GENETICS - History (UNIT 1)

Study for Test 1

28 flashcards · Other · by John Mark Webb

  1. MENDEL 1864 Principles of Heredity TWO laws/principles of heredity principle of segregation principle of independent assortment These two principles come into play during meiosis and specifically Prophase 1 of meiosis 1. Simple inheritance means there is 1 gene coding for a single trait. This is also called "discontinuous". Used the word "factors" instead of genes.

  2. PRINCIPLE OF SEGREGATION diploid = 2 sets of chromosomes 1 from father 1 from mother haploid = 1 set of chromosomes This law states that when gametes (the egg and sperm cells) form during meiosis, the pair of alleles for each gene separate, or segregate. Each gamete ends up with only 1 copy of each gene, which means that the gametes are haploid. An allele is one of two or more versions of a gene. An individual inherits two alleles for each gene, one from each parent.

  3. PRINCIPLE OF INDEPENDENT ASSORTMENT Describes how different genes independently separate from one another when reproductive cells develop. Provides a tremendous amount of variability. During meiosis, the pairs of homologous chromosome are divided in half to form haploid cells, and this separation, or assortment, of homologous chromosomes is random. 223 types of gametes 8 billion different types of sperm/eggs

  4. GALTON 1890s polygenics is a complex (multifactorial) inheritance pattern discovered the uniqueness of fingerprints eugenics society

    Examples of human polygenic inheritance are height, skin color, eye color and weight. Polygenes exist in other organisms, as well.

  5. GARROD 1909 supported simple inheritance inborn errors of metabolism diseases of urine alkaptouria

  6. HARDY-WEINBERG 1908 founded the science of population genetics Hardy-Weinberg equilibrium p + q = 1 allele frequencies p2 + 2pq + q2 = 1 phenotype frequencies p2 = probability of the dominant allele q2 = probability of the recessive allele 2pq = heterozygous probability

  7. DNA was discovered in 1871 by isolating it from trout sperm. SUTTON AND BOVERI 1902 DNA was responsible for heredity.

  8. Early 1900s - DNA or proteins for heredity? DNA was too simple... ACGT bases cannot possibly account for the complexity of life Proteins... 20 different amino acids in humans high variability in amino acid structure... => high variability in protein structure => high variability in life forms

  9. GRIFFITH 1931 studied streptococcus pneumoniae discovered 2 strains: smooth with capsule => virulent (kills the host) rough without capsule => avirulent (does not kill the host) heat treated virulent => killed bacteria, no virulence heat treated virulent + avirulent => virulence main idea: transformation of avirulent to virulent strains THIS DID NOT PROVE THAT DNA WAS RESPONSIBLE FOR HEREDITY. THIS GAVE BASELINE INFORMATION.

  10. AVERY, MACLEOD, McCARDY 1944 "DNA or proteins for heredity?" studied streptococcus pneumoniae injected purified protein into avirulent bacteria and it stayed avirulent injected purified DNA into avirulent bacteria and it became virulent DNA was responsible for transformation

  11. HERSHEY AND CHASE 1952 studied bacteriophage (this is a virus that infects bacteria) used radioisotopes: 32P is found in nucleotides, therefore DNA, not proteins 35S is found amino acid methionine, not found in nucleotides, therefore not DNA

  12. Isotopes have different numbers of neutrons. A radioisotope is an isotope that is unstable and decays.

  13. WATSON AND CRICK 1953 did no work of their own, but used other research to determine structure of DNA... got a lot of their information from Rosalind Franklin because she used X-ray crystallography send x-rays through molecules and picking up where atoms are in those molecules DNA is crystallized and then x-rays are shot through it understood 2 primary ideas about the structure of DNA with this picture: very regular very helical, coiled Semi-conservative replication was hypothesized.

  14. CHARGAFF 1951 another key contributor to Watson and Crick... A% = T% G% = C% implications of this is that if you know the percent of one base, you can know the amounts of the other bases

  15. Linus Pauling thought that DNA was a coiled helical shape, but that it was a triple stranded helix.

  16. DNA STRUCTURE nucleotide is the fundamental unit nucleic acid (DNA and RNA) sugar is either ribose or deoxyribose phosphate group is what gives the acidic part, donates a proton base are the 4 different bases, with nitrogens in the rings

  17. NUCLEOTIDE TRIPHOSPHATE ribonucleotides: ATP CTP GTP UTP deoxyribonucleotides: dATP dCTP dGTP dTTP

  18. SOME TERMINOLOGY... nucleotide = fundamental unit dinucleotide = two nucleotides oligonucleotide = anything up to 10-15 polynucleotide = nucleic acid

  19. DNA vs. RNA Structural Differences double-stranded vs. single-stranded deoxyribose vs. ribose A, T, C, G vs. A, U, C, G DNA vs. RNA Functional Differences cellular control through production of proteins and regulation of cell cycle vs. protein synthesis

  20. BASE PAIRING hydrogen bonding G-C = 3 H bonds A-T = 2 H bonds transcription and replication are natural scenarios where H bonds break when breaking H bonds, we say denature or melting point (heat, 100ºC) vs. annealing point (bringing the H bonds back together) human genome: haploid = 3 billion bp diploid = 6 billion bp human chromosome is 50-250 million bp

  21. DNA CHARACTERISTICS antiparallel (organization of deoxyribose sugars) 10 base pairs per turn 34 A per turn right-handed helix alpha diameter of 20 A (it is constant)

  22. C values (haploid base pairs) viruses = thousands to tens of thousands of base pairs bacteria = hundred thousand to millions fungi = tens of millions animals = hundreds of millions fish = 1,500,000,000 amphibians = 6,600,000,000 birds = 1,100,000,000 mammals = 3,000,000,000 plants = 2,700,000,000 to 53,000,000,000 C value paradox = complexity does not mean high number of base pairs, as seen by plants and amphibians

    viruses, bacteria, fungi, birds, fish, mammals, amphibians, plants

  23. CHROMOSOMAL RESEARCH Painter 1923 seminiferous tubules of mental patients n = 48?? Cytogenetics advances... 1950s cell culturing... allow to culture cells (WBCs) in labs colchicine... (mitotic index) stops spindle fiber formation squash technique... heating a slide and rolling thumb on slide hypotonic media... put into a watery environment, cells will swell and will burst on slide, gets better representation of chromosomes phytohaemoglutinin (PHA)... (mitotic index) mitogen, speeds up cell cycl…

  24. Chromatin is the DNA and stuff during interphase. You cannot see it with a microscope. Considered uncondensed. Chromosomes are what the chromatin becomes when you move into mitosis. Considered condensed.

  25. 1961 Denver Conference of Cytogenetics KARYOTYPE Organization order: homologous pairs size centromere position banding pattern autosomes (22 sets) vs. chromosomes (23rd set) They goofed on 21 and 22. There are more base pairs in 22 than there are in 21. They did not fix the order.

  26. When the centromere is in the center, it is metacentric. When the centromere moves up as you read the karyotype from left to right, it is considered acrocentric.

  27. 1971 Paris Conference Looked at the ultrastructure of the individual bands of the chromosomes. Learned there were n = 320. 1980 High resolution banding. n = 1200

  28. CHROMOSOME COMPOSITION Only a third of the chromosome is DNA. About two-thirds of the chromosome is structure by proteins. DNA = 31% RNA = 5% Histones = 36% Non-histone proteins = 28%