뒤로General Biology: Inheritance and Genetics
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Mendelian inheritance refers to the patterns of inheritance first described by Gregor Mendel, involving dominant and recessive alleles where heterozygous individuals show the dominant trait.
Dominant alleles mask the effect of recessive alleles in heterozygotes, while recessive alleles only show their trait when homozygous.
Incomplete dominance occurs when heterozygotes show a blend of both alleles, producing an intermediate phenotype.
Codominance occurs when both alleles are fully expressed in heterozygotes, showing both traits simultaneously.
Multiple alleles means more than two allele forms exist for a gene, but an individual can only have two alleles.
Polygenic inheritance involves multiple genes contributing to a single trait, often producing continuous variation.
Sex-linked inheritance refers to genes located on sex chromosomes, often showing different patterns in males and females.
The law of independent assortment states that alleles of different genes assort independently during gamete formation if genes are unlinked.
Pedigree analysis uses family trees to track inheritance patterns and determine if traits are dominant, recessive, or sex-linked.
Dominant disorders usually appear in every generation and affect both sexes equally in autosomal cases.
Recessive disorders often skip generations and can appear when both parents are carriers but unaffected.
Blood type shows multiple alleles (A, B, O), codominance (A and B alleles), and dominant/recessive patterns (O is recessive).
There are 6 possible genotypes (AA, AO, BB, BO, AB, OO) and 4 phenotypes (A, B, AB, O) in human blood types.
During meiosis, alleles segregate so each gamete carries one allele per gene, explaining inheritance patterns.
Linked genes are located close on the same chromosome and tend to be inherited together, violating independent assortment.
Environmental factors can influence how a genotype is expressed, so phenotype is not always a perfect predictor of genotype.
The Human Genome Project mapped all human genes, improving understanding of inheritance, genetic disorders, and mutations.
Genetic testing raises ethical issues like privacy, discrimination, and psychological impact on individuals and families.
Hemophilia is X-linked recessive; carrier mothers have a 50% chance of passing the allele to sons who will be affected.
In codominance, both alleles are fully expressed; in incomplete dominance, heterozygotes show a blended intermediate trait.
Mendelian genetics is called simple because heterozygotes show only the dominant phenotype, with clear dominant/recessive relationships.
Dihybrid crosses predict offspring ratios for two traits, assuming genes assort independently unless linked.
Crossing red and blue flowers (incomplete dominance) produces purple heterozygotes; combining with tall/short traits can be done via dihybrid crosses.