Genetics, Evolution, and Biodiversity Strand 5

Meiosis Occurs in reproductive cells to form gametes that combine to form a new organism Specific process where the nucleus of the cell is duplicated and then halved End product is four cells that are genetically different and contain half of the normal DNA this condition is called haploid Crossing over and independent assortment lead to increased genetic variability When gametes combine they become diploid Occurs in body (somatic) cells to replace or repair dead cells and tissues Specific process where the nucleus of a cell is duplicated Cytokinesis is when one cell becomes two End product is two identical cells containing the full set of DNA in humans this condition is called diploid We normally contain two sets of chromosomes that code for the same traits called homologous chromosomes Mitosis

Predicting Genetics Phenotype Observable characteristic or behavior of an organism Genotype Genetic makeup of an organism Allele Variant form of a gene that in combination make up the genotype and determine the phenotype Dominant Allele Always shows in the phenotype Recessive Allele Only shows in the phenotype when there are two Homozygous Genotype containing two of the same allele Heterozygous Genotype containing two different alleles Punnett Square A tool used to “cross” individuals to determine all of the possible genotypes/phenotypes of the offspring

Monohybrid and Dihybrid Crosses Because alleles assort independently, any combination can be put into a gamete even when looking at two traits Typically used when crossing two heterozygous individuals Monohybrid cross (left) crossing individuals only looking at one trait Dihybrid cross (right) crossing individuals while looking at two traits

Pedigree Analysis Diagrams to represent inheritance of traits over generations Males are represented by squares Females are represented by circles Affected individuals are shaded in This can be a variety of genotypes (heterozygous, homozygous dominant or recessive) These are used to determine what genotype the affected condition is

Infectious Diseases Caused by something wrong in an individual’s DNA Nondisjunction Chromosomes that do not separate during Meiosis create gametes with the incorrect number of chromosomes Trisomy 21 Klinefelter’s Syndrome Turner’s Syndrome Mutations Mistakes in DNA replication causing a change in the protein product Huntington’s Disease Sickle Cell Anemia Caused by introduction of foreign organisms into the body Bacteria Small living cells causing problems Can be treated by antibiotics Tuberculosis Viruses Non-living things that inject DNA or RNA into cells to hijack cellular machinery to make more viruses NOT treatable by antibiotics Ex: The Flu Prions Misfolded proteins that cause other proteins to misfold Mad Cow Disease or Kuru Genetic Disorders

Change over time Evolution is a change in a population over time Darwin suggested this is due to natural selection Adaptive traits become more frequent in a population over time because they increase the fitness of the organism increasing fitness means increasing the likelihood it will survive and reproduce Passing down its DNA These traits can be behavioral or structural

Fossil Record Under the right conditions, organisms’ structures can be preserved as fossils Looking at fossils shows us what life looked like in the past Dinosaurs!!! The deeper the fossil the older the organism Looking at multiple layers simultaneously allows us to see evolutionary trends

Genetic Mutation Mistakes can happen when DNA is being copied or repaired causing mutations Mutations are very common and will usually have no affect on the organism's health Mutations can also lead to detrimental disorders and adaptive effects are very rare, but can happen Location of the mutation matters In somatic cells it only affects that individual In reproductive cells it can be passed down to offspring Mutations are one of the sources for new genetic material that natural selection can act on If a mutation causes an advantageous trait, the fitness of that organism will increase The organism will survive longer and reproduce more than other members of the species thus passing down the genes

Carrying Capacity Resource availability affects population size Carrying capacity is the relative maximum number of individuals an ecosystem can support There are many factors that influence carrying capacity Food availability Water supply Environmental conditions Living space Before carrying capacity is reached growth rate is exponential Once carrying capacity is reached the growth rate of the population levels off

Population Pyramids Graphs that show how many individuals in a population are at each age Interpreting the graph allows us to determine the population growth Changes in population are affected by Emigration Immigration Birth rate Death rate

Human Population Growth The human population has grown exponentially due to our advances in technology, agriculture, medicine, construction, and energy use since the industrial revolution Typically the environment influences the phenotype of an organism but humans modify the environment to match their needs