Biology Comp Study Guide. Meiosis I and II. Punnett Square. 1 Made By Abby Carroll

Transcription

1 Biology Comp Study Guide Meiosis I and II Punnett Square 1

2 DNA strand vs. RNA strand Transcription 2

3 Translation 3

4 Mutations example o Original sequence: T A C A C C T T G G C G A C G A C T o mrna sequence: A U G U G G A A C C G C U G C U G A o Amino acid sequence: methionine, tryptophan, asparagine, arginine, cysteine, stop Mutations o Any change in the DNA sequence o Errors in replication Replication Transcription Cell division External agents o Mutations in reproductive cells The sperm or egg can show up in the offspring New trait Sometimes there is benefits The protein doesn t work Structural and functional problems They may not survive o The DNA sometimes makes mistakes copying, inserting and incorrect base, shipping a base etc. these mistakes are called mutations o From the Latin word which mutene meaning to change o The changes in the DNA sequence that effect the genetic information o Gene mutations result from changes in a single gene o Chromosomal mutations involve changes in whole chromosomes o Gene mutations Point mutations are mutations that affect one nucleotide, because they only occur at a single point in the DNA sequence Some point mutations simply substitute one nucleotide for another, the substitution generally (not always) change one for the amino acids in a protein When point mutation involves insertion or deletion a nucleotide, a much bigger change results If a nucleotide is deleted, the base is still read in groups of three but now the groups are shifted for every colon that follows, inserting a nucleotide has a similar effect Called frame shift mutations because they shift the reading frame of a genetic message Affect every amino acid after the point of insertion or deletion After a protein sort is unable to perform regular functions o Chromosomal mutations Chromosomal mutations involve change in the whole chromosome 4

5 Involves changes in the number and structure of chromosomes May change the location of genes on chromosomes and even number of copies of the same genes Opposite of deletion: duplication, where a segment of a chromosome is repeated Deletion means a loss of a part of the chromosome When part of a chromosome becomes oriented in the reverse of its usual direction, the result is an inversion A translocation occurs when part of one chromosome breaks off and attaches to another non-homologous chromosome In most cases non-homologous chromosomes exchange segments so that two translocations occur at the same time o Point mutations: substitution A change of a single base pair in DNA Types of point mutations Missense: the substitution changes the amino acid Silent: the substitution does not change the amino acid Non-sense: the substitution changes the amino acid by a stop Sickle cell anemia: missense mutation Cystic fibrosis: non-sense mutation o Frame shift mutations: Single base is added or deleted Change in the reading frame of the strand Shifts reading set of 3 codons Tay Sachs disease: invert mutation Williams disease: deletion mutation o Chromosomal alterations Sometimes parts of a chromosome is broken off and lost in phases of meiosis or mitosis They can break and rejoin improperly in crossing over More common in plants Zygotes usually dies or is sterile o Causes mutations Spontaneous mutations Mutagens Agents that can cause change in DNA Radiation (x-rays, cosmic, ultraviolet, nuclear) Chemicals (benzene, asbestos) High temperatures o Repairing DNA Enzymes proof read the DNA and replace incorrect nucleotides 5

6 They work well, but not perfectly More exposure to a mutagen, the less likely it will be repaired o Chromosomal mutations Usually in crossing over Involves changes in the number or structure of the whole chromosome Types of chromosomal mutations Deletions Duplications Inversions Translocations Deletion: piece of chromosome it lost Duplication: piece of DNA is copied too many times Inversions: segment flips what it reads Translocation: pierce of a chromosome breaks off and joins a different nonhomologous chromosome o Mutations Most mutations are mutual meaning that they have little or no effect on the gene function Mutagens cause defective proteins are usually harmful Harmful mutations are associated with many genetic disorders can cause cancer Mutations are also a source of genetic variability and can be useful Can help an organism survive and reproduce Provide variation in population for natural selection to act upon o Polyploidy Condition in which and organism has extra sets of chromosomes Lethal to humans but beneficial to some plants Triploid 3N or tetraploid 4N plants are often larger and stronger than diploid plants 6

7 Chromosomal mutations Point mutations 7

8 o Darwin Species vary globally Species vary locally Species vary over time Nature provides the change and humans select the changes they want (artificial selection) o Evolution in nature Struggle for existence (limited resources: food space ) Variation and adaptation Competition for resources Characteristics that affect fitness must be heritable o More Fitness: a measure of the ability to survive and produce more offspring relative to other members of the population in a given environment Survival of the fittest o Natural selection Occurs when certain organisms with certain variations survive and reproduce and pass their variations to the next generation As a result each generation consists largely of offspring from parents with their variations that aid survival o Publishing of the book Ideas of species diversity were later called evolution Wrote little, and told his wife to publish it if her died 1858 a short essay by Russell Wallace summarized evolutionary change which was published with Darwin s work 1859 he published on the origin of species Proposed natural selection Evolution happens over millions of years and is still occurring o Natural variation and artificial selection Natural variation is differences among individuals within a species Variation (proposed by Darwin) would be inherited or passed on to the next generation Selective breeding would determine what individuals to use for breeding based on natural variation that they found, called artificial selection Fattest pigs, fastest horses By using artificial selection, breeders are able to produce a wide range of plants and animals that were different from their ancestors In artificial selection nature provided the variation among different organisms and humans selected those variations they found useful; o Struggle for existence 8

9 Used Malthus s population growth to bas work on Struggle for existence means that members of each species compete regularly for food living space and the necessities of life Predators hat are faster get more food Prey that is faster can run away and survive Central to Darwin s theory of evolution o Survival of the fittest Key factor for struggle for existence How well suited an organism is to its environment Ability of an individual to survive and reproduce in its specific environment is called fitness Fitness is a result of adaptations (Darwin proposed) Adaptation is an inherited characteristic that increases and organisms chance for survival Successful adaptations allow organisms to become better suited to their environment, and therefore survive and reproduce Adaptation can be physical or more complex features such as behavior like hunting in groups Darwin proposes fitness is central to natural selection, generation after generation of individuals compete to survive and produce offspring Fitness means less if you are less suited to your environment means you die and have no offspring) more means that you reproduce and have offspring survival of the fittest referred to as natural selection in both artificial and natural selection any certain individual of the population produce new individuals natural selection traits being selected and therefore increasing over time contribute to an organisms fitness in its environment, no human direction over time natural selection results in changes in the inherited characteristics of a population these changes increase a species fitness in its environment natural selection not is in an individual but changes over time in a population over many successive generations o Decent with modification Darwin proposed that organisms have different structures, go to different shelters and different habitats Each species has descended with changes from other species over time (called decent with modification) 9

10 This implies that all living organisms are related to each other, this is known as common decent All species living and extinct were derived from common ancestors o Evidence of evolution Darwin argues that living things have been evolving over millions of years Evidence for this process can be found in the fossil record, the geographic distribution of living species, homologous structure of living organisms, and similarities in early development o Fossil record Records of evolution Different layers of rock means different types of earth history You can see how species die, or if studied in sequential layers of rock, you can see how a species has changed and produced different species over time o Geographical distribution of living things Darwin observed that some different animals who ere descended from different animals have similar behaviors, he concluded it was because they were in the same environment and had the same pressures of natural selection Animals that were different in different places (Galapagos islands and South America) were from the same mainland ancestor and had to adapt to their environment o Homologous body structures Some structures in different animals have similarities in structure and function Or limbs vary in from and function but are made from the same basic bones Limbs have adapted in ways that enable organisms to survive in their different environments Despite the different functions these limb bones all develop from the same clumps of cells of growing embryo structures such as these which have different mature forms but develop from the same embryonic tissues which are called homologous structures Provide evidence that all four l imbed animals have descended with modification from common ancestors Hot all homologous structures serve important functions The organs of many animals are reduced in size they are vestigial structures or traces of homologous organs in other species Vestigial organs may resemble legs, tails, etc. Presence of a vestigial organ may not affect and organisms ability to survive and reproduce Like our tailbones o Similarities in development Early stage embryos of different animals are similar and very hard to tell apart 10

11 Some groups of embryonic cells develop in the same order and in similar patterns to produce the common cells and tissues growing in similar ways produce homologous structures o Summary of Darwin s theory Individual organisms in nature differ from one another, some of this variation is inherited Organisms in nature produce more offspring than can survive and many of those that do survive do not reproduce Because more organisms are produced that can survive members of each species must compete for limited resources Because each organism is unique each has different advantages and disadvantages in the struggle for existence Individuals well suited to their environment survive and reproduce most successfully, the characteristics that make them best suited in their environment are passed into offspring, individuals whose characteristics are not as well suited to their environment die to leave less offspring Species change over time over long periods of time, natural selection causes changes in the characteristics of a species such as in size and form, new species arise others die Species today have descended with modification from species that lived in the past All organisms on earth are united into a single tree of live by common decent o Natural selection key parts Variation All populations have some Mutations and genetic recombination (sex) provide differences among organisms Over repopulation As Malthus said there is never enough to keep up with population growth Not all that are born can survive Includes the idea of competition Inherited Variations may be passed down to offspring Differentiation survival and reproduction Favorable variations are the ones that get passed on and increase the population Mutations and recombinations of alleles make a change in genes in a population over time A gene pool is all of the alleles of a populations genes, these genes can get mixed in different combinations in the pool Six of any specific allele in the gene pool is called allelic frequency o Genetic equilibrium 11

12 Occurs when the populations allelic frequency remain the same over many generations A population that is in genetic equilibrium is not evolving Evolution is when the genetic equilibrium is disrupted Any factor that affects genes in a gene pool changes the allelic frequency Which change in populations genetic equilibrium Which change in the process of evolution We refer to these factors as mechanisms of genetic change Genetic change means change in the gene pool over time Mutations Genetic drift Migration or gene flow Natural selection These all have effects on natural selection o Mutations Environmental factors Radiation, chemical Random chance Errors in DNA replication etc. Many mutations are deadly There mutations are quickly eliminated from the gene pool Occasionally mutations result in useful variations and new genes become part of the gene pool by process of natural selection o Genetic drift The change in allelic frequencies by random events Genetic drift has a huge effect on small populations that include docents of a small number of organisms Like stepping on ants o Migration or gene flow The movement of genes in and out of a population Gene flow is the movement of genes in and out of a populations gene pool When individuals leave a population the genes are then lost from the pool When individuals enter the population genes are added to the gene pool The fish moving to a new bowl o Natural selection Natural selection is usually the most significant factor that causes change in both small and large gene pools Mutations, genetic drift, and migration have a greater effect only in smaller isolated populations (like islands) 12

13 It is a process by which individuals which are more fit for the environment survive and reproduce The interaction of populations and the environment results in changing allelic frequencies There are four types of natural selection Stabilizing selection Directional selection Disruptive selection Sexual selection o Stabilizing selection Occurs when the trait are most fit and the environment and extreme traits are eliminated Thus the most common form of selection and works in all populations all the time Birth weight o Directional selection Occurs when individuals within one extreme variations are the most fit to the environment This causes a gradual shift in allelic frequency to that extreme o Disruptive selection Occurs when both extremes of variations are most fit There is selection against the middle variations Graphs of types of selection 13

14 o Sexual selection The competition for mates within a population causing differences to occur in the allele frequencies of two genders Males tend to be chosen for their phenotypes and females tend to be chose the males o Isolating mechanism Gene pool is the sum of the alleles As new species evolve, populations become reproductively isolated from each other Reproductive isolation is when the members of two populations cannot interbreed and produce fertile offspring, the populations have separate gene pools They respond to natural selection and genetic drift separately Behaviors, geographic, temporal, and reproductive isolation o Behavioral isolation Occurs when two populations are capable of interbreeding but have differences in courtship rituals etc. o Geographic isolation Two populations become separated by genetic barriers such as rivers, mountains, or bodies of water Don t guarantee the formation of new species Two formerly separated populations can interbreed, they remain a single species Geographic barriers may separate certain types of organisms but not others Birds o Temporal isolation Two or more species reproduce at different times o Testing natural selection in nature Darwin said that: Natural selection happened to the Galapagos finches They adapted differently to their environments They all came from a common ancestor Grants saw they depended on two assumptions Oder for beak size and shape to evolve there must be enough inheritable variation in those traits to provide raw material for natural selection Differences in beak size and shape must produce differences in fitness that causes natural selection to occur o Variation Grants measure as many individual birds as possible Who lives and dies Who reproduces Wing and beak length Beak depth and color Feather color 14

15 Bird mass The Grants concluded that there is great variation o Natural selection Different seasons and less or more food means there is more drastic effects on natural selection Different sizes of beaks means that they are more likely to survive (the Grants found this) and found changes in the population of bird s o Rapid evolution Grants have evidence of evolution The next generation has larger beaks to get access to the little food that there is o Speciation in Darwin s finches Speciation in the Galapagos finches occurred by founding of a new population, geographic isolation, changes in a populations gene pool, reproductive isolation, and ecological competition o Founders arrive From South America the Galapagos managed to survive and reproduce o Separation of population Went over to another island and finches became isolated reproductively and by gene pools o Change in the gene pool Population adapted to their environments, beaks, etc. o Reproductive isolation Finches mate with the same size beaks Mating behavior Causes reproductive isolation meaning there are now a new species o Ecological competition Different species live in the same place must compete for resources o Continued evolution Isolation in different islands, genetic changes, and reproductive isolation makes many different finch species Δ Environment (they must adapt) Characteristic change you will either. Have an advantage Have a disadvantage Survive Die Reproduce You re still dead Mutation Gene flow forces of natural selection change Genetic drift Evolution 15

16 o Members of a species compete for space, food, mates, etc. The result is that some organisms are less likely to survive o Genetic variation is found naturally in all populations o Makes some different adaptations to the environment to the others o Adaptation is any inherited characteristic that increases an organisms chance for survival Help with the survival in an environment Behavioral Echolocation Physical Katydid camouflage Chemical Creosote (rain plants) o Survival of the fittest organisms which are better adapted to the environment will survive and reproduce passing on their genes o Natural selection results in changes in the inherited characteristics of a population These changes increases a species fitness in its environment o Decent with modification Each species was descended with modification from other species over time Suggests that all living species are related to each other, all species living or extinct share a common ancestor Evidence of evolution o Biography o Fossil record o Anatomy and embryology o Genetics and molecular biology o Testing natural selection Biogeography o The study of where organisms live now and where their ancestors lived in the past o Patterns in the distribution of living things and fossil species tells us hoe modern organisms evolved from their ancestors o If Darwin s theory of evolution is correct you would expect to find closely related yet different species living in a geographic region as they spread into nearby habitats and ecosystem Finches turtles in the Galapagos Fossil records o Fossils are remains of ancient organisms and are found in layers of rock in the earth o The record is incomplete and has enormous gaps o Layers of rock tell the history of the earth while the fossils found within the rock tell the history of life 16

17 o Fossils are thought to be the same age as the rock which it is found it o Fossil record shows change over time Tik-Taalik has basic wrist bones, neck, and fingers A tetrapod (four limbs) What we are related to and evolved from Anatomy and embryology o Homologous structures are similar structures found in different species derived from a common ancestor Structure may or may not be used for similar functions For examples, bones of forelimbs in some vertebrates are made from the same clump of undifferentiated cells in the embryo o Vestigial structures are homologous structures that have no current purpose or function Appendix, and pelvic bones in whales o Embryos of animals with backbones are very similar o The same group of undifferentiated cells (stem cells) develop in the same order to produce the same tissues and organs o All evolved from a common ancestor o Similarities in DNA and protein synthesis suggest relatedness o Similar karyotypes suggest and evolutionary relationship between humans and chimps Test natural selection in nature o Studies show natural selection in action involve descendants of the finches Darwin observes in Gallegos islands o The finches that Darwin saw were different but he hypothesized they descended from a common ancestor o Peter and Rosemary Grant tested Darwin s hypothesis that relied on two assumptions For beak size and shape to evolve there must be enough heritable variation in the traits to provide raw materials and natural selection Differences in beak size and shape must produce differences in fitness causing natural selection to occur o When food is scarce so individuals with large beaks are more likely to survive o Grants documented evolution happening rapidly sometimes only in decades Symbiosis o Avoid direct competition o Allows two species to live together and share space and a food supply o Mutualism: both organisms benefit Bees and flowers Interesting fact: without bees, we would only survive for three more years before we would all die o Commensalism: one organism benefits while the other is unaffected Fish following a larger fish for protection 17

18 A clownfish and sea anemone o Parasitic: one organism benefits and one dies Fungus making ants go crazy and have stuff grow out of their head Worms in humans (hookworms) Evolutionary players o Thomas Malthus: 1798 published Principles of Population and he said that the human population will grow beyond the space and food needed to sustain it; Impact on Darwin- Which organisms survive and why? o Jean-Baptiste Lamarck: 1809; first hypotheses was how organisms change over time; organisms have the desire to become more complex and perfect Impact on Darwin- his idea was right; but his mechanism was wrong- Darwin wanted to find an answer as to how species develop. o Charles Darwin: 1831 he developed a scientific theory explaining how modern organisms evolved over very long periods of time through descent from common ancestors he published On the Origin of Species. Darwin and Evolution: Species vary globally. Species vary locally. Species vary overtime. o Bred pigeons using artificial selection Nature provides the change and humans select the changes they want. o Asked the question how does this work in nature? (natural selection= answer) A struggle for existence Variation and adaptation Competition for resources Characteristics that affect fitness must be passed on and heritable o Fitness A measure of the ability to survive and produce more offspring relative to other members of the population in a given environment. Darwin called this Survival of the Fittest. o How natural selection works Occurs when certain organisms with certain variations survive, reproduce, and pass on their variation to the next generation As a result, each generation consists largely of offspring from parents with theses variations that aid in survival o Key parts of natural selection (VOID) Variation- all populations have some Mutations and genetic recombination (sex) provide differences among organisms Over repopulation 18

19 As Malthus said, there is never enough food to keep up with population growth Not all that are born can survive This included the idea of competition Inheritance- Variations may be passed on to offspring Differential survival and reproduction- favorable variations are the ones that get passed on to the increase in the population 19