Mutations & Genetic Engineering

Indicator B – 4.8: Compare the consequences of mutations in body cells

with those in gametes.

Indicator B – 4.9: Exemplify ways that introduce new genetic characteristics

into an organism or a population by applying the principles of modern genetics.

1.  Mutation 2.  Point mutation 3.  Frameshift mutation 4.  Mutagen 5.  Clone 6.  Genetic engineering 7.  Recombinant DNA 8.  Transgenic 9.  Genomics 10.  Human Genome Project 11.  Gene therapy 12.  Artificial selection (selective breeding)

A mutation is any change in the DNA sequence that causes a change in the amino acid sequence, thus a variation in the protein.

� Mutations can occur many ways: ¡  They can be inherited from the parent(s). ¡  They can occur in an egg or sperm cell just after

fertilization. ¡  They can be acquired during the organism’s

lifetime.

Fertilized Egg

Mutation Occurs

Brain Pancreas Bone Reproductive

Body Cells of Offspring

Mutation

Sperm Egg

� Mutations in Gametes

¡  Can be passed on to offspring.

¡  May result in poorly formed or nonfunctional proteins.

¡  May be lethal.

� Mutations in Somatic Cells ¡  Not passed on to

offspring. ¡  Can interfere with cell

function. ¡  Due to mitosis, the

mutation will be passed on to other cells.

� Two types: ¡  Gene Mutations ¡  Chromosomal Mutations

�  Result from changes in a single gene.

�  Point mutation ¡  Occur at a single point. ¡  A nucleotide can be

substituted for another and can change the entire sequence of amino acids therefore messing with the protein.

Normal Reading Frame:

THE FLY HAD ONE RED EYE Point Mutation on Reading Frame:

THE FLY HID ONE RED EYE Remember: DNAàRNAàAmino Acidsàproteins.

� Due to a point mutation in the Beta Globin gene.

� DNA should be C T C but is actually C A C. � RNA should be G A G but is actually G U G. � This change causes a change in the amino acid.

Normal hemoglobin & RBC Sickled hemoglobin & RBC

�  Frame-shift Mutation ¡  Involves deletions

and insertions of nucleotides.

¡  Can change the entire reading frame of the codon, thus causing problems with the protein.

Normal Reading Frame:

THE FLY HAD ONE RED EYE Insertion:

THE FLY QHA DON ERE DEY Deletion:

THE FLH ADO NER EDE YE Remember DNAàRNAàAmino Acidsàproteins.

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�  Involves changes in the number or structure of chromosomes.

�  May change the locations of genes on the chromosomes and even the number of copies of some.

�  Four types: ¡  Deletion ¡  Duplication ¡  Inversion ¡  Translocation

May lead to genetic

disorders

You have extra sex chromo-somes. 47XXY 47XXX 48XXXY 48XXYY 49 XXXXY

Turner Syndrome Cri du Chat Syndrome

Down Syndrome is the most recognizable

of these, but there are others.

� Polyploidy usually leads to death in animals.

� Some plants are successful with extra set(s) of chromosomes.

In some cases mutations are beneficial to organisms. Beneficial mutations are changes that may be useful to organisms in different changing environments. These mutations result in phenotypes that are favored by natural selection and increase in population.

Antibiotic resistant bacteria is an example of a beneficial mutation-at least from the point of view from the bacteria.

� Mutations can lead to genetic disorders.

� By examining a pedigree, geneticists can also see the likelihood of an individual inheriting a genetic disorder.

A pedigree is a chart constructed to show an inheritance pattern within a family through multiple generations. Through the use of a pedigree chart and key, the genotype and phenotype of the family members and the genetic characteristic can be tracked.

Unaffected Female

Unaffected Male

Mating

Offspring Affected female offspring

Unaffected male Offspring

§  Changes are possible that will NOT lead to a change in the protein…not a mutation.

� Mutations occur about 1/100 000 000 bases. � Wobble position: 3rd base in codon provides

protection against mutation. � Ex: CCA, CCG, CCC, CCU = proline � DNA has proofreading enzymes that can repair

mismatches before transcription.

The role of DNA polymerase is to proofread a frame before it is ready to be translated. Often, this enzyme can catch a mutation before it goes through translation, but not always. If the mutation is caught and correct, the organism will never be affected. However, if it doesn’t then the organism will be affected.

� Mutagens are factors such as radiation, chemicals, ultraviolet light, etc. that can cause changes in DNA. Some are natural, others are not.

Check out some mutagens....and what they do!

Mutagens