Session 15-Mutations Flashcards
What is a mutation?
Change in a DNA sequence
What can mutations be a result of? (4)
DNA replication errors made during cell division (mitosis and meiosis)
Exposure to ionising radiation (mutagen)
Exposure to chemicals (chemical mutagens)
Infection by viruses
Where do germ line mutations occur?
In the eggs or sperm and affect all cells in the body and can be passed onto offspring
Where do somatic mutations occur?
In a body cell and isn’t passed onto offspring
True or false: all mutations are bad
FALSE
Why are RNA translation errors common?
RNA polymerase do not proofread like DNA polymerase
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
TRUE - multiple copies of RNA produced so unlikely that same mistake will be made twice, RNAs quickly degrade and RNAs are not inherited molecules
True or false: mitochondrial DNA (mtDNA) affects germ line and somatic mutations
TRUE
Which organs do mitochondrial diseases have the greatest effect on?
Heart, brain and muscles
What are some of the frequently observed features of mitochondrial disease?
Muscle weakness and wasting Problems with movement Diabetes Kidney failure Heart disease Dementia Hearing loss Vision abnormalities
Why do mitochondrial somatic mutations build up over time?
mtDNA has limited ability to repair itself when it is damaged
What has a build up of somatic mutations in mtDNA been associated with?
Some forms of cancer and increased risk of age-related diseases such as heart disease, AD and Parkinson’s
What are the three germ line mutations which lead to an incorrect DNA sequence? (Affects genes)
Substitution
Insertion
Deletion
What are the structural chromosomal germ line mutations?
Deletion
Duplication
Inversion
Translocation
What is the germ line mutation that affects the number of chromosomes?
Non disjunction
What is anaphase lag?
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
What do primordial germ cells (PGCs) differentiate into in the foetal female gonad?
Oogonia
What is a primary oocyte surrounded by flattened epithelial cells called?
Primordial follicle
True or false: once PGCs arrive in the male gonad, they remain there until puberty
TRUE
How much sperm does a human male produce per day?
100 million
Why do PGCs in males only start to differentiate into spermatozoa at puberty?
They are only needed when oocytes are available to fertilise
Would you expect the IVF embryo aneuploidy rate to over or underestimate the in vivo rate?
Overestimate
What is a morula?
Solid ball of cells resulting from division of fertilised ovum
What could happen if a very early embryo was exposed to radiation (a mutagen)? (3)
Death/aborted
Teratogenesis
Cancer when born
What features would allow a germ cell mutation to be inheritable?
Not lethal to the gamete
Not impair gamete function
Not be lethal at fertilisation
Allow production of viable adult with normal reproductive capacity
Complete the sentence:
In general, recessive mutations cause loss of function and often affect ___________ pathways
Biochemical
Complete the sentence:
In general, dominant mutations cause increased function and often cause __________ ______________
Structural abnormalities
