the 'code of life'

WHY?
DNA contains the code for each protein an organism needs
proteins are specific to what job they do in an organism

the structure (order) of the nitrogenous bases found in DNA determine the function the protein obtains
More about Chromosomes
A complete set of chromosomes are in EVERY SINGLE cell of an organism.
humans: 23 chromosomes
dogs: 39 chromosomes
fruit fly: 4 chromosomes
cabbage: 9 chromosomes

Sex Chromosomes- chromosomes that determine gender

Autosomal Chromosomes- name for other chromosomes

Except for sex cells, all other cells contain ONE PAIR of each chromosome (22 pairs)
each pair has genes that code for the same protein
one from male parent and one from female parent
humans: 23 pairs = 46 chromosomes
one chromosome = thousands of GENES
Closely related organisms may have the same genes that code for the same proteins.


two types of nucleic acids
DeoxyriboNucleic Acid
(DNA)
RiboNucleic Acid

(RNA)
*think of a 2 way street!
Leading Strand: continuous
-nucleotides are added, by enzymes, freely.

Lagging Strand: discontinuous
-replicates in small segments (Okazaki Fragments)
enzymes to know: DNA helicase, polymerase, RNA primase, DNA ligase
Full transcript