Lecture 24Outline of Last Lecture1. Be able to solve any punnett square genetics problem.Outline of Current Lecture1. Pleiotropy: discuss how a single gene can affect many features of the organism.2. Discuss the the inheritance of X-linked genes in mammals. 3. Discuss what it means to be hemizygous, and what is means to be a mosaic. What is a Barr Body, and what is dosage compensation?4. Define linkage, and relate it to specific events in meiosis.5. Show how data from a test cross involving alleles of two loci (‘two point test cross’) can be used to distinguish between independent assortment and linkage.6. Know how to calculate allele frequency using the Hardy-Weinberg equation.7. Explain how prenatal testing, carrier screening, and newborn screening can be used to detect genetic conditions before and after birth. I. Pleiotropy- Pleiotropy is a mutation of the genes caused by many possible factors in meiosis. Pleiotropy could either be an insertion of a gene to the end of an incorrect gene, too many genes, not enough genes, so on. These can occur by spindle fibers failing to separate chromatids properly, genes not lining up on the metaphase plate, etc. What you need to know most importantly is that Pleiotropy is a negative condition of the genes.II. X Linked Genes in MammalsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. BIOL 101 1st Edition- In mammals, the X gene in an offspring is always obtained by the mother. This means all male mammals inherit their mother’s X chromosome. Female offspringget an X from the mother and an X from their father. However if any genetic defect is on the mother’s X chromosome, the male offspring are guaranteed to getit, and any female offspring are guaranteed carriers if the male is not a carrier.III. Chromosome Defects- Hemizygous means you have only 1 member of a chromosome pair instead of thetwo. - To be Mosaic means you have two or more populations of cells in your body withdifferent genetic makeups. - A Barr Body is an inactive X chromosome in somatic (non-reproductive) cells.- Dosage Compensation is when an allele allows another allele to by active in the phenotype. Such as in fruit flies, an ee in the genotype FFee could result in the FFnot being expressed, even though it is dominant.IV. Linkage- Linkage is when genes tend to be close to eachother during prophase one, which allows for crossing over.V. Two Point Test Cross- You can use a test cross to see roughly how far genes are from eachother. In this way, you can see how likely it is for a gene to cross over during linkage based on how close they are to eachother.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. BIOL 101 1st EditionVI. The Hardy-Weinberg EquationThe Hardy-Weinberg equation: Basic assumptions1. Mutation is not occurring2. Natural selection is not occurring3. The population is infinitely large4. All members of the population breed5. All mating is totally random6. Everyone produces the same number of offspring7. There is no migration in or out of the population (This can’t ever be fully true in a population, but if you know the frequency you can tell the genotypic ratio.)Equations:Allele Frequency: Dom + rec = 1 (p + q = 1)Genotype Frequency: p2 + 2pq + q2 = 1 Example:1. Two alleles at a gene - A and a2. Frequency of the A allele = p3. Frequency of the a allele = q4. Allele frequencies: p + q = 15. Genotype frequencies: p2 (AA) + 2pq (Aa) + q2 (aa) = 1VII. Screening- Prenatal screening can be done to check if the genes are proper and have no malformations, and if done at a later date during pregnancy, can be used to check any malformation of the fetus. When there is a percent chance of the child havinga gene defect, specific phenotypes can be observed to deduct whether or not further testing must be done. An example of this would be looking for Down syndrome symptoms in the puffiness of eyes or the flatness in the bridge of nose phenotypes.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. BIOL 101 1st