Summary Chromosomes are made up of DNA and proteins. Other types of mutations include: Deletion: some of the genetic material breaks off and is lost Inversion: a broken segment flips around and reattaches Translocation: a part from one chromosome breaks off and attaches to a different chromosome If one of these mutations is going to happen, it will occur during meiosis.
Related Lessons. View All Related Lessons. Aaron Lauer. Chromosome Duplications. Samantha Broders. Compare: deletion mutation. See also: mutation. Mutations can also influence the phenotype of an organism. This tutorial looks at the effects of chromosomal mutations, such as nondisjunction, deletion, and duplication. Citation: Clancy, S. Nature Education 1 1 Deletions and duplications of single-base pairs typically arise during homologous recombination and cause diseases.
But what happens when a mutation occurs over multiple genes? Aa Aa Aa. Chromosomal Duplications. Bar gene in fruit flies results in decreased eye sizes. B A fly with a heterozygous Bar mutation has an extra copy of the gene on one chromosome, resulting in an eye size about half the size of normal eyes.
C A fly with a homozygous Bar mutation has an extra copy of the gene on both chromosomes, resulting in an eye size about one-fourth the size of normal eyes. D A fly with a heterozygous double Bar mutation has three Bar genes on one chromosome, resulting in an eye size about one-eighth the size of normal eyes. This results in a large, round red eye. This results in a vertical, oblong eye about half the size of the normal eye. This results in an oblong eye about one-fourth the size of the wild-type eye.
This results in an oblong eye about one-eighth the size of the wild-type eye. Figure 1. Chromosomal Deletions. All amphibians from this speciation event carry the beta-globin gene. Approximately MYA, a globin gene duplication event occurred in the reptile and mammal lineages, resulting in a gene with the regions 5-prime-betaprime-omega. This caused a split into two genetic lineages; one carried the omega region, and one did not. Approximately MYA, two speciation events took place.
In the omega lineage, the speciation event led to one unknown species and mammalian species with the omega region of the globin gene. In the non-omega lineage, the sauropsid species was split from the rest of the remaining species.
All sauropsids from this speciation event carry the beta-globin gene. Approximately MYA, two more speciation events took place. In both the omega and non-omega lineages, the speciation event separated the monotremes from other mammals.
All monotremes from the omega lineage speciation event carry the omega-globin gene. Approximately MYA, a globin gene duplication event in the non-omega lineage resulted in a globin gene with regions 5-prime-epsilon-betaprime-omega. The epsilon-globin and beta-globin genes arose via duplication of a proto beta-globin gene in the ancestor of therian animals.
Approximately MYA, three speciation events occurred. In the omega lineage, marsupials were separated from an unknown species. All marsupials resulting from this speciation event carry the omega-globin gene.
In the epsilon and non-epsilon lineages, the marsupials were separated from the eutherians. In the epsilon lineage, the speciation event resulted in marsupials carrying the epsilon-globin gene. In the non-epsilon lineage, the speciation event resulted in marsupials carrying the beta-globin gene.
Approximately MYA, two globin gene duplication events occurred. A gene duplication event in the non-omega monotremes resulted in a new lineage with the gene 5-prime-epsilon-P-beta-Pprime-omega. The epsilon-P and beta-P globin genes arose via duplication of a proto beta-globin gene in the monotreme lineage. In the epsilon-P lineage, this resulted in monotremes with the epsilon-P-globin gene. In the non-epsilon-P lineage, this resulted in monotremes with the beta-P-globin lineage.
A gene duplication event in the epsilon lineage of eutherians resulted in a gene with the regions 5-prime-epsilon-gamma-betaprime. This resulted in two separate eutherian species: the epsilon-globin eutherians and the gamma-globin eutherians. Approximately MYA, a globin gene duplication event in the non-epsilon lineage of eutherians resulted in a gene with the regions 5-prime-epsilon-gamma-delta-beta-three-prime.
This resulted in two separate eutherian species: the delta-globin eutherians and the beta-globin eutherians. Clustering of Breakpoints: Recombination Hotspots. Figure 4. Figure Detail. Figure 5: The presence of peaks in crossover activity, which are embedded in 'cold' DNA, are reminiscent of recombination patterns in maize and might be typical of higher eukaryotes with complex genomes.
Genes in the region are shown as boxes above the plot. The peaks in recombination activity represent the six crossover hot spots characterized by sperm analyses see main text. The most active crossover hot spot, DNA3 is indicated with a dashed box. Where the crossovers are: recombination distributions in mammals. Nature Reviews Genetics 5, All rights reserved.
Figure 6: Homology-driven forces affect the occurrence and evolution of segmental duplications SDs. Non-allelic homologous recombination NAHR between highly identical SDs causes further rearrangements depending on the location and orientation of the SD copies involved. Tandem duplications and intervening deletions can occur as a result of NAHR between adjacent duplicated sequences.
Nature Reviews Genetics 7, Deletions, Duplications, and Disease. Figure 7. Human Molecular Genetics 3 , — Chen, H. Human Molecular Genetics 8 , — Clark, A. If there is a gain or loss of genetic material, the translocation is described as unbalanced. Deletions occur when a chromosome breaks and some genetic material is lost. Deletions can be large or small, and can occur anywhere along a chromosome.
Duplications occur when part of a chromosome is abnormally copied duplicated. This type of chromosomal change results in extra copies of genetic material from the duplicated segment. An inversion occurs when a chromosome breaks in two places; the resulting piece of DNA is reversed and re-inserted into the chromosome.
Genetic material may or may not be lost as a result of the chromosome breaks. An inversion that includes the chromosome's constriction point centromere is called a pericentric inversion.
An inversion that occurs in the long q arm or short p arm and does not involve the centromere is called a paracentric inversion.
An isochromosome is a chromosome with two identical arms. Instead of one q arm and one p arm, an isochromosome has two q arms or two p arms. As a result, these abnormal chromosomes have an extra copy of some genes and are lacking copies of genes on the missing arm. Unlike normal chromosomes, which have one centromere, a dicentric chromosome contains two centromeres.
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