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Nucleic Acids: DNA and RNA
Transcript of Nucleic Acids: DNA and RNA
Genes are segments of chromosomes that code for proteins
One gene is transcribed & translated into One protein.
DNA is packaged into chromosomes
two strands of nucleotides twisted into a double helix
THE BIG PICTURE:
DNA & RNA
an enzyme unzips DNA at H bonds
a different enzyme adds
that are 'complimentary' to each strand
made of DNA + protein
tightly packed into chromosomes for mitosis
made of DNA + protein
chromatin that supercoils until it is short and thick
name used during mitosis
Produce a temporary RNA copy complimentary to part of 1 DNA strand
mRNA will be used to take DNA code to ribosome & make protein
Steps (in Nucleus)
1. Initiation: large enzyme complex partially unzips DNA strands at start of gene
if DNA is… then add RNA
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
Made of protein & rRNA (ribosomal RNA)
2 Subunits, large & small
Subunits produced in nucleolus, come together in cytoplasm
Anticodon & Codon
if mRNA codon = CAU
then tRNA anticodon = GUA
and amino acid = His
Use chart, look up mRNA to find aa
Ribosome & mRNA attach
tRNA complimentary to 1st codon brings 1st aa
tRNA complimetary to next codon brings next aa
Amino acid chain moves over
Old tRNA leaves ribosome
REPEAT steps until stop codon is reached
Release factor attaches to stop codon.
Polypeptide released & ribosome falls apart & mRNA freed & reused
Change In A Single Gene
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
Mutation in Chromosome Structure
Mutation: any change in the DNA sequence
1. point mutation:
RNA polymerase adds RNA nucleotides complimentary to 1 DNA strand:
DNA is the blueprint for protein synthesis which provides genetic material
DNA makes us all different!
Importance of DNA:
produce 2 identical DNA's
each distributed to 2 new cells
2 new DNA molecules each identical to the original
each new DNA has 1
& 1 new
small subunit of ribosome holds mRNA
large subunit of ribosome holds protein
Peptide bond forms between 2 aa’s
AA order: pro-gln-asn-phe-gly
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
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
provides the blueprint for protein synthesis by the arrangement of nitrogenous bases
a specific location on a chromosome, consisting of a segment of the DNA, that codes for a specific protein
DNA is a nucleic acid
(only in DNA)
Nucleotides that make up nucleic acids (DNA and RNA) have 3 parts:
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
nitrogenous base, a simple sugar and a phosphate.
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:
Type of sugar used
molecule structure and shape
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.
Decoding the DNA Code
DNA = the 'code of life'
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
*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