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OZZIE SKINNER MT(AMT), CLT, MAOM

JAMES A. HALEY VA HOSPITAL

MOLECULAR DIAGNOSTICS

03/23/2013

MUTATIONS What and how do mutations occur?

A mutation is a permanent change in the DNA sequence of a gene Can cause problems with growth, development, and function of the body’s systems

Mutations in a gene's DNA sequence can alter the amino acid sequence of the protein encoded by the gene

These changes can affect many genes along the chromosome and disrupt the proteins made from those genes

The effects of structural changes depend on their size and location, and whether any genetic material is gained or lost

Can affect the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus

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MUTATIONS What and how do mutations occur?

Mutations range in size from a single DNA building block

(DNA base) to a large segment of a chromosome

Gene mutations occur in two ways: they can be inherited

from a parent or acquired during a person’s lifetime Hereditary (or germline) mutations: are passed from parent to child

Acquired (or somatic) mutations: occur in the DNA of individual cells at some time during a person’s life

These changes can be caused by environmental factors or if a mistake is made as DNA copies itself during cell division

Acquired mutations in somatic cells (cells other than sperm and egg cells) cannot be passed on to the next generation

Some genetic changes are very rare; others are common in the population

Genetic changes that occur in more than 1 percent of the population are called polymorphisms 3

MUTATIONS Affects on health and development

A gene is a recipe for making a protein

Each cell depends on thousands of proteins to do their jobs in the right places at the right times

By changing a gene’s instructions for making a protein, a mutation can cause the protein to malfunction or to be missing entirely

When a mutation alters a protein that plays a critical role in the body, it can disrupt normal development or cause a medical condition

A condition caused by mutations in one or more genes is called a genetic disorder

Incompatible with life: changes occur in genes that are essential for development, and often disrupt the development of an embryo in its earliest stages

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MUTATIONS Affects on health and development

Only a small percentage of mutations cause genetic disorders

Some mutations alter a gene’s DNA base sequence but do not change the function of the protein made by the gene

Often, gene mutations that could cause a genetic disorder are repaired by certain enzymes before the gene is expressed (makes a protein)

Although most mutations that change protein sequences are harmful or neutral, some mutations have a positive effect on an organism (e.g. 32 base pair deletion in human CCR5/Delta 32 mutation/HIV resistance)

5“Mutations are often Bad, but,……………………..…..………… some can be Good”

MUTATIONS

First, Smallpox, then The Black Death of 1348 Came out of the East, and reached the shores of Italy in

the spring of 1348. Unleashed a rampage of death across Europe. Within three years, anywhere between 25% and 50% of

Europe's population had fallen victim to the pestilence.

The plague presented itself in three interrelated forms: The bubonic variant (the most common)

+ swellings or buboes that appeared on a victim's neck, armpits or groin.

+ Victims had a life expectancy of up to a week

+ Infected fleas that attached themselves to rats and then to humans spread this bubonic type of the plague.

Pneumonic plague

+ attacked the respiratory system and was spread by merely breathing the exhaled air of a victim.

+ life expectancy was measured in one or two days.

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Oriental rat flea“Regurgitates”

MUTATIONS The Black Death, 1348 Septicemic version of the disease attacked the blood system

Having no defense and no understanding of the cause of the pestilence, the men, women and children caught in its onslaught were bewildered, panicked, and finally devastated

The plague disease, generally thought to be caused by Yersinia pestis. (Gram negative, bipolar staining coccobacilli)

The "black death" again devastated Europe during the 14th century over a 5 year period causing 25 million deaths

Who was to blame?

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MUTATIONSThe Black Death, 1348 - DNA evidence

Survivors However, some were able to survive the devastating Black Plague,

such as the residents of Eyam, England The village had quarantined itself in order to stop the plague from

spreading beyond the village

Investigation In October 2010 a multinational medical group investigated the role

of Yersinia pestis in the Black Death They tested DNA and protein signatures specific for Y. pestis in

human skeletons from widely distributed mass graves all over Europe that were associated archaeologically with the Black Death.

The new research ends the debate about the etiology of the Black Death, and decidedly demonstrates that Y. pestis was the causative agent of the epidemic plague that devastated Europe during the Middle Ages

The obvious question,

How did the residents of Eyam survive?. 8

MUTATIONS They developed the Delta 32, CCR5 Mutation in the gene for the human chemokine receptor 5 (

CCR5)

How HIV Enters the White Cells – The Mechanism

Some rare strains of HIV infect via the CXCR4 receptor so by no means does a positive result for CCR5 delta 32 allow someone to engage in risky behavior

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Chromosome 3

MUTATIONSMutations are caused by:

Radiation: Alpha particles, Beta particles, Gamma rays, Cosmic rays, and X-rays,

can wreak havoc on the molecules of your DNACytosine and Thymine – are most vulnerable to radiation that can

change their propertiesThe effect of the radiation may not be to kill the cell, but to alter its

DNA code in a way that leaves the cell alive but with an error in the DNA blueprint

VirusesViruses that use RNA as their genetic

material have rapid mutation rates

An advantage since these viruses will evolve constantly and rapidly, and thus evade the defensive responses of e.g. the human immune system.

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MUTATIONSMutations are caused by: Transposons: (jumping genes)

Sequences of DNA that can move or transpose themselves to new positions within the genome of a single cell

The mechanism of transposition can be either "copy and paste" or "cut and paste“

Oncogenes (genes that cause tumors) may be activated by the random reshuffling of transposons to a position adjacent to the oncogene

Barbara McClintock found that they were responsible for a variety of types of gene mutations: insertions, deletions and translocations

In developing somatic tissues like corn kernels, a mutation that alters color will be passed on to all the descendant cells

This produces the variegated pattern

which is so prized in Indian corn

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MUTATIONSMutations are caused by:During DNA replication: (SNP/Point mutation)

The replacement of a single base nucleotide with another nucleotide of the genetic material, DNA or RNA

Single-nucleotide polymorphisms may fall within coding sequences of genes, non-coding regions of genes, or in the intergenic regions (regions between genes)

Often the term point mutation also includes insertions or deletions of a single base pair

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MUTATIONS

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MUTATIONSMutations are caused: During DNA replication: (SNP/Point mutation)

Point mutations can also be categorized functionally: Nonsense mutations: Premature stop codon in a DNA sequence

or in the transcribed mRNA Nonsense mutations are known to cause Cystic fibrosis, Beta

thalassaemia , and Hurler syndrome Start codon (ATG) Methionine DNA stop codons are TAG, TAA, and TGA RNA stop codons are UAG, UAA, and UGA

14Lack the enzyme to break down long chains of sugar molecules

MUTATIONSMutations are caused by: During DNA replication: (SNP/Point mutation)

Point mutations can also be categorized functionally: Missense mutations: point mutation in which a single nucleotide

is changed, resulting in a codon that codes for a different amino acid

Missense mutations are known to cause sickle-cell disease

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sickle-cell disease

Aspartic acid

Glutamine

MUTATIONSMutations are caused by: During DNA replication: (SNP/Point mutation)

Point mutations can also be categorized functionally: Silent mutations: DNA mutations that do not result in a change to the

amino acid sequence of a protein A point mutation that changes a codon to a synonym (one that codes for

the same amino acid) is also known as a synonymous mutation About 50 genetic diseases have been linked to synonymous mutations This includes silent mutations in CFTR, the gene that is linked with

Cystic fibrosis.

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MUTATIONSMutations are caused by: Deletions:

A mutation in which a part of a chromosome or a sequence of DNA is missing

Deletion is the loss of genetic material Deletions can be caused by errors in chromosomal crossover during

meiosis (process of cell division in sexually reproducing organisms)

Small deletions are less likely to be fatal; large deletions are usually fatal

Deletions genetic disorders can range from:

Male infertility to Duchenne muscular dystrophy to “Cri du chat”

ExampleOriginal The fat cat ate the wee rat.

Deletion The fat ate the wee rat.17

Notice anything unusual? Cri du chat syndrome / 5p- syndrome

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MUTATIONSMutations are caused by: Duplications

Duplications occur when part of a chromosome is copied (duplicated) too many times

This type of chromosomal change results in extra copies of genetic material from the duplicated segment

Duplications arise from an event termed unequal crossing-over that occurs during meiosis between misaligned homologous chromosomes (corresponding chromosomes from each parent)

Duplications of oncogenes are a common cause of many types of cancer

ExampleOriginal The fat cat ate the wee rat.

Duplication The fat cat cat ate the wee rat.

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MUTATIONSMutations are caused by: Inversions

An inversion involves the breakage of a chromosome in two places; the resulting piece of DNA is reversed and re-inserted into the chromosome

Genetic material may or may not be lost as a result of the chromosome breaks

An inversion that involves the chromosome’s constriction point (centromere) is called a pericentric inversion

An inversion that occurs in the long (q) arm or short (p) arm and does not involve the centromere is called a paracentric inversion

Example

• Original: The fat cat ate the wee rat.

• Insertion: The fat tar eew eht eta tac.20

MUTATIONSMutations are caused by: Inversions

On the left of the diagram is human chromosome

number 5 (of 23)

On the right of the diagram is the matching

chromosome from a chimpanzee

The region from p14.I to q14.I, the order has been

flipped

Evolutionist calls this a inversion mutation between

Man and Chimp

Overall, there are nine inversion mutations between

man and chimpanzee

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Chromosome 5

MUTATIONSMutations are caused by: Isochromosomes

An isochromosome is a chromosome with two identical arms

Instead of one long (q) arm and one short (p) arm, an isochromosome has two long arms or two short arms

As a result, these abnormal chromosomes have an extra copy of some genes and are missing copies of other genes

Associated diseases Girls with Turner syndrome Pallister-Killian syndrome Some tumors

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MUTATIONSMutations are caused by: Dicentric chromosomes: human chromosome 2

Unlike normal chromosomes, which have a single constriction point (centromere), a dicentric chromosome contains two centromeres

Dicentric chromosomes result from the abnormal fusion of two chromosome pieces, each of which includes a centromere.  These structures are unstable and often involve a loss of some genetic material

Associated diseases Myelodysplasia (MDS):

A collection of conditions that result when

bone marrow cells produce damaged

cells that don't mature properly

Acute Myeloid Leukemia (AML)

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MUTATIONSMutations are caused by: Ring chromosomes Ring chromosomes usually occur when a chromosome breaks in two places and

the ends of the chromosome arms fuse together to form a circular structure

The ring may or may not include the chromosome’s constriction point

In many cases, genetic material near the ends of the chromosome is lost

Ring chromosomes may form in cells following genetic damage by mutagens like radiation, they may also arise spontaneously during development

Associated diseases Ring chromosome 20 syndrome - epilepsy Ring chromosome 14/13-mental retardation Ring chromosome 15 - dwarfism

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MUTATIONSMutations are caused by: Translocation: juxtapositioning

When chromosomes break and the fragments rejoin to other chromosomes

A gene fusion may be created when the translocation joins two otherwise separated genes, the occurrence of which is common in cancer

It is detected on cytogenetics or a karyotype of affected cells

Translocations can be balanced or unbalanced

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MUTATIONSMutations are caused by: Translocation: balanced translocation

In a balanced translocation, pieces of chromosomes are rearranged but no genetic material is gained or lost in the cell

When a person's cells divide to create egg or sperm cells for reproduction, the egg or sperm cells can end up with extra genetic material or missing genetic material

This could lead to miscarriage depending on which chromosome and genes are affected

In about 4.5% of all couples with recurrent miscarriages, one or both parents has a balanced translocation

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MUTATIONSMutations are caused by: Translocation: unbalanced translocation

An unbalanced translocation occurs when a child inherits a chromosome with extra or missing genetic material from a parent with a balanced translocation

This is usually in the form of a loss of genetic material, called Monosomy and a gain to genetic material, which is Trisomy

Monosomy/ Trisomy Both types of are “aneuploidy” :

(having an abnormal number of

chromosomes)

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MUTATIONSMutations are caused by: Trisomy 21/Downs S.

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MUTATIONS

Mutations are caused by: Monosomy X - genotype 45, X,

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MUTATIONS

Different Types of Mutations

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MUTATIONSMyostatin- is a gene that limits muscle growth The protein is a member of a superfamily of molecules called transforming

growth factors beta (TGF-b) or growth differentiation factor 8 Discovered that a mutation in the myostatin gene is responsible for increased

muscle mass, also known as 'double muscling‘ Scientists hope that myostatin inhibitors may be able to treat diseases such as

muscular dystrophy There is some concern about the possibility of abuse of myostatin inhibitors

by athletes In humans, myostatin is encoded by the

MSTN gene Animals lacking myostatin, have significantly

larger muscles

Transgenic Rainbow Trout

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MUTATIONSMyostatin-related muscle hypertrophy

•

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Who wants some “rump roast?”

myostatin modulator

“It taste God awful;You said it tasted like chicken”. You lied mama, you lied.

If you see me coming at you, don’t run. My muscles are so tight, I couldn’t catch a cold.

Siblings

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Shukran