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Flashcards by kyrstenblackmon, updated more than 1 year ago
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Created by kyrstenblackmon
almost 9 years ago
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| Question | Answer |
| Genetics | The study of how traits are inherited from one generation to the next |
| Gene | The basic unit of heredity Composed of DNA and located on chromosomes |
| Allele | Alternative form of a gene |
| Genotype | The genetic makeup of an individual |
| Phenotype | The physical manifestation of an individual's genetic makeup May correspond to a single or several different genotypes |
| Mendelian Genetics | By Gregor Mendel Formed genetic crosses and analyzed the inheritance of traits in progeny |
| Genetic Cross | Crossing true-breeding individuals with different traits, mating them and studying the inheritance in the progeny |
| Mendel's Laws | 1. Law of Segregation 2. Law of Dominance 3. Law of Independent Assortment |
| Mendel's Law of Segregation: Four Principles of Inheritance | 1. Genes exist in alleles-a gene controls a specific trait 2. An organism has two alleles, one from each parent 3. The two alleles segregate during meiosis-gametes only carry one allele 4. If two alleles are different, only one is expressed and is dominant-The silent allele is recessive |
| Homozygous | Organisms that carry two copies of the same allele |
| Heterozygous | Organisms that carry two different alleles |
| Mendel's Law of Dominance | The dominant allele is expressed in the phenotype |
| Monohybrid Cross | A cross between two true-breeding organisms in which only one trait is being studied |
| Parental (P) Generation | The individuals being crossed |
| Filial (F) Generation | Progeny generations |
| Punnett Square | One way of predicting genotypes expected from a cross Indicates all potential progeny genotypes Helps to calculate the relative frequencies of different genotypes and phenotypes |
| Test Cross (Back Cross) | A diagnostic tool to determine the genotype of an organism An organisms with a dominant phenotype of unknown genotype is crossed with a phenotypically recessive organism The appearance of the recessive phenotype in the progeny indicates that the phenotypically dominant parent is genotypically heterozygous |
| Dihybrid Cross | A cross between two organisms in which two traits are followed |
| Mendel's Law of Independent Assortment | A dihybrid cross may occur if the parents differ in two traits as long and the genes are on separate chromosomes and assort independently during meiosis |
| Crossing Over | Exchanges information between chromosomes and may break the linkage of certain patterns |
| Non-Mendelian Inheritance Patterns | 1. Incomplete Dominance 2. Codominance |
| Incomplete Dominance | If the phenotype of the heterozygote is an intermediate of the phenotypes of the homozygotes Progeny phenotypes are apparently blends of the parental phenotypes |
| Codominance | Occurs when multiple alleles exist for a given gene and more than one of them is dominant Each dominant allele is fully dominant when combined with a recessive allele, but if two dominant alleles are present the phenotype will express both dominant alleles simultaneously EX: ABO Blood Group |
| Sex Determination | Sex chromosomes pair during meiosis and segregate during the first meiotic division Each gamete has a single sex chromosome, since the female has two of the same then sex is determined by the male |
| Sex-Linked Genes | Genes located on the X or Y chromosome Most are located on the X chromosome |
| Sex Linkage | Recessive genes on the X chromosome will be expressed in men because there is no dominant gene to mask it Much more common in men Cannot be passed from mother to daughter or father to son Can be passed from father to carrier daughter or grandfather to grandson Skips generations |
| Drosophila Melanogaster | The fruit fly Several advantages for genetic research 1. Reproduces often 2. Reproduces in large numbers 3. Large and easily recognizable chromosomes 4. Few chromosomes 5. Mutations occur relatively frequently |
| Environmental Factors | Can affect the expression of a gene due to interactions between the environment and the genotype EX: Drosophila wings and Himalayan hare fur |
| Genetic Problems | Alteration of chromosome number and structure due to abnormal cell division during meiosis or mutagenic agents Results in abnormal characteristics in offspring |
| Nondisjunction | The failure of homologous chromosomes to separate properly during meiosis I OR The failure of sister chromatids to separate properly during meiosis II Results in trisomy or monosomy-usually lethal May also occur with sex chromosomes |
| Chromosomal Breakage | May occur spontaneously or be environmentally induced by mutagenic agents or X rays Chromosome with a missing fragment has a deficiency |
| Mutations | Changes in the genetic information of a cell Can lead to tumors if occurring in somatic cels Are only transmitted if present in gametes Most occur in noncoding regions of DNA and are silent |
| Mutagenic Agents | Induce mutations Cosmic rays, X rays, UV rays, radioactivity, and chemical compounds (colchine-inhibist spindle formation-causes polyploidy and mustard gas) Sometimes carcinogenic |
| Mutation Types | Nitrogen bases are added, deleted, or substituted, altering the amino acid sequence A genetic error with the wrong base or no base on the DNA at any position |
| Point Mutation | Nucleic acid is replaced by another nucleic acid Between one and three nucleotides Three effects on the codon: 1. Code for same amino acid-silent 2. Code for different amino acid-missense 3. Code for stop codon-nonsense Genome length does not change |
| Frameshift Mutation | Nucleic acids are deleted or inserted in the genome Frequently lethal Length of genome changes |
| Examples of Genetic Disorders | 1. Phenylketonuria (PKU)-caused by the inability to produce the proper enzyme for the metabolism of phenylalanine. May result from an impaired conversion of phenylalanine to tyrosine 2. Sickle Cell Anemia-red blood cells become crescent shaped because they contain defective hemoglobin and carry less oxygen. Caused by a substitution of valine for glutamic acid-single base pair substitution |
| Cytoplasmic Inheritance | Regulated by plasmids |
| Plasmids | Small, circular rings of cytoplasmic DNA that contain accessory genes |
| Bacterial Genome | Consists of a singular circular chromosome located in the nucleoid region and may contain plasmids |
| Episomes | Plasmids capable of integration into the bacterial genome |
| Replication | Begins at a unique origin of replication and proceeds in both directions simultaneously 5'-3' |
| Genetic Variance | Increased through transformation, conjugation, and transduction |
| Transformation | A foreign plasmid is incorporated into the bacterial chromosome via recombination |
| Conjugation | Sexual mating The transfer of genetic material between two bacteria that are temporarily joined |
| Transduction | When fragments of the bacterial chromosome accidentally become packaged into viral progeny during a viral infection The closer two genes are on a chromosome, the more likely they will transduce together |
| Virion | Viral progeny that can affect other bacteria and introduce new genetic arrangements through recombination with the host cell's DNA |
| Recombination | Occurs when linked genes are separated Occurs by breakage and rearrangements of adjacent regions of DNA when organisms carrying different genes or alleles for the same traits are crossed |
| Gene Regulation | Allows bacteria to control their metabolism Based on the accessibility of RNA pol to the genes Directed by an operon Done by inducible or repressible systems |
| Operon | Consists of structural genes, an operator region, and promoter region on the DNA before the protein coding genes |
| Structural Genes | Contain sequencers of DNA that code for proteins |
| Operator Region | The sequence of non transcribable DNA that is the repressor binding site |
| Promoter Region | The noncoding sequence of DNA that serves as the initial binding site for RNA pol |
| Regulator Gene | Codes for the synthesis of a repressor molecule that binds to the operator and blocks or permits RNA pol to transcribe structural genes |
| Inducible Systems | Require the presence of an inducer for transcription to occur Repressor binds to the operator and prevents RNA pol from binding Inducer-repressor complex must form for transcription to occur Proteins synthesized are the inducers and enzymes are only transcribed when needed |
| Repressible Systems | In a constant state of transcription unless a corepressor is present Repressor can bind to operon when repressor-corepressor complex is formed Proteins produced are repressible because they are normally being synthesized |
| Corepressor | End-products of the biosynthetic pathways they control |
| Constitutive | Enzymes which are always being synthesized because operons are incapable of being turned off due to mutations or deletions that code for defective repressors |
| Bacteriophage | A virus that infects its host bacterium by attaching to it, boring a hole in the cell wall, and injecting its DNA Enters the lytic or lysogenic cycle once inside the host |
| Lytic Cycle | Phage DNA takes control of host and manufactures bacterial progeny The bacterial cell bursts (lyses) and new virions are released to infect other bacterial cells |
| Virulent Bacteriophages | Bacteriophages that replicated by the lytic cycle, killing their host cells |
| Lysogenic Cycle | Bacteriophage does not lyse host cell Becomes integrated in bacterial genome as a provirus and lies dormant and replicates with the bacterial genome May reemerge and enter lytic cycle spontaneously or by environmental factors Normally resistant to superinfection by similar phages |
| Provirus | Harmless form of a virus integrated in the bacterial genome |
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