Gene Linkage And Epigenetics Flashcards
What does di and hybrid mean in a dihybrid cross
Di: two
Hybrid: different and heterozygous
Un-linked autosomal genes, Dihybrid cross ratio
9:3:3:1
Total of 16 punnet squares
Test-cross explained.
Crossing an organism with a dominant phenotype to an organism with a recessive phenotype in order to find if it is homozygous or heterozygous. The offspring will tell you all you need to know; if only dominant phenotypes show, then the original dominant phenotype must be homozygous dominant. If a recessive phenotype shows in any offspring then we know it is heterozygous.
Phenotypic ratios of test crossing a monohybrid
1:1
Phenotypic ratios of test crossing a dihybrid
1:1:1:1
Independent assortment and it’s paradox?
Genes are assorted independently when switching chromosomes and synapsis occurs. Only exception to this law is genetic linkage.
Recombination frequency
The likelihood of 2 genes or alleles that begin together on the same chromosome and recombine on another chromosome after meiosis.
A greater recombination frequency correlates strongly with
the greater distance along the chromosome.
A low recombination frequency correlates strongly with
A low distance on the chromosome.
The closer the alleles are on the chromosome the more
Highly linked the alleles are.
In a complementary dihybrid crossed gene you would expect a …….ratio?
9:7
Complementary gene or epistasis
A particular set of alleles at one gene can mask a particular set of a second gene. Epistatic relationships.
Unlinked genes
Genes on different chromosomes assort independently into gametes
Linked gene
Genes on the same chromosome generally stay together in gametes
What ratio would you expect to get in a self cross of a dihybrid with both dominant alleles on the same chromosome?
AB/ab x AB/ab
3:1
What ratio would you expect to get in a test-cross of a dihybrid with both dominant alleles on the same chromosome?
AB/ab x ab/ab
50/50 or 1:1
When to use a Chi-squared test?
Testing wether genes are significantly linked or not, with a goodness of fit test.
Epigenetics
External and environmental influences impacting genes and how they work.
Epigenetic trait
Are stable both mitotically and meitically, and result in a heritable phenotype by changing gene expression without altering DNA sequence.
External signs that stimulate a cellular response; stress, pathogens, toxins are termed ……. In genetics
Epigenators
RNA and DNA binding proteins that interact with genetic elements to trigger a response are termed……
Initiators
Enzymes / proteins that interact with DNA to sustain change are termed…..
Maintainers
siRNA
Small interfering RNA
End result of an epigenetic pathway is…
A functional gene that does not always result in expressed phenotype.
