Lecture 3 - Plant Genome Plasticity - Polyploidy Flashcards

Question

The story of cotton?

Answer 1

cotton is a tetraploid parental genome - came from different continents - africa and the new world - although at the beginning when the tetraploid was formed - it must have been together - otherwise it would have occured naturally (slide 28-30,LT3)

Answer 2

- intergenomic colonisation - repetitive sequences specific from A - genome are found in the G- genome in gossypium polyploids ( probably transposable elements) they can be observed using colonisation of one allogenome by the other - the repetitive sequences specific from the A plant are found in the D genome – using this ‘painting technique’ so tracing the transposable elements – so oer millions of years will jump between the genomes

Answer 3

1 mya – spontaneous hybridization – to a wild hetroploud AB ( emmer wheat ) – which is the direct ancestor of the Durum wheat – which is a heterploid Bread wheat arose by AB genome mix , so mix with heteroploid and diploid to make a hexioploid …. During this time farming was starting in middle east – they collected big seeds compared to the normal – and ended up producing plants – that have been sown and harvested ever since that day Because its 3 genomes are very similar, wheat can tolerate loss of one copy of any chromosome Each plant has 7 chromosomes ( all cereals related to wheat have 7 chromosome pairs ) Wheat can tolerate the loss of one of these pairs – so if it happens they can still be a viable plant – because they have back u genes Chromosomes of 1 A will not interact with chromosome 1 D ( they are separated by millions of years !) This is a useful breeding tool!

Answer 4

All 4 chromosome sets’ are the same – All can pair at meiosis This makes breeding/genetics difficult. Potato is an autopolyploid – 4 copies of every chromosome – so every chromosome goes with each other – so difficult to produce plants with different things..

Answer 5

- much more complicated - much more difficult to detect - chromosomes become scrambled by rearrangements - divergence or loss of duplicate genes - Bits of chromosomes / fusions of chromosomes , a big mix of chromosomes ….

Answer 6

Detection is now quite easy because of sequenced genomes Dating (or at least relative dating) of the events can be achieved if sequences are available from many taxa The mode of polyploid formation (allo- or autopolyploidy?) is often unclear In some ways this is difficult and easy … now we can sequence everything !!!! By comparison of the sequences , and looking at diveregnce of base pairs you can figure out the timings …. In the ancient past its hard to work out if allo or autoploidy actually happened

Answer 7

Arabidopsis – we think has arisen because of two separate polyploidy events… A lot of duplicated genes were removed and only remnents were seen after it … the genome decided to simplify right down.. This can be detected by comparing the entire genomes , and line up the sequences of each of the 5 chromosmes , and look for diagonals – which would show whether they are similar or not… The outcomes of ancient polyploidization can be seen by comparing a genome sequence against itself,

Answer 8

Since the duplication event rice has been affected much less than barley by subsequent rearrangement Common events are insertions of whole chromosomes or chromosome arms into centromeric regions and telomere-telomere fusions

Answer 9

-Gene buffering Slower response to selection but more adaptive potential. -Dosage effect Additive effect of the alleles increases the number of phenotypes. -Increased allele diversity and heterozygosis More possible allele combinations and opportunities for breeding. -Novel phenotypic variation Genome interactions and changes in gene expression notes: Gene buffering: multiple copies of a gene would retard the response to natural/artifitial selection due to mutation or recombination. Buffering effect even when genes are mutated. multiple copies of gene, some are mutated to null allele. Presented simple segregation ratios and linear expression instead of segregate as quantitative traits. Allele dosage: some key regulator genes preserved their function. All copies operate in the same manner. Increase diversity: intergenomic heterozygosity has positive effects. More seed yielding in brassica, longer and stronger fiber in cotton. New phenotypes in synthetic allopolyploids that stabilized over generations. Man different mechanisms explain novel variation

Lecture 3 - Plant Genome Plasticity - Polyploidy Flashcards

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