Mutations and Detection

Question 1

What are the 3 types of chromosomal abnormalities?

Answer 1

Numerical, structural, mutational

Question 2

What are the 2 kinds of structural translocations?

Answer 2

Reciprocal or Robertsonian

Question 3

What occurs in a reciprocal abnormality?

Answer 3

Equal parts of 2 chromosomes are swapped over, so no DNA is lost or gained.

Question 4

What is the outcome of a reciprocal abnormality?

Answer 4

If gamete receives both normal chromatids, they will have a normal zygote. If gamete received both translocated chromatids, they will have a balanced translocation. If gamete receives one normal and one translocated chromatid, they will have unbalanced translocation

Question 5

What does unbalanced translocation result in?

Answer 5

In reciprocal, a partial trisomy/monosomy. In robertsonian, a trisomy or monosomy

Question 6

What are the 4 types of structural abnormality?

Answer 6

Translocation, Insertion, Deletion, Inversion

Question 7

Which kind of mutation can lead to trisomy 21 and what is the disease associated with this?

Answer 7

Robertsonian translocation can lead to trisomy 21 which is down syndrome

Question 8

Germline vs Somatic?

Answer 8

Germline involves germ cells - egg and sperm. Somatic involves all other chromosomes

Question 9

What is a polymorphic genetic mutation?

Answer 9

No phenotypic effect associated. Very common and found in more than 1% of out genomes

Question 10

What is a non-coding mutation?

Answer 10

One which occurs in a region of DNA that doesn’t code for proteins. Could still have an effect if its in a promoter region

Question 11

What are the 4 coding mutations?

Answer 11

Silent, missense, nonsense and frameshift

Question 12

What is a silent mutation?

Answer 12

One that doesn’t affect the outcome of protein as the 3-base codon codes for the same amino acid as before the mutation

Question 13

What is a missense mutation?

Answer 13

A change in a codon which leads to another amino acid being transcribed. Could have a serious effect

Question 14

What is a non-sense mutation?

Answer 14

Amino acid changed to a ‘stop’ codon so protein is shorter. Could have serious effect

Question 15

What is a frameshift mutation?

Answer 15

Codon added or deleted so all other codes shift and many amino acids are changed. Has large detrimental effect usually as it produces totally different protein product

Question 16

What are the 5 listed methods of detecting mutations?

Answer 16

PCR
Gel electrophoresis
DNA analysis
Restriction fragment length polymerisation (RFLP)
Amplification refraction mutation system (ARMS)

Question 17

What occurs in a numerical mutation?

Answer 17

Number of chromosomes is altered, usually +/- 1

Question 18

What is an example of two numerical mutations?

Answer 18

(-45, X) leads to only 1 X chromosome - Turner syndrome. (-47, XXY) leads to extra X chromosome in men - infertile, tall male with small testes

Question 19

What increases the chance of a child having Down syndrome?

Answer 19

Mothers age. Older woman has has her ova sitting in meiosis 1 for a long time, so more likely mutation has occured

Question 20

Which trisomy is more commonly seen and why?

Answer 20

Smaller chromosomes, e.g. 18, 21. These typically are Afrocentric. This is because trisomy in larger chromosomes (smaller numbers) do not survive typically.

Question 21

What is the process of a mutation as a result of non-dysjunction?

Answer 21

When homologous chromosomes fail to separate at meiosis resulting in a germ cell containing 24 chromosomes rather than 23

Question 22

What is sickle cell known to provide resistance to?

Answer 22

Malaria