Lecture 20 Flashcards
Linkage
If 2 genes are close together on the same chromosome. Alleles F1 received from their parents are more likely to be transmitted together
When alleles of different genes tend to stay together during meiosis the genes are said to be linked
Recombinants
New phenotypes in a test cross offspring are called recombinants
Phenotypes with different combinations of traits than the original parents
What stage is recombination produced by
Crossing over process in prophase 1 meiosis
Genetic recombination
A change in combination of alleles of genes in a given chromosome, Neolithic product or individual
Recombinant
Individual chromosome; neurotic product, or individual that possess a new combination of alleles due to crossing over
Meiosis product
A gamete in animals but a spore in plants
When doing crosses with dihybrid show do u decide if you are dealing with gene pairs that are on different chromosomes or on the same chromosome
If ohenotypic ratio of this cross is 1:1:1:1 what can u assume
If phenotypic ratios is mostly parental phenotypes what can u conclude
Test cross between
Dihybrid cross X homozygous recessive
U can conclude alleles of 2 genes are assorting independently of each other. Therefore they’re on different chromosomes
2 genes are linked and some are the same homologous chromosome
Linkage mapping
Based on assumption crossing over is just as likely to occur at any point on chromosome.
Therefore. The closer 2 genes are, the harder it is to have crossing over between them
Map unit
Distance alone a chromosome within which crossing over occurs 1% of the time in test cross offspring
Recombinants/ total x 100
1/10=0.1 X 100=1 map unit
When does linkage mapping not work
It’s only useful when organisms can be easily crossed and produce lots of offspring
Not useful for long generation times. Or species in which u can’t do experimental crosses
If genes are more than 50 map units apart what happens
Recombinant frequencies will suggest they’re independently assorting
