Gene Technology 2

Question 1

Genome Sequencing

Answer 1

Finding the sequence of bases in a DNA molecule

Question 2

Genome

Answer 2

Total Genetic make-up of an organism

Virus - genetic info in its DNA strand (or RNA retrovirus)

Prokaryote - comp of single loop of naked DNA and any plasmids present

Eukaryote - complete nucleotide sequence in a haploid set of chromosomes

Question 3

Genome Sequencing Organsims

Answer 3

•orgs that are used in genetic research - used extensively in study of heredity and gene function

•orgs that can cause disease - bacterium E. coli pathogenic, and parasites Plasmodium - malaria

•orgs that can provide valuable info about evolutionary ancestry of the modern human - chimpanzees and neanderthal

Question 4

Proteome

Answer 4

Entire set of proteins expressed by a genome

Question 5

The Human Genome

Answer 5

•more than 3 billion base pairs

•more than half of non-coding DNA consists of variable repeat sequences

•98% DNA does not code for proteins

•2% DNA codes for proteins and includes 21000 genes

•Single nucleotide substitutions occur in coding & non-coding areas - variants called SNPs

•in polypeptide-coding genes , SNPs represent allelic differences and are used as markers of variation

•SNPs vary in only about 0.1% human genome - accounts for thousands diff alleles

•SNP alleles identified which are linked to genetic disease, predisposition to disease and to diff responses to drugs

Question 6

SNPs

Answer 6

Single Nucleotide Polymorphisms

Question 7

Applications of Genome Sequencing

Answer 7

1. Creating Phylogenetic Trees
2. Detecting Genetic Disease
3. Detecting Predisposition to Certain Diseases
4. Analysing genomes of pathogens
5. Creating 3D models of protein structure
6. Producing Personalised Medicine

Question 8

What does Genetic Testing using Microarrays commonly determine

Answer 8

•genotypes in multiple regions of a genome - defected detected for diagnosing disease

•gene expression for a large number of genes simultaneously

Question 9

Gene Expression

Answer 9

A gene is expressed when its switched on so that mRNA is transcribed to encode the synthesis of a protein

Question 10

Microarrays

Answer 10

Gene Chips or DNA Chips

Consist of hundreds to tens of thousands of different DNA probes anchored within spots to a solid surface

Each spot contains many molecules of particular probe - diff spots possess probes comp to diff known genes

Question 11

Principle behind microarray technology

Answer 11

Hybridisation between the DNA probe and any complementary single stranded DNA obtained from tissue tested

Question 12

Genotyping

Answer 12

DNA from person being tested extracted, genes cut out, made single stranded and labelled w/ fluorescent dye

After adding to microarray, DNA fragment hybridises with probe, colour change occurs

Computer analysis of results will reveal whole range of genes in persons genome incl faulty alleles of particular genes

Question 13

Testing for Gene Expression

Answer 13

mRNA extracted from tissue and converted, using reverse transcriptase enzyme, into single stranded copy DNA (cDNA) each w/ fluorescent tag

Labelled cDNA molecules added to microarray and will hybridise with any complementary probe

Hybridisation of cDNA and probe indicates that gene was expressed in the tissue

Question 14

Diagnosing Activity of Oncogenes Using Microarrays

Answer 14

Labelled cDNA prod from mRNA extracted from healthy and cancer tissue
-diff fluorescent dyes used to tag

Mixture of both sources added to microarray so both hybridise probes

Microarray scanned with laser - exciting tags and generating signals - strength dependant on amt of cDNA binding to probes at each spot

Spots with both colours tags mixed show genes that are active in both healthy and cancer tissue

Spots of healthy colour are switched off in cancer tissue

Spots of cancer colour are switched on in cancer tissue - some of which oncogenes which may be deactivating or activating other genes

Question 15

Pharmacogenetics

Answer 15

Study of genetic differences in drug metabolic pathways - which affect individual responses to drugs

Question 16

Inactivation of Drugs

Answer 16

CYP2 enzymes responsible for breakdown drugs - activity depends on which allele responsible for production

Some rapid-metabolising some poor metabolisers

Clinical effect greater in poor metabolised because of rate of elimination of drug

Question 17

Standard dose of drugs rapid vs poor metabolisers

Answer 17

Rapid Metabolisers may get no benefit from drug

Poor metabolisers may suffer effects of an overdose

Question 18

Activation of Drugs

Answer 18

Codeine mist be first converted by enzyme CYP2D6 to its active form morphine before becoming effective

Gene encoding for enzyme is CYP2D6 - variant alleles

Poor metaboliser gets no pain relief - Rapid incr risk of breathing problems

Question 19

Personalised Medicine

Answer 19

Choosing treatments for people based on knowledge of individual personal genetic profiles rather than using the same treatment for all

Question 20

Breast cancer gene

Answer 20

30% HER2 gene
Activity shut down by trastuzumab - expensive and ass with cardiac toxicity

Question 21

Designer Drugs

Answer 21

Drugs created to match an individuals genetic profile