Week 7 - CoastalZone.com

hollandmercifulBiotechnology

Dec 11, 2012 (4 years and 6 months ago)

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Week 7


DNA Chapter 13


Nucleus contains DNA.


DNA is composed of molecular subunits called nucleotides. Each nucleotide
consists of 3 parts

1.

a five carbon sugar, deoxyribose

2.

a phosphate group

3.

a nitrogen containing organic compound called a base.


There
are four bases: cytosine (C), thymine (T) are called pyrimidine bases,



Adenine (A) and guanine (G) are called purine base


Consider these four bases as an alphabet, the sequence in which they occur
determines the genetic message…


Double helix discover
ed by Watson and Crick…2 strands.


Adenine (A) always pairs with thymine (T) and guanine (G) always pairs with
acytosine (C), so that by knowing one sequence you will always be able to know
its corresponding sequence.


In the Synaptic Phase of Interph
ase the DNA “unzips” and each side is used as a
template to replicate a complete DNA strand…each replicated DNA strand
consists of one new strand and one old strand, this is called semiconservative
replication.


DNA replication is never 100% accurate…some

errors in replication occur…if
there is a change the change would be passed on to all subsequent generations.
Mutations.


DNA is organized into chromosomes and is wound around a protein called
histones. Read about how DNA is organized on page249.


Chapt
er 14 RNA and protein synthesis


Proteins you will remember are one of the important groups of organic
compounds. Proteins are critical to cell life at various times, serving in the
transport of oxygen, cell movement, etc.


Proteins are larger complex mo
lecules composed of amino acids joined by
peptide bonds. Long chains of amino acids are called polypeptides…(pg 254)


While the gene is the fundamental unit of heredity, but DNA does not actually
generate any of the proteins that express genetic messages.


Ribonucleic acid (RNA) acts as a messenger to the protein from the DNA.


RNA synthesis is similar to DNA replication in that the DNA strand unzips and in
a process called transcription RNA is synthesized in the nucleus. The RNA then
detaches from the
DNA template and leaves the nucleus. The DNA molecule
“rezips”.


The RNA goes to a ribosome which reads the message and produces a specific
polypeptide chain…this product is called translation.


In RNA thymie is replace by the base uracil. Uracil will l
ink up with adenine like
thymie would. RNA are not double helixes but are single strands. There are 3
main tyes of RNA:

1.

Messenger RNA


carries coded instruction fro protein snthesis

2.

Transfer RNA


carries specific amino acides to ribosomes during
protei
n assembly

3.

Ribosomal RNA


make up part of the ribosomes.


Pg 255 firefly gene in tobacco plant


Chp 16

Recombinant DNA Technology and Genetic Engineering



Concerns about developing ecologic or health issues with new bacteria.


Page 295 second paragraph
“Recent history has failed to bear out these
worries…:


Chp 17 Darwin and Natural Selection


Pg 302


Evolution


genetic changes that occur in a population over time.


Artificial Selection
-

choosing plants and animasl for breeding based on
characteristic
s



Natural selection


pg 306

1.

Overproduction

2.

Variation

3.

Competition

4.

Survival to reproduce


Neo
-
darwinism or Synthetic Theory of Evolution
-

emphasizes the genetics of
populations rather than just individuals… more generally accepted than
Darwinism.


Sci
entific evidence in support of the Theory of Evolution



Fossil Record

-

bias in the fossil record…fossils are not a random
sample of life in the past because of the conditions which must exist for fossils to
exist.



Comparative Anatomy of different orga
nisms

(pg 308, figure 17
-
7)


Infer the presence of homologous traits in ancestors. Features similar in
structure in different species are said to be homologous


Features that are not homologous but have similar functions are said to be
analagous. (lungs o
f mammals and trachae of insects)



Analagous organs demonstrate the different ways in which species
adapted to the world…convergent evolution



Vestigial organs…parts that no longer serve and apparent function…in
humans, reduced tail bones, wisdom teeth,
muscles that move ears, the
appendix. Whales and pythons have vestigial rear legs. Blind cave dwellers
have vestigial eyes.



Distribution of Plants and Animals


biogeography


evolution of a species
occurs just once…center of origin (a range of origin)



Related species have similar patterns of development


embryos



Biochemical and Molecular Comparisons


the genetic code is universal
(the same amino acid codes occur in different species) and certain proteins


Chapter 18, Microevolution and Speciati
on

Pg 320


VARIATION…


Population…gene pool includes all possible alleles…where an individual can
have only two possible alleles of a trait…


If a population is not undergoing evolutionary change the frequencies of each
allele will remain constant from ge
neration to generation. Small changes in the
frequency of alleles over several generations are indications of
evolution….microevolution

small gradual changes in a population over time.


Hardy
-
Weinberg Principle


Genetic equilibrium…not undergoing evoluti
onary change. Phenotypes
approximately the same from year to year or generation to generation. The
frequency of genotypes can be mathematically determined The Hardy Weinberg
Principle shows that the process of inheritance by itself will not cause changes

in
allele frequencies.


In a stable (never occurs in nature) system the proportion of alleles in successive
generations will always be the same as long as :

1.

Random mating
-

mates must not be selected by genotype

2.

No mutations



3.

Large population size


mo
del is statistically based so that there must
be a large enough sample…

4.

No migration…

5.

No natural selection…


EVOLUTION OCCURS WHEN THERE ARE CHANGES IN ALLELE
FREQUNECIES IN THE GENE POOL!


Variation is introduced through mutations.


Genetic Drift


produc
tion of random evolutionary changes in small breeding
populations…changes in the gene poll from generation to generation…tends to
decrease genetic differences within a population but increase differences among
different populations.


Founder Effect
-

Indiv
iduals establishing a new colony represent only a small
portion of the gene pool and genetic variation of the original population. This
form of genetic drift is called the founder effect.


Genetic Bottlenecks
-

Depletion of food supply or disasters


Gene
Flow
-

Migration of individuals is also migration of alleles, gene flow


Natural Selection results in allele frequency changes that increase adaptation to
the environment


natural selection checks the random effects of mutation,
genetic drift and gene flo
w. Phenotypes “selected” because of advantages in
environment, underlying genotypes go with them…


SELECTION


Note the figure on page 327, Figure 18
-
4

Stabilizing selection tends to weed out phenotypes at the edges of the
population


Directional selecti
on tends to select for a certain trait toward the edge of a
population, favors one phenotype over another


Disruptive section tends to select for the edges and against the most common
phenotype



GENETIC VARIATION IS NECESSARY FOR EVOLUTION


Genetic Polymo
rphism



Genetic Variation by Heterozygous Advantage
-



“Nuetral” Mutations
-

effect phenotype in small immeasurable ways…


Reproductive Isolation


biological species concept…members of a species
freely interbreed with other members of the species, pro
duce fertile offspring and
do not interbreed with other species in nature.


Isolation Mechanisms
-


temporal isolation (seasonal isolation) (pg 331)





Behavioral isolation (sexual isolation) courtship
signals





Mechanical isolation (parts)


SPECIATION


Allopatric Speciation
-

geographic isolation over a long period of time (pg 333
Fig 18
-
10)


Sympatric Speciation





Chapter 19 Macroevolution and the History of Life




Macroevolution refers to major evolutionary events that occur in groups of
species o
ver long periods of time….large phenotypic changes such as wings, or
the hoof, the thumb, standing…


These new features all are derived from existing structures. An existing feature
is changed in some way which allows the phenotype an adaptive advantage…


How do such changes occur?


Rates of growth determined by regulatory genes…example of infant body
proportions on page 340…


Adaptive Radiation


one or two species expand to fill a variety of ecological
roles “quickly”


Adaptive Zones are new ecologica
l roles or ways of living not previously used by
the organism.. Night flying to catch insects…grazing on grass during migration,
swimming at the oceans surface…see Figure 19
-
4 on page 342


Adaptive radiation appears to occur more often during periods of e
nvironmental
change but it is difficult t determine of changes in the environment “trigger”
adaptive radiation


Mammals existed with dinosaurs but didn’t go through adaptive radiation until
dinosaurs were extinguished…


Is there a cause and effect relation
ship?


Extinction:



The end of the line…2 types
-

background extinction and mass extinction


Background Extinction is Continuous low levels of extinction


Mass extinctions of numerous species over a period of time (often followed by
mass speciation)


EVOLU
TIONARY CHANGE


Punctuated equilibrium


long periods of stasis (no change) followed by short
periods of rapid speciation


Gradualism


evolution proceeds at more or less a steady rate


LIFE


Life began from nonliving matter in a combination and recombinat
ion of simple
molecules into more complex molecules, into macromolecules that were the
precursors of cells.


In the early periods of earth the atmosphere contained little free oxygen, carbon
dioxide, carbon monoxide, water vapor hydrogen and nitrogen made

up the bulk
of the atmosphere. Probably contained ammonia, hydrogen sulfide and methane
as well.


Ultrviolet radiation would work to break down the ammonia, methane and
hydrogen sulfide.


Oceans were formed as the world cooled and water vapor condensed

and
formed the oceans.


Four requirements of the environment to form life from nonliving matter:

1.

No free oxygen


oxygen is very reactive and would break down
(dissolve) the organic macromolecules before life could develop

2.

A source of energy
-

high energy
availability in this early earth, electric
storms, radiation, solar radiation, heat from volcanism, etc.

3.

Chemical building blocks


water vapor and inorganic compounds
present as ions (to dissolve in water)

4.

Time


time for accumulation, and chance (4.6 bi
llion years)


The earliest cells were prokaryotes


fossils found 3.1 to 3.5 billion years ago


Early form of life
-

stromalites very old but some living stromalites are still
found in hot springs and salt water pools



Early cells were heterotrophs that is

they had to find and absorb the
molecules they used for food as opposed to synthesizing them.


Anaerobes


living in a low or no oxygen environment


Autotrophs (make own food from photosynthesis)
-

cyanobacteria first organisms
to split water to obtain hy
drogen necessary to reduce CO2 for food. O2 released
as a by product. Over time O2 accumulates in atmosphere…


Some organisms grew to tolerate and then use oxygen.


ENDOSYMBIONT THEORY
-

organelles such as mitochondria and chloroplasts
may have originat
ed from a mutually beneficial symbiotic relationship Early
eukaryotes were combination of cells that originally lived apart but that grew to
depend on the relationship with each other…ingested but not digested by the
cell..


FOSSIL RECORD


Geolgoic Time
is divided into five eras (Archean, Proterozoic, Palezoic, Mesozoic
and Cenozoic). Each era is divided into periods and periods are divided into
epochs.