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Principles of Disease > Chromosome Mutations and Abnormalities - Second Lecture > Flashcards

Chromosome Mutations and Abnormalities - Second Lecture Flashcards

1
Q

What are the three different types of chromosomal abnormalities?

A

Numerical, structural, mutational

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2
Q

What is the result of non-disjunction?

A

Two gametes with disomy (meiosis 1)

1 gamete with disomy - (meiosis 2)

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3
Q

What is trisomy 21 known as?

A

Down’s Syndrome

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4
Q

What is trisomy?

A

The addition of an extra chromosome

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5
Q

What is responsible for 50% of first trimester miscarriages?

A

Trisomy mutations

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6
Q

What are the features of someone with down’s syndrome?

A

Characteristic facial dysmorphologies IQ less than 50 Average life expectancy (50-60 years) Alzheimer’s disease in later life

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7
Q

What is trisomy 13 known as?

A

Patau syndrome Incidence: 1 in 5000 Multiple dysmorphic features and mental retardation

About 5% die within first month, very few survive beyond first year Non-dysjunction (90%), maternal origin Unbalanced Robertsonian translocation (10%)

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8
Q

What is Trisomy 18 known as?

A

(Edwards syndrome) Incidence: 1 in 3000 Severe developmental problems; most patients die within first year, many within first month

Non-disjunction (90%), maternal origin

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9
Q

What is 45, X mutation known as?

A

Turner syndrome Incidence: 1 in 5000 to 1 in 10000 (liveborn) Incidence at conception much greater, about 97% result in spontaneous loss

Females of short stature and infertile Neck webbing and widely spaced nipples Intelligence and lifespan is normal Female because there is no Y chromosome

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10
Q

What is 47,XXY mutation known as?

A

(Klinefelter syndrome) Incidence: 1 in 1000 Tall stature, long limbs Male but infertile, small testes, about 50% gynaecomastia Mild learning difficulties

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11
Q

What are the terms used to describe complete or incomplete retention of DNA during a mutation?

A

Balanced or unbalanced

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12
Q

What is the definition of a balanced translocation?

A

There is still a complete set of DNA between the two chromosomes, if the translocation takes place in a non-critical location, there will be no major effects to the individual

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13
Q

What is meant by reciprocal translocation?

A

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

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14
Q

What are the different types of Structural abnormalities?

A

Deletions Insertions Inversions Translocations

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15
Q

What is the effect of unbalanced translocation on the gametes produced?

A

Production of gametes with, partial trisomy and partial monosomy, this will result in offspring with abnormal phenotypes

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16
Q

What are accrocentric chromosomes?

A

One of the arms of the chromosome is very short

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17
Q

What is robertsonian translocation?

A

When the two longer arms of accrocentric chromosomes combine, the short arms are lost and also fuse together

18
Q

What does Robertsonian translocation result in

A

Balanced - normal gametes

Unbalanced - Trisomy and Monosomy

19
Q

What is pericentric inversion?

A

When the inversion takes place over the centromere

20
Q

What is polymorphism?

A

The natural genetic variation within a populaiton

21
Q

What are the different types of genetic mutations?

A

Germline or somatic

Gene disruption /disease-associated

Polymorphism

22
Q

What are the types of non-coding mutations?

A

Coding mutations -

Silent – synonymous e.g. CGA (Arg) to CGC (Arg) (GIVES THE SAME AMINO ACID)

Missense (A MISSENCE MUTATION IS A POINT MUTATION WHICH A SINGLE NUCLEOTIDE CHANGE RESULTS IN A CODON THAT CODES FOR A DIFFERENT AMINO ACID)

Nonsense (CODON FOR AMINO ACID IS CHANGED TO A CODON THAT CODES FOR A CHAIN TERMINATING CODON)

Frameshift – deletion / insertion

23
Q

What are transitions - point mutations?

A

Purine to purine or pyrimidine to pyrimidine

24
Q

What are transversions?

A

Purine to pyrimidine or vice versa

25
Q

Learn Mutation Nomenclature

A

.

26
Q

What do we use to detect mutations?

A

Polymerase chain reaction (PCR)

Gel electrophoresis

Restriction fragment length polymorphism (RFLP) analysis Amplification refractory mutation system (ARMS)

DNA sequencing

27
Q

What do we need for PCR?

A

Sequence information

Oligonucleotide primers

DNA Nucleotides

DNA polymerase

28
Q

What are the three stages of PCR?

A

Denaturation - 93-95 degrees celcius

Anneal - 50-70 93-95 degrees celcius

Extend 70-75 93-95 degrees celcius

29
Q

Why is taq polymerase used?

A

Heat resistant

30
Q

What is used to separate DNA fragments?

A

Gel electrophoresis

31
Q

What is the charge of DNA?

A

Negatively charged

32
Q

What does Gel Electrophoresis allow?

A

Visualisation of DNA fragments

33
Q

What are the advantages of Gel Electrophoresis

A

Speed Ease of use Sensitive Robust

34
Q

What are the PCR applications?

A

DNA cloning

DNA sequencing

In vitro mutagenesis

Gene identification

Gene expression studies

Forensic medicine

Typing genetic markers

Detection of mutations

35
Q

What are the advantages of Amplification Refractory Mutation System?

A

Cheap

Labelling not required

Primer design critical

36
Q

What is the principle of the Amplification Refractory Mutation System?

A

Specific primers anneal to sample DNA

If a mutant primer is used and amplification occurs then the presence of a mutant allele can be conformed

If a normal normal primer is used and amplifiacation occurs then the presence of a wild type allele can be confirmed

37
Q

What are the disadvantages of Gel electrophoresis?

A

Need sequence information

Limited amplification size

Limited amounts of product

Infidelity of DNA replication

38
Q

What is the action of endonuclases?

A

Recognise specific DNA sequences

Always cut DNA at the same site

39
Q

How are endonucleases used to detect mutations?

A

They cut the DNA at a portion of mutated nucleotide sequence - cutting of the DNA strand only occurs at mutated site, length of travel on the gel therefore gives indication of mutation

Two bands gives indication of a carrier

40
Q

What are the Advantages / disadvantages of restriction endonucleases?

A

Simple Cheap

Non-radioactive

Requires gel electrophoresis

Not always feasible

41
Q

What is used for DNA sequencing?

A

Chain terminatino method , sanger sequencing, dideoxynucleotides are used

42
Q

What is the Advantages / limitations of DNA sequencing?

A

Gold standard for mutation detection

Automation and high throughput

Expensive equipment

Poor quality sequence read (First part of sequence (15 to 40 bases) Deterioration after 700-900 bases)

Next generation sequencing 18 billion bp in 4 days (about 6 human genomes)

Principles of Disease (48 decks)

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