What is a chromosome?

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Standard 2 Cell Division
Chromosomes Boogie
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Chromosome

• Condensed form of chromatin
• A threadlike structure of nucleic acids and
  protein
• Always paired with an identical copy of itself

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CHROMATID
SISTER CHROMATIDS
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Chromosome
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Types of Chromosomes

• Autosomes
• The 1st 22 pairs of chromosomes in humans.
• Sex Chromosomes
• 23rd pair
• In females, the sex chromosomes are the 2 X
  chromosomes.
• Males have one X chromosome and one Y
  chromosome.
• The Y chromosome is what makes a baby boy.

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Types of Cell Division

• Asexual Offspring are identical to parents
• Examples
• Budding yeast
• Binary Fission bacteria
• Sexual Offspring have a combination of genetic
  information from 2 parents
• (sperm and egg)
• Examples Animals and plants

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Numbers of Chromosomes

• Haploid Cells with 1 set of genetic info
• Ex sperm and eggs
• Diploid Cells with 2 full sets of genetic info
• Ex body cells

Two Haploid cells unite to make Diploid
Cells Aka Zygote
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Why do cells divide?

• Growth
• Reproduction (Development)
• Repair or Replace

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What Happens in Cell Division

• Replicates the DNA exactly.
• Movement of the two copies of DNA to opposite
  ends of the cell.
• Separates into two daughter cells.

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Cell Cycle

• Interphase
• The phases that prepares cells for Mitosis
• Chromosomes appear as threadlike coils
  (chromatin)
• 90 of cell cycle
• Three phases
• G1- Growth
• S- DNA Replication
• G2- Growth (prepares to divide)

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Mitosis

• 1 cell becomes 2 cells
• both new cells are identical to the original
• (all cells except sperm eggs do this)

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Mitosis

• Cell division occurs in a series of 4 stages, or
  phases.
• Stages
• Prophase
• Metaphase
• Anaphase
• Telophase

PMAT
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Prophase
"BEFORE/ PAIR"

• Mitosis begins (cell begins to divide)
• You can see chromosomes start to form

Late
Early
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Metaphase
"MIDDLE"

• Chromosomes line up in the center of the cell

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Anaphase
"AWAY/ ANTI"

• Chromatids or chromosomes separate and begin to
  move to opposite ends of the cell

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Telophase
"TWO"

• Two new nuclei form
• Chromosomes appear as chromatin Mitosis ends

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Cytokinesis
"Split"

• Become two identical new cells
• Half the size of the original

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http//www.youtube.com/watch?vCrTpRILtVYcfeature
related
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What Stages of Mitosis can you find?
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Meiosis

• 1 cell becomes 4 cells called gametes
• Male gametes Sperm
• Female gametes Eggs

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The Difference?

• Meiosis is Mitosis twice
• without
• Interphase in between
• Mitosis is in my toes, but
• Meiosis is in my ovaries

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Why Meiosis?

• Fertilization
• Union of haploid sperm and egg (n)
• Diploid Zygote is formed (2n)
• The chromosome number is reduced, so at
  fertilization there is the correct of
  chromosomes.

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Why Meiosis?

• Cuts chromosome number in half by separating
  homologous chromosomes
• Homologous Chromosomes occur in pairs and have
  the same genetic information, one inherited from
  mom and one from dad.
• Creates variation for Evolution
• Makes offspring unique

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Meiosis creates variation in 3 ways

• 1) Law of Segregation
• chromosome pairs separate during meiosis
• 2) Law of independent assortment genes are
  separated randomly (shuffle)
• 3) Crossing Over
• chromosome parts break off reattach to other
  chromosomes creates new chromosome

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Crossing Over
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Mitosis vs. Meiosis

• Mitosis Creates Diploid Cells (2N)
• Cells with 2 full sets of genetic info
• Human body cells have 46 chromosomes each
  (diploid or 2N is 46)
• Happens in Somatic Cells (body cells) and make up
  the entire organism expect the sperm and eggs

• Meiosis Creates Haploid Cells (N)
• Cells with 1 set of genetic info
• Human sperm eggs have 23 chromosomes (haploid
  or N is 23)

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MITOSIS
MEIOSIS
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Meiosis(Go back to Table)

• Interphase (approx 90 of time)
• DNA Replication
• Prophase 1 Tetrad (chromosome pair) forms
• Crossing over occurs
• Metaphase 1
• Chromosomes move to midline
• Anaphase 1
• Homologous chromosomes separate
• Anaphase 2
• Sister chromatids separate
• The Rest is Just Like Mitosis

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The Differences
Mitosis Meiosis
1 cell becomes 2 4
Cell Types In my__________ In my__________
Haploid or Diploid
Why/Importance
Phases PMAT
Diagram
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Chromosomes

• How do we look at the chromosomes of an
  individual?
• The collection of chromosomes found in an
  individuals cells

Karyotype
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Chromosomes

• How is it made?
• Chemically treated to stop them in metaphase
  (from blood or amniotic fluid)
• Chromosomes are stained
• The chromosomes are then photographed
• Chromosomes are cut out
• Arranged in pairs from largest to smallest
• Chromosomes are numbered in 23 sets

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1-Chromatin
2 Chromosome Scatter
3 Karyotype
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Chromosomes Abnormalities

• Nondisjunction (NOT-COMING-APART)
• Chromosomes fail to separate during anaphase of
  Meiosis
• 2. Mutations changes in chromosome structure

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Nodisjunctions

• What if a chromosome is missing?
• Most do not survive to be born
• If a chromosome is missing the condition is
  called Monosomy
• EX Turners Syndrome (XO)

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Nondisjunctions

• What if a cell has an extra chromosome?
• The condition in which a cell has an extra
  chromosome is called Trisomy
• Example Trisomy 21
• (Down Syndrome)

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Nondisjunction
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Mutations

• Deletion part of the chromosome breaks off
• Duplication part of the chromosome is repeated

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Cancer

• Mutations in genes that control normal cell
  division can lead to cancer.
• Increasing your risk
• Sun without sun block
• Smoking or being around 2nd hand smoke
• Working with known cancer causing chemicals.
• Eating foods with preservatives such as nitrates
• Cooking Foods in plastics that contain dioxin

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• Proto-Oncogenes are normal genes that code
  proteins involved in a cell's normal growth
• Oncogenes tell cells to make proteins that cause
  excessive cell growth and division.

Oncogenes are Mutant Forms of Proto-Oncogenes
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Tumor Suppressor Genes

• Normal genes whose ABSENCE can lead to cancer.
• Why dont we all get cancer?
• Genes come in pairs, one from each parent
• A defect in one copy will not cause cancer
  because the other normal copy is still
  functional.