Chromosomal Biology 2

Question 1

What is non-disjunction?

Answer 1

Failure of homologous chromosomes or sister chromatids to separate properly during cell division

Question 2

Name autosomal aneuploidy syndromes.

Answer 2

Down Syndrome
Patau Syndrome
Edwards Syndrome

Question 3

In Down syndrome where is the extra chromosome?

Answer 3

21

Question 4

In Patau syndrome where is the extra chromosome?

Answer 4

13

Question 5

In Edwards syndrome where is the extra chromosome?

Answer 5

18

Question 6

Name sex chromosomes aneuploidy syndromes.

Answer 6

Turners syndrome (45, X)
Klinefelter syndrome (47,XXY)

Question 7

What are the classes of chromosomal structural abnormalities?

Answer 7

balanced or unbalanced arrangements 
translocations 
deletions 
insertions
inversions

Question 8

What are the two kinds of translocations?

Answer 8

Reciprocal and Robertsonian

Question 9

What is reciprocal translocation?

Answer 9

Involves breaks in two chromosomes with formation of two new derivative chromosomes

Question 10

What is Robersonian translocation?

Answer 10

Fusion of two afrocentric chromosomes

Question 11

What can unbalanced translocation lead to?

Answer 11

a partial trisomy and a partial monosomy

Question 12

What are the different types of coding mutations?

Answer 12

Silent/synonymous (polymorphism)
missense
nonsense
frameshift (insertion/deletion)

Question 13

What are the two kinds of point mutations?

Answer 13

Transitions - purine to purine or pyrimidine to pyrimidine

Transversions - purine to pyrimidine, pyrimidine to purine

Question 14

What techniques can be used to detect mutations?

Answer 14

Polymerase chain reaction (PCR)
gel electrophoresis
restriction fragment length polymorphism (RFLP) analysis
amplification refractory mutation system (ARMS)
DNA sequencing

Question 15

What is needed for PCR?

Answer 15

sequence information 
oligonucleotide primers 
DNA 
nucleotides 
DNA polymerase

Question 16

What are the 4 steps of PCR?

Answer 16

denature, anneal, extend, repeat

Question 17

What does electrophoresis do and how?

Answer 17

separates DNA fragments by size
by applying electric field, DNA is negative charged so it is separated through agarose gel matrix allow visualisation of DNA fragments

Question 18

What are the advantages of electrophoresis?

Answer 18

speed
ease of use
sensitive
robust

Question 19

What are the applications of PCR?

Answer 19

DNA cloning 
DNA sequencing 
in vitro mutagenesis 
gene identification 
gene expression studies 
forensic medicine 
typing genetic markers 
detection of mutations

Question 20

How does ARMS work?

Answer 20

By using normal and mutant primers and detecting amplification using both, will show if mutant or wild type DNA

Question 21

What are the advantages of ARMS?

Answer 21

cheap

labelling not required

Question 22

What are the disadvantages of ARMS?

Answer 22

electrophoresis required
primer design critical
need sequence information
limited amplification size

Question 23

What are restriction endonuclease?

Answer 23

Enzymes from bacterial cells which degrade DNA of invading viruses (by recognising specific DNA sequences (always cut at same site on DNA))

Question 24

How can these be used in detecting mutations?

Answer 24

If the DNA is mutant endonuclease won’t recognise it and so won’t cut it so only one long fragment will show up on electrophoresis, if normal shows up as two fragments, and if heterozygous shows up as one long and two shorter fragments.

Question 25

What are the advantages and disadvantages of using restriction endonuclease?

Answer 25

Simple
cheap
non-radioactive

requires gel electrophoresis
not always feasible

Question 26

What does the Sanger Sequencing method use?

Answer 26

Dideoxynucleotides

Question 27

What are the advantages and disadvantages of Sanger sequencing?

Answer 27

Gold standard for mutation detection
automation and high throughput

expensive equipment
poor quality sequence read