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