1. Lesson 8.1
CHROMOSOMES

2. Chromosome One DNA strand & attached proteins
Condensed version of chromatin (long DNA strand)
Duplicated in preparation for mitosis
one chromosome (unduplicated)
one chromosome (duplicated)

3. How much do you think a chromosome is made up of DNA/proteins?

4. Don’t forget what DNA looks like!
twisted ladder
double helix
Watson + Crick

9. Each chromosome consists of 2 identical parts called
sister chromatids.
The point at which the sister chromatids are connected is called the centromere
The kinetochore is the part of the centromere that attaches to the spindle fiber.

11. 2 Types of chromosomes Autosomes –body chromosomes
Sex chromosomes – determine the sex
X or Y
females XX
Males XY

12. What are 3 similarities between Homologues?
shape
size
genes

13. Hmm.. Is a chromosome in a DNA? Or is DNA in a chromosome?
DNA is in a chromosome

15. EUKARYOTIC PROKARYOTIC
FOUND?
LOOKS LIKE?
FOUND?
LOOKS LIKE?
attached to
cell membrane
in nucleus X
circular
<<LINK>>

17. Chromosome Structure 1 strand of double helix Supercoil =chromatin DNA
one
1 strand of double helix
Supercoil
=chromatin
histone

18. Histones:
proteins that are entwined in regularly arranged bead-like groups along the DNA
Keeps DNA strong so it gives shape to chromosomes

19. nucleosome - DNA wrapped around 1 histone WHERE IS THE NUCLEOSOME?!

20. Nonhistones:
other proteins that control certain parts of the DNA
Ex. DNA helicase –
Unzips 2 strands of DNA in replication

21. increases SURFACE AREA!
C. Chromatin:
DNA strands are very tightly wound into a supercoiled string, which is coiled again, forming chromatin.
This allows for a great deal of genetic information to be compacted into a small area.
increases SURFACE AREA!

22. One, loooong strand of DNA

23. Segment of DNA that holds instructions to make a
D. Genes:
Segment of DNA that holds instructions to make a
that will show a TRAIT
protein E

24. For example… trait The color of your hair is a:
The building blocks that make up the pigmentation of your hair are:
The instructions on how to assemble these proteins is found on a:
proteins
gene

25. Comparison of Gene and Codon
holds instructions
makes proteins
CODON
1. Codes for amino acids
2. 64 possible codons
3. 3 nucleotide sequence
4. Codon is part of a gene
5. Found in mRNA
GENE
1. Codes for a trait or protein
2. Thousands of different ones
3. Has many nucleotides
4. Made of codons
5. Found in DNA

26. ~23,000 genes have been identified in the HUMAN GENOME PROJECT
Less on smaller x’s
More on larger X’s
SHOWS CHROMOSOMES PRESENT IN A CELL

27. Epigenetics – altering genes by messing with OUTSIDE DNA stuff like RNA or HISTONES!

28. Lots of DNA !
Stretched out, the DNA from one human body cell would be more than _______ !!!!! There are over 6 billion nucleotides
A single line of DNA from a salamander cell would extend for ten meters
20m long

29. 3 nucleotides
=CODON
=1 amino acid

30. II. Chromosome Number 2n n DIPLOID Body cells Humans 46
Two of each type of chromosome – (homologous pairs)
HAPLOID n
Gametes (sperm or egg cells)
One of each chromosome type
Humans 23

31. Is an organism MORE complex if it has MORE chromosomes???
Nope!

32. EVERY SPECIES HAS A SPECIFIC # OF CHROMOSOMES

33. in this example...
least
most
closest

34. What is the animal that has the highest # of GENES ?

35. Microscopic WATER FLEA (DAPHNIA) has 8000 more genes than humans!

36. III. Human Chromosome Number46
Diploid chromosome number (2n) =
Two sets of 23 chromosomes each
One set from father
One set from mother
Mitosis produces cells with 46 chromosomes--two of each type
Meiosis produces cells with 23 chromosomes – one of each type

37. Understanding Cell Division
What instructions are necessary for inheritance?
When you grow, how do you stay “you”?
How is DNA passed into new cells made?
How do you make “half” of a cell ready to make a baby?
How is DNA cut in half in a sex cell?
DNA
mitosis
meiosis

38. homologous pairs
1 X, 1Y
2 X's

39. organized pic of our 46 chromosomes
autosomes
sex chromosomes

40. Roles of Mitosis Multicellular organisms Unicellular organisms Grow
Replace Cells
Unicellular organisms
Asexual reproduction

41. cell that has just finished mitosis

42. Division Mechanisms binary fission Eukaryotic organisms
Mitosis
Meiosis
Prokaryotic organisms
_____________________________ (= mitosis)
binary fission

43. 2 new bacteria!
Binary fission

44. 3 easy steps to divide a bacteria…err.. BINARY FISSION:
1. chromosomes make copies
2. cell grows til about 2x its size!
3. cell wall forms in between the copied chromosomes and the cell SPLiTS!

45. <<LINK>>
IV. Cell Cycle
Cycle starts when a new cell forms
During cycle, cell increases in mass and duplicates its chromosomes
Cycle ends when the new cell divides
<<LINK>>

46. A. Stages of Interphase G1 (GAP 1) S (DNA SYNTHESIS) G2 (GAP 2)
Interval or gap after cell division – cell grows
S (DNA SYNTHESIS)
Time of DNA synthesis (replication)
G2 (GAP 2)
Interval or gap after DNA replication- prepares for cell division

47. The Cell Cycle Go S stops G1 synthesizes growth cell copy of DNA GROWS
cytokinesis G2
prepares
to divide
mitosis
Fig. 8.4, p. 130

48. 1. G1 Phase
after cell division, daughter cells are small and ATP is low
rapid cell growth occurs
certain enzymes used in DNA synthesis are made
cell carries out routine functions
chromosomes are not visible – long thin strands – chromatin

49. GDF 11 protein (growth differentiation factor) might be key to YOUTH bc it freezes cells at the G0 stage!

50. 2. S Phase
DNA replication; chromosomes – sister chromatids form
3. G2 Phase
preparation for mitosis
energy level restored (ATP)
Materials needed to manufacture mitotic structures are made and stockpiled
Increase in protein synthesis (enzymes)
4. Go Phase – (after G1) some cells do not divide again (nerve cells)

51. Which phase is DNA copied??
S phase

52. 1. Control of the Cycle
Once S begins, the cycle automatically runs through G2 and mitosis
The cycle has a built-in molecular brake in G1
Cancer involves a loss of control over the cycle, malfunction of the “brakes”

53. Neoplasms – ignore Go stage
Masses of cells that have lost control over how they grow and divide
Benign tumor
Malignant tumor (cancer)

54. Cancer Characteristics
Plasma membrane and cytoplasm altered
Cells grow and divide abnormally
Weakened capacity for adhesion; cells can move to new tissues
Lethal unless eradicated

55. 2. Stopping the Cycle Some cells normally stop in interphase
Neurons in human brain
Adverse conditions can stop cycle
Nutrient-deprived amoebas get stuck in interphase

56. B. Mitosis M Phase (Nucleus Divides)
Period of nuclear division
Usually followed by cytoplasmic division
Four stages:
Prophase
Metaphase
Anaphase
Telophase

57. 3. The Spindle Apparatus Consists of two distinct sets of microtubules
Each set extends from one of the cell poles
Two sets overlap at spindle equator
Moves chromosomes during mitosis

58. Spindle Apparatus one spindle pole one of the condensed chromosomes
spindle equator
microtubules organized
as a spindle apparatus
one spindle pole

59. Stages of Mitosis
Prophase
Metaphase
Anaphase
Telophase

60. a) Mitosis begins with Early Prophase
Duplicated chromosomes begin to condense and are now visible

61. (Plant cells have no centrioles, but spindle still forms)
b) Late Prophase
Centrioles move away from each other to opp. poles
(Plant cells have no centrioles, but spindle still forms)
Nuclear envelope starts to break up

62. c. Transition to Metaphase- (pro-metaphase))
Spindle microtubules become attached to the two sister chromatids of each chromosome at the kinetochore
Pairs of chromatids begin moving toward equator

63. d) Metaphase (meet in the middle)
All chromosomes are lined up at the spindle equator
Chromosomes (sister chromatids) are maximally condensed
Kinetochores split
this stage is used to prepare KARYOTYPES

66. e) Anaphase (move apart)
Sister chromatids of each chromosome are pulled apart centromere first as spindle fiber shorten
Cell elongates
Once separated each chromatid is a chromosome

67. f) Telophase
Chromosomes decondense (uncoil) until no longer visible – chromatin
Spindle fiber breaks apart
Two nuclear membranes form around each set of unduplicated chromosomes
Cell continues to elongate

68. g) Cytokinesis – Cell Dividing
Two mechanisms
Cell plate formation (plants) from within until a barrier is formed between the two cells (cell wall)
Cleavage (animals) cleavage furrow forms near equator

69. 1) Cell Plate Formation Plant cells

70. 2) Animal Cell Division
pinching off

72. h) Results of Mitosis Two daughter nuclei
Each with same chromosome number as parent cell
Chromosomes in unduplicated form

73. Why is mitosis so IMPORTANT for:
UNICELLULAR ORGANISMS?
It’s how they reproduce! (asexual)
MULTICELLULAR ORGANISMS?
keeps cells a small size (high SA: low V)
Allows each cell to differentiate (different functions)
Fixes your boo-boos 
Makes you an ADULT!

77. telophase
late telophase
metaphase
anaphase
prophase

78. Lesson 8.3 Meiosis
How does the number of chromosomes in an individual remain constant if sexual reproduction occurs?
Bc EGG & SPERM (GAMETES) cells have half the # of chromosomes!

79. Asexual Reproduction Single parent produces offspring
All offspring are genetically identical to one another and to parent

80. Sexual Reproduction Involves Produces DIVERSITY among offspring
Meiosis – reducing the chromosome number from diploid to haploid to make gametes
Fertilization
Produces DIVERSITY among offspring

81. Homologous Chromosomes Carry Different Genes
Cell has two sets of each chromosome (2x23=46)
One chromosome in each pair from mother, other from father
gene for eye color
brown
blue
Mom’s
Dad’s

82. Sexual Reproduction will Shuffle Alleles

84. homologous chromosomes
Meiosis: One Replication and Two Divisions Mitosis: One Replication and One Division*
Meiosis:
Anaphase I – _________________________ separate
Anaphase II – sister chromatids separate
Mitosis:
Anaphase - ___________________________ separate*
Meiosis: 4 haploid nuclei form
Mitosis: 2 diploid nuclei form*
homologous chromosomes
sister chromatids

86. Meiosis I

87. Meiosis II

88. B4 we start.. Lets go over some vocab!

89. chromosome

90. Duplicated chromosome = an “X” = (common name – “chromosome”)

91. Synapsis – coming together
When one “X” pairs up with his partner “X”

92. Tetrad = pair of Homologous chromosomes = 4 chromosomes = 2 “X’s”

93. Crossing-over
When chromatid parts are exchanged with their partner’s chromatid parts

94. Genetic recombination
When crossing over mixes up the genes

95. Genetic recombination
Changing the genetic material
genes are
mixed up

96. LAW OF INDEPENDENT ASSORTMENT
When traits are assorted (crossed over) independently from each other
It’s not the COLOR of your eyes changes how TALL you are….

97. LAW OF SEGREGATION When homologous chromosomes (X’s) randomly separate
It’s not like all the mama chromosomes go on one side of the cell and the papa chromosomes go to the other….

98. Chiasmata
Place where homologous chromosomes touch and exchange genes

99. MEIOSIS I – Interphase I
Similar to mitosis
where DNA replicates to form identical chromatids which remain attached at their centromere

100. Prophase I DNA condenses into chromosomes Nuclear membrane dissapears
Centrioles start moving to opposite sides
Spindle fibers start forming
Each duplicated chromosome pairs with homologue –
SYNAPSIS occurs -process that forms TETRADS
Homologues can swap segments (non-sister chromatids)
CROSSING OVER

101. Prophase I DNA coils into chromosomes Spindle fibers appear
Nucleus disappears
Chromosome pairs line up next to each other

102. Prophase I Chromatin condenses into chromosomes
Nuclear membrane dissapears
Centrioles start moving to opposite sides
Spindle fibers start forming
Each duplicated chromosome pairs with homologue –
SYNAPSIS occurs -process that forms TETRADS
Homologues can swap segments (non-sister chromatids)
CROSSING OVER

103. Crossing Over
In tetrad formation each chromosome (duplicated) becomes zippered to its homologue
All four chromatids are closely aligned
Non-sister chromosomes exchange segments

104. Effect of Crossing Over
After crossing over, each chromosome contains both maternal and paternal segments
Creates new gene combinations in offspring
Chiasma - chromosome with both parents’ DNA

106. Random Alignment

107. Possible Chromosome Combinations1 2 3
Possible Chromosome Combinations or or or

109. Metaphase I Chromosomes (tetrad) meet in the middle
The spindle fibers are fully formed & attached to tetrad centromeres
Random assortment of chromosomes (like blind dates )

110. Anaphase I *Homologous chromosomes* move apart
The sister chromatids remain attached and move together

111. Telophase I Cytokinesis occurs Nuclear membranes reform
Spindle fibers disappear
Each cell has a HAPLOID # of chromosomes that are doubled (sister chromatids)

112. For example…
4 chrom.
2 chrom.
each
diploid
2 sets
haploid
only 1 set

113. Meiosis II  just like Mitosis

114. Prophase II Centrioles start to move back to opposite poles
Nuclear membrane starts to dissapear
Spindle fibers start forming
NO replication of chromosomes
NO tetrad formation

115. Metaphase II *Sister chromatids* meet in the middle
Spindle fibers should be attached to centromeres by now

116. Anaphase II
Sister chromatids separate to become independent chromosomes

117. Telophase II Cytokinesis occurs
Nuclear envelope reforms around each set of chromosomes
Four haploid (n) cells – each about ¼ the size of original cell

118. 2
Start with 4 chromosomes 4
haploid 2
diploid 2 2 2
haploid 2

121. Oogenesis – making egg cells
three polar bodies (haploid)
first polar body (haploid)
oogonium (diploid)
primary oocyte (diploid)
secondary oocyte (haploid)
ovum (haploid)
Meiosis I,
Cytoplasmic Division
Meiosis II,
Cytoplasmic Division
Growth
Oogenesis – making egg cells

122. Find the: ovum & polar bodies

123. Spermatogenesis Spermatogenesis – making sperm cells spermato- gonium
(diploid )
primary spermatocyte (diploid)
secondary spermatocytes (haploid)
sperm (mature, haploid male gametes)
spermatids
(haploid)
Spermatogenesis
Meiosis I,
Cytoplasmic Division
Meiosis II,
Cytoplasmic Division
Growth
cell differentiation, sperm formation
Spermatogenesis – making sperm cells

124. Find the: spermatids & sperm

126. Fertilization Male and female gametes unite and nuclei fuse
Fusion of two haploid nuclei  diploid nucleus
2 gametes coming together is random 
More Independent Assortment!
Adds to variation among offspring

127. When are 3 EVENTS that MIX up the genes so each kid is slightly different?!
1. Crossing over during prophase I
2. Random alignment of “X” chromosomes at metaphase I
3. which sperm gets to which egg released that month at fertilization

128. Prophase I Metaphase I Anaphase I Telophase I
ProphaseII Metaphase II Anaphase II Telophase II

129. MITOSIS vs MEIOSIS Sister chromatids line up
Homologous chromosomes line up

130. Mitosis & Meiosis Compared
1 Division
Makes 2 diploid cells
Sister chromatids split
No pairing of chromosomes
Meiosis
2 Divisions
Makes 4 haploid cells
Homologous chromosomes split
synapsis

131. Mitosis & Meiosis Compared
Functions
Asexual reproduction
Growth, repair
Occurs in somatic (body) cells
Produces clones (genetically identical)
Meiosis
Function
Sexual reproduction
Occurs in germ (sex cell-making) cells
Produces variable offspring (genetic recombination)