BIO 107 1nd EditionExam # 3 Study Guide Lectures: 21 - 29Week 8 (Lecture 21)Mendelian GeneticsWhat are the basics of Mendelian genetics?Mendel deduced that genetic variation occurs because of alleles, or different versions, of a trait.There are dominant and recessive alleles. The same letter is used for each, but the dominant type is capital and the recessive is lowercase. They are observed as a phenotype and are coded in the DNA as a genotype.What is the Law of Segregation?The Law of Segregation proposes that each allele in an organism, say diploid, is separated and not passed to the gametes together.Week 9 (Lecture 22) GeneticsWhat are punnett squares and how are they used?Punnett squares are tables used to visualize the possible outcomes of a genetic cross. They are used by placing the possible gametes of one parent along one axis and the possible gametes of the other parent on the other axis. The possible progeny are then found by combining the two gamete types where they cross. A punnett square is shown below: parents are Aa and aaA aa Aa aaa Aa aaProgeny can be Aa or aa.What are the laws of independent assortment? Genes for different traits are assorted randomly All possible combinations of phenotypes can be seen with enough progeny Distinct trait combinations can be seen in the progeny that are not seen in the parents. An example in a punnett square is shown below:Parents are AAbbCc and AaBbccAbC AbcABc AABbCc AABbccAbc AAbbCc AAbbccaBc AaBbCc AaBbccabc AabbCc AabbccWhat are the probability rules? Addition rule – either/or results, probability of multiple outcomes is the sum of each outcome Multiplication rule – and/then results, probability of independent events occurring together is the product of each eventWhat is a test cross?A test cross is the cross of a parent with a dominant phenotype and a homozygous recessive parent to see if any of the progeny are homozygous recessive. It shows if the parent with the dominant phenotype is homozygous or heterozygous. A heterozygous cross will show homozygous recessive progeny.Week 10 (Lectures 23-25) GeneticsWhat are the misconceptions with test crossing? If there are few progeny, then it can be hard to determine the unknown parent. Once one progeny is sown to be homozygous recessive, then it is clear that the parent is heterozygous The popular genotype in a population does not mean it is the dominant oneWhat is the difference between incomplete dominance and codominance?In codominance, both alleles are dominant and can both be expressed, such as AB blood type.inincomplete dominance, neither allele is dominant over the other and a mix of sorts is observed.What are the differences between epistasis, polygenetic inheritance, and a pleiotropy effect?Epistasis is the effect when one gene affects the expression of another. One gene can cancel the effects of another such in Labrador coat color. Polygenetic inheritance is when multiple genes affect the phenotype. Pleiotropy is the opposite, one gene affects many phenotypes.How are the other extensions of Mendelian genetics created? Environmental effect- things like pH and soil composition can affect petal color in plants Mosaicism and other phenomena- mutations in cell division, the fusing of multiple zygotes, or chromosomal inactivation. (it is not limited to just these)Pedigree AnalysisWhat is pedigree analysis and how is it used?Pedigree analysis is the examination of a family to find inheritance patterns. A pedigree is made from the family tree and phenotypes are marked. Based on how the trait being examined showsup, it can be deduced if the trait is dominant or recessive, sex-linked, or any other possible characteristics. A pedigree is shown below:Square= maleCircle= femaleColored= affectedUncolored= unaffectedFrom this pedigree, it can be deduced that the trait being looked at is X-linked and dominant.Chromosomal Basis of InheritanceWhy is it important to base inheritance off of chromosomes instead of just Mendelian genetics?Some inheritance patterns do not follow Mendelian genetics such as sex linking. Basing inheritance on chromosomes where the genes are located at specific loci on a chromosomes helps explain the phenomenon.Who was the scientist credited with discovering chromosomes and what other explanations did he contribute?Thomas Morgan was the scientist credited with discovering chromosomes. He also contributed the explanations of sex-linked traits and the crossing over of chromosomes. He used the fruit flyas a model.What is X-inactivation?X-inactivation is when a mammal has two X chromosomes (female) and one copy is inactivated to affect phenotype. This is a random process. What is the difference between the X and Y chromosome?The X chromosome is much larger and contains 800+ genes unrelated to sex. The Y chromosome only has 40-80 genes and is only found in males.What is commonly seen in an X-linked recessive trait?If the trait being observed is X-linked and recessive, it is commonly seen in males. Since males only have one X chromosome, they do not have the chance for a dominant allele to be present to cancel the recessive allele. It is rare to see affected females since they have two X chromosomes. What is gene linkage?Gene linkage is the idea that genes located on the same chromosome will be passed together. This can be altered by the crossing over of genes from one set of chromosomes to the other.Why is the recombination frequency?It is the likelihood of genes being recombined based on how far they are from each other on thechromosome. The unit of measurement is the Morgan (M). A 1% chance is 1 cM or about 1 million nucleotides. This allows for gene mapping on the chromosome based on the chance of recombination.What are problems that can occur in chromosomal inheritance and what causes them? Aneuploidy- the addition or subtraction of one chromosome. This can occur from non-disjunction in meiosos I or II or from errors in crossing over or DNA repair. Polyploidy- there is a complete extra set of chromosomes in the cells. This can occur from an interspecies cross.What is maternal imprinting?It is when a gene is methylated in the egg or sperm and the resulting phenotype can be modified. What is the genetic material and who helped discover it?DNA is the genetic material. Morgan found that the genetic material was found in chromosomes, but could not deduce if it was the proteins or the DNA. Griffith used mice and pneumonia
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