advanced genetics chapter 9
TRANSCRIPT
CHAPTER 9
ADVANCED GENETICS
POPULATION GENETICS
The sum of all the alleles that
all individuals of a population
of organisms can possess is
called its gene pool.
The more genetic variability in
a population, the larger the
gene pool.
VARIATION
Variation in a population is
the range of genotype
differences between
individuals from the same
gene pool.
GENE FLOW
As people are born and
die or move to or away
from an area, there is a
constant incoming and
outgoing of genetic
information.
The ebb and flow of
genetic material in a
population is called gene
flow.
ALLELE FREQUENCY
Some alleles are more
common than others.
How often an allele shows
up in a gene pool is the
allele frequency.
Example: blue eyes
SOURCES OF GENETIC VARIABILITY
1. Reproduction
2. Lateral gene transfer
3. Mutations
REPRODUCTION
Different types of alleles
combine when two
parents reproduce.
Additional genetic
variation happens during
crossing over in meiosis, in
which chromosome pairs
switch information to form
new combinations of
alleles.
LATERAL GENE TRANSFER
Single-celled organisms such as bacteria can
exchange genes through plasmids.
Plasmids are small, circular DNA molecules that
function like chromosomes.
MUTATIONS
A cell can make mistakes when copying or
decoding DNA.
Mutations in somatic cells are not passed down to
offspring.
Mutations in gamete cells can be passed down to
introduce variation and new traits into a
population.
Mutations are usually harmful to an organism or
population.
MUTATIONS
The number of mutations sustained by an
organism or population is its mutation load.
Genetic load- a measure of the health and fitness
of a population.
Heavier mutation= heavier genetic load= less
healthy population.
GENETIC EQUILIBRIUM
In large populations with
thousands of individuals,
the allele frequency is
stable. This is called
genetic equilibrium.
THE HARDY-WEINBURG PRINCIPLE
Allele frequencies in a
population will remain
constant from generation
to generation for a
population in genetic
equilibrium.
Possible only in large
populations.
GENETIC DRIFT
No population is ever truly at equilibrium because
it is constantly changing.
Small populations are at risk for genetic drift,
which is a change in the allele frequency based on
random events.
GENETIC DRIFT- BOTTLENECK EFFECT
Genetic drift can happen
when a large portion of
the population dies
(bottleneck effect).
GENETIC DRIFT- FOUNDER EFFECT
Genetic drift can also
happen when a small
population moves to a
new area (founder effect)
and starts a new
population.
GENETIC DRIFT- THE FOUNDER EFFECT
GENE MUTATIONS
Gene- a section of DNA that can be decoded to
create a certain protein.
Mistakes in the process of decoding, copying and
using DNA can sometimes occur, called
mutations.
A mutation represents a genetic error that is
produced when a nucleotide base in a section of
DNA is added, deleted or substituted in either
replication or decoding (transcription or
translation).
MUTAGEN
Some mutations happen randomly, and some are caused by a mutagen, a physical or chemical substance that changes genetic structure.
A mutagen could be any toxin in the form of a virus, radiation, or a chemical (cigarette smoke, pollutants, dyes, etc.).
TYPES OF MUTATIONS Germ mutations- mutations in
gametes or in cells that produce
gametes.
Get passed down to the next generation
Affect every cell in the offspring
produced
Somatic mutations- mutations in cells
that don’t make gametes (body cells).
Not passed down to the next generation
Affect only a few cells of the original
organism
TYPES OF MUTATIONS
Point mutation- when just one nucleotide base changes in the DNA chain, whether it is substituted, added or deleted.
Substitution may not be harmful to the organism.
If a nucleotide base is added or deleted, the base shifts the whole codon, producing a frameshiftmutation.
This means that when RNA is coded from the DNA, it will probably make a very different protein than it would have before the mutation.
This is likely to cause problems for an organism.
FRAMESHIFT MUTATION
CHROMOSOMAL MUTATIONS Telomeres are the tips of
chromosomes.
An enzyme called telomerase keeps the telomeres stable during meiosis.
If a mutation that stops the production of telomerase occurs, the telomeres get shorter and shorter, leading to cell death.
If a mutation causes telomerase to be produced continually, the telomeres mutate, which can lead to uncontrolled cell division.
CHROMOSOMAL MUTATIONS
Deletion- the complete loss of
a segment of the chromosome.
Inversion- the chromosome
fragment reattaches in an
inverted position (upside
down).
NONDISJUNCTION
The failure of the chromosomes to separate is
called a nondisjunction.
A nondisjunction leads to gametes that either have
extra chromosomes or not enough (aneuploidy).
A monosomy (2n-1) has one less chromosome
A trisomy (2n+1) has one extra chromosome
A nondisjunction doesn’t change the entire set of
chromosomes of an organism. It simply adds or
subtracts a chromosome from an otherwise normal
set.
NONDISJUNCTION- ANEUPLOIDY
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POLYPLOIDY Cells with three or more sets of chromosomes exhibit polyploidy.
Occurs when gamete cells do not divide properly.
2n 2n2n 2n 2n2n
2n 2n 2n
2n
1n 1n 1n
3n 4n
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MUTATIONS AND CELL GROWTH
When a mutation
affects genes that
control cell growth,
mutated cells can
begin to divide
uncontrollably.
This produces an
abnormal mass of cells
called a tumor.
TUMORS
Benign tumors don’t spread to other parts of the body.
Malignant tumors can spread to other parts of the body, meaning they metastasize.
Malignant tumors can cause major parts of an organism to shut down, as they interfere with life-sustaining processes.
CANCER
CANCER TREATMENT
The main goal of treating cancer is to destroy
abnormal cells in ways that do the least amount of
damage to healthy cells.
The best ways to kill abnormal cells are to poison,
burn, or cut them out.
In most patients, a combination of these therapies
are used.
CANCER TREATMENT
Chemotherapy uses chemicals to poison and
disrupt cell processes in abnormal cells so that
they can’t divide, killing the cells and shutting down
their reproduction.
Radiation therapy uses high doses of energetic
radiation to burn cancer cells in ways that slow
down or stop their growth completely.
Surgery is used to cut out clumps of abnormal cells
that have formed a tumor.
Substances like radiation, tobacco smoke,
and certain chemicals that increase one’s
cancer risk are called carcinogens.
GENOMICS
Genomics is the study of
genomes, or the complete set of
genetic information present in
an organism.
The Human Genome Project
was a scientific study to identify
and list all human genes, the
phenotypes they express, and
the variations in these
phenotypes.
GENOMICS
Researchers have found that the genomes of two
different people share 99.9% of the same
information.
1.5% codes for making proteins.
24% contains codes that control genes.
59% is code that is duplicated in other places in
human DNA.
GENETIC ENGINEERING
Genetic engineering is the
process of deliberately
manipulating the genes within
an organism in ways other than
natural processes.
It involves changing an
organism’s DNA by inserting
new genetic material.
READING DNA
To begin studying an
organism’s genome,
researchers must isolate
DNA from that organism.
DNA molecules/
chromosomes are too long
to work with easily, so they
must be divided into
pieces.
READING DNA
Restriction enzymes are used
to cut the DNA in specific
places into pieces for study.
The DNA is then sequenced to
determine the order of
nucleotides in an organism’s
DNA.
SHOTGUN SEQUENCING
Restriction Enzymes
MANIPULATING DNA
Genetic engineers often need to make multiple
copies of a section of DNA before working on
them.
They use the cell’s own natural process of DNA
replication to generate millions of copies of
DNA in just a few hours.
The process of making multiple copies of a
gene under study is called the polymerase
chain reaction (PCR).
POLYMERASE CHAIN REACTION
RECOMBINANT DNA
-DNA that has had small sections of DNA from another organism (same or different species) inserted.
GENETICALLY MODIFIED ORGANISMS (GMOS)
GMOs are organisms that have undergone
genetic engineering.
Geneticists can use recombinant DNA to
introduce genes from other living things of the
same species or of different species.
Organisms that contain genes from a different
species are called transgenic organisms.
TRANSGENIC ORGANISMS
GENE THERAPY
Genetic engineering used to change a gene in an organism to relieve a genetic disorder is called gene therapy.
Gene therapy relies on a microscopic vehicle known as a vector to deliver recombinant DNA.
Vectors are usually bacteriaor viruses.
GENE THERAPY VECTORS
Scientists use vectors to transfer
new genetic material to an
organism in order to change its
DNA.
After the new DNA has been
inserted, the therapeutic DNA
produces proteins needed to
reverse a disease.
GENE THERAPY PROBLEMS
Gene therapy is never a permanent solution.
Sometimes the treatment doesn’t last for long
periods of time or even work at all.
Often gene therapy must be continued for life.
Scientists are still experimenting with gene
therapy in clinical trials.
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DNA FINGERPRINTING
The process of using fragments of DNA to identify
individuals is called DNA fingerprinting.
No two people have the same DNA, except for
identical twins.
DNA FINGERPRINTING USES
DNA profiling can be used to clear the innocent
and incriminate the guilty.
Another important use is identifying lost family
members or the remains of people killed in natural
disasters or accidents.
DNA testing can also be used to diagnose
inherited disorders in newborns, such as cystic
fibrosis, hemophilia, sickle-cell disease, etc.
GEL ELECTROPHORESIS1. DNA is isolated from a sample.
2. The isolated DNA is cut with a
restriction enzyme.
3. Fragments of DNA are loaded into the
well of a gel.
4. An electric current moves the
negatively charged DNA fragments toward
the positive end of the gel.
5. As they move through the gel, the DNA
fragments are sorted by size with the
smallest pieces moving the farthest.
6. Bands of different lengths of DNA are
revealed by staining the finished gel.
DNA FINGERPRINTING (PROFILING) IN FORENSICS
DNA FINGERPRINTING (PROFILING) IN FORENSICS
Suspect 2
DNA FINGERPRINTING TO SHOW PATERNITY
DNA FINGERPRINTING TO SHOW PATERNITY
Male 2