Pedigrees review (article) | Pedigrees | Khan Academy
In autosomal dominant inheritance, only one copy of a disease allele is Autosomal recessive diseases are observed more frequently in consanguineous relationships (relationships in Affected males are related through carrier females. Genetic Dominance: Genotype-Phenotype Relationships As the study of inheritance expanded beyond the seven traits Mendel initially examined and the sickle red blood cells less efficient at transporting oxygen through the bloodstream. However, the scientific study of patterns of inheritance is conventionally said to have or a sex chromosome, and on whether the allele is dominant or recessive . that entered into a symbiotic relationship with the cells billions of years ago. from the mother through the egg cell, so mitochondrial inheritance is through the .
The smaller Y chromosome contains a number of genes responsible for the initiation and maintenance of maleness, but it lacks copies of most of the genes that are found on the X chromosome. As a result, the genes located on the X chromosome display a characteristic pattern of inheritance referred to as sex-linkage or X-linkage.
Females XX have two copies of each gene on the X chromosome, so they can be heterozygous or homozygous for a given allele. However, males XY will express all the alleles present on the single X chromosome that they receive from their mother, and concepts such as 'dominant' or 'recessive' are irrelevant. A number of medical conditions in humans are associated with genes on the X chromosome, including haemophilia, muscular dystrophy and some forms of colour blindness.
Non-Mendelian inheritance patterns Complex and multifactorial inheritance Some traits or characteristics display continuous variation, a range of phenotypes that cannot be easily divided into clear categories.
In many of these cases, the final phenotype is the result of an interaction between genetic factors and environmental influences. An example is human height and weight. A number of genetic factors within the individual may predispose them to fall within a certain height or weight range, but the observed height or weight will depend on interactions between genes, and between genes and environmental factors for example, nutrition.
Traits in which a range of phenotypes can be produced by gene interactions and gene-environment interactions are known as complex or multifactorial.
Pedigrees and Modes of Inheritance
Mitochondrial inheritance Animal and plant cells contain mitochondria that have their evolutionary origins in protobacteria that entered into a symbiotic relationship with the cells billions of years ago.
The chloroplasts in plant cells are also the descendants of symbiotic protobacteria. As a result, mitochondria and chloroplasts contain their own DNA. Mitochondria are scattered throughout the cytoplasm of animal and plant cells, and their DNA is replicated as part of the process of mitochondrial division. A newly formed embryo receives all its mitochondria from the mother through the egg cell, so mitochondrial inheritance is through the maternal line.
Patterns of inheritance — University of Leicester
Genomic imprinting The expression of a small number of human genes is influenced by whether the gene has been inherited from the mother or father. This process - called genomic or parental imprinting - usually means that the organism expresses one of its alleles but not both.
In many cases the non-expressed allele is inactivated - for example, by DNA methylation. High levels of DNA methylation are known to inhibit gene activity. Imprinting involves three stages: This work is licensed under a Creative Commons Licence. To start reading a pedigree: Determine whether the trait is dominant or recessive. If the trait is dominant, one of the parents must have the trait.
BBC Bitesize - GCSE Biology (Single Science) - Genetic inheritance - Edexcel - Revision 4
Dominant traits will not skip a generation. If the trait is recessive, neither parent is required to have the trait since they can be heterozygous. Determine if the chart shows an autosomal or sex-linked usually X-linked trait. For example, in X-linked recessive traits, males are much more commonly affected than females. In autosomal traits, both males and females are equally likely to be affected usually in equal proportions. Autosomal dominant trait Pedigree showing the inheritance of freckles across three generations.
The diagram shows the inheritance of freckles in a family. The allele for freckles F is dominant to the allele for no freckles f. At the top of the pedigree is a grandmother individual I-2 who has freckles.
What is the genotype of individual I-2? Since freckles are dominant to no freckles, an affected individual such as I-2 must at least have one F allele.Incomplete Dominance, Codominance, Polygenic Traits, and Epistasis!
The trait shows up in all generations and affects both males and females equally.