Lecture 13 Flashcards
what is the unit of transmission in meiosis?
chromosomes
not genes
linked genes can not undergo…
independent assortment
frequency of crossing over on a single chromosome is proportional to…
distance between them
crossing over results in
recombination
chromosome maps indicate
relative location of genes on chromosome
three consequences of linkage in meiosis
independent assortment
linkage without crossing over
linkage with crossing over
linkage without crossing over is called
complete linkage
is linkage exhibited in independent assortment
no
linkage with crossing over
generates recombinant gametes
what does complete linkage produce
parental (noncrossover) gametes
crossing over occurs between
non-sister chromatids
crossing over produces what
both parental and recombinant gametes
the number of linkage groups corresponds to
haploid number of chromosomes
linkage ratio refers to
phenotypes
chiasmata are
synapsed chromosomes in meiosis that wrap around each other
what shape are chiasmatas
x-shaped intersection with points of overlap
(points of genetic exchange)
percentage of offspring resulting from recombinant gametes depends on?
distance between two genes on same chromosome
what is less likely to have a chiasma
two genes located close to each other along a chromosome
the frequency of crossing over is…
proportional to distance between any two loci on single chromosome
one cM corresponds to about how many base pairs in humans on average
1 million
relative distance between two loci influences amount of…
recombination and crossing over
the closer the loci reside the …..
less likely of single-crossover event
the farther apart the loci…
the more random crossover
single crossovers are when..
two linked genes are greater than 50 map units apart
double crossovers result from
double exchanges of genetic material
three-point mapping criteria
- genotype of organism producing crossover gametes must be heterozygous at all loci
- cross must be constructed to determine genotype of all gametes by observing phenotypes of offspring.
-Sufficient number of offspring must be produced for representative sample crossover.