Mitosis Meiosis and Heredity
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Transcript of Mitosis Meiosis and Heredity
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Mitosis and Meiosis
Lab Instructor: Kristin Flores
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Learning Objectives
• Cell division – Mitosis– Cytokinesis
• Gametogenesis and meiosis
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Important terms
• G1, S, and G2 = Interphase• Fertilization – fusion of egg and sperm nuclei• Zygote – fertilized egg • Gametogenesis – formation of gamete• Spermatogenesis and Oogenesis
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Cell division
• NUCLEAR DIVISION1. Mitosis: produces two nuclei, both containing identical chromosomes
I. Prophase II. MetaphaseIII. Anaphase IV. Telophase
2. Cytokinesis: divides the cytoplasm; ensures that each new cells contains all the metabolic machinery necessary to sustain life
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Cell Cycle
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“C” Words (pg 59)
• CHROMATIN- thread like DNA + protein• CHROMOSOME - Coiled/Condensed DNA + protein• SISTER CHROMATIDS - duplicated chromosome• CENTROMERE – holds chromosomes together• CENTROSOME – microtubule organizing center• CENTRIOLE – microtubule being organized
• Centrosomes contain centrioles
• HOMOLOGOUS CHROMOSOMES – similar in size and carry genes for same trait, but different expression
• CYTOKINESIS – cytoplasmic division
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Mitosis: Nuclear division
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Mitosis: Nuclear division
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Onion Root Tip and Whitefish blastula
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Meiosis• NUCLEAR REDUCTION
MEIOSIS I: Replication and crossing over occurResults in two cells, both with same number
of chromatids as the parent cell
MEIOSIS II: Divides the cytoplasm and ensures that each
new cells contains all the metabolic machinery necessary to sustain life
Results in four cells, all with half the number of chromosomes as the parent cell
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Meiosis: Nuclear reduction
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Spermatogenesis• Same basic events as mitosis
• NO interphase between meiosis I and II• Synapsis and crossing over occurs in Prophase I
• For every 1 diploid primary spermatocyte you put in, you get 4 haploid sperm out.
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SpermatogenesisSeminiferous tubule
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Oogenesis• Same basic events as mitosis
• NO interphase between meiosis I and II• Synapsis and crossing over occur in prophase I
• Arrested in Prophase I until puberty• Once a month, one egg continues to metaphase II where it is again halted• Will only complete meiosis upon fertilization
• For every 1 diploid primary oocyte you put in, you get 1 egg and 2-3 polar bodies• Polar bodies = “dumping grounds”; woman will just reabsorb them
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Oogenesis
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Meiosis: Nuclear reduction
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MITOSIS VS. MEIOSIS
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1.Somatic ?
2.Reproductive cells?
3.Chromosome number of the daughter cells
reduced to half compared to that of parents?
4.Chromosome numbers in daughter cells
remains same as that in parents?
5.Spermatogenesis and Oogenesis?Interactive Mitosis Images:
http://jbworld.jbs.st-louis.mo.us/science/resources/mitosis/mitosistut.html
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Lab activities
• Prepare onion root squash mount (handout)• Examine mitosis models and whitefish blastula
slides • Examine spermatogenesis on slides
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Heredity
Lab Instructor: Kristin Flores
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Learning Objectives
• Heredity terms• Mendel’s Laws of Inheritance• Determining genotype using Punnet Squares
and test cross of Drosophila
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Meiosis Review• Genetic diversity is produced by recombining
the diploid cell's genetic complement to generate a haploid gamete.
• This diversity depends upon the segregation and assortment of combination of alleles.
• Importantly, diploid organisms can bear recessive alleles of genes that are can be completely masked by the other (usually wild type) allele.
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Important Terms
• Genotype- genetic constitution (genes present)• Phenotype- physical expression of genotype• Alleles- alternate forms of a gene that occupy a
given locus.
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Important Terms
• Homozygous- identical alleles (FF, aa, BB)
• Heterozygous- both dominant and recessive alleles are present (Ff, Aa, Bb)
• Dominant trait- expressed in heterozygous conditions (Hh, Kk, Bb)
• Recessive trait- expressed only when homozygous recessive (aa, dd, jj)
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Mendel’s Laws of Inheritance • Gregor Mendel formulated his "Laws of Inheritance" from his
famous pea experiments.
• "Law of Segregation” - Each organism contains two alleles for each trait, and the alleles segregate during the formation of gametes during meiosis.
• "Law of Independent Assortment" suggests that alleles of each gene separate independently of the other genes.
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Determining Genotype
Gamete Genotype
Gamete Genotype
Diploid Genotype
F F FF
F f Ff
f f ff
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Example• Purple flowers are dominant
(A) over white flowers (a) Genotype Phenotype
AA Purple
aa White
Aa Purple
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Punnet Squares
• Used to determine genotype of offspring• How do we determine genotype of parents?
– One parent is white flower (aa)– One parent is purple flower (Aa or AA)
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Punnet Square
a a
A Aa Aa
A Aa Aa
White FlowerPu
rple
Flo
wer
Homozygous dominant = Offspring all purple
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Punnet Square
a a
A Aa Aa
a aa aa
White FlowerPu
rple
Flo
wer
Heterozygous dominant = Offspring 50% purple and 50% white
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Sex Linked Cross Example
• Yellow Body is recessive mutation carried on X chromosome (Xf)
• We crossed Yellow Body female with wild type male
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Punnet Square
XF Y
Xf XfXF XfY
XfXfXF XfY
Wild TypeYe
llow
Bod
y
Offspring: males all Yellow Body, females all wild type
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Punnet Square
a a
A Aa Aa
A Aa Aa
Mutated WingN
orm
al W
ing
Offspring all normal wing
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Punnet Square
a a
A Aa Aa
a aa aa
Mutated WingN
orm
al W
ing
Offspring 50% normal wing and 50% mutated wing
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Test Crosses
• We are using all recessive traits• Flies with these characteristics must be
homozygous recessive (tt)• Mated with wild type flies (Tt or TT)• Determine if wild type parent was Tt or TT
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Sex Determination
Female Male
http://berkeley.edu/news/media/releases/2002/07/images/fruitflies.jpg
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Lab activities
Drosophila melanogaster– Determine sex and phenotype
• Separate males and females first• Determine phenotype second• Determine genotype of parents