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Jul 8, 2009 · Several basic modes of inheritance exist for single-gene disorders: autosomal dominant, autosomal recessive, X-linked dominant, and X-linked recessive. However, not all genetic conditions will follow these patterns, and other rare forms of inheritance such as mitochondrial inheritance exist.
- 2009/07/08
Jul 31, 2022 · Mendel’s results, that traits are inherited as dominant and recessive pairs, contradicted the view at that time that offspring exhibited a blend of their parents’ traits. However, the heterozygote phenotype occasionally does appear to be intermediate between the two parents.
Sexually reproducing organisms inherit their genetic sequences from both parents (2 x chrom.) A I —> spindle fibres contract and split the bivalent, hom. Chromosomes move to opposites. Phenotype —> the observable characteristic of a specific trait (determined by genotype and env.)
Dominant = only one allele of a gene necessary to express the trait. Recessive = both alleles of a gene must be identical to express the trait. Heterozygous = alleles of a particular gene are non-identical. Homozygous = alleles of a particular gene are identical
- Autosomal Dominant
- X-Linked Dominant
- Autosomal Recessive
- X-Linked Recessive
- Y-Linked
When a disease is caused by a dominant allele of a gene, every person with that allele will show symptoms of the disease (assuming complete penetrance), and only one disease allele needs to be inherited for an individual to be affected. Thus, every affected individual must have an affected parent. A pedigree with affected individuals in every gener...
In X-linked dominant inheritance, the gene responsible for the disease is located on the X-chromosome, and the allele that causes the disease is dominant to the normal allele in females. Because females have twice as many X-chromosomes as males, females tend to be more frequently affected than males in the population. However, not all pedigrees pro...
Diseases that are inherited in an autosomal recessive pattern require that both parents of an affected individual carry at least one copy of the disease allele. With AR traits, many individuals in a pedigree can be carriers, probably without knowing it. Compared to pedigrees of dominant traits, AR pedigrees tend to show fewer affected individuals a...
Because males have only one X-chromosome, any male that inherits an X-linked recessive disease allele will be affected by it (assuming complete penetrance). Therefore, in XR modes of inheritance, males tend to be affected more frequently than females in a population. This contrasts with AR and AD, where both sexes tend to be affected equally, and X...
Only males are affected in human Y-linked inheritance (and other species with the X/Y sex determining system). There is only father-to-son transmission. This is the easiest mode of inheritance to identify, but it is one of the rarest because there are so few genes located only on the Y-chromosome. A common, but incorrect, example of Y-linked inheri...
What is the difference between dominant and recessive traits? Dominant traits are always expressed when the connected allele is dominant, even if only one copy of the dominant trait exists. Recessive traits are expressed only if both the connected alleles are recessive.
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What is the difference between dominant and recessive traits?
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The mode of inheritance refers to how a trait is inherited: is it dominant or recessive? Is the gene located on a sex chromosome, an autosome, or the mitochondrial chromosome? We will look at six modes of inheritance in this module: autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive , Y-linked, and mitochondrial ...
