Mis Trabajos

Modes of Inheritance
1. Modes of inheritance are the rules explaining the common patterns of inheritance.
2. A Mendelian trait is caused by a single gene.
3. Traits can be dominant or recessive and recur in a predictable pattern in subsequent generations.
4. Autosomal Dominant Inheritance: Autosomal dominant traits do not generally skip generations and can affect both sexes.
5. AutosomalRecessive Inheritance: Autosomal recessive traits can skip generations and can affect both sexes. Blood relatives that have children together have a much higher risk of having a child with a rare recessive disorder.
6. Punnett squares apply Mendel's first law to predict recurrence risks for inherited disorders or traits.
7. A Mendelian trait applies anew to each child.
On the Meaning ofDominance and Recessiveness
1. At the biochemical level, recessive disorders often result from alleles that cause the loss of function or production of a normal protein.
2. Dominant disorders can result from production of an abnormal protein that interferes with the function of a normal protein or result from a gain of function.
4.3 Following the Inheritance of Two Genes-Independent Assortment
1.Mendel's law of independent assortment considers genes transmitted on different chromosomes.
2. The phenotypic ratio of 9:3:3:1 of a dihybrid cross indicates that a gene on one chromosome does not influence transmission of a gene on a different chromosome.
3. In meiosis, random assortment of maternally and paternally derived chromosomes results in gametes that have different combinations ofgenes.
4. Punnett squares and probability are used to predict recurrence of more than one trait.
4.4 Pedigree Analysis
Pedigrees Then and Now
1. Pedigree charts depict family relationships and transmission of inherited traits.
2. Squares represent males and circles represent females.
3. Horizontal lines indicate parents, vertical lines show generations, and elevated horizontal lines depictsiblings.
4. Symbols for heterozygotes are half-shaded, and for individuals with a particular phenotype, completely shaded.
Pedigrees Display Mendel's Laws
1. Pedigrees can reveal mode of inheritance, and can include molecular information, carrier status, and input from other genes and the environment.
2. Interpretation of pedigrees can be complicated by lack of information, adoption,children born out of wedlock, assisted reproductive technologies (i.e. artificial insemination), lack of penetrance.
Extensions and Exceptions to Mendels Laws

5.1 When Gene Expression Appears to Alter Mendelian Ratios
1. A number of factors can appear to disrupt Mendelian ratios.
Lethal Allele Combinations
1. Homozygous recessive lethal alleles eliminate a progeny class.
Multiple Alleles
1. Agene can have more than two alleles, but a diploid individual only has one or two of them.
2. Different allele combinations can produce different phenotypes and different severities of symptoms.
Different Dominance Relationships
1. Incomplete dominance of an allele produces a phenotype in the heterozygote that is intermediate between that of either homozygote.
2. Codominant alleles are bothexpressed in a heterozygote.
Epistasis-When One Gene Affects Expression of Another
1. In epistasis, one gene masks the effect of another. An example of epistasis in humans is the Bombay phenotype.
2. The Bombay phenotype results in O type blood for individuals homozygous recessive for the recessive "h" allele.
Penetrance and Expressivity
1. Genotypes vary in penetrance (percent ofindividuals affected) and expressivity (severity of symptoms).
2. Penetrance and variable expression are not well understood biochemically and are probably due to the complex biochemical environment all genes function in.
Pleiotropy-One Gene, Many Effects
1. A gene with more than one phenotypic effect is pleiotropic.
Phenocopies-When It's Not in the Genes
1. A trait caused by the environment but...