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In genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) (sign: Δ) is a mutation (a genetic aberration) in which a part of a chromosome or a sequence of DNA is left out during DNA replication. Any number of nucleotides can be deleted, from a single base to an entire piece of chromosome. [1]
DNA replication may also be blocked and/or the cell may die. In contrast to a DNA damage, a mutation is an alteration of the base sequence of the DNA. Ordinarily, a mutation cannot be recognized by enzymes once the base change is present in both DNA strands, and thus a mutation is not ordinarily repaired.
This is because spermatocytes go through a larger number of cell divisions throughout a male's life, resulting in more replication cycles that could result in a DNA mutation. [5] Errors in maternal ovum also occur, but at a lower rate than in paternal sperm. [5] The types of mutations that occur also tend to vary between the sexes. [7]
Eukaryotes initiate DNA replication at multiple points in the chromosome, so replication forks meet and terminate at many points in the chromosome. Because eukaryotes have linear chromosomes, DNA replication is unable to reach the very end of the chromosomes. Due to this problem, DNA is lost in each replication cycle from the end of the chromosome.
Bloom syndrome is an autosomal recessive disorder, caused by mutations in the maternally- and paternally-derived copies of the gene BLM. [13] As in other autosomal recessive conditions, the parents of an individual with Bloom syndrome do not necessarily exhibit any features of the syndrome.
Each autosomal gene is therefore represented by two copies, or alleles, with one copy inherited from each parent at fertilization. The expressed allele is dependent upon its parental origin. For example, the gene encoding insulin-like growth factor 2 (IGF2/Igf2) is only expressed from the allele inherited from the male. Although imprinting ...
Autosomal recessive inheritance, a 25% chance, and (purple) a 50% carrier chance. Autosomal recessive traits is one pattern of inheritance for a trait, disease, or disorder to be passed on through families. For a recessive trait or disease to be displayed two copies of the trait or disorder needs to be presented.
Two strains of flies are white-eyed because of two different autosomal recessive mutations that interrupt different steps in a single pigment-producing metabolic pathway. Flies from Strain 1 have complementary mutations to flies from Strain 2 because when they are crossed the offspring can complete the full metabolic pathway and thus have red eyes.