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Genetic Information Storage Structures

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Title: Genetic Information Storage Structures


1
Chromosomes
  • Genetic Information Storage Structures

2
Chromosome Structure
DNA wrapped around histone proteins forming
bead-like units or nucleosomes These are
coiled forming a super coil which coils to form
a chromosome
3
  • Gene
  • Segment of DNA on chromosome that codes for the
    making of a polypeptide chain or protein

4
Chromosome Copies
  • Review
  • DNA is copied, creating a chromosome with two
    identical sides called
  • sister chromatids
  • which are connected at the centromere

5
Chromosomes usually occur in pairs that are
similar to each other Homologous Chromosomes
Humans have 23 pairs How many total?
6
Chromosome Number
  • Diploid (2n) -
  • Cells containing both members of a homologous
    pair
  • Ex Somatic (Body) Cells

7
Haploid (n) Cells containing one member of
a homologous pair Gametes (Reproductive
cells - sperm and egg)
8
Chromosomes and Development
  • Sexual Reproduction
  • Fusion of two haploid cells from two parents
  • What type of cell would this make???

9
Zygote Diploid cell formed from sexual
reproduction (fertilized egg) Has full set of
DNA to develop into new organism
10
Meiosis
Production of Gametes (One diploid cell
produces four haploid cells)
11
Overview of The Process of Meiosis
1
Chromosomes duplicate
2
Homologous chromosomes separate
3
Sister chromatids separate
Homologous pair of chromosomes in diploid parent
cell
Homologous pair of duplicated chromosomes
Sister chromatids
Interphase before meiosis
Meiosis II
Meiosis I
Figure 8.14
12
Two parts
  • Meiosis I
  • Homologous chromosomes separate into two
  • haploid cells

2. Meiosis II Chromatids of each chromosome
separate forming at total of four haploid
cells
13
Interphase
Chromosomes/DNA replicate
14
Prophase I
Chromosomes condense Nucleolus breaks
down Homologous chromosomes pair up forming a
tetrad (synapsis) Crossing-over
occurs (exchange of sections of chromosomes and
thus the genetic information
15
Crossing Over
(Where crossing over occurs)
16
Metaphase I
Homologous chromosomes move to the middle and
spindle fibers attach
17
Anaphase I
Homologous chromosomes separate and begin moving
to opposite sides Nondisjunction can occur
18
Nondisjunction
19
Telophase I
Cytoplasm divides and nuclei form Two new cells
have ½ the number of chromosomes of the original
cell
20
MEIOSIS II
JUST LIKE MITOSIS )
21
Prophase II
Chromosomes condense Nucleus breaks down No
replication occurs!
22
Metaphase II
Chromosomes (2 chromatids each) line up in the
center
23
Anaphase II
Chromatids separate and move to opposite poles of
the cell
24
Telophase II
Cytoplasm divides Nuclei form around four
haploid cells
25
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26
Formation of sperm and egg - Only one egg is
usually produced due to unequal dividing of the
cytoplasm Other three cells are called polar
bodies
However, four sperm are produced!
27
Meiosis allows for Genetic Recombination- Source
of variation among organisms because of crossing
over and independent assortment of homologous
chromosomes
28
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33
Mitosis vs. Meiosis
4
2
YES
NO
DIPLOID
HAPLOID
YES- ASEXUAL
YES - SEXUAL
YES
NO
2
1
NO
YES
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