BIOL 4003, Week 1 Notes
BIOL 4003, Week 1 Notes 4003
U of M
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This 6 page Class Notes was uploaded by Rachel Heuer on Wednesday January 20, 2016. The Class Notes belongs to 4003 at University of Minnesota taught by Robert Brooker in Spring 2016. Since its upload, it has received 25 views. For similar materials see Principles of Genetics in Biology at University of Minnesota.
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Clutch. So clutch. Thank you sooo much Rachel!!! Thanks so much for your help! Needed it bad lol
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Date Created: 01/20/16
Chapter 2 Lecture 1 Mendel used pea plants to study laws regarding plant hybrids - Used garden peas because of distinct characteristics (varieties), easy to make crosses 2 types of crosses: o Self Fertilization (Pollen and egg from same plant) § The natural way o Cross Fertilization (Pollen and egg from different plant) § Removed and manipulated the anthers (where pollen is produced) of immature plants (prior to self-fertilization) § Transfer pollen from white flower à remove anther of purple flower à allow seed production à plant seeds Studied seven characters that bred true o Characters are morphological characteristics o Trait or variant describes specific properties of a character § Eye color is character, blue or brown eyes is a trait o Variety that produces same trait over again are true breeders o Mendel studied seven characters: § Height (tall vs dwarf) § Flower color (purple or white flowers) § Flower position § Seed color (yellow and green seeds) § Seed shape (wrinkly or round) § Pod color § Pod shape o Each characteristic had only two variants (tall vs dwarf i.e.) o First experiment was a single factor cross (single characteristic being observed) (Fig. 2.5) - For all of Mendel’s studies: o F1 showed only one of two parental traits (all tall or purple) (all progeny had at least one dominant allele and showed same characteristics) o F2 showed 3:1 ratio of two parental traits (F2 progeny had different characteristics) o These results refuted a blending mechanism of heredity o Suggests the Particulate theory of inheritance § Traits does not blend or change when being passed on - Each plant gets an allele (discrete hereditary factor) from each parent - The two alleles may be identical or different - When two factors of character are different and present in plant one variant is dominant to the other (tall is dominant to dwarf à recessive) - During gamete formation half the gametes get one allele, half get the other randomly - Mendel’s Law of segregation: During reproduction, alleles segregate randomly so that half of the gametes receive one factor and half of the gametes receive the other - Punnett Squares: - Write down the genotypes of both parents (male and female) - Write down the possible gametes each parent can make - Make an empty Punnett Square (2 x 2) - Put gametes on top and left side and cross gametes - Determine the relative proportions of genotypes and phenotypes of the offspring Lecture 2 - Two factor crosses o Crossing plants that differ in two characters - Two possible inheritance patterns (Fig. 2.7) o Linked assortment: Variants of different characteristics are linked (possible that two different genes are linked to eachother, although alleles of the same genes are not linked) o Independent assortment: Variants of different characteristics (different genes) are not linked in any manner - Independent assortment proved to be the correct type o Due to the fact that the F2 generation had seeds with novel combinations (phenotype pairs not found in parents) § Also called nonparentals or recombinant models o Predicted ratio for independent assortment for F2 is 9:3:3:1 o Law of independent assortment: During gamete production characteristic alleles split up independently and are applied randomly o Can do punnett square for two factor crosses o Don’t do punnett square for problems with 3 or more different genes (other, better ways to do it) o à forked-line method or multiplication method (problem S3) - For humans, it is not ethical to control parental crosses o Use pedigree analysis instead (family trees) § Usually used to determine inheritance pattern of genetic diseases (pattern of inheritance of traits in humans) § Genes that play a role in disease my exist as normal allele (wild-type) or mutated allele that causes symptoms § Can either be dominant or recessive • Recessive o Two heterozygotes will have 25% affected offspring o Two affected individuals à 100% affected • Dominant o An individual will have inherited the gene from at least one affected parent o May have been caused via mutation during gamete formation Probability and Statistics - Laws of inheritance can be used to make predictions about genetic crosses - Probability: Likelihood event will happen in the future o Probability = # of times an event occurs / total number of events o Accuracy depends on sample size o Deviation between observed/expected § Due to random sampling error (large for small samples, small for large samples) o Used to predict the outcome of crosses - Product Rule o Chance that two or more independent events will occur is equal to the product of the respective probabilities (chance of ABC = chance A x chance b x chance c) o Can use for probability of alleles from several different genes - Binomial expansion equation o Represents all of the possibilities for a set of unordered events - Chi squared test: o Method used to determine how well data fits a hypotheses o Used to determine goodness of fit § Does not prove hypothesis correct o Chapter 3 Chromosomes: Structures within living cells that contain genetic material (genes) - Composed of DNA and Proteins (which provide organized structure) à chromatin Prokaryotes: Bacteria and Archaea - No nucleus, one chromosome, outer membrane, and flagellum Eukaryotes: Protists, fungi, humans, and plants - Nucleated, nucleolus (makes ribosomes), compartmentalized Cytogenetics: Field of genetics that involves the microscopic examination of chromosomes - Examines the chromosomal composition of a particular cell or organism o Allows for detection of abnormalities o Relates individuals of similar or different species Animals have two types of cells: - Somatic Cells: Blood, skin, muscle (body cells) - Germ Cells: Gametes (reproductive) such as sperm and egg (Fig. 3.2) Two look at chromosome get culture, spin to pellet, collect pellet and place in hypotonic solution (cell expands to make chromosomes separate to be more visible), then visualized with a microscope after staining - Karyotype: Diagram of chromosomes organized in anorganism Humans have 23 pairs of chromosomes, 46 total (22 pairs of autosomal, 1 of gametes) (23 from mother, 23 from father) (In a dividing cell there would be more) - In eukaryotic species, chromosomes are inherited in sets - Most eukaryotes are diploid o 2 sets of chromosomes - No correlation between number of chromosomes and body complexity - Each chromosomes in a pair is called a homolog, identical in size o 2 homologs (one from each parent) make a homologous pair o Same banding pattern and centromere location o Same genes o Not same alleles necessarily - Genes are in chromosomes - Location of gene in chromosome is called the locus Cell Division - One purpose of cell division is asexual reproduction o How unicellular organisms reproduce - Another purpose is for multicellularity - Prokaryotes reproduce via binary fission: Replicate chromosome à divide in two (FtsZ protein makes ring that pinches off cell wall, forming a septum) (similar to tubulin in eukaryotes) - Eukaryotes reproduce via cell cycle (Fig 3.5) o G1 starts diploid o Goes to S phase when decides to divide § In S phase chromosomes replicate completely § G2 there are 2 copies of everything (sister chromatids) (preparing to divide synthesizing needed proteins) o M-phase has mitosis and meiosis, then cytokinesis § Starts with sorting of chromosomes then cytokinesis (cell divides into two daughter cells) o Gap 1 (G1) à Synthesis (S Phase) à Gap 2 (G2) à M-Phase Lecture 4: - G1, G2, and S phase are referred to as interphase - A cell can stay in G0 for a very long time o G0 means not planning on dividing soon or will never divide again - Mitosis has 5 phases: o Prophase, Prometaphase, metaphase, anaphase, telophase - Meiosis is way for cell to reproduce sexually o Parents (diploid) make gametes with half the amount of genetic material (haploid) § Two gametes fuse during fertilization to create new diploid o Begins like mitosis, after cell has progressed through interphase o Unlike mitosis, it involves 2 successive divisions to reduce chromosome content (Meiosis I and Meiosis II_ o Understand metaphase I and anaphase I of meiosis o Sexual reproduction is common way for eukaryotic organisms to produce offspring § Parents (diploid) make gametes through gametogenesis with half the amount of material (haploid_ o Chromosome theory of inheritance and sex chromosomes § Describes how transmission of chromosomes account for Mendelian patterns of inheritance § Established how chromosomes carry and transmit genetic inheritance of traits § 1) Chromosomes contain DNA § 2) Chromosomes are replicated and passed from parent to offspring § 3) Nucleus contains homologous pairs (diploid) § during meiosis, each homolog segregates into one of the two daughter nuclei § 4) During formation of gametes different types of nonhomologous chromosomes segregate independently § 5) Each parent contributes one set of chromosomes to its offspring § Mendel’s law of segregation can be explained by the homologous pairing and segregation of chromosomes during meiosis (Fig 3.15) § Mendel’s law of independent assortment can be explained by the relative behavior of different (nonhomologous) chromosomes during meiosis (Fig 3.16) § Line up during metaphase § Separate during anaphase § Independent assortment occurs due to random alignment during meiosis § Homologous chromosomes segregate from each other à this leads to the segregation of the alleles into separate gametes o Sex Determination § Factors other than chromosomes can also determine sex § Humans has 44 autosomes and 2 sex chromosomes § Males have XY (Heterogametic) • Presence of Y determines male § Females have XX (homogametic) § Some animals have X- vs XX § x/a=.5 = fly becomes a male § x/a=1= gly becomes a female § In birds, male has ZZ (homogametic) § Whereas female has ZW § For bees, males are haploid (produced from unfertilized haploid eggs) • Females are diploid (produced from fertilized eggs) • Number of chromosomes is what matters
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