Genetics - Genetic Testing

Question 1

What is karyotyping?

Answer 1

It is a technique that produces an image of an individual’s chromosomes

The chromosomes are ordered in size and grouped together in their pairs

Question 2

What does karyotyping detect?

Answer 2

It is used to detect abnormal numbers or structures of chromosomes

Question 3

What are the three types of chromosome structures?

Answer 3

Metacentric

Sub-metacentric

Acrocentric

Question 4

What are metacentric chromosomes?

Answer 4

Those which have the centromere in the centre so that both sections are of equal length

Question 5

What are submetacentric chromosomes?

Answer 5

Those which have the centromere slightly offset from the centre leading to a slight asymmetry in the length of the two sections

Question 6

What are acrocentric chromosomes?

Answer 6

Those which have a centromere which is severely offset from the centre leading to one very long and one very short section

Question 7

What are FISH studies?

Answer 7

It is a technique that identifies where a particular gene falls within an individual’s chromosomes

Question 8

How do we conduct FISH studies?

Answer 8

We use fluorescent probes that are complementary to the genes we are trying to locate within the chromosome

Question 9

What are the four types of FISH probes?

Answer 9

Unique Sequence Probes

Centromeric Probes

Telomeric Probes

Whole Chromosome Probes

Question 10

What are unique sequence probes?

Answer 10

These probes bind to specific small segments of certain chromosomes

Question 11

What two chromosomal abnormalities are detected by unique sequence probes?

Answer 11

Microdeletion

Microduplication

Question 12

What are centromeric probes?

Answer 12

These probes target the centromeric region of the particular chromosome

Question 13

What is the function of centromeric probes?

Answer 13

They allow us to enumerate the number of centromeres and thus chromosomes of a particular kind

Question 14

What are telomeric probes?

Answer 14

These probes bind to telomeres, which are the repeat sequences found at the end of the chromosomes

Question 15

What are whole chromosome probes?

Answer 15

These probes are usually collections of smaller probes, each of which bind to a different sequence along the length of a given chromosome

Question 16

What two chromosomal abnormalities are detected by whole chromosome probes?

Answer 16

Translocations

Rearrangements

Question 17

What does PCR testing detect?

Answer 17

It is used to detect where DNA is replicated, allowing genes of interest to be screened for

Question 18

What are the five substances required to carry out PCR?

Answer 18

Sequence Information

Oligonucleotide Primers

DNA

Nucleotides

DNA Polymerase

Question 19

What are the three PCR steps?

Answer 19

Denaturation

Annealing

Elongation

Question 20

What is denaturation?

Answer 20

This is where the sample is heated to allow the double-stranded DNA to be separated into single strands

This is due to the fact that the heat is able to break the hydrogen bonds between the nucleotide base pairs in the two strands of DNA

Question 21

What temperature is used during denaturation?

Answer 21

93-95 degrees

Question 22

What is annealing?

Answer 22

This is where the sample is cooled

The DNA primer will bind to the target DNA sequences on the two DNA strands

Question 23

What temperature is used during annealing?

Answer 23

50-70 degrees

Question 24

What is elongation?

Answer 24

New strands of DNA are made using the original strands as templates

A DNA polymerase enzyme joins free DNA nucleotides together

The order in which the free nucleotides are added is determined by the sequence of nucleotides in the original DNA strand

Question 25

What temperature is used during elongation?

Answer 25

70 - 75 degrees

Question 26

What is the result of one PCR cycle?

Answer 26

Two double-stranded sequences of target DNA, each containing one newly made strand and one original strand

Question 27

What is gel electrophoresis?

Answer 27

It is used to separate DNA, RNA fragments or proteins based on their size and charge

Question 28

How do we conduct gel electrophoresis?

Answer 28

It involves running a current through an agarose gel containing the molecules of interest Based upon their size and charge, the molecules will travel through the gel in different directions and speeds, allowing them to be separated from one another

Question 29

What is restriction fragment length polymorphism (RFLP) analysis?

Answer 29

It is a technique that exploits variations in homologous DNA sequences, known as polymorphisms

Question 30

How do we conduct RFLP analysis?

Answer 30

It involves a fragmenting a sample of DNA with the application of enzymes, known as restriction endonucleases These enzymes can selectively cleave a DNA molecule wherever a short, specific sequences is recognised We then transfer these DNA fragments to a blotting sheet, where we add a labelled DNA probe This DNA probe determines the length of the fragments which are complementary to the probe A restriction fragment length polymorphism is said to occur when the length of a detected fragment varies between individuals, indicating non-identical sequence homologies

Question 31

What are restriction endonucleases?

Answer 31

They are enzymes from bacterial cells which are able to recognise specific DNA sequences and always cut DNA at the same site

Question 32

What is an amplification refractory mutation system (ARMS)?

Answer 32

It is a method for detecting any mutation involving single base changes or small deletions

Question 33

How do we conduct ARMS?

Answer 33

It involves the application of sequence-specific PCR primers that allow amplification of DNA when the target allele is contained within the sample Therefore, the presence or absence of a PCR product allows us to determine the presence or absence of the target allele If the target allele is present, then amplification of the DNA sequence will occur

Question 34

What does ELISA testing detect?

Answer 34

It is used to screen for specific antibodies in a patients serum

Question 35

What does Eastern blot testing detect?

Answer 35

The post-translational modification of proteins

Question 36

What does Western blot testing detect?

Answer 36

It is used to separate and identify proteins

Question 37

What disease is detected using Western blot testing?

Answer 37

Mad cow disease