* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Document
Dominance (genetics) wikipedia , lookup
Genetic code wikipedia , lookup
Skewed X-inactivation wikipedia , lookup
No-SCAR (Scarless Cas9 Assisted Recombineering) Genome Editing wikipedia , lookup
Polymorphism (biology) wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Hybrid (biology) wikipedia , lookup
Pharmacogenomics wikipedia , lookup
Genomic imprinting wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Biology and consumer behaviour wikipedia , lookup
Genome evolution wikipedia , lookup
Medical genetics wikipedia , lookup
Holliday junction wikipedia , lookup
Genetic drift wikipedia , lookup
Behavioural genetics wikipedia , lookup
Y chromosome wikipedia , lookup
Heritability of IQ wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
X-inactivation wikipedia , lookup
History of genetic engineering wikipedia , lookup
Designer baby wikipedia , lookup
Public health genomics wikipedia , lookup
Gene expression programming wikipedia , lookup
Genetic testing wikipedia , lookup
Human genetic variation wikipedia , lookup
Homologous recombination wikipedia , lookup
Genetic engineering wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
Population genetics wikipedia , lookup
Quantitative trait locus wikipedia , lookup
Neocentromere wikipedia , lookup
Discovery Genetic linkage was first discovered by the British geneticists William Bateson, Edith Rebecca Saunders and Reginald Punnett shortly after Mendel's laws were rediscovered. The understanding of genetic linkage was expanded by the work of Thomas Hunt Morgan. Linkage A linkage map is a genetic map of a species or experimental population that shows the position of its known genes or genetic markers relative to each other in terms of recombination frequency, rather than a specific physical distance along each chromosome. Thomas Hunt Morgan's Drosophila melanogaster genetic linkage map. This was the first successful gene mapping work and provides important evidence for the chromosome theory of inheritance. The map shows the relative positions of allelic characteristics on the second Drosophila chromosome. The distance between the genes (map units) are equal to the percentage of chromosomal crossover events that occurs between different alleles. Dihybrid cross is a cross between two pure lines (varieties, strains) that differ in two observed traits. In Mendelian sense, between the alleles of both these loci there is a relationship of complete dominance - recessive. For example: RRYY/rryy parents result in F1 offspring that are heterozygous for both R and Y (RrYy).The rules of meiosis, as they apply to the dihybrid, are codified in Mendel's first law and Mendel's second law, which are also called the Law of Segregation and the Law of Independent Assortment, respectively. Crossing over Crossing over occurs between prophase 1 and metaphase 1 and is the process where homologous chromosomes pair up with each other and exchange different segments of their genetic material to form recombinant chromosomes. It can also happen during mitotic division, which may result in loss of heterozygosity. Crossing over is essential for the normal segregation of chromosomes during meiosis. Crossing over also accounts for genetic variation, because due to the swapping of genetic material during crossing over, the chromatids held together by the centromere are no longer identical. So, when the chromosomes go on to meiosis II and separate, some of the daughter cells receive daughter chromosomes with recombined alleles. Due to this genetic recombination, the offspring have a different set of alleles and genes than their parents do. In the diagram, genes B and b are crossed over with each other, making the resulting recombinants after meiosis Ab, AB, ab, and aB Recombination A current model of meiotic recombination, initiated by a double-strand break or gap, followed by pairing with an homologous chromosome and strand invasion to initiate the recombination repair process. Repair of the gap can lead to crossover (CO) or non-crossover (NCO) of the flanking regions. CO recombination is thought to occur by the Double Holliday Junction (DHJ) model, illustrated on the right, above. NCO recombinants are thought to occur primarily by the Synthesis Dependent Strand Annealing (SDSA) model, illustrated on the left, above. Most recombination events appear to be the SDSA type.