CROSSING OVER- PROCESS & FUNCTION
INTRODUCTION
Crossing over is the exchange of chromosome segments or genetic material between non-sister chromatids of homologous chromosome.
It is also known as chromosomal cross over. It is essential for the normal segregation of chromosomes during meiosis.
IMPORTANT POINTS
- The physical basis of crossing over was first demonstrated by Harriet Creighton and Barbara McClintock in 1931.
- It occurs during Pachytene stage of prophase 1 of meiosis cell division.
- It occurs when synapsis takes place (synapses means pairing of homologous chromosome).
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SYNAPSIS MEANING- PROCESS & FUNCTION - It results in recombinant chromosomes during sexual reproduction that is the final phases of genetic recombination. Recombination results in a new arrangement of maternal and paternal alleles on the same chromosome.
- The crossing over varies from 0-50% and will never cross 50% and the non-cross over vary from 50-100%.
FUNCTION
Crossing over increases the variability of a population. When all the progeny are genetically identical to one another, there is no scope for genetic errors to be corrected, or for new and beneficial combinations to arise.
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LINKAGE AND CROSSING OVER-AN OVERVIEW
MITOSIS & MEIOSIS- CELL DIVISION
CELL STRUCTURE AND FUNCTION
DIFFERENCE BETWEEN GENE AND ALLELE
MENDEL’S LAW OF INHERITANCE
DIFFERENCE BETWEEN PHENOTYPE AND GENOTYPE