BIOL 112 Lecture Notes - Lecture 13: G2 Phase, Hydroxycarbamide, Cyclin D
16 May 2018
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Lecture'13''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''(19/02/18)'
• Temujin(&(Borte'arranged'to'be'married'at'age'of'11'
o His'wife'was'abducted'in'raid'while'he'was'away,'but'they'raided'back'and'saved'
her'
o Had'4'sons''
o Conquered'almost'all'of'Asian'continent''
o Became'known'as'Genghis'Khan'
o His'oldest'son'should'have'gotten'the'position'as'Genghis'Khan'became'older,'
but'there'were'doubts'that'he'was'really'his'son'(since'he'was'born'right'after'
his'wife'returned'from'being'abducted)'
o He'divided'it'up'between'his'4'sons'
o Invasion'of'Europe'never'happened'because'he'died'during'the'trip'
• Heredity(
o Who'is'related'to'who?'
o Important'aspect'of'our'lives,'society,'experience''
o If'question'of'heredity'had'not'been'an'issue,'perhaps'Europe'would'have'been'
invaded'by'Mongolians'
o The'Mystery'of'Heredity'
§ All'organisms'come'from'other'organisms'
§ All'organisms'resemble'their'parents'(species'will'give'rise'to'their'same'
species)'
§ Siblings'are'not'identical'
o Parents'Share'
§ Ancient'Greeks'figured'that'males'and'females'must'share'some'
“essence”'that'mixes'to'produce'the'progeny'(tended'to'believe'that'it'
was'pretty'much'just'the'male,'and'female'was'just'fertile'“land”)'
§ Essence'='cells'(discovered'with'microscope'development)'
o The'Egg'&'Sperm'
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2'
§ 1'division'of'cells'takes'about'15'minutes'
• Cell(Theory(
o All'organisms'consist'of'cells'
o Cells'divide'to'produce'new'cells'
o Higher'organisms'fuse'their'cells'(sperm'&'egg,'pollen'&'egg)'to'produce'a'new'
organism''
• Cells'make'more'cells'by'dividing'&'growing''
o Mother'cell'à'dividing'cell'à'daughter'cell'A'&'daughter'cell'B'
• Dividing'cells'devote'a'lot'of'their'resource'to'segregating'their'chromosomes''
o Daughter'cells'need'to'inherit'mitochondrion,!DNA'(most'important),'organelles'
(e.g.'golgi'apparatus),'ribosomes,'etc.''
o Done'through'chance''
§ At'least'thousands'of'ribosomes'in'cell,'so'low'chance'all'end'up'in'one'
daughter'cell'
§ Dozens'of'mitochondria'in'cell,'so'1/212'chances'of'not'getting'any'
mitochondria'(low'chance)'
§ Problems'with'DNA'is'that'they'need'to'be'copied'&'it’s'divided'into'
pieces'(chromosomes)'
• Chromosomes'='a'single'strand'of'DNA'(about'1400'nm'across)'
• 2'types:'circular'(in'bacteria)'&'linear'(most'other'organisms)'
• When'cell'is'getting'ready'to'divide,'we'can'see'the'chromosomes'
because'they'condense'by'associating'with'proteins'(e.g.'
histones)'à'chromatin'='combo'of'protein'&'DNA''
• Normally'DNA'is'spread'out'like'spaghetti'(cannot'differentiate'
individual'strings)'until'the'cell'is'getting'ready'to'divide''
• Karyotype'='a'way'of'organizing'&'identifying'chromosomes'
o Take'a'cell'that'is'getting'ready'to'divide'
o Flatten'it'(mitotic(squash)'
o Stain'the'chromosomes'with'a'dye'(binds'to'protein'&'DNA'in'a'particular'
manner)'
o Take'a'picture'
o Cut'out'chromosomes'&'line'them'up'according'to'banding'pattern'(a'given'
chromosome'will'always'have'the'same'banding'pattern,'2'arms'of'
chromosomes'are'the'same'because'they'are'copies'of'each'other)'
o Discover'='there'is'2'of'each'chromosome'(each'chromosome'has'2'identical'
chromatids'='arms)'
§ 22'pairs'of'matching'chromosomes,'and'one'set'that'is'either'XY'or'XX'
§ Total'of'46'chromosomes'in'humans'
§ Bacteria'have'1'chromosome'
• Number'of'chromosomes'is'not'important;'just'a'way'to'divide'up'
DNA'
3'
§ Chromosomes'typically'in'almost'identical'pairs'='homologs'
§ Just'before'cell'division,'each'chromosome'has'been'replicated'once'to'
produce'2'chromatids''
o Terminology+
§ Normally,'chromosome'is'a'single'piece'of'DNA''
§ When'looking'at'karyotype'we'actually'see'2'pieces'of'DNA,'the'2'
chromatids,'bound'by'a'centromere'
§ Therefore,'we'call'these'“mitotic(chromosomes”'to'indicate'that'they'
represent'a'special'case'
§ Question:'When'looking'at'human'karyotype,'how'many'strands'of'DNA'
are'represented?'
• Answer:'92'pieces'of'DNA'because'each'chromosome'is'2'
chromatids'and'each'chromatid'is'a'separate'strand'of'DNA'
• Segregating'chromosomes'is'exacting'(exactly'1'copy'of'DNA'ONLY,'not'any'more'than'
that)'
o Probability'of'1'copy'going'into'each'daughter'cell'='50:50'for'each'chromosome,'
for'46'chromosomes'probability'is'1/246'(with'just'random'assigning)'à'this'
would'almost'never'happen''
o Down'Syndrome'results'from'an'extra'chromosome'21'
§ Usually'an'extra'chromosome'leads'to'death'in'uterus'or'in'early'
childhood,'down'syndrome'is'one'of'the'only'ones'that'survive'for'longer'
than'that'
• 1st'problem'of'cell'division:'make'sure'all'chromosomes'are'duplicated'before'the'cell'
divides'&'that'each'cell'only'gets'1'copy.'
• Steps+of+Cell+Division/Cell+Cycle:+
o Chromosome'(DNA)'replication'='S(phase'
§ Have'2'chromatids'for'each'chromosome'
§ Each'homolog'has'2'chromatids'(each'homolog'
is'replicated)'
§ Then,'G2'phase'where'there'is'a'“check-point”'
to'make'sure'everything'is'ready'for'the'next'
phase''
o Mitosis'(M)'='process'by'which'somatic'cells'make'
identical'copies'(clones)'of'themselves'by'creating'
daughter'cells'that'inherit'one'copy'of'each'
chromosome'(condensation'only'occurs'in'preparation'for'this'step)'
o OR'
o Meiosis'(M)'='process'by'which'germ'cells'make'non-identical'copies'of'
themselves'by'creating'daughter'cells'that'have'one'of'each'homolog'
o Cytokinesis'='dividing'the'cytoplasm'in'2'(optional)'
' '
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BIOL 112 Full Course Notes
Verified Note
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Document Summary
If question of heredity had not been an issue, perhaps europe would have been invaded by mongolians: the mystery of heredity. All organisms resemble their parents (species will give rise to their same species) Siblings are not identical: parents share. Ancient greeks figured that males and females must share some. Essence that mixes to produce the progeny (tended to believe that it was pretty much just the male, and female was just fertile land ) Essence = cells (discovered with microscope development: the egg & sperm. At least thousands of ribosomes in cell, so low chance all end up in one daughter cell. Dozens of mitochondria in cell, so 1/212 chances of not getting any mitochondria (low chance) 22 pairs of matching chromosomes, and one set that is either xy or xx. Bacteria have 1 chromosome: number of chromosomes is not important; just a way to divide up. Chromosomes typically in almost identical pairs = homologs.
