Outcome 1 - Fungi

Question 1

Yeast can exist in _ or _ states.
___ cells can undergo mitosis to reproduce _____.
When nutrients are lacking ___ cells can fuse together and undergo ____ to produce spores.
The products are 4 ______ (2___ and 2___) which are called ____ and found in an ____.

Answer 1

Yeast can exist in haplod or diploid states.
Haploid cells can undergo mitosis to reproduce asexually.
When nutrients are lacking diploid cells can fuse together and undergo meiosis to produce spores.
The products are 4 haploid spores (2 of mating type a and 2 of mating type alpha) which are called ascospores and found in an ascus.

Question 2

The model yest organism used is

Answer 2

Saccharomyces cerevisaie

Question 3

In yeast the hapliod spores are arranged ___ within the ____. These ____ tetrads can be be isolated from the ___ and their genotypes analysed.

Answer 3

In yeast the hapliod spores are arranged randomly within the ascus. These unordered tetrads can be be isolated from the ascus and their genotypes analysed.

Question 4

When can crossing over events occur within the reproductive cycle of Saccharromyces cerevisaie

Answer 4

Prior to meiosis, chromosome doubling occurs. In yeast, crossing over occurs at this stage

Question 5

If genes are linked, then those genotypes are unlikely

Answer 5

to be found separate from each other and will tend to move together if crossing over occurs.

Question 6

To anlysis tetrads in saccharomyces cerevisia we look at

Answer 6

segregation of different heterozygous markers in haploid spores. This allows detection of whether genes show linkage and whether they are closely located on the chromosome

Question 7

What is PD, NPD and TT

Answer 7

PD is parental ditypes eg (AB AB ab ab) if parents are AB x ab
NPD is non-parental ditypes eg (Ab Ab aB aB)
TT is tetrotype eg (AB, ab, Ab, aB)

Question 8

If genes are unlinked frequency of PD-NPD is ____

If genes are linked frequency of PD-NPD is _____

Answer 8

If genes are unlinked frequency of PD:NPD = equal
because PD and NPD are produced by random assortment and are therefore equally likely
If genes are linked frequency of PD:NPD = PD>NPD

Question 9

No crossover = 
Single crossover = 
2 strand double crossover = 
3 strand double crossover =
4 strand double crossover =

Answer 9

No crossover = PD
Single crossover = TT 
2 strand double crossover = PD 
3 strand double crossover = TT
4 strand double crossover = NPD

Question 10

The equation to map the distance between two linked genes is

Answer 10

= (1/2 x no. of TT) + 3(no. of NPD)
___________________________ x 100(cM)
Total no. of tetrads