A&P 5

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A&P 5
2012-02-29 22:30:53

Molecular biology of cells
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  1. name the functions of the nucleus
    • bounded by double membrane
    • contains materials needed to control ALL parts of the cell
    • storage of the genetic material: DNA, packaged loose (euchromatin) when in use, packaged into tight structures (heterochromatin; chromosomes) when DNA must be divided between 2 daughter cells
    • 3 forms of RNA (protein coding material) are made in the nucleus
  2. state the relationship between DNA, RNA, & protein
    • DNA makes RNA makes Protein
    • DNA replicates itself
    • DNA makes RNA by transcription, and the conversion of RNA code to Protein is translation
    • DNA & RNA are the same basic structure,
    • process of which DNA makes RNA
    • same language, different format
    • copying one form to another in the same language
  4. define TRANSLATION
    • process of which RNA code converts to Protein
    • different language: sequence of A, C, G, U
    • converting information from one "language" to another
  5. name the steps involved in the CENTRAL DOGMA & recognize exceptions to the CENTRAL DOGMA
    • DNA makes RNA (transcription)
    • RNA makes Protein (translation)
    • EXCEPTIONS: some viruses use RNA as their genetic material- reverse transcriptase (goes backward) RNA converts to DNA
    • DNA is inserted into the host cell, this is destructive, damage to host cell DNA results in diseases, cancer, HIV (they use RNA as genetic material)
    • enzyme, uses RNA as a template to make DNA
    • after that step the usual sequence (DNA-> RNA->Protein) is followed
  7. identify the structural properties of DNA important for function as a biological information carrier
    • DNA consists of 2 antiparallel strands (one goes up while the othe goes down) & RNA consists of 1 strand
    • these #'s come from where 1 base is joined to the next along the deoxyribose-phosphate backbone
    • DNA & RNA is always made & always read in a 5' to 3'(5 prime to 3 prime) direction
    • DNA is visible throug light microscope when packaged into chromosomes during cell division, otherwise it's euchromatin: unspooled, "loose" DNA strands
    • the base pairing of DNA & its directionality are the 2 most important features of this essential molecule
  8. explain 5' to 3'
    • the 5' carbon is where we start reading & where enzymes that work on DNA start their work
    • the 3' end is where everything ends up
  9. describe RUNGS
    hydrogen bonded base pairs
  10. Define GENE
    • Region of DNA that codes for a protein
    • (part of DNA that is made into protein)
  11. Define messenger RNA
    Carries the code for a primary sequence of amino acids in protein
  12. Describe process by which DNA is transcribed to a pre-mRNA
    RNA transcribed from DNA has regions that are not used to code for protein synthesis, RNA must be edited to its final form BEFORE it’s shipped out of the nucleus
  13. Define RNA polymerase
    Enzyme that makes RNA from DNA template
    • Promoter- starting point of RNA synthesis
    • Terminator- stopping point of RNA synthesis
  15. Define EXON
    expressed region of DNA- made into protein
  16. define INTRON
    intervening region of DNA- NOT made into protein
  17. discuss introns & exons together
    in order to create mRNA from hnRNA (heterogeneous nuclear RNA), the intons must be sliced out and the exons stitched together (editing)
  18. define SPLICEOSOME
    organelle that slices out introns & stitches together exons, made up of several small nuclear ribonucleoprotein particles, or snRNPs
  19. define LARIAT
    structure formed (loops), the intron is cut out, and the ends of the exon are stitched together
  20. define snRNPs
    "scissors & paste" in editing process
  21. explain the process by which pre-mRNA is edited to a messenger RNA (mRNA)
    • when RNA polymerase touches down on DNA , it has to open up the DNA double helix, and start making RNA from a DNA template
    • that hnRNA is then processed by snRNPs w/in the nucleus to form a final, edited transcript, which is officially called mRNA, passes through a pore in the nuclear envelope
  22. discuss THALASSEMIAS
    • they are blood disorders
    • they result from abnormal transcription and/or translation of alpha & beta-globin genes
  23. define: 5'-untranslated region
    • where promoter is found
    • segment of DNA BEFORE the gene
    • contains sequences that regulate transcription & translation
  24. define: 3'-untranslated region
    • where terminator is found
    • segment of DNA AFTER the gene
    • contains signals for the termination of transcription & also may have info about the stability of mRNA (some mRNAs need to hang around a long time & get translated over & over, while others should disappear in a puff of smoke after they're used once
  25. explain how mRNA is translated into protein
    • mRNA carries the coded message from nucleus to ribosome, ribosome is made up of ribosomal RNA & proteins
    • together, rRNA & protein in ribosomes are a protein factory
    • factory is supplied w/ amino acids for protein synthesis by tRNA that bring the correct amino acid for the next "word" in the genetic code
  26. what are the 3 major players in RNA?
    • tRNA- transfer RNA- "trucks" that take amino acids to growing protein strand
    • mRNA-messenger RNA- carries coded message
    • rRNA-ribosomal RNA- w/ proteins, forms ribosomes (protein factories): small & large subunits
  27. define ANTICODON
    • set of three ribonucleotides which will bind to the mRNA
    • complementary sequence of tRNA bases
  28. describe the process of ribosome assembly on mRNA
    • ribosome finds start
    • ribosome reads along mRNA & decodes mRNA to make polypeptide (immature protein)
    • ribosome finds stop
    • ribosome disassembles & translation stops
  29. define CODON
    • 3 base pairs on mRNA coding for an amino acid
    • (sequence of mRNA bases that codes for a protein)
  30. summarize the stepS in mRNA translation to form protein
    • step1- ribosome attaches to mRNA
    • step2- AUG(start codon) matches up to tRNA-methionine (*always start w/ AUG & always matched w/ mthionine)
    • step3- next tRNA- amino acid arrives
    • step4- peptide bond forms
    • step5- ribosome shifts 3 mRNA bases (met-tRNA is released, open spot occupied by new amino acid-tRNA)
    • step6- polypeptide chain grows
    • step7- ribosome reaches stop codon polypeptide released
  31. define ACCEPTOR ARM
    stem that carries amino acid
  32. define GENETIC CODE
    3 base sequence representing each amino acid
  33. what is always the start codon?
  34. what are the 3 stop codons?
    "umber" "amber" & "ochre"
  35. how many start and stop codons are there?
    1 start & 3 stop codons
    "clowns" unique, oddballs
    "gays" polar, charged
    "boys" polar, uncharged
    "girls" nonpolar
  40. how many combinations code are there for the 20 amino acids?
    64 cominations code (makes 64 individual codons)
    • change in the sequence of DNA which changes the mRNA made from the coding strand
    • it's a general term for MUTATION
  42. define MUTATION
    • noticeable changes in the organism
    • if change in DNA (or mRNA) results in a change in the amino acid sequence, which then changes the function of the resulting protein
  43. what are the 2 types of mutations?
    point mutation & frameshift mutation
  44. describe POINT MUTATIONS
    • "swapping", they don't change the reading frame (sometimes they don't change protein sequence), they change one base
    • 3 types: 1-silent mutations- no observable change (same), 2-missense mutations (sickle cell) change 1 amino acid to another (noticeable change, different), 3-nonsense mutations- change codon that codes for an amino acid to a stop codon, resulting in abnormally short protein (noticeable change, stop codon)
    • change the reading frame
    • types: either add (insertion mutation) or subtract (deletion mutation)
  46. codons are read as 3-letter combos, that a string of bases can be read in 1 of 3 "frames" the frame is "set" by 2 things:
    • 1- which strand of DNA is made into RNA
    • 2- where the AUG (start) codon is found
  47. give an example of a mutation causing disease & explain
    • Sickle Cell Anemia (point mutation-missense)
    • mutation of beta globin gene
    • changes glutamate to valine
    • sickling protects red blood cells against infection
    • distribution of sickle cell mutation is a good match to the distribution of malaria-tropical regions
  48. describe the synthesis of mRNA molecule
    • messenger RNA
    • allows us to make different proteins
    • very unstable
    • allows for transcriptional control of protein production
    • made by RNA polymerase II
  49. describe the synthesis of rRNA
    • ribosomal RNA
    • more stable
    • (mostly) made by RNA polymerase I
    • combines w/ protein to form protein factories (ribosomes)
    • makes RNA large & small units
  50. describe the synthesis of tRNA
    • transfer RNA (shaped like cloverleaf)
    • also stable
    • made by RNA polymerase III
    • "trucks" takes amino acids to "parking spaces" (P & A sites)
  51. describe the synthesis of snRNA
    makes SnRNP (aka spliceosome)
  52. define CHROMATIN
    DNA strand
  53. define CHROMOSOMES
    • visible (only during mitosis) packaging of DNA & histones into X-shaped structures
    • consists of 2 identical chromatids
  54. define CHROMATIDS
    • 2 identical halves of the chromosome, joined @ centromere (recall that the mitotic spindle attaches at the centromere and tears the 2 chromatids apart)
    • each chromatid is one continuous DNA molecule
  55. define HISTONES
    • special group of proteins
    • positive charge to neutralize electrical charge of DNA, allows tighter packing
  56. what are the 2 phases of somatic cell cycle?
    Mitotic phase (Mitosis (M phase) (prophase, metaphase, anaphase, & telophase) & Cytokinesis) & interphase (G0, G1, S, & G2)
  57. cell division & the cell cycle
    all cells make copies of themselves in the growing embryo, replace themselves: skin, bon marrow, intestinal lining, & others CANNOT divide after birth: muscle, heart muscle, and brain (nerves)
  58. describe G1 phase
    • (46 DNA molecules)
    • cell duplicates organelles & cytoplasmic components
    • in order to enter the next phase, S phase, cell in G1 must pass a checkpoint
    • process takes about 8-10 hours
  59. describe G0 phase
    • if the cell does NOT pass the checkpoint at G1phase, then it goes to G0phase
    • or if the cell is quiescent (not actively dividing) the cell remains in G0phase
    • exs: brain cells, muscle cells, & heart muscle cells
    • other cells (ex: liver & kidney) may wait in G0phase for up to several years, but can prepare for division if needed
  60. describe S phase
    • DNA replication, so that it can be divided equally between daughter cells in mitosis
    • process takes about 8 hours
  61. describe G2phase
    • cell now carries double the amount of normal DNA (in G1 it had 46 DNA molecules, now it has 92)
    • duplication of centromeres
    • there is another checkpoint, that needs to be passed, to get from G2 to M phase
    • process takes about 4-6 hours
  62. describe MITOSIS (M phase)
    • process of nuclear division
    • actual active division of the cell
    • interphase not a "true" phase of mitosis
    • 4 stages w/in mitosis: prophase, metaphase, anaphase, & telophase
    • last step in mitosis, CYTOKINESIS (process of cell division), cells must physically divide into 2 daughter cells
    • diploids
  63. describe the process of DNA replication & its relationship to cell cycle
    • occurs in the S phase of cell cycle
    • # of chromosomes is called "n" haploid
    • 2 copies of each gene "2n" diploid
    • DNA strands separated (one helicase(enzyme) unwinds DNA
    • match up strands as they go down
    • 2 strands of the DNA double helix are anti-parallel (1 runs 5'-->3'left to right & the other runs 5'-->3' right to left)
    • DNA is only "built" 5'-->3'
    • as DNA is replicated 2 strategies are used: leading strand & lagging strand
  64. describe OKAZAKI FRAGMENTS (DNA replication)
    • deal w/ lagging strand
    • they are smallish fragments of DNA being made in the required 5' to 3' direction
    • okazaki fragments are filled in by DNA Ligase, one at a time, stitching the 5' to 3' strand together
  65. describe LAGGING STRAND
    • created on lower fork, RNA primers, DNA primase, & DNA polymerase working together
    • okazaki fragments
  66. describe LEADING STRAND
    • built continuously 5'-->3'
    • DNA polymerase makes leading strand
  67. define DNA LIGASE
    enzyme that fills in gaps between the okazaki fragments, one at a time stitching the 5' to 3' strand together
  68. define DNA HELICASE
    uncoils (opens up) the helix
  69. define TOPOISOMERASE
    inserts swivel that keeps the intact double helix from getting supercoiled (keeps it from knotting) from spinning as replication proceeds
  70. describe PROPHASE (stage in mitosis)
    • 1st phase of mitosis
    • DNA is tightly packed into chromosomes
    • nuclear envelope breaks down
    • mitotic spindle forms (which grows out of centrosome)
  71. describe METAPHASE (stage in mitosis)
    • 2nd phase of mitosis (middle phase(meta) of mitosis)
    • everything in the parent cell lines up in the middle and microtubules of the mitotic spindle attach to anchors (centromeres) found in the middle of each chromosome
    • karyotype test takes place here (to diagnose trisomy 21)
  72. describe ANAPHASE (stage in mitosis)
    • 3rd phase in mitosis
    • "ana"- backward
    • phase where the contents of the 2 daughter cells move backwards away from eachother
    • chromatids (arms of chromosomes) are torn apart into 2 equal pieces by the action of mitotic spindle
    • they then back up & take their places on either end of the elongating cell
  73. describe TELOPHASE (stage in mitosis)
    • end phase of mitosis
    • mitosis is completed
    • cleavage furrow appears in middle of parent cell
    • as furrow deepens, cell is split into 2 daughter cells
    • in each of daughter cells, nuclear envelopes reform & mitotic spindle comes apart
  74. define CYTOKINESIS
    • "cell motion"
    • daughter cells move apart
    • process of cell division
  75. define MEIOSIS
    • germ cells (sperm & eggs) they are haploid-carry only 1 copy of each gene
    • they join @ fertilization
    • when these germ cells join, the normal 2n amount of DNA is restored (n(23) + n(23) =2n(46))
    • mechanism of cell division to evenly divide up the replicated 4n amount of DNA between four daughter cells
    • to go from 4n to n, it requires 2 steps: meiosis I & meiosis II
  76. how does Meosis I differ from Mitosis (2 ways)
    • 1. meiosis I is a reduction division, so DNA content of each daughter cell is halved
    • 2. crossing-over is a feature of Meiosis I, non-joined chromatids(from same region of same chromosome) "swap" & DNA is scrambled (gene swapping-mixing genetic material)
  77. describe MEIOSIS I
    • aka reduction division
    • splits the pairs
    • crossing-over- non-sister chromatids swap genetic material
    • content of each daughter cell is halved
    • still goes through phases of Mitosis (PMAT)
  78. describe MEIOSIS II
    • splits the chromosomes
    • same steps basically but getting 4 daughter cells out of the 2 from meiosis I
  79. describe CROSSING OVER (meiosis)
    • ensures "shuffling" of genetic material
    • important benefit of sexual reproduction
    • w/out it siblings would be identical
    • tool used to determine the physical location of genes
    • genes which are close together on the same chromosome rarely get separated during crossing over
    • genes which are far apart on the same chromosome are more likely to be separated
  80. define CENTIMORGAN (cM)
    • unit for measure (for crossing over) of genetic distance, physical distance between genes
    • a 1% chance of crossing-over is called "1 centimorgan (1cM)"
  81. compare & contrast MITOSIS & MEIOSIS
    • mitosis creates 2 daughter cells that are identical to the "parent", somatic(body) cells, splits pairs
    • meiosis halves (4 daughter cells) the DNA content in meiosis I & then meiosis II resembles mitosis, germ cells, splits chromosomes
  82. compare & contrast HAPLOID & DIPLOID cells
    • haploid (N) use meiosis to divide- germ cells(gametes) reproductive cells, when they join they make a diploid embryo
    • diploid (2N) use mitosis to divide- somatic cells (majority of body)
    • those where inheriting one copy will give you a condition or disease
    • capital letters
  84. dedefine ALLELES
    inherited characteristics that come in pairs
    • those where inheriting one copy makes you a carrier and inheriting two copies will give you a condition or disease
    • lower case letters
    • child inherits one copy of a gene from mother and one from father- called alleles
    • each parent's gametes are haploid- contain one allele each
  87. define PUNNETT SQUARES
    • used to analyze mendelian genetics
    • capital letters for dominant allele
    • small letters for recessive allele
  88. describe ALBINISM
    • lacking of skin pigmentation
    • (aa on square) recessive recessive
    • autosomal recessive genetic disease
    • children have to receive 2 copies of the mutant gene to have albinism
    • AA- unaffected Aa-unaffected carriers aa- affected (albino)
  89. describe SICKLE CELL ANEMIA
    • a person needs 2 good copies of the hemoglobin gene to make normal red blood cells (HbA/HbA)
    • one mutated copy produces sickle trait (HbA/HbS)
    • 2 mutated copies produce sickle cell anemia (HbS/HbS)
    • this is an example of a co-dominant trait- neither is recessive