Lecture 51. Non-Mendelian Inheritance Flashcards
What plant was used to discover transposable elements?
Maize
What are transposable elements?
DNA sequences that can change their position within the genome
When does ‘jumping’ occur
During mitosis
What can affect ‘jumping’?
Environment (e.g temperature stress)
What happens when a transposable element enters an exon?
Gene switches off
What happens when a transposable element enters a promoter?
Gene switches on
What are transposable elements also known as?
‘Jumping’ genes
Do ‘jumping’ genes just occur in plants?
No, they also occur in animals
What is epigenetics the study of?
Heritable changes in gene expression that are not caused by heritable changes in DNA sequence
What is methylation?
Methyl group can tag DNA and activate or repress genes
What happens when DNA is coiled around a histone?
DNA is inacessible for transcription so gene is inactive
What organelles did Ruth Sager find contain DNA?
Mitochondria and chloroplasts (mtDNA & cpDNA)
What is the biochemical evidence of symbiosis in mitochondria?
Mitochondria communicate with the nucleus via trafficking of proteins and RNAs
What is the genetic evidence of symbiosis in mitochondria?
The nucleus contains genes that encode mitochondrial proteins
What is the mitochondrial genome?
Circular genome
Contains genes for tRNAs, rRNAs, cytochrome oxidase, ATPase subunit & NADH-dehydrogenase
What is the size of the mitochondrial genome in humans?
~16kb
What is the size of the mitochondrial genome in yeast?
~80kb
What is the size of the mitochondrial genome in plants?
~100kb to 2 Mb
What is the chloroplast genome?
Circular genome
Contains genes for redox proteins involved in electron transport for photosynthesis
Also contain a lot of non-coding DNA
What is the size of the chloroplast genome?
~80-600kb
Why do the mitochondria and chloroplasts have the exact same phenotype and genotype as the mother?
Meiotic segregation does not take place in organelles because they are acquired at cell division from the maternal cytoplasm
What are the two types of petite yeast mutants?
Segregational and vegetative
What are segregational mutants?
Mendelian segregation following meiosis
Genes are located in the nucleus
What are vegetative mutants?
Non-Mendelian pattern of inheritance
Genes are located in the mitochondria
What ratio does the tetrad of progeny show after crossing a wild type with a segregational petite?
2:2
What ratio does the tetrad of progeny show after crossing a wild type with a neutral petite?
4:0
What ratio does the tetrad of progeny show after crossing a wild type with a suppressive petite?
0:4
What do neutral petites lack?
Most of their mitochondrial DNA
What do suppressive petites lack?
Small segments of mtDNA
What parent do yeast offspring inherit mitochondria?
Both parents
What is MERRF?
Myoclonic epilepsy & ragged-red fiber disease
What nucleotide substitution causes MERRF?
Lysine in tRNA
What are the symptoms of MERRF?
Spasms and abnormal tissues, accumulation of lactic acid in the blood, and uncoordinated movement
What are the uses of mitochondrial genome sequencing?
Maternity analysis
Phylogenetic systematics
Population genetics
Why do mitochondrial genome sequencing?
Easy to isolate and PCR amplify mtDNA due to high copy
number per cell
Maternal inheritance mtDNA enables analysis of maternal population structure without confusion of male-mediated gene flow
No recombination of mtDNA so very slow to evolve
Mutations that do occur are rapidly fixed in a population
What can phylogenetic analysis using mtDNA trace?
Roots of humanity
What is maternal inheritance?
Maternal phenotypes that are caused by variation in genes located in the nuclear genome
What are examples of maternal inheritance?
Maternal factors (proteins or mRNA) that are deposited in the oocyte prior to fertilisation
Shell coiling in snails
What is genomic imprinting?
A form of gene expression in which an allele of the affected gene is marked or ‘imprinted’ in one of the parents, and can be passed on through meiosis to the offspring
How is the epigenetic mechanism marked?
By methylation or histone modification
