Download Changes in signal transduction pathways can alter

Living systems store, retrieve,
transmit and respond to
information essential to life
processes.
Big Idea #3
Genetic
Information is
passed through
DNA
But errors or
mutations may
occur despite
repair enzymes
DNA is copied during
Interphase for identical
cells and asexual
reproduction
Meiosis creates
gametes which are
fussed together for
genetic variation
Mutations MAY
alter cellular
activities and
phenotypes
store, retrieve,
transmit, and
respond
Biotechnology makes
it possible engineer
heritable changes
Genetic Variation
is caused by
sexual
reproduction,
Conjugation in
bacteria, and
lysogenesis in
viruses
Changes in phenotype
Cell Signaling
and environment can
RTR
result in mutations in
DNA
Mendel described a
Transmission of nonheritable
model of genetics
information influences behavior
within and between cells,
organisms and populations.
But most traits don’t follow this pattern
DNA, and in some cases RNA, is the
primary source of heritable
information.
• Genetic information is transmitted through
DNA
• Prokaryotes have circular chromosomes;
Eukaryotes have linear chromosomes
• History:
– Structure (Watson/Crick, Wilkins, and Franklin)
– Experiments (Avery, Hershey/Chase)
• Replication is semiconservative
– Requires leading and lagging strands (ALL built 5-3)
– Enzymes: DNA polymerase, ligase, RNA polymerase,
helicase, and topoisomerase
• DNA and RNA
– Made of nucleotides, covalent bonds
– DNA- deoxyribose; RNA- ribose
– DNA- Thymine; RNA- Uracil
– DNA double stranded;
RNA single
• mRNA, tRNA, rRNA, and RNAi
• Transcription- RNA
polymerase builds
mRNA
– Initiation, Elongation,
Termination
• Post Transcription
modification
– Poly-A tail, GTP cap,
Excision of introns
• Translation occurs in the
ribosome.
• Steps to understand in Translation
1. The mRNA interacts with the rRNA of the ribosome to
initiate translation at the (start) codon.
2. The sequence of nucleotides on the mRNA is read in
triplets called codons.
3. Each codon encodes a specific amino acid, which can be
deduced by using a genetic code chart. Many amino
acids have more than one codon.
4. tRNA brings the correct amino acid to the correct place
on the mRNA.
5. The amino acid is transferred to the growing peptide
chain.
6. The process continues along the mRNA until a “stop”
codon is reached.
7. The process terminates by release of the newly
synthesized peptide/protein.
• Phenotypes are determined by protein
activities
– Enzymatic reactions
– Transport by proteins
• Genetic Engineering allows us to manipulate
DNA
– Electrophoresis,
plasmid-based
transformation,
PCR
In eukaryotes, heritable information is passed to
the next generation via processes that include the
cell cycle and mitosis or meiosis plus fertilization.
• Interphase
– Growth, DNA synthesis, preparation for Mitosis
• Cell Cycle is regulated by checkpoints (MPF)
• Cyclin and CDK control the cell cycle
• Cells may enter no division stage when it specializes,
but it can reenter the cell cycle when given
appropriate cues. Nondividing cells may exit the cell
cycle; or hold at a particular stage in the cell cycle.
• Mitosis passes a complete genome from the
parent of offspring (replication, alignment,
separation)
– Mitosis occurs after DNA replication
– Cytokinesis
– Growth, repair, and asexual reproduction
• Meiosis, a reduction division, increase
variation
– Homologous chromosomes pair, separate
independently and create gametes
– Fertilization involves the fusion of two gametes
The chromosomal basis of inheritance provides an
understanding of the pattern of passage
(transmission) of genes from parent to offspring.
• Segregation and Independent Assortment can be
applied to genes on different chromosomes
• Terms to know: Monohybrid , dihybrid, sexlinked, linked genes
• Disorders:
– Sickle cell, Tay-Sachs, Huntington’s
– Xlinked, Trisomy 21, Klinefelters
• Ethical, social, and medical issues
– Reproductive issues and ownership of genetic info
The inheritance pattern of many traits cannot
be explained by simple Mendelian genetics.
• Many traits are from MANY genes
• Sex linked recessive traits are always
expressed in males
• Nonnuclear inheritance
– Mitochondrial DNA is transmitted form the egg
Gene regulation results in differential gene
expression, leading to cell specialization.
• DNA sequence used for regulation
– Promoter, terminator, enhancer
• Bacteria and viruses
– Inducers turn on gene expression
– Repressors inhibit gene expression
– Regulatory proteins stimulate (positive control) and
inhibit by (negative control). Binding!
• Some genes are always turned on like Ribosomal
genes
• Eukaryotes
– Transcription factors bind to promoter region to start
transcription
– Activators (increase expression) some are repressors
(decrease expression)
• Gene expression accounts for phenotypic
differences with similar genes
A variety of intercellular and intracellular
signal transmissions mediate gene expression.
• Cytokines- cell replication
• Mating pheromones in yeast
• Levels of cAMP in bacteria
Changes in genotype can result in changes
in phenotype.
• May lead to the amount of protein produced
– Mutations may be positive/negative/neutral depending
on environmental context
• Mutations ( random change in genome)
• Mutations may change phenotype or fertility
• Changes in genotype lead to natural selection
– Antibiotic resistance mutations, pesticide mutations,
sickle cell heterozygous advantage
• Selection results in evolutionary change!
Biological systems have multiple
processes that increase genetic variation.
• The imperfect nature of DNA replication and
repair increase variation (Mutation)
• Transformation, transduction, conjugation, and
transposition
• Sexual reproduction in eukaryotes
– Crossing over, independent assortment, random
fertilization
Viral replication results in genetic variation, and viral
infection can introduce genetic variation into the hosts.
• Viral replication is
– Highly efficient allowing for rapid evolution
– RNA viruses lack replication error-checking mechanisms
thus
– Related viruses can combine info if they infect the same
host
– HIV has rapid evolution *retrovirus/reverse transcriptase
– Transduction and Transposons in incoming DNA
• Lytic vs. Lysogenic
Cell communication processes share common features
that reflect a shared evolutionary history.
• Stimulatory or inhibitory signals from other cells,
organisms, or the environment start signal
transduction (ligand, light wave)
• Bacteria use quorum sensing
• In multicellular organism signal transduction
pathways coordinate the activities in the cell that
support function of the organisms.
– Epinephrine=glycogen breakdown in mammals
– Temperature=sex determination in some vertebrates
– DNA repair mechanisms
Cells communicate with each other through direct
contact with other cells or from a distance via
chemical signaling
• Cell-to-cell
– Immune cells interact by cell-cell contact, antigenpresenting cells (APCs), helper T-cells and killer T-cells.
– Plasmodesmata between plant
• Short Distance
– Neurotransmitters
– Plant immune response
– Morphogens in embryonic development
• Long distance
– Insulin, HGH, Thyroid, testosterone, estrogen
Signal transduction pathways link signal
reception with cellular response.
• Rectption: ligand binds to receptor protein
– G-protein
– Ligand-gated ion channels
– Receptor tryosine kinases
• Transduction: signal converted to cellular response
– Signaling cascades, amplification
• Response: response to the msg
– Protein synthesis, protein modification,
Changes in signal transduction
pathways can alter cellular response.
• Signal transduction is blocked
– Diabetes, heart disease,
cancer,
– Effects of neurotoxins,
poisons, pesticides
– Drugs
Individuals can act on information and
communicate it to others.
• Organisms exchange information in response to
internal change and external cues. This may result
in reproductive success
– Fight of flight
– Predator warning
– Plant-plant interactions due to herbivory
• Different mechanisms
– Visual, audible, tactile, electrical and chemical signals,
find food, establish territory
• Bees dance, birds song, packing behavior, coloration
• Response to communication lead to natural
selection
Animals have nervous systems that detect external
and internal signals, transmit and integrate
information, and produce responses.
• Cell body, axon, dendrites, synapse, myelin sheath
• The structure allows for detection, generation,
transmission, and integration of signal information
• Action potential
– Maintained by
Na/K+
– Membranes
are polarized
by electrical
potentials
(Na+ and K+
channels)
• Neurotransmitters are chemical messengers:
acetylcholine, epinephrine, norepinephrine
• The response may be stimulatory or inhibitory