Anatomy & Physiology I
Unit Four
DNA & RNA Structure
The monomers are nucleotides
Nitrogen base
Functions:
Heredity
Protein synthesis
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Phosphate group
Pentose sugar
DNA & RNA Structure
Examples:
•DNA
•RNA
Double
Single
stranded
stranded,
with three
double
helix
forms –
molecule
tRNA, rRNA,
and mRNA
DNA &
RNA
Structure
DNA & RNA Functions
DNA & RNA Base
Pairing
DNA & RNA Base Pairing
DNA replication
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A T G C A T T G A AG C T G G T A G
TACGTAACTTCGACCAT C
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RNA transcription
| | | | | | | | | | | | | | | | | |
AU G C A U U G A AG C U G G U A G
TACGTAACTTCGACCATC
| | | | | | | | | | | | | | | | | |
DNA Replication
Protein Synthesis
Protein synthesis goes on all the time in most cells
This very important process is directed by the
genetic code on DNA
Protein Synthesis
Protein synthesis occurs in two processes:
~ transcription (production of RNA
from DNA)
~ translation (production of
proteins from RNA)
Both processes are fueled by ATP
Protein Synthesis: Transcriptio
Protein Synthesis:
Transcription
RNA polymerase attaches to specific areas of the
DNA (genes) and “unzips” the hydrogen bonds
The RNA polymerase also begins the building of the
RNA by adding RNA nucleotides in accordance with
the DNA base sequence
Protein
Synthesis:
Transcriptio
n
Protein Synthesis: Transcriptio
Protein Synthesis:
Transcription
Once transcribed, mRNA and tRNA are sent out of
the nucleus and to the ribosomes in the cytoplasm
rRNA is transferred to the nucleolus to become a
part of newly formed ribosomes
Protein Synthesis: Translation
mRNA carries a series of codons that code for
specific amino acids
A codon is a sequence of three nucleotide bases on
mRNA
Since there are only four RNA bases and there are
three in each codon, there are 64 condon
possibilities
Protein Synthesis: Translation
The genetic code is the use of these 64 codons
coding for 20 amino acids
Remember - the synthesis of a specific protein
requires a specific sequence of amino acids
Protein Synthesis: Translation
Therefore the sequence of codons on mRNA must be
sequentially specific
The genetic code is commaless and non-overlapping,
meaning it is read in frames of three without gaps or
overlaps
Protein Synthesis: Translation
There is one initiation codon - AUG
There are three stop codons - UAA, UAG & UGA
Protein Synthesis - Translation
Translation is the process by which RNA produces
proteins in ribosomes
- mRNA carries the code from DNA
- tRNA carries amino acids to the
ribosome
- rRNA is a component of the
ribosome
Protein Synthesis: Translation
By way of the genetic code, RNA “translates” from
the language of nucleic acids to that of proteins
Protein
Synthesis:
Translation
Protein Synthesis: Translation
Protein Synthesis: Review
Protein Synthesis: Review
Interphase
G1 – organelles
double
S – DNA replicates
G2 – proteins
produced
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Significance of Cell Division
Cell division (mitosis) is an efficient
process that assures the correct
number of chromosomes will be found
in the new daughter cells
Significance of Cell Division
Chromosome number is a critical characteristic in
determining a species and the viability of an
organism
Correct chromosomes numbers are essential for
successful fertilization events
Significance of Cell Division
In animals, increasing or decreasing chromosome
numbers has deleterious effects
Significance of Cell Division
The functions of cell division are:
~ growth
~ repair
~ replacement
Cellular homeostasis is the maintaining of a constant
number of body cells
Significance of Cell Division
Cellular homeostasis is maintained by a number of
factors:
+ cell size
+ nutrient availability
+ DNA damage
+ growth factors
+ cell population density
Significance of Cell Division
Surface to volume ratio determines the maximum
size a cell can obtain
The amount of nutrients available is a factor in the
rate of growth
Growth factors such as cyclins, Cdks and hormones
influence the speed and amount of cell growth
Significance of Cell Division
The density of cells also controls cell growth – loss of
cells stimulates cell division, adequate numbers of
cells inhibit the process
Cancer
Cell division is orchestrated by
proteins and hormones so that
growth and division is controlled
Cancer cells are normal body cells
that are transformed. In this
transformed state, they ignore the
controls of cell division and
multiply unchecked
Cancer
Normally, the immune system
destroys these cancer cells, but
some may escape destruction
and then form a tumor
A tumor is a mass of cancer cells
found within otherwise normal
tissue
Cancer
A tumor is said to be benign if
the cancer cells remain within
the tumor. These can usually be
removed through surgery
A malignant tumor contains
cancer cells that are invasive,
meaning they spread to other
tissues. A person with a
malignant tumor is said to have
cancer
Cancer
Remember - cell division is
orchestrated by proteins and
hormones so that growth and
division is controlled
Oncogenes are those that initiate
cell division, but in an accelerated
and exaggerated process
Cancer
Tumor suppressor genes are
those that prevent cell division
and promote normal cell death
If tumor suppressor genes are
altered, inactivated or removed
the result can be cancer
Cancer
Cancer can occur through
genetic abnormalities, activating
oncogenes and/or inactivating
tumor suppressor genes
Environmental influences can also
affect the activity and inactivity of
these genes
Cancer
Environmental influences include:
~ diet
~ exercise
~ sun exposure
~ smoking
~ altering of DNA