Lecture 19

Question 1

How does the fertilization of maize work

Answer 1

Each “grain” of pollen has 2 sperms, each haploid, that with interact with an egg cell and a central cell
The central cell is diploid, so when one of the identical sperms gets with it, it because triploid, the endosperm

Question 2

Outer layer of the endosperm

Answer 2

Called the aleurone, its a triploid tissue that surrounds the actual embryo

Question 3

Dominant negative allele

Answer 3

It’s an allele that can override the dominant allele to produce what would be the recessive phenotype

Question 4

What can be the cause of genetic instability in maize

Answer 4

Could be chromosome breakage such that the negative dominant allele can no longer repress the dominant allele it was repressing because it’s no longer there
Test was to use genes near that C1, make them dom, make the C version recessive and see if expression changes, and it did

Question 5

Ac element

Answer 5

This is the activator element that allows the Ds (transposon) element to jump to a new location
Activates the mobility
Everywhere there were Ac elements there were breaks in chromosomes and the spotted phenotype, where there were no spots there was still that Ds element but not the Ac

Question 6

Autonomous vs non-autonomous

Answer 6

Autonomous in that it can chose to jump around the genome by itself, Ac
Non-autonomous in that it cannot jump by itself, needs help, in this case Ds needing Ac

Question 7

Classes of transposable elements

Answer 7

Retrotransposons: in eukaryotes
Transposons: both in prokaryotes and eukaryotes

Question 8

Ac today, what we know it now as

Answer 8

A transposase, thus why it was able to help Dc jump, and its flanked by inverted repeats
Transposase can basically cut out a gene, grab it, take it somewhere else in the genome, make another cut, splice it in there

Question 9

Retro-transposons

Answer 9

Similar to retro-viruses, that means that somewhere in evolution it popped into human genome to say
Retrotransposons are flanked by LTRs and the retrotransposon has its own reverse transcriptase (thus how it can travel)
Needs an ORF1 to be autonomous, found in LINEs, a subset of retros, but its not all of them