Module 4 Flashcards
Genes on the same chromosome go through - together
Meiosis
What is crossing over?
When homologous chromosomes pair at meiosis, chromosomes occasionally break and exchange parts
When does crossing over occur?
Meiosis
What is a recombinant?
An individual organism or cell having a genotype produced by recombination
What is recombination?
Any process in a diploid or partly diploid cell that generates new gene or chromosomal combinations not previously found in cell
Physically linked alleles are inherited together or separately?
Inherited together
What is a recombinant frequency?
The proportion of recombinant cells or individuals
What are chromosome maps?
A representation of all chromosomes in the genome as lines, marked with positions of genes known
What are chromosome maps based upon?
Based on analysis of recombinant frequency
What can be seen as a major exception to Mendel’s second law?
Genetic linkage
What is absolutely needed to calculate RFs?
You need recombinants and parental phenotypes
What is coupling?
It indicates if the recessive alleles for two genes are flowing down to F1 from a single P0 parental, both recessive alleles in one parental
What is repulsion?
Indicates if recessive alleles for two genes are flowing down to F1 from segregation of different P0 parental, one recessive alleles from each parental
What is cis formation?
In a heterozygote having two mutant sites within a gene or within a gene cluster
What is trans formation?
In a heterozygote with two mutant sites within a gene or gene cluster
Coupling is related to - formation
Cis
Repulsion is related to - formation
Trans
What is the site of crossing over?
Chiasmata
Where was the evidence for crossing over found?
Maize
When does cross over happen?
At the end of meiosis
How many chromatids are involved in crossing over?
2 out of 4
If there was no crossing over, what would happen?
Only parental gametes formed
If crossing over happened before DNA duplication, what would occur?
Outcome is 100% recombinant
If crossing over happened after completion of meiosis I, what would occur?
100% parental gametes
What is recombination caused by?
Physical exchange between homologous in prophase of first meiotic division and after S-phase
How is frequency of double cross over calculated?
It is the product of frequencies of each event
What is within the calculable values of RF?
50
Calculations for RF
number of recombinant gametes/ P+ R gametes x 100
What is deletion mapping?
The use of a set of known deletions to map new recessive mutations by pseudodominance
What is duplication mapping?
Introducing extra wild type pieces of chromosomes can rescue recessive genotype
What is a locus?
The chromosomal site where a specific gene is located
What is interference?
The observed double crossover frequency differs from the expected double crossover frequency
What is linkage?
The tendency for genes located in close proximity on the same chromosome to be inherited together
The (higher, lower) the combination frequency, the farther apart two genes are on a chromosome
Higher
What is the definition of a map unit?
Percent chance of a crossover between two locations on a chromosome
