Variation Flashcards
Which individuals are considered genetically identical?
Clones and monozygotic twins
Finish the sentence: Monozygotic twins have no genomic differences, but have a few…
epigenetic differences
What are the 4 types of variation?
- Single nucleotide polymorphisms (SNPs)
- Indels (insertions and deletions)
- Copy number variations (CNVs)
- Structural rearrangements
Describe allele:
Term to describe alternative forms of a heritable trait
Describe polymorphism:
Variation within a population of a given trait
What is meant by single nucleotide polymorphism?
Difference at a single nucleotide
What is the importance of Single nucleotide polymorphisms?
- Dr James Watson’s genome contained 3.3 million SNPs relative to the human genome project reference, ~0.1% of the genome differed
- approx. 10 million common SNPs in humans
- SNP rate versus chimpanzee ~1%
What is indels (insertions/deletions)?
-insertion or deletion of 1 or a few nucleotides
What is the significants of indels?
~4 x 105 indel polymorphisms identified in human genome, ~30% of these are tandem repeat expansion polymorphisms
- can be analysed by PCR & gel electrophoresis
- short tandem repeats are multi-allelic
- used in genetic profiling
What are short tandem repeats?
Multi-allelic
What are the effects of base substitution in coding regions?
- Silent substitution
- Missense substitution
- Nonsense substitution
What does missense substitution do to the coding region?
Changes amino acid
What does nonsense substitution do to the coding region?
Changes coding for an amino acid to coding for a stop codon
What are the effects of base insertion/deletion in coding region?
Cause frame shift to the left or to the right
What are the classifications of mutations?
Transition and transversions
What does the transition mutation occur between?
Purine to purine or pyrimidine to pyrimidine
What does the transversion mutation occur between?
Purine to pyrimidine or to pyrimidine to purine
Can small changes in the genome have a large effect on phenotype?
Yes
What genetic variation causes sickle cell anaemia?
Single nucleotide polymorphism
What genetic variation causes cystic fibrosis or albinism?
Indels
What are highly heritable ‘Mendelian’ diseases?
- Variation in a single gene is sufficient to causes diseases
- More than 100 such genes know to humans
- Most diseases are rare
Define mutant:
An organism containing a rare allele caused by mutation
Define wild type:
The normal allele/organism
Does genetic variation have much effect on phenotypic effect?
No, but some exceptions
Can base substation have a large or small effect on phenotypic effects?
Large
What mutation is more like to produce a rise in non-functional protein?
Frameshift mutation
