Environmental Expression of genes:
Certain genes are expressed under particular conditions, such as, temperature, geographic location, etc….
Examples: fruit flies….wings……temperature… 16ºC
-
straight 25ºC
-
curly
Himalayan rabbit… below 33ºC black in color… above… white
Oncogenes…..cancer
Green plants…. Size…shape….fullness
MUTATIONS
2 types
inherited
non
-
inherited
-
sex cell
-
body cell
1.
Chromosomal alterations:
-
seen phenotypically
Examples:
-
non
-
disjunction
-
polyploidy
-
more than one set of chromos
common in plants causing them to appear fuller,
vigorous, sterile (produce plants w/o seeds) ex.
potatoes, apples, watermelon, wheats
-
changes in chromo structure
-
breaking off or
attachment to another chromo
a
-
translocation: movement of part of a chromo
to a non
-
homologous chromo
b
-
Addition/ Deletion
-
parts are added or lost
C
-
Inversion
-
when the reading is upside down or
inverted
d
-
Duplication/ deletion
-
when a base is repeated or
completely
not included
2
-
Gene Mutation:
-
change in the chemical structure
-
some noticeable and
some are not ex. Albinism
-
most are recessive because you are not generally
homozygous
for a mutation
-
obviously not generally advantageous… most are lethal
Examples:
-
Point mutation
: affects one nucleotide, usually one is substituted
for another
-
Frame Shift
: occurs when there is an addition or deletion of a nucleotide
-
this totally shifts the
transcription of mRNA which in turn GREATLY affects the
function of the protein
3. Mutagenic Agents:
a. radiation
b. chemicals( medications, exposure on the job…..)
Detection of Genetic Defects:
1. Amniocentesis
2. Karyotyping
-
enlarged photo of homologous chromos
3. Screening
-
body fluids( sweat, urine….) detect presence or lack of certain enzymes
HOW DO WE GET AND KEEP DESIRED TRAITS???
1. Artificial Selection: mating individuals with desired traits
2. Inbreeding: breeding organisms with very similar genetic material/ or mating
organisms that have been
selectively breed
3. Hybridization: 2 species… 2 traits…. Hybrid population
4. Preservation: mutant recessive
–
vegetative propagation…grafting
Genetic engineering is when humans control breeding outcomes by either controlling DNA or the organisms that breed.
examples include:
selective breeding
In breeding
Induced mutations ( by radiation or chemicals)
-
this has proven successful with Bacteria ex. Oil digesters
-
successful with plants ex. Certain drugs prevent the
separation of chromos during meiosis( polyploidy)..
Strawberries
CONTROL OF DNA:
-
extracting
-
cutting/ splicing
-
requires the use of restriction enzymes…. The new DNA made
is called recombinant
DNA
-
separating…. Gel electrophoresis
TRANSFORMATION:
-
DNA outside the cell is taken in and it incorporates itself in the DNA within the
cell
-
bacteria
-
DNA molecule is called a plasmid…. If we incorporate a specific
piece of DNA into a
bacterial plasmid we can use them to help us make proteins
ex. Insulin…. Interferon
APPLICATIONS OF GENETIC ENGINEERING
-
Transgenic animals and plants( genetically modified)
… extra growth hormone…. Built in pesticides…..plants who make
human abs…golden rice…
CLONING:
-
involves the removal the nucleus from an egg cell and the insertion( generally) of
a somatic cell nucleus into that egg and then implantation of the cell into the uterus
of the “mother”
ex. DOLLY
Types of cloning include:
-
reproductive
-
theraputic
-
DNA
LAST, but NOT LEAST Population Genetics
Population genetics is the study of genetic characteristics of a species and of the factors that affect frequencies of genes
in
the
population.
A. Population
-
all members of a species in a given geographical location at a given time.
Ex. All the whitetail deer living in a mountain valley or all the dandelions
inhabiting a vacant lot
B. Gene Pool
-
sum total of all the inheritable traits in a given population
C. Gene Frequency
-
% of each allele for a particular trait in a population. Possible to
predict by applying simple statistical formulas to experimental data.
Ex. 60% of genes controlling ability to taste PTC paper are recessive, 40%
are dominant
Celebrity Sheep Died at Age 6
Dolly, the first mammal to be cloned from adult DNA, was put down by
lethal injection Feb. 14, 2003. Prior to her death, Dolly had been suffering
from lung cancer and crippling arthritis. Although most Finn Dorset sheep
live to be 11 to 12 years of age, postmortem examination of Dolly seemed to
indicate that, other than her cancer and arthritis, she appeared to be quite
normal. The unnamed sheep from which Dolly was cloned had died several
years prior to her creation. Dolly was a mother to six lambs, bred the old
-
fashioned way.
** also possible to predict proportion of a population that is homozygous and heterozygous
HARDY
-
WEINBURG PRINCIPLE:
-
the gene pool( gene frequencies) of a population should remain stable over many generations as long as
certain conditions are met.
1
-
ideal conditions include….large pop…sexes represented equally…random
mating…no migration in or
out…no mutations of genes or chromos occurs
** these conditions are rarely met in reality so therefore genetic stability cannot normally occur. Gene pools are instead in
a
steady state of dynamic change. This along with variation caused by genetic mechanisms is the driving force behind
evolution.
p2 + 2pq + q2 = 1
and
p + q = 1
p = frequency of the dominant allele in the population
q = frequency of the recessive allele in the population
p2 = percentage of homozygous dominant individuals
q2 = percentage of homozygous recessive individuals
2pq = percentage of heterozygous individuals
QOD: Decode the following message:
9 12, 15, 22, 5 7, 5, 14, 5, 20, 9, 3, 19
TRANSLATION….TRANSCRIPTION….REPLICATION
Hydrogen
bonds
Nucleotide
Sugar
-
phosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
DNA Structure
Growth
Growth
Replication fork
DNA polymerase
New strand
Original strand
DNA polymerase
Nitrogenous
bases
Replication fork
Original strand
New strand
DNA
Replication
DNA strand is opened by restriction enzymes…..mRNA reads the open
segment( translation) A
—
U G
---
C….mRNA than leaves the nucleus and
enters the cytoplasm in search of rRNA….once rRNA is found the single
strand of mRNA attaches to rRNA…..tRNA now enters the picture
(transcription)… tRNA reads each codon ( 3 bases)… a codon codes for
a specific amino acid..(replication) the AA are put in order to form a
specific polypeptide( a codon chart is used to assist in interpreting the
codons….
RNA
DNA
RNA
polymerase
Transcription
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
Messenger RNA
Messenger RNA is transcribed in the nucleus.
Transfer RNA
The mRNA then enters the cytoplasm and
attaches to a ribosome. Translation begins
at AUG, the start codon. Each transfer
RNA has an anticodon whose bases are
complementary to a codon on the mRNA
strand. The ribosome positions the start
codon to attract its anticodon, which is part
of the tRNA that binds methionine. The
ribosome also binds the next codon and
its anticodon.
mRNA
Start codon
Ribosome
Methionine
Phenylalanine
tRNA
Lysine
Nucleus
Translation
mRNA
The Genetic Code
Transcribe and Translate a
Gene
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