Lecture 15

Question 1

What does ploidy mean

Answer 1

Refers to the number fo sets of chromosomes we have
Humans have 2 sets, diploid
Yeast are haploid, just teh 1 copy
Etc

Question 2

Monosomic vs trisomic

Answer 2

Both aneuploids, monosomic is just one less chromosome and trisomic is one more, so the right number of sets give or take 1

Question 3

Autopolyploidy vs allopolyploidy

Answer 3

Polyploidy meaning more than 2 sets of chromosomes, 2 or more
Auto meaning 2 or more of the same type, so 2 strawberry plants being crossed and producing a polyploid
Allo meaning 2 or more but not necessarily of the same type, maybe its a cross or something so its not identical copies of dna

Question 4

What are the potential consequences of autopolyploidy in plants

Answer 4

Increase in size of fruit/yield, size of flower and leave in general is larger
Triploid organisms are often sterile (germline consequence)

Question 5

Can triploids generate “normal” gametes, also what counts as normal

Answer 5

Normal would be 1n, and yes they can if all “extra” chromosomes segregate to the other cells
This would give you 2 haploid normal gametes and two diploid gametes, which if they are crossed with other normal gametes will give rise to a triploid organism
Thing is the odds of this happening are low so most of the time we get 1n+ x number of chromosomes, not complete sets, and this is why they’re generally sterile cuz the gametes are non-viable

Question 6

How do we calculate the chance/probability of getting a viable gamete from a triploid organism

Answer 6

Viable as in a haploid where all extra chromosomes segregate to one daughter cell
P(euploidy)= (1/2)^ n-1
Where n is the number of chromosomes, we subtract one because the first chromosome to randomly segregate doesnt have a 50% (1/2) chance of segregating, it just does it

Question 7

What causes autopolyploidy

Answer 7

It can be induced/intentional, like by chemical disruption of chromosome segregation or by manipulated fertilization of a diploid germ cell with a polyploid germ cell
It can also be spontaneous, errors in meiosis or fertilization by multiple sperms

Question 8

What effect does colchicine have on cells in mitosis

Answer 8

In disrupts microtubules function such that they dont pull apart aka segregate chromosomes, they leave them together and we get a tetraploid cell
Note that this treatment doesnt even let cells divide, basically net effect is a doubling of genetic info

Question 9

How do we get seeds for triploid plants if theyre sterile

Answer 9

Best way and the commercially used way is to cross a tetraploid plants with a diploid plant, gametes will have 2n and 1n respectively, their joining gives 3n