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Flashcards in Biotechnology and Evidence for Evolution Deck (48)
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1

What is genetic engineering

Allows foreign modified DNA to be introduced into another cells

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What are the implications of genetic engineering

Can replace fault genes with healthy ones

Can produce synthetic hormones such as insulin for diabetics

Can produce vaccines

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Types of genetic engineering

Both types are cut by restriction enzymes

1. Straight cut and blunt ends
2. Staggered cuts and sticky ends

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Step 1 of genetic engineering

Isolate gene
Cut the gene using restriction enzyme at restriction site

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Step 2 of genetic engineering

Isolate a plasmid
Cut the plasmid with same restriction enzyme

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Step 3 of genetic engineering

Sticky ends and plasmid DNA anneal to each other
Spliced together by ligase

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Step 4 of genetic engineering

Bacteria takes up recombinant plasmid
Copies of recombinant plasmid are made
Copies placed into host cells
Host cells produce protein the gene codes for

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What is electrophoresis

Profiling technique
Used to determine individuals DNA profile

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Step 1 of electrophoresis

DNA fragments placed into cavities

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Step 2 of electrophoresis

Electric current passed through gel

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Step 3

DNA moves through to positive electrode from negative electrode

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Step 4

Smaller fragments move fast
Larger fragment move slower and shorter
Forms bands of gel

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Step 5

Forms a DNA fingerprint

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Implications of Electrophoresis

Tracing ancestry
Forensic science
Identifying hereditary diseases

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Definition of DNA sequencing

The determination of the precise order of nucleotides in a sample of DNA

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What is DNA sequencing

When building a DNA strand each new nucleotide is bonded to the hydroxyl group of the previous strand,
no hydroxyl group to bond to, no additional nucleotides can be added, so chain is terminated

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Step 1 of DNA sequencing

Double stranded DNA molecule is extracted

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Step 2 of DNA sequencing

Denatured at 90-96 degrees
split into two
only work with the template strand

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Step 3 of DNA sequencing

A primer is then annealed to the template strand

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Step 4 of DNA sequencing

The copies of the unknown DNA strand are made using 4 reactions mixtures
→ Template DNA strand with primers attached
→ DNA polymerase
→ Large amount of normal deoxynucleotides (dNTPs)
→ Small amount of fluorescently dyed synthetic nucleotides called Dideoxynucleotides (ddNTPs) that don't have the hydroxyl groups present

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Step 5 of DNA sequencing

DNA polymerase works in the reaction mixtures by adding nucleotides to the primer to complete the complementary strand

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Step 6 of DNA sequencing

DNA polymerase continues to add free nucleotides until a synthetic dideoxynucleotide is used without the OH group which terminates the elongation of the sequence

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Step 7 of DNA sequencing

We are left with a range of strands of varying lengths, all ending with one of the 4 possible fluorescently dyed dideoxynucleotides
→ This allows us to overlay the strands of various lengths to reveal the complete sequence of bases of the unknown strand

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How to determine the sequence

multiple copies are added to an electrophoresis gel
a current is passed through the samples of varying lengths they move away from the negative electrode towards the positive electrode

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Implications of DNA sequencing

point mutations, insertions and deletions can be detected

Diseases which can be determined such as cystic fibrosis

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Definition of Polymerase Chain Reaction

Used to multiply segments of DNA through a series of repeated cycles

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Step 1 of PCR

Denaturing

Solution is heated (94-98) degrees
The heat disrupts the hydrogen bonds causes separation of the DNA strands into single strands

28

Step 2 of PCR

Annealing

Temperature reduced to 50-65 degrees to allow a primer, to join the complementary strand

At this temperature the primers anneal with the complementary sequence of DNA to start the replication from taq polymerase

Forward and reverse primers are needed for both sides as they are designed to bracket the DNA region to be

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Step 3 of PCR

Extending

Temperature rose again to 72 degrees
Taq polymerase binds to primers
The Taq polymerase synthesises new DNA strand
Segments of single stranded DNA are replicated

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Applications of PCR

DNA profiling
DNA from fossils can be amplified
Detect hereditary diseases

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Gene Therapy

Aims to treat genetic abnormalities by replacing fault gene with healthy gene

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Cell Replacement

Stem cells are undifferentiated cells that are capable of mitotic divisions for long periods of time. stem cells are used in genetic engineering

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Gene therapy and cell replacement

Stem cells is taken from patient
Mutant gene replaced with normal gene
Cells multiply
Cells transferred back into patient

34

Human Genome Project

Enables us to identify mutation in a gene
Enabled us to identify the abnormal protein causing the disease
Gene therapy and genetic engineering are treatments which help genetic diseases

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Ethical Considerations

Autonomy, respect the right for an individual to be tested, if tested, to know and share the information
Confidentiality, the genetic information is treated sensitively
Equity, the right to fait and equal treatment regardless of genetic information

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Comparative DNA studies

In each species, the sequence of nucleotides varies. If more similar the DNA sequence then the organisms are more closely relate and are more likely to have a common ancestor.

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Example of Comparative DNA studies

Endogenous Retrovirus, a viral sequence that has become apart of an organism's genome

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Comparative Mitochondrial DNA studies

The higher the degree of similarity between mtDNA of two individuals the closer their evolutionary relationship

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Example of Comparative Mitochondrial DNA studies

MtDNA

40

Comparative Protein Sequence Studies

Every protein has a number of amino acids. Similarity of amino acid sequence is evidence of close evolutionary relationship

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Example of comparative protein sequence studies

Ubiquitous protein, Cytochrome C which performs basic tasks for cellular energy. To compare Cytochrome C sequences they need to be aligned so that the maximum number of positions containing the same amino acid can be determined. The more similarity between the molecules, the more recently they have diverged from a common ancestor

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Phylogenetic Trees

Comparative studies allow scientists to work out the evolutionary relationship between groups of organisms

Phylogenetic tree represents the evolutionary relationships between organisms derived from a common ancestor

The ancestral organism forms the base of the tree and these organisms that have arised from it are placed on the ends of the branches

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Comparative Embryology Studies

Comparative embryology studies will show how the closely related organisms will show similar anatomical development in the embryonic stages of life which will show they all share a common ancstor

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Example of Comparative Embryology Studies

In all vertebrae species:
- Embryonic gill pouches
- Presence of a tail
- Two chambered heart

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Comparative Homologous Structures

Organs that are very similar in structure but have different functions due to environmental selection pressure. Organisms possessing homologous structures that are similar are more likely to share a common ancestor

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Example of Homologous Structures

Forelimb of the vertebrae

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Comparative Vestigial Organs

The structures which are the remains of organs that were required in ancestral form. These organs are no longer essential. These organs suggest ancestral relationship with organisms that have functional forms of the same organs

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Example of Vestigial Organs

- Nictitating membrane
- Third molars
- Appendix