Free PowerPoint Backgrounds Non-Mendelian Genetics
Free PowerPoint Backgrounds Today, we know that genes often do not follow Mendel’s Laws all the time! There are exceptions….. Incomplete dominance Co-dominance Multiple Alleles Polygenics Environmental genes Sex linkage
Free PowerPoint Backgrounds INCOMPLETE DOMINANCE AND CODOMINANCE
Free PowerPoint Backgrounds Incomplete dominance Characterized by a blending of traits. Phenotype of offspring falls somewhere between each parent, when genotype is heterozygotic. EX: Red horses (RR) crossed with white horses (rr) produce Rr heterozygotes that are “pink” in color.
Free PowerPoint Backgrounds Co-dominance Characterized by the expression of both alleles. Even the recessive allele affects the organism.
Free PowerPoint Backgrounds EX: Blood type - A and B are both dominant! I A =A, I B =B I A I A = A type I A I B = AB type I B I B = B type
Free PowerPoint Backgrounds Check for Understanding IN YOUR OWN WORDS, describe to your partner the difference between incomplete and co-dominance. Be ready to share.
Free PowerPoint Backgrounds On your own, determine which type the following are: Green eyes crossed with brown eyes = hazel eyes Blue feathers crossed with purple feathers = some blue and some purple feathers
Free PowerPoint Backgrounds Practice Cross a red flower with a white flower when red is incompletely dominant to white. List all the possible phenotypes for the offspring and their probabilities. Cross a I A I B individual with a I A I B individual. List all the possible phenotypes for the offspring and their probabilities.
Free PowerPoint Backgrounds MULTIPLE ALLELES, POLYGENICS, AND ENVIRONMENTAL GENES
Free PowerPoint Backgrounds Multiple Alleles Multiple Alleles: When there are more than just 2 alleles for a trait. – Example: Rabbit hair color and human blood types.
Free PowerPoint Backgrounds Practice Cross a heterozygous Brown (carrier for chinchilla) rabbit with a homozygous Himalayan rabbit Order of dominance: C > c Ch > c h > c
Free PowerPoint Backgrounds Practice I A =A, I B =B, i=O I A I A or I A i= A type I A I B = AB type I B I B or I B i = B type ii = O type Cross a I A I B individual with an I B i individual
Free PowerPoint Backgrounds Polygenic traits Characterized by many genes are needed to affect a single trait. Eye color Hair color
Free PowerPoint Backgrounds Polygenic traits
Free PowerPoint Backgrounds Environmental genes Phenotype that changes as genes are exposed to external stimuli, like temperature.
Free PowerPoint Backgrounds GENE LINKAGE
Free PowerPoint Backgrounds Linked Genes If two genes are located on the same chromosome, they will most often be inherited together. These are called linked genes. – Chromosomes assort independently, not individual genes
Free PowerPoint Backgrounds Do linked genes always stay together? Crossing over can separate genes that were once on the same chromosome. – Helps increase diversity Genes that are farther apart on a chromosome are separated by crossing-over more often than those that are close together.
Free PowerPoint Backgrounds Gene mapping By using the rate of crossing-over between two genes (or recombination rate) we can discover how far apart the genes are from one another. We can map out where the genes are on a chromosome using these recombination rates.
Free PowerPoint Backgrounds Exact location on chromosomes Gene Map of the Fruit Fly
Free PowerPoint Backgrounds Autosomes vs. Sex Chromosomes Two of our 46 chromosomes are sex chromosomes. They determine the gender of an individual – Females are XX – Males are XY
Free PowerPoint Backgrounds Sex linked traits Some genes are on the Y chromosome Ex: Ear Hair Those carried on the X are more abundant EX: Muscular Dystrophy When a gene is on one of the sex chromosomes, it is called sex linked.
Free PowerPoint Backgrounds Sex-linked Genes Most sex-linked disorders are located on the X chromosome that is much larger and contains many more genes than the Y chromosome. More than 100 sex-linked disorders have been mapped on the X chromosome. Males only have one X chromosome so any alleles on the X chromosome are expressed even if they are recessive traits.
Free PowerPoint Backgrounds Sex Linked X-linked dominant – Found in females more often than in males. X-linked recessive – Found in males more often than females Y-linked – Only found in males
Free PowerPoint Backgrounds Colorblindness Colorblindness: Inability to see specific colors. – Most common type is red-green colorblindness. – 1 in 10 males and 1 in 100 females. – Why the difference? – It is a recessive allele resulting in males getting it if it is on the X chromosome. It must be on both X chromosomes for a woman to have it.
Free PowerPoint Backgrounds Ex: Red/Green Colorblindness
Free PowerPoint Backgrounds Lets do a Punnett Square to show this EX: Hemophilia X h X h or Xh Y = hemophilia. Males CAN’T be carriers of an X-linked gene!
Free PowerPoint Backgrounds Cross a color-blind male and a carrier female? How many of their children will be colorblind?
Free PowerPoint Backgrounds Cross a color-blind male and a non- carrier female? How many of their children will be colorblind?
Free PowerPoint Backgrounds X-CHROMOSOME INACTIVATION
Free PowerPoint Backgrounds X-Chromosome Inactivation In females, one X chromosome is randomly switched off. The switched off chromosome forms a dense region in the nucleus called a Barr body. A cat’s fur will be different colors depending on which X chromosome is turned on in different parts of the body.
Free PowerPoint Backgrounds X-Chromosome Inactivation