Bio 101 Test 6 Mitosis

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Bio 101 - Test 6 Mitosis Meiosis Ch 9
10Mendelian Genetics Ch 11Human heredity Ch
12
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About Chromosomes

• What is a chromosome?
• Eukaryotic DNA multiple linear diploid
  chromosomes
• Number of chromosomes (types) depends on species
• Chromosomes replicate

Unwound form of DNA Chromatin
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• Terms chromosome vs chromatid
  chromatin vs condensed chromosome centro
  mere vs centriole dulipcated
  chromosome vs homologous pair
• 2 cell types 1. somatic cell body diploid
  2 sets 2. gamete sex cell M
  F haploid 1 set
• Human genome has 23 types of chromosome 22
  autosomes 1 sex chromosome (23) human
  conception 23M 23F 46 chromosomes NOTE
  these are NOT stuck together NOT identical
• How do corresponding M F chromosomes compare?
  Same genes in same corresponding positionsbut
  Are they exactly alike? Alleles different
  forms of a gene

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Eukaryotic cell division

• 2 ways that Eukaryotic cells divide
  1. Mitosis cell division
  for growth, healing asexual repro. 1
  diploid set ? 2 identical diploid sets (1 round)
• somatic cells only somatic
  cells genetically identical cloning?
• 2. Meiosis cell division (2 rounds) for
  gamete formation 1 diploid set ? 2 diploid
  sets ? 4 haploid sets NOT identical
  genetic variability strategy of sexual
  reproduction
• What is replication? It precedes cell division
  46 X 2 92

?
?

? replication ?
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Cell cycle
90
Replication happens here 23 x 2 ? 23 x 2
x 2
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Mitosis Ch 9

• cell division for growth, healing asexual
  repro. 1 diploid set ? 2 identical diploid
  sets somatic cells
• Interphase replication 90 of cycle
  sochromatin
• then Mitosis P M A T
• 1. Prophase chromatin condenses ? visible
  chromosomes homologous pairs vs dupl.
  chromosomes membrane breaks centrioles
  move to poles

Early prophase Late prophase
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more Mitosis

• 2. Metaphase replicated chromosomes line
  up at equator end-to-end spindle fibers attach
  to chromatids decision made
• notice of fibers one per chromatid what
  is going to get separated from what? so what is
  a spindle fiber? Elastic connective tissue
  and what if it gets old and loses its
  elasticity?

Transition to metaphase
Metaphase
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and more still

• 3. Anaphase centromere breaks down
  chromatids not held together fibers retract to
  separate chromatids what is
  being separated here? what is staying
  together (NOT separated)? and remember
  what happens when those fibers get old and
  lose their elasticity?

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last one

• 4. Telophase centrioles back to original
  position nuclear membrane forms x 2
  
• THEN..
• Cytokinesis cleavage furrow
  ..and we start over again

Telophase Cytokinesis
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How is Mitotic cell division controlled?

• Limited number telomeres clock - aging CNS?
  vs skin - no?
• Speed connective tissue vs skin
• Crowding contact inhibition monolayer
• Directional growth connective vs skin
• What else? Hormones ex. estrogen
  Growth factors FGF Proteins ex
  kinases Either induction or repression
• Consider an embryo tissue differentiation
• Cancer loss of control abnormal cells?
  How? Why? Malignant vs benign
  Metastasized (systemic) vs contained
  (local)

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Types of cancers NOT on test

• Carcinoma malignancies (M) derived from
  epithelial cells most common forms of
  breast, prostate, lung, colon cancers
• Melanoma more rare but highly aggressive
  carcinoma (?)
• Lymphoma / leukemia M of blood / bone marrow
  cells
• Sarcoma M of connective tissue (other than
  blood)
• Mesothelioma M of respiratory mesothelium
  asbestos
• U.S. adult cancers male prostate 33 of
  cases (Wikipedia) lung 31 of
  deaths female breast 32 of
  cases lung 27 of deaths
• Good news? Most active most susceptible
  Great progress is being made

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A new generation of anti-cancer drugs
NOT on test

• Angiogenesis inhibitor a sort of replication
  inhibitor
• Tyrosine kinase inhibitors prevent ATP
  production prevent signal transduction
• How do they find this stuff? Look for
  unusual gene sequences, then. Look for
  over-expression of particular genes

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Meiosis Ch 10

• cell division (2 rounds) for gamete formation
  1 diploid set ? 2 diploid sets ? 4
  haploid sets NOT identical genetic
  variability strategy of sexual
  reproduction
• Interphasethen. P M A T.P M A T
  meiosis 1 meiosis 2 2 (like
  TWO) rounds of cell division Why? Do ya know?
  Huh? Do ya?
• 1 X 92 (interphase is interphase)
  ? 2 X 46 (NOT identical)
  ? 4 X 23 Haploid gametes

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• How is genetic variability assured in sexual
  reproduction? 1. Crossing over when? Prophase
  1 2. Independent assortment when? Metaphase
  1 3. Random (?) combination of gametes
• Prophase 1 chromatin condenses ? visible
  chromosomes homologous pairs vs dupl.
  chromosomes membrane breaks centrioles
  move to poles ?AND. Replicated chromosomes line
  up at equator but how? synapse
  arrangement mom 1 next to dad 1etc
• why? XX XX XX XX

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• What is crossing over? How does it work?
• The result? Swapped alleles between homologous
  pairs
• Would swapping alleles between chromatids
  in a dupl. chromosome change anything?

So, vs Mitosis 1. Prophase is longer 2.
Side-by-side 3. Crossing over
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• Metaphase 1 Chromosomes already lined up
  so all thats left to do is... Spindle fibers
  attach notice of fibers (vs
  Mitosis) one / dupl. chromosome what is
  going to get separated from what?
• The decision is made Independent
  Assortment decision made independently at
  each chromosome

So, vs mitosis
Metaphase is shorter
Metaphase 1 of meiosis
vs
XX XX XX XX
Metaphase - mitosis
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• Anaphase telophase similar to Mitosis
• Second round of cell division separates
  chromatids one from another just like Mitosis

1st round 2nd round
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• Summary Mitosis vs Meiosis
  
• What cell types are involved? What are the
  objectives?
• Why are there 2 rounds of cell division in
  Meiosis?
• What is separated in each case? What stays
  together?
• Difference in the reason why they have 2 x 46?
• What is a zygote?

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Heredity Ch 11

• Transfer of traits from parent to offspring
  inheritance
• Gregor Mendel 1860 Austrian Monk / Botanist
  
• -conducted experiments breeding green pea
  plants -he made various crosses and observed
  inheritance of characteristic traits in the
  offspring
• -observed inheritance of consistent
  predictable ratios
• -fortunately the observed traits were
  Mendelian 1. simple controlled by a single
  gene 2. had only 2 alleles ex. flower
  color 3. complete dominance relationships D
  or R 4. his genes were NOT linked genes
  control of observed traits on different
  chromosomes

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• So what did Mendel really do (and he eventually
  realized it)? True breeding purple x true
  breeding purple True breeding white
  x true breeding white but.. True breeding
  purple x true breeding white and.
  What if we cross 2 of these offspring?
• Monohybrid cross Cc x Cc Phenotype
  ratio 31 Genotpye ratio 121
• Punnett squares
• Genotypes homozygous dominant
  CC homozygous recessive cc
  heterozygous Cc

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• For Mendelian traits there were only 3
  genotypes yielding only 2
  phenotypes
• From his work arose the Laws of Segregation
  1. Traits are separated into packets which occur
  in pairs 2. Two forms of each trait exist
  dominant recessive 3. The forms segregate
  randomly giving predictable ratios
• In todays terminology. 1. Traits separated
  into genes which are diploid 2.
  Two alleles of each trait exist dominant
  recessive 3. Alleles segregate randomly
  giving predictable ratios
• Keep in mind that Mendel only perceived the
  phenotypes
• Test cross used to determine genotype of
  organism with dominant phenotype CC or Cc?
  Cross with cc to find out.

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• Mendel found that alleles for the same gene can
  segregate and recombine different
  combinationsbut what about
• Independent assortment A gene for 1 trait does
  not influence (carry with) the gene for another
  trait AS LONG as they are on separate chromosomes
  (NOT linked)
• flower color on chrom 1 A purple a
  white plant height on chrom 2 B tall b
  short
• AB parent x ab parent just as likely to yield Ab
  or aB ?

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• We can test this with a Dihybrid cross If
  we cross AaBb X AaBb we get all possible
  combinations Monohybrid cross gave P 31 G
  121 Dihybrid cross gives P 9331

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• Single gene recessive disorders autosomal
  disorders expressed only in homozygous
  recessive individuals, with Heterozygous
  individuals serving as carriers
• Ex. 1 Albinoism P melanin p no
  melanin
• Consider normal parents that yield an albino
  child 1. what is the genotype of both
  parents?
• 2. what is likelihood of the child being
  albino?
• Ex. 2 Sickle cell anemia H normal
  hemoglobin h altered hemoglobin
  
• Ex. 3 Tay-Sachs disease a fatal condition
• how does the genotype ratio work on this
  one?

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All traits are not simple Mendelian traits

• 1. Incomplete dominance 3 genotypes
  yield 3 phenotypes CC red Cc pink cc
  white DONT think mixed Ex.
  Cc X cc
• 2. Co-dominance 2 of 3 alleles are
  equally dominant 6 genotypes yield 4
  phenotypes O is universal donor why?

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• 3. Pleiotropy 1 genotype yields many phenotypes
  (symptoms) consider a gene controlling
  something with global affects such as protein
  production but which protein? Ex.
  Sickle cell anemia PKU
• 4. Epistasis epi upon 1 gene affect
  expression of another Ex. albinoism
  1 gene says melanin Yes or No
  another group says, if Yes, how much
• 5. Polygenic inheritance multiple genes
  affect a single trait also called the
  dosage affect Ex. skin
  pigmentation 7 genes control greater dose of
  dominant alleles darker skin pigmentation

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• 6. Multi-factorial traits nature vs nurture
  Traits affected by both Genetic
  Environmental influence No way to predict
  phenotype other than empirical probability Dr.s
  have kids that become Dr.s why?
• Trait Environmental influence
• Consider height nutrition weight exerc
  ise, nutrition intelligence nutrition,
  friends, interests
• heritability is a measure of the genetic
  contribution to a multi-factorial trait on a
  scale of 0 1.
• Consider Similarity in MF trait in adoptee and
  natural child Twins separated at birth yet
  retain similarities
• identical monozygotic same genes, same
  sex
• fraternal dizygotic no more similar than
  any siblings

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Human genetics Ch 12

• Linked genes (vs slide 22) what if genes for 2
  or more of Mendels pea traits HAD been on the
  same chromosome?
• would these genes be able to assort
  independently?
• would this prevent variability arising
  from crossing over?
• overall, how (much) would linkage affect
  genetic variability?
• Linkage map used to determine relative distance
  between linked genes by measuring
  frequency of gene separation via
  crossing-over consider relative
  likelihood of separating ? pink from
  orange VS pink from green

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• Human sex determination chromosome 1
  22 autosomes chromosome 23 is the sex
  chromosome X or Y
• ovum (X) sperm (X) XX female
  homogametic ovum (X) sperm (Y) XY
  male heterogametic
• Sex-linked genes linked to X chromosome

Y X
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Genetic anomalies

• RememberSingle gene recessive disorders
• What about Sex-linked recessive disorders
  almost always (we will say always) on X
  chromosome who is most likely to inherit
  these? can dad be a carrier? does dad
  affect the son? what if mom is a carrier
  and dad is normal? chance of son
  expressing? chance of daughter expressing?
  
• Ex hemophilia, color blindness (G or R
  cones), MD?
• what if it is a terminal condition
  male? female?

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• Abnormal chromosome number via
  non-disjunction Aneuploidy wrong of a
  particular chromosome can happen in 1st or 2nd
  round of cell division monosomy worse than
  trisomy autosomes worse than sex chromosome
  Ex. Trisomy 21 Down syndrome or
  mongolism
• Polyploidy many copies wrong of
  every chromosome actually can be a good
  thing in plants Ex Triploid wheat

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Monitoring for genetic anomalies

• Alpha feta protein screening std. blood test by
  law too high spina bifida incomplete
  closure of spine too low Downs or other
  aneuploidy
• Amniocentesis gt 35 amniotic fluid drawn
  from uterus genetic karyotype gives more
  information, BUT carries some risk 1/200
  spontaneous abortions
• Chorionic Villus Sampling chorionic villi
  (amnion forming tissue) sampled risk of
  mortality low can do early on