Consider an opaque horizontal plate that is well insulated on its back side. The irradiation on the plate is 2500 W/m2 , of which 500 W/m2 is reflected. The plate is at 227 C and has an emissive power of 1200 W/m2 . Air at 127 C flows over the plate with a heat transfer convection coefficient of 15 W/m2 K. Determine the emissivity, absorptivity, and radiosity of the plate. What is the net heat transfer rate per unit area?
Mendelian Genetics Introduction o Gregor Mendel- 1856-1868 o Characteristics of organisms are controlled by genes o A gene is a portion of the DNA that codes for a given polypeptide chain- protein o Genes control the characteristics display- blonde or brunette o Genetics- the study of how genes control these characteristics and how they are passed from one generation to the next- inheritance o The laws Mendel developed were not widely accepted until about 1900 when 3 other scientists came up with the same results Thought of a gene as a particle that was passed from parent to offspring o All sexually reproducing organisms are diploid- two sets of chromosomes- 2 sets of genes for each characteristics Genes and Characteristics o Although each individual has 2 genes for each characteristic there may be several forms of alternative genes in a population o Alleles- alternative forms of genes for each characteristic o A particular combination of alleles present in an organism is the genotype o The way genes express themselves is you phenotype o Homozygous alleles- identical alleles o Often one allele masks the effects of the other allele- dominant o Allele that gets masked- recessive Recessive traits only express themselves if they are homozygous Mendel’s Laws of Heredity o Often practical to determine whether a certain phenotype is homo or heterozygous for the dominant allele The homozygous dominant breeds true o Test cross- useful for plant and animal breeders looking for stock that breeds true o Mendel’s Law of Dominance When an organism is heterozygous for a given trait the allele that is expressed is said to be dominant and the allele that is masked is recessive o Mendel’s Law of Segregation When gametes are formed the alleles that control a given trait separate from each other into separate gametes and retain their individuality o Mendel’s Law of Independent Assortment Members of one gene pair separate from each other independently from members of other gene pairs Probability vs Possibility o Probability- chance of something happening (# of events 1 outcome/ # of possible outcomes) Monohybrid Crosses o Genetics cross in which a single characteristic is followed from one generation to the next o 5 basic steps whether its mono or dihybrid Assign a symbol for each allele- capital letter for dominant and lowercase for recessive Determine the genotype of each parent and indicate a mating (Ee x Ee) Determine all possible types of gametes each parent can produce and place it in a Punnett square Determine all gene combinations that can result when these gametes unite Determine the phenotype of each possible gene combination Results can be expressed as a ratio- 3:1 This 3:1 ratio is always expected in a monohybrid cross between 2 heterozygous parents Dihybrid Cross o Genetic cross in which 2 pairs of alleles of 2 characteristics are followed from one generation to the next o Same 5 basic steps from above apply o With this there are 16 possible outcomes 9:3:3:1 ratio That ratio is always expected when two heterozygous alleles from each parent are crossed Real world example o So far we have looked at cases that there is a dominant and a recessive allele- but things don’t always work out like that Some alleles aren’t dominant Some characteristics are determined by 2 or more alleles Some characteristics are determined by gene interactions Some characteristics are inherited differently depending on the sex of the offspring Some genes control more than one characteristic o Lack of Dominance- in some cases both alleles express themselves Ex: snapdragon flower color alleles- neither allele is dominant or recessive o Multiple alleles- refers to the fact that some characteristics are determined by 3 or more different alleles- however an individual can only have a max of 2 alleles for a given characteristic Ex: IA, IB, i- A and B show lack of dominance when they are present in the same person, but both A and B are dominant over the O allele o Polygenic Inheritance So far each characteristic we’ve looked at were determined by an allele at one locus Some characteristics are determined by multiple pairs of alleles on the same of different chromosomes Ex: alleles for skin color are located at a minimum of 3 different loci and the dark allele is dominant at each allele o Pleiotropy- when the gene has more than one effect on the phenotype of the organism- often- sometimes good and bad Ex: sickle cell anemia o Linkage Alleles that are located on the same chromosome tend to be inherited together- linkage group Because of crossing over during meiosis I the closer two genes are together on the same chromosome the more likely they will be inherited together o Sex Linked Genes Many organisms have autosomes and sex chromosomes In humans and other animals there are two kinds of sex chromosomes X and Y Because the Y chromosome is so much smaller than the X chromosome it doesn’t have any of the alleles located on the “extra” portion on the X chromosome Therefore in males the presence of a single allele on the extra portion of the X chromosome will be expressed whether it is dominant or recessive Ex: colorblindness and hemophilia- recessive and on the X- more men than women are colorblind and have hemophilia Sex Influenced gene- autosomal genes who’s expression depends on whether the person is male or female Ex: gene for baldness- men can be heterozygous, but women have to be homozygous Sex hormones influence the activity of the genes- on/ off Environmental Influence on Gene Expression o Specific phenotype is determined not only by genes but also by the environment by which the organization develops o Even 2 organisms with identical genotypes may have different phenotypes Ex: diet effects growth- twins o Sometimes the physical environment determines if certain genes functions- color and thickness of animal fur