Chapter 10 Genetics PDF

Chapter 10 Genetics PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  GE...

Chapter 10 Genetics PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  GENETICS Genetics - Study of heredity and variation of inherited characters Greek word “genetikos” - means genesis, origin, beginning. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 1. genotype - the genetic make-up (the assemblage of alleles) of an individual. 2. phenotype - the physical or chemical expression of an organism s genes. 3. gene - a discrete unit of hereditary information that usually specifies a protein; a region of DNA (locus) located on a chromosome that specifies a trait (characteristic). 4. alleles - genes governing variations of the same characterist ic (trait) that occupy corresponding positions (loci) on homologous chromosomes; alternative forms of a gene. 5. dominant allele - an allele that is always expressed when present, regardless of whether the organism is homozygous or heterozygous for that gene. 6. recessive allele - an allele that is only expressed when the organism is homozygous for that allele and not expressed when heterozygous (when paired with a dominant allele). 7. homozygous - possessing a pair of identical alleles for a particular locus (gene). 8. heterozygous - possessing a pair of unlike alleles for a particular locus (gene). 9. carrier - a heterozygous individual not expressing a recessive trait but capable of passing it on to its offspring. 10. parent generation (P) - the generation that supplies gametes to the filial generation. 11. filial generation (F,) - the generation that receives gametes from the parental generation. 12. hybrid - an offspring resulting from the mating between individuals of two different genetic constitutions. 13. dihybrid cross - a genetic cross that takes into account the effect of alleles at two separate loci (two different genes). 14. monohybrid cross - a genetic cross that takes into account the effect of alleles at a single locus (single gene). Mendelian theory of Inheritance Law of Dominance - states that, in a heterozygote, the dominant allele is expressed exclusively. Law of Segregation - states that when an organism is making gametes, it separates its gene pair, or alleles so that each one is individually packaged. Law of Independent Assortment – states that alleles of different genes are inherited independently of one another. Thus, an allele inherited for one gene doesn't influence or affect the ability to inherit an allele of a different gene. Sample Problem 1. In peas, seeds may be round (R) or wrinkled (r). What proportion of the offspring in the following crosses would be expected to be wrinkled? a. RR x rr b. Rr x Rr c. Rr x rr 2. Two pea plants heterozygous for the characters of pod color and pod shape are crossed. Draw a Punnett square to determine the phenotypic ratios of the offspring. 3. A man with type A blood marries a woman with type B blood. Their child has type O blood. What are the genotypes of these three individuals? What genotypes, and in what frequencies, would you expect in future offspring from this marriage? 4. In tigers, a recessive allele of a particular gene causes both an absence of fur pigmentation (a white tiger) and a cross-eyed condition. If two phenotypically normal tigers that are heterozygous at this locus are mated, what percentage of their offspring will be cross-eyed? What percentage of cross- eyed tigers will be white? Exceptions of Mendelian Inheritance Exception 1: Multiple Genes - polygenic traits Exception 2: Multiple Alleles – (ABO blood, Rabbit color) Exception 3: Codominance Exception 4: Incomplete Dominance Exception 5: Pleiotropy - has multiple effects on the phenotype Exception 6: Gene Linkage – Two linked genes tend to assort together, and inheriting one would increase the likelihood that you inherit another. 5. In one of the matings of rabbits, the litter contained 4 grey bunnies, 2 white (albino) bunnies, and 2 himalayan bunnies. What were the genotypes of the parents? Modern Genetics Terminologies 1. haploid - the condition of having only one set of chromosomes per cell (n) 2. diploid - the condition of having two sets of chromosomes per cell (2n) 3. gamete - a haploid (n) sex cell in plants and animals (egg or sperm) 4. zygote - diploid (2n) cell resulting from the union of two gametes in sexual reproduction 5. chromatin - the complex of DNA, RNA and proteins that makes up uncondensed eukaryotic chromosomes. 6. chromosome - structures within the nucleus of eukaryotic cells composed of chromatin and visible at cell division (condensed chromatin). 7. homologous chromosomes - chromosomes that are similar in morphology (shape and form) and genetic constitution. In animals one set comes from the father and the other from the mother. 8. chromatids - one of the two halves of a duplicated chromosome 9. centromeres - specialized constricted region of a chromatid, that contains the kinetochore; sister chromatids are joined at the centromere during cell division 10. recombination - exchange of genetic material between chromosomes 11. crossover - the breaking and rejoining of homologous (non-sister) chromatids during early prophase I of meiosis, resulting in recombination 13. disjunction - separation of homologous chromosomes (or sister chromatids) during anaphase 12. synapsis - the pairing of homologous chromosomes during prophase I of meiosis.