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 & heteroploidy?

Answer 3

Triploidy is the prescnene of an extra set of chromosmes (total 69)
Tetraploidy is the pressne of 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

What numerical abnormality causes severe developmental problems with most dying in the first month or year of life?

Answer 10

Trisomy 18 or Edwards syndrome

Question 11

What is Turner syndrome?

Answer 11

45,X

A lack of a sex chromosome from the father.

Question 12

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

Answer 12

• Short stature & infetile
• 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 because all DNA is present.

Question 16

What is an unblanced translocation?

Answer 16

Parents chromosome have undergone a balanced translocation.

So they can form gametes that are lacking 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

The 2 long arms are fused and the short ones lost, this way no gnentic material is lost.

Question 19

What are the 2 types of deletion?

Answer 19

Terminal - DNA removed form the chromosme end

Interstitial - DNA removed from an innner part of the 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 the 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

When a base changes but the 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 a STOP codon.

Question 26

How does a frameshift mutation occur?

Answer 26

Deletion or insertion shifts the 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 the DNA you started with. | Can be repeated many times to produce huge numbers of copies.

Question 30

What does Gel Electrophoresis do?

Answer 30

Seperated DNA fragments by size through agarose gel matrix by applying an electric field to the -ve DNA so you can visualize the 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 Endonucleases always cut DNA at speciic points in a chain of bases . So use an endonuclease then PCR to see the length of the cut section. This will tell if its 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

They stop a DNA polymersation reaction so you can analyse a small section of DNA

Question 36

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

Answer 36

The dideoxynucleotides are dyed with fluorescant dye so you can see which bases ones join where