Diagnostic DNA Tests

Question 1

How we can detected protein abnormalities?

Answer 1

biochemical tests for the presence of excess

substrate or lack of product.

Question 2

The mutation that cause PKU?

Answer 2

phenylalanine hydroxylase (that
catalyses the conversion of Phenylalanine →Tyrosine) is defective (eg. amino acid 408 is
tryptophan instead of arginine).

Question 3

Screening for PKU is most commonly by?

Answer 3

direct

measurement on blood>

Question 4

What happen on babies having this disease pku?

Answer 4

phenylalanine enters the blood. ▪ In days, phenylalanine accumulation causes
brain damage.

Question 5

Treatment of pKU must be initiated by the ?

Answer 5

second week

Question 6

Spina bifida can be detected on week ?

Answer 6

13

Question 7

What is spina bifida?

Answer 7

Abnormality that leaves a proteins of spinal cord to exposed

Question 8

At which week we do the operation to treat spina bifida

Answer 8

24

Question 9

Genetic screening meaning ?

Answer 9

detects human gene mutations

directly at the DNA level.

Question 10

advantage of testing DNA for mutations directly is ?

Answer 10

Any cell can be tested at any time in the life cycle. • DNA tests allow pre-natal diagnosis.

identify people who are predisposed to, or
carriers (heterozygotes)

Question 11

Pre-implantation

screening).meaning ?

Answer 11

PCR allows testing from

an 8 cell embryo before implantation.

Question 12

Cells are obtained in Pre implantation screening from ?

Answer 12

chorionic villus sampling (10th

week of pregnancy) or amniocentesis (13 - 17th week).

Question 13

Routine methods of DNA testing are?

Answer 13

➢ Allele-specific cleavage
, ➢ Allele-specific oligonucleotide hybridization, and
➢ Allele-specific PCR.

Question 14

Which DNA test is Easier and faster than allele-specific cleavage?

Answer 14

Allele-specific Oligonucleotide Hybridization

Question 15

Which DNA test can detect any known sequence change?

Answer 15

Allele-specific Oligonucleotide Hybridization

Question 16

Allele-specific PCR relies on the?

Answer 16

last base of a primer matching
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with the template.

Question 17

PCR results:?

Answer 17

• If the DNA is normal – only the normal sequence primer
will give a product.
• If the sequence is mutant – only the mutant primer will
give a product.
• If both sequences are present (in a heterozygote) then
both primers will give a result.

Question 18

Diagnosing Infectious Disease mechanism?

Answer 18

Little target sequence (template) is required
and specificity of primers (must match
pathogen DNA) means tests are extremely
sensitive.

Question 19

Testing for HIV Infection by blood and DNA test ?

Answer 19

Traditional test detects antibodies to the virus.
May take weeks for body to produce sufficient antibodies to yield a positive result (chance of a false negative result).

•DNA extracted from a blood sample can be
analysed by PCR in combination with a tagged hybridization probe

Question 20

Advantages of DNA test of HIV?

Answer 20

➢ Earlier treatment ➢ Prevention of transmission ➢ Screening of newborns

Question 21

DNA Fingerprinting.

What is the Two types of inherited sequence are informative

Answer 21

• Single nucleotide polymorphisms (SNPs).
• Short tandem repeats (STR) - these are repetitive DNA
sequences giving rise to side-by-side repeats in the
chromosome. Ideally the number of repeats differs in
the two parents. Use 8 different STRs to generate
unique patterns

Question 22

Uses of DNA fingerprinting include?

Answer 22

➢ DNA matching technology
➢ Criminal investigations
➢ Paternity / Family relatedness
➢ Forensic pathology

Question 23

DNA Fingerprinting

From where you can get the DNA ?

Answer 23

blood, semen, hair, or

tissue samples.

Question 24

Example of using DNA in Paternity / Family relatedness?

Answer 24

Baby 81

Russian Royal Family

Question 25

Investigating Gene Function at the Genome Level?

Answer 25

DNA microarrays (“chips”) permit the screening
of thousands of sequences at the same time.

Question 26

Classes of DNA Microarrays (“Chips”)?

Answer 26

1. Arrays of cdnas (prepared in advance) delivered
   by direct microspotting to a glass surface (chip)
2. Arrays of oligonucleotides synthesized directly
   onto the chip surface

Question 27

Applications of DNA Chips

Answer 27

1. Expression screening

➢ Monitoring of RNA expression levels for the genome
2. Screening of DNA variation
➢ Use oligonucleotide arrays to:

• Assay mutations in known disease genes • Catalogue human single nucleotide
polymorphism (SNP) markers

Question 28

Expression Screening by DNA Chips steps ?

Answer 28

• Carried out as a differential hybridization
• Prepare mRNA from two sources; usually
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control and disease (e.g. cancer)
• Convert mRNA to cDNA
• Label each cDNA population with a different
fluorescent tag (red and green commonly used)

Question 29

What the Data Provides

From Expression Screening by DNA Chips.?

Answer 29

• Inducible gene expression -response to environmental
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change or infection
• Tissue- and cell type- specific gene expression • Developmental stage-specific gene expression
• Gene expression during cancer; difference between
cancers

Question 30

Inducible Gene Expression – Response to Infection

Example ?

Answer 30

Ebola virus

• Zaire variant kills humans; Reston variant affects
monkeys not humans.
• Analysis of 1,400 genes expressed in lymphocytes.
• Two key sets of genes are activated in Ebola Zaire, but
not in Ebola Reston.

Question 31

What’s on the horizon ?

Answer 31

Fetal gene screening using maternal blood
Cost per genome now <
US$10,000 and falling
eg. Materni21T, a Down’s syndrome test (Sequenom, USA)
• Whole genome sequencing