Session 15-Mutations

Question 1

What is a mutation?

Answer 1

Change in a DNA sequence

Question 2

What can mutations be a result of? (4)

Answer 2

DNA replication errors made during cell division (mitosis and meiosis)
Exposure to ionising radiation (mutagen)
Exposure to chemicals (chemical mutagens)
Infection by viruses

Question 3

Where do germ line mutations occur?

Answer 3

In the eggs or sperm and affect all cells in the body and can be passed onto offspring

Question 4

Where do somatic mutations occur?

Answer 4

In a body cell and isn’t passed onto offspring

Question 5

True or false: all mutations are bad

Answer 5

FALSE

Question 6

Why are RNA translation errors common?

Answer 6

RNA polymerase do not proofread like DNA polymerase

Question 7

True or false: long-term effects on an organism whose cell has made a transcription/translation error will not be as bad as if the mistake was in the genome itself

Answer 7

TRUE - multiple copies of RNA produced so unlikely that same mistake will be made twice, RNAs quickly degrade and RNAs are not inherited molecules

Question 8

True or false: mitochondrial DNA (mtDNA) affects germ line and somatic mutations

Answer 8

TRUE

Question 9

Which organs do mitochondrial diseases have the greatest effect on?

Answer 9

Heart, brain and muscles

Question 10

What are some of the frequently observed features of mitochondrial disease?

Answer 10

Muscle weakness and wasting 
Problems with movement 
Diabetes
Kidney failure
Heart disease
Dementia 
Hearing loss
Vision abnormalities

Question 11

Why do mitochondrial somatic mutations build up over time?

Answer 11

mtDNA has limited ability to repair itself when it is damaged

Question 12

What has a build up of somatic mutations in mtDNA been associated with?

Answer 12

Some forms of cancer and increased risk of age-related diseases such as heart disease, AD and Parkinson’s

Question 13

What are the three germ line mutations which lead to an incorrect DNA sequence? (Affects genes)

Answer 13

Substitution
Insertion
Deletion

Question 14

What are the structural chromosomal germ line mutations?

Answer 14

Deletion
Duplication
Inversion
Translocation

Question 15

What is the germ line mutation that affects the number of chromosomes?

Answer 15

Non disjunction

Question 16

What is anaphase lag?

Answer 16

If the duplicate chromosomes do not pair properly at the metaphase plate, the pair won’t move properly to each pole during anaphase, resulting in one cell having two copies of the chromosome while the other cell has none

Question 17

What do primordial germ cells (PGCs) differentiate into in the foetal female gonad?

Answer 17

Oogonia

Question 18

What is a primary oocyte surrounded by flattened epithelial cells called?

Answer 18

Primordial follicle

Question 19

True or false: once PGCs arrive in the male gonad, they remain there until puberty

Answer 19

TRUE

Question 20

How much sperm does a human male produce per day?

Answer 20

100 million

Question 21

Why do PGCs in males only start to differentiate into spermatozoa at puberty?

Answer 21

They are only needed when oocytes are available to fertilise

Question 22

Would you expect the IVF embryo aneuploidy rate to over or underestimate the in vivo rate?

Answer 22

Overestimate

Question 23

What is a morula?

Answer 23

Solid ball of cells resulting from division of fertilised ovum

Question 24

What could happen if a very early embryo was exposed to radiation (a mutagen)? (3)

Answer 24

Death/aborted
Teratogenesis
Cancer when born

Question 25

What features would allow a germ cell mutation to be inheritable?

Answer 25

Not lethal to the gamete
Not impair gamete function
Not be lethal at fertilisation
Allow production of viable adult with normal reproductive capacity

Question 26

Complete the sentence:

In general, recessive mutations cause loss of function and often affect ___________ pathways

Answer 26

Biochemical

Question 27

Complete the sentence:

In general, dominant mutations cause increased function and often cause __________ ______________

Answer 27

Structural abnormalities