Chromosomal Abnormalities

Question 1

What is trisomy?

Answer 1

extra copies of a chromosome

Question 2

What is monosomy?

Answer 2

A diploid chromosome complement where one lacks its homologous partner

Question 3

What is triploidy & teroploidy?

Answer 3

Triploidy - extra set of chromosomes (total 69)
Tetraploidy - 2 extra sets of chromosomes (total 92)

Question 4

How do numerical abnormalities mainly arise?

Answer 4

When chromosmes dont divide properly during meiosis (non-junction)

Question 5

What is another name for trisomy 21?

Answer 5

Downs syndrome = Trisomy 21

Question 6

What are characteristics of trisomy 21?

Answer 6

Maternal (chances increase with age)
Distinc facial characteristics
Alzhiemers in later life
IQ < 50
50-60 yr life expectancy.

Question 7

What is Trisomy 13 called?

Answer 7

Patau Syndrome = Trisomy 13

Question 8

Characteristics of trisomy 13?

Answer 8

Mental retardation
Dysmorphic features
Maternal
Most die in 1st year

Question 9

What is Trisomy 18 called?

Answer 9

Edwards Syndrome = Trisomy 18

Question 10

Characteristics of Trisomy 18

Answer 10

Severe developmental abnormalities
Most die in first month or year of life

Question 11

What is Turner syndrome?

Answer 11

45,X
Lack of a sex chromosome from father

Question 12

What are characteristics of 45,X (turners syndrome)?

Answer 12

• Short stature & infertile
• All female
• Neck webbing & widely spaced nipples
• 97% die at conception

Question 13

What is 47, XXY called?

Answer 13

Klinefelter Syndrome = 47,XXY

Question 14

What are characteristics of Klinefelter syndrome?

Answer 14

• Tall & long limbed
• Infertile, small testes
• 50% develop breasts (gynaecomastia)
• Mild learning difficulties.

Question 15

What is a balanced translocation?

Answer 15

Non-Homologous Chromosomes break and repair with some DNA swapped
Usually fine since all DNA is present.

Question 16

What is an unblanced translocation?

Answer 16

Parents chromosome have undergone balanced translocation.
Can form gametes that lack some material & have some duplicated

Question 17

What kind of chromosoes are affected by robertsonian translocations?

Answer 17

Those with one long arm and one short containing no coding DNA. (Acrocentric)

Question 18

How are two chromosmes fused in robertsonian translocation?

Answer 18

2 long arms are fused and short ones lost
No genetic material is lost

Question 19

What are the 2 types of deletion?

Answer 19

Terminal - DNA removed form chromosome end
Interstitial - DNA removed from inner part of chromosome

Question 20

What are the 2 types of inversion?

Answer 20

Paracentric - Part of one arm is inverted
Pericentric - DNA on either side of centromere is inverted (both arms change)

Question 21

What is polymorphism?

Answer 21

Mutations in genes with no phenotypic effect

Question 22

What are 4 sub-types of Coding mutations?

Answer 22

Silent
Missense
Nonsense
Frameshift

Question 23

What is a silent coding mutation?

Answer 23

Base changes but amino acid is unchanged

Question 24

What is a missense coding mutation?

Answer 24

One amino acid is changed to another

Question 25

What is a nonsense coding mutation?

Answer 25

One amino acid is changed to STOP codon

Question 26

How does a frameshift mutation occur?

Answer 26

Deletion or insertion shifts whole chain along

Question 27

What does PCR stand for?

Answer 27

Polymerisation Chain Reaction

Question 28

What are the 3 steps of PCR?

Answer 28

Denature, Anneal, Extend

Question 29

What is the result of PCR?

Answer 29

Two copies of DNA Repeated many times to produce huge numbers of copies

Question 30

What does Gel Electrophoresis do?

Answer 30

Separated DNA fragments by size through agarose gel matrix Applying electric field to -ve DNA Can visualise DNA.

Question 31

What does ARMS stand for?

Answer 31

Amplification Refractory mutation system

Question 32

What does RFLP stand or?

Answer 32

Restriction Fragment Length Polymerisation

Question 33

How does RFLP work?

Answer 33

Certain Endonuclease always cut DNA at specific points in a chain of bases . Uses Endonuclease then PCR to see length of cut section Show if normal, mutant or heterozygous

Question 34

Whats another name for Sanger DNA sequencing?

Answer 34

Chain Termination method

Question 35

Why are dideoxynucleotides used in SANGER DNA sequencing?

Answer 35

Stop DNA polymersation reaction Can analyse small section of DNA

Question 36

How can the base sequence be determined in chain termination DNA sequencing?

Answer 36

Dideoxynucleotides dyed with fluorescent dye Can See where bases joins