Genetics Midterm Study Guide
Genetics Midterm Study Guide BIOL 3250
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This 8 page Study Guide was uploaded by Anzlee on Thursday October 6, 2016. The Study Guide belongs to BIOL 3250 at Middle Tennessee State University taught by Mohamed Salem in Fall 2016. Since its upload, it has received 69 views. For similar materials see Genetics in Biology at Middle Tennessee State University.
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Date Created: 10/06/16
Genetics Midterm Study Guide *Review: Top Hat Questions Applications of Why to Study Genetics: • everyone has genes (23,000; 23 pairs of chromosomes) • biomedical field is leaning towards sequencing genomes to produce specific medicines • Human Genome Project- started 1990 o goal: to decode genome- all of DNA found within all chromosomes (about 3 billion nucleotides) o first published sequence was released in 2003 o first one took three years and cost billions; now can be done in less than a week and costs less than $1000; shows how far we’ve come in the past 13 years o Main Question: How do defective genes cause disease? • Requires multiple fields; Bioinformatics: computer science, statistics, and biology DNA • Deoxyribonucleic acid wraps around proteins which forms chromosomes • DNA can form proteins, which are the workers of the cell, through translation (DNA à (via RNA polymerase) mRNA à (via tRNA) amino acids, which make up proteins • Mapping human genome requires knowing every location of genes within chromosomes o Cracking the Code of Life: notice the different organizations did this in a different manner • How long is all of the DNA in our body combined? o Each strand of DNA is 6 ft. o 37.2 trillion cells in the human body o 223.2 trillion feet of DNA in the human body (equal to 70 trips from the sun and back; the distance from earth to Pluto) Controversial Genetic Technologies -Knowledge of genetic specifics in individuals may lead to negative effects • DNA Fingerprinting- largely in question, but now more well-accepted • Mammalian cloning o First mammal cloned- Ian Wilmut et al.- Dolly the sheep; 1997 o Fears that this will be applied to humans led to legislative bands on human cloning Genetic Technologies • Can allow for modifying animals in various ways o ex. process for mice to glow green, used as a tracer to identify genes Chapter 1: The Relationship Between Genes and Traits • Interdisciplinary study of heredity and variation within biology • Gene- segment of DNA that produces a functional product such as a polypeptide o Only 1%-2% of genes code for proteins o Genes provide the blueprint that leads to traits within organisms; traits are the characteristics • Living cells are composed of biochemicals o Nucleic acids, proteins, and carbohydrates are all macromolecules; polymers constructed from monomers DNA Stores Information for Protein Synthesis • DNA contained in large structures called chromosomes (DNA and proteins) • DNA is a polymer of nucleotides, which contains nitrogenous bases (adenine, thymine, cytosine, and guanine); sequence stores information to form proteins o Types of proteins: § Structural: tubulin- forms microtubules, which play a role in shape and movement § Contractile: myosin- muscle contraction § Hormonal: insulin- regulates glucose blood levels § Enzymes- accelerate chemical reactions; catalyst • Catabolic- help break down molecules; provide energy • Anabolic- help synthesize molecules; provides components o Genetic Code- directs order of amino acid base code Gene Expression • Expression: when information in DNA is accessed o Transcription: genetic code is copied into RNA o Translation: sequence of RNA uses genetic code to make amino acid sequence for protein Traits are Visible Due to DNA • Morphological- appearance • Physiological- functions of organism • Behavioral- way organism responds to environment • 4 Levels of Biological Organization: o Molecular- genes expressed o Cellular- proteins function o Organism- traits can be observed o Population- genes and traits within a species can be studied Genetic Variation • Differences in inherited traits • Morphs- different forms within a species • Due to changes in DNA including: o Gene mutations o Changes in chromosome structure o Changes in chromosome number § Ex. down syndrome- extra copy of chromosome 21 • Also due to effects of environment • Reproduction is when parents pass genes to offspring, which enhances genetic variation • Genetic composition of a species evolves o Genetic diversity o Natural selection o Time Fields of Genetics • Transmission- shows inheritance patterns as passed through offspring; ex. Mendel • Molecular- biochemical approach; very big with technological advances • Population- focuses on genetic variation and evolution Chapter 3: Reproduction and Chromosome Transmission • Chromosomes are made of two sister chromatids • Chromosomes exist in cytoplasm of prokaryote cells; in nucleus in eukaryotic cells • Cytogenetics- form of studying chromosomes to find abnormalities o Karyotyping- way to track genetic abnormalities by ‘typing the nucleus’ § Cells are injected with … • Eukaryotic chromosomes are inherited in sets; most species are diploid o Homologous chromosomes- pair of similar chromosomes • Locus- physical location of gene on its chromosome Cell Division • Cells must divide because the there is a very specific surface area : volume of the cell ratio o Important for cell transport of food and oxygen, which allows the cell to survive • Eukaryotes require a more complicated process than simple binary fission to reproduce • Mitosis o Goes through stages known as the cell cycle: Sexual Reproduction • Meiosis o S phase that duplicates chromosomes and are arranged into homologous pairs • Meiosis 1-reduce number of chromosomes to half; crossing over/genetic recombination*, random separation of chromosomes (independent assortment) * • Meiosis 2- duplicates cells by separating chromosomes o allows for genetic variation! n 2 • Spermatogenesis- produce sperms in testes of males • Oogenesis- formation of eggs in ovaries of females Mendelian Genetics • Phenotype- physical trace of trait • Genotype- genetic trace of trait • Dominant or recessive genes • Mendel- father of genetics o Found that during gamete formation, the traits are randomly segregated through the law of independent assortment • Monohybrid crosses- single factor controlled phenotypes o Ex. tall or dwarf plants o Punnett Square to predict outcome of crosses • Dihybrid crosses- multiple factors o Ex. round/wrinkled seeds and green/yellow seeds o Punnett Square to predict outcome of crosses • How are genes linked?? o Crossing over is the only way to create variation between linked genes! Modern Genetics • Loss of function allele- defective copy of allele (usually recessive) • Pedigrees- a way to determine inheritance when parental crosses cannot be controlled Probability and Statistics • Probability- chance something will occur o Number it occurs, divided by the total number of events • Accuracy relies on size of sample • Mutually exclusive- events that cannot occur at the same time (sum rule) • Independent events- not connected; multiply individual possibilities (product rule) • Chi-Square Test- test validity of hypothesis; measure goodness of fit 2 (observed in each category * expected in each category) expected in each category o Multiply everything by the sum of calculations for each category= X 2 o Degree freedom: number of categories – 1 Unique Inheritance Patterns • Follow Mendelian Genetics: law of segregation and law of independent assortment • Environment- high impact on unique inheritance patterns • How can a mutant allele be dominant? o Protein encoded gains a new function o Protein acts antagonistically o Mutant has loss of function; wild type does not make enough proteins -Types: • Incomplete dominance- heterozygous genotype shows intermediate phenotype o Ex. pink flower • Incomplete penetrance- inherited from dominant mutant allele; may or may not be shown o Environment has a large impact o Ex. poly-dactyly • Overdominance- heterozygote is more present than the homozygotes; heterozygote advantage o Molecular level- two alleles that produce different proteins o Ex. sickle cell anemia • Multiple Alleles- for each gene locus only two alleles are found in diploid populations, but within populations, various alleles exist o Ex. coat coat in animals § If a dominant trait is not present, all recessive colors can be present o Typically, a hierarchy in dominance is present Sex-Linked Genes • X-linked genes o Genes located in X chromosome o Females have two o Males have one- hemizygous; typically mean they express the gene more often • Few Y-linked genes Sex-Influences Traits • Hormones control expression of gene in heterozygous individuals Lethal Alleles • Essential genes- genes required for survival vs. nonessential genes • Lethal allele can cause death o Typically have mutations o Usually recessive o Some may work later in life, ex. Huntington’s disease Genetic Interactions • Multiple genes affect outcome of one trait o Ex. pigmentation • Combine with environmental influences • Complementation- when both parents are recessive for a specific abnormality, but the normal trait is expressed • Gene redundancy- one gene compensates for another, which does not change the phenotype • Suppressor mutation- second mutation that overpowers phenotype of first mutation o Ex. hairlessness is a dominant mutation Ch. 5: Non-Mendelian Inheritance • Maternal Effect Genes- nuclear genes where genotype of mother determines phenotype of children o Father and children genotypes have no effect o Due to accumulation of gene information in egg from mother • Epigenetic Inheritance o Epigenome § Tells cells what type of cells they will be § Alters how genes are expressed and in what extent o Dosage compensation- compensation in number of active X chromosomes in male and females § Cells can count X chromosomes § X-inactivation depends on X-inactivation area on the Xist § Xist codes for long RNA that coats the inactive X (few genes are expressed from inactive X chromosome, one is this Xist gene) o Modification changes gene expression but is not inherited • Genomic Imprinting o Expression dependent on whether inheritance of gene was from mother or father • DNA Methylation o Methyl group is added to cytosine or adenine of DNA o Tagged which leads to expression or non-expression of gene Video About Epigenetics • Ex. identical twins- genetically identical; one may have cancer and another may be at risk but won’t express it because of their different epigenomes • Reactivation of genes is a growing process that has allowed for success in the medical field • We can alter our epigenetics and also that of our future generations • Studies show that epigenetic differences can accumulate with age Genetic Linkage and Mapping in Eukaryotes • Law of independent assortment- not true all the time • Linked assortment- where haploid gametes have multiple genes located on the same chromosome • Crossing over- only way to break linkage o Much rarer than independent assortment o Between two individual chromatids • Genetic maps- used to estimate distance between genes o Higher probability to crossover with larger distance • Each chromosome has a hundred-thousand genes • Each gene has a particular locus, or place, on the gene • Chromosomes are called linkage groups o 24 total chromosomes = 24 linkage groups • Map distance = number of recombinant offspring/total number of offspring * 100 o Recombinant offspring- the amount of offspring that are not like original parents o Units of distance- centiMorgans (cM) or map units (mu) o 1% recombination frequency = 1 map unit Chapter 8: Variation in Chromosome Structure and Number Genetic Variation • Most common form- single nucleotide polymorphism; single base change • Chromosomal aberrations- changes of chromosomes number or structure • Cytogenetics/Karyotyping- examination of chromosome pair with microscope • Mutations Include: o Deletion- loss of segment o Duplication- repetition of segment o Inversion- rearrangement of segment o Translocation- segment attached to another chromosome § Simple- one-way transfer § Reciprocal- two-way transfer; affects two chromosomes o Copy number variation- variation in copy number between various individuals
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