During meiosis, homologous chromosomes (1 from each parent) pair along their lengths. The chromosomes cross over at points called chiasma. At each chiasma, the chromosomes break and rejoin, trading some of their genes. This recombination results in genetic variation.
What is variation in chromosome?
Changes in chromosome number can occur by the addition of all or part of a chromosome (aneuploidy), the loss of an entire set of chromosomes (monoploidy) or the gain of one or more complete sets of chromosomes (euploidy). Each of these conditions is a variation on the normal diploid number of chromosomes.
What are the 3 causes of variation?
Major causes of variation include mutations, gene flow, and sexual reproduction. DNA mutation causes genetic variation by altering the genes of individuals in a population. Gene flow leads to genetic variation as new individuals with different gene combinations migrate into a population.
What causes genetic variation?
Mutations, the changes in the sequences of genes in DNA, are one source of genetic variation. Another source is gene flow, or the movement of genes between different groups of organisms. Finally, genetic variation can be a result of sexual reproduction, which leads to the creation of new combinations of genes.
What is the Behaviour of chromosomes during mitosis?
One remarkable aspect of chromosome motility is that chromosomes exhibit an oscillatory behaviour, whereby they move both towards and away from the spindle equator throughout all stages of mitosis.
How do variations in chromosome structure arise?
Structural Abnormalities: A chromosome’s structure can be altered in several ways. Deletions: A portion of the chromosome is missing or deleted. Duplications: A portion of the chromosome is duplicated, resulting in extra genetic material. Translocations: A portion of one chromosome is transferred to another chromosome.
What is the behavior of homologous chromosomes during metaphase?
In metaphase I, the homologous chromosomes line up at the metaphase plate. In anaphase I, the homologous chromosomes are pulled apart and move to opposite poles. Sister chromatids are not separated until meiosis II.
What is the behavior of homologous chromosomes during prophase in meiosis?
During prophase I homologous chromosomes make contacts with each other called chiasmata and “crossing over” occurs. This is where chromosomes exchange sections of DNA. This is important for generating genetic diversity but is also crucial mechanically to hold homologous chromosomes together.
What are the two main causes of variation?
The two main causes of variation are mutation and genetic recombination in sexual reproduction.
What are 3 reasons to explain genetic variations in meiosis?
Genetic diversity arises due to the shuffling of chromosomes during meiosis.
- Process of Meiosis. A man produces sperm and a woman produces eggs because their reproductive cells undergo meiosis. …
- Crossing Over. …
- Random Segregation. …
- Independent Assortment.
Do mutations decrease genetic variation?
Mutations can introduce new alleles into a population of organisms and increase the population’s genetic variation.