Chapter 13 - Mendelian Genetics and Probability

The transmission of genetic information is an important function in living organisms. * During protein synthesis, information is transported inside an organism from the nucleus to the ribosome. * Information is passed down from generation to generation by inherited units of chemical information known as genes.
Through the processes of conjugation, transformation, or transduction, information can be passed across individuals of the same generation. * DNA and RNA are the bearers of this genetic information in all circumstances. * All forms of life have DNA, RNA, and ribosomes. * DNA and RNA employ a genetic code that all living species share. * This provides compelling evidence for the shared ancestry of all living species on Earth.
Mendel's rules of segregation and independent assortment describe how genetic inheritance works. * Mendel's rules of segregation and independent assortment describe how genetic information is passed down from generation to generation. * It is crucial to emphasize that Mendel's rules of segregation and independent assortment only apply to features that are coded for by genes on distinct chromosomes. * Genes that are near together on the same chromosome are related and are more likely to be inherited together. * The principles of segregation and independent assortment established by Mendel do not apply to connected genes. * ^^According to Mendel's rule of segregation, each organism has two variants of each trait (called alleles), one from each parent, and these alleles segregate, or separate, independently into gametes.^^ * This segregation takes place during the anaphase of meiosis. * The alleles on those chromosomes will separate during anaphase I.
The alleles on those chromosomes will partition into different gametes during anaphase I. * Each gamete receives one variant (or allele) for a characteristic. * When two gametes fuse during fertilization, the child has two alleles for the characteristic. * @@According to Mendel's law of independent assortment, genes for distinct characteristics segregate independently of one another.@@
During metaphase I of meiosis, this independent sorting occurs. * In pea plants, for example, acquiring the gene for purple blossom color is a separate event from inheriting the allele for wrinkled peas. * This is due to the fact that the gene for pea blossom color is on a different chromosome than the one for pea form. * In metaphase I of meiosis, these chromosomes assort separately. * In metaphase I of meiosis, these chromosomes assort separately.
A pedigree is a chart that shows how a trait is passed down across generations. * Horizontal lines between two people in a pedigree indicate that they have had children together. * Vertical lines represent the offspring of these people. * Circles are often used to symbolize ladies, whereas squares are used to represent males.
Examining the inheritance pattern of a characteristic presented in a pedigree can provide information about the trait's likely mode of inheritance. * Because only one allele for the characteristic is necessary for it to be produced, dominant traits tend to be exhibited in at least one parent and their children. * Because the parents are heterozygous carriers of the trait, recessive characteristics are frequently displayed in kids but not in either parent. * Males are more likely than females to have sex-linked recessive characteristics. * Having two copies of the same allele for a characteristic is referred to as being homozygous (i.e., AA or aa).
^^Heterozygous—having two distinct alleles for a characteristic (for example, Aa); Mendel called this a "hybrid."^^ * ^^Dominant—only one copy of the allele is required for the characteristic to be present.^^ * Dominant characteristics require just one copy of the allele for the trait to be expressed in the phenotype; dominant traits are those that are expressed in heterozygous organisms. * Recessive—requires two copies of the allele for the trait to be expressed in the phenotype; heterozygous organisms do not exhibit recessive characteristics.
$A dihybrid cross examines the outcome of crossing two organisms (both heterozygous for the same two characteristics).$ * Math is your friend when it comes to solving dihybrid crosses! * Treat each attribute independently, calculate the odds of each result for each trait, then solve the issue using probability rules.