Lecture 5 Flashcards
how can we study individual meiotic events?
looking at TETRAD –> 4 spores made by meiosis of haploid (no homologous chromosomes)
held together by ascus
what undergoes crossing over?
NON-SISTER CHROMATIDS, not chromosomes
when does crossing over occur in meiosis?
AFTER replication
what would we see if crossing over occurred before replication?
start with AB and ab –> get 2 Ab and 2 aB, i.e. only recombinant no parental
what would we see if crossing over occurred after replication?
start with AB and ab –> get 2 parental, 2 recombinant
can multiple crossovers occur in a single meiotic event?
yes, can involve multiple chromatids
describe crossover events and number of parental vs recombinant if you start with ABC/abc and progeny are:
ABC
AbC
aBc
abc
2 crossover events involving 2 chromatids –> in recombinants, b is changing
2 recombinant, 2 parental types
describe crossover events and number of parental vs recombinant if you start with ABC/abc and progeny are:
ABc
AbC
aBC
abc
3 crossover events involving 3 chromatids –> in recombinants, B and C are changing
3 recombinant, 1 parental types
describe crossover events and number of parental vs recombinant if you start with ABC/abc and progeny are:
ABc
Abc
aBC
abC
4 crossover events involving 4 chromatids –> in recombinants, A, B, C all changing
4 recombinants
how is crossover affected if genes are further apart?
genes that are further apart are more likely to crossover and make recombinants
relative distance btwn 2 genes is reflected in _____ ______
relative distance btwn 2 genes is reflected in recombination frequency
what is 1 genetic map unit equal to?
1 mu = frequency at which 1/100 meiosis products is recombinant
what is the max recombination frequency?
RF of 2 genes cannot exceed 50%
