Title: Chromosomes
1Chromosomes
- PART 1
- Honors Genetics
- Ms. Gaynor
2Why is Cell Division Important?
- Unicellular organisms
- Reproduce by cell division ? increasing the
population.
3Why Do Multicellular Organisms Depend on Cell
Division?
- Development Growth
- Repair (ex tissue renewal)
- Maintenance
4Cell Division (Mitosis)
- Makes 2 genetically identical daughter cells from
1 parent cell - Before cells divide
- They duplicate their genetic material ? ensures
that each daughter cell receives an exact copy of
the genetic material, DNA
5Organization of the Genetic Material
- All of a cells DNA (genetic information) is
called its genome - In prokaryotes
- Genomesingle, long DNA molecule in a circle
- In eukaryotes
- Genome several DNA molecules grouped in clumps
(called chromosomes)
6DNA Molecules
- DNA (in nucleus of eukaryotes) can be in 2 forms
- Chromatin DNA is not tightly packed together
(loosely coiled) - Occurs during interphase
- Chromosomes tightly packed together (TIGHTLY
coiled) - Occurs during mitosis (cell division)
7Tightly coiled?
Not tightly coiled?
8(No Transcript)
9How Does DNA Fit into a Small Cell?
- Prokaryotic organisms
- No nucleus instead have a nucleiod region
- DNA 1 chromosome
10How Does DNA Fit into a Small Cell?
- Eukaryotic organisms split their DNA into several
pieces (called chromosomes) - stored within the cell's nucleus
- DNA is coiled around proteins known as histones
- Uses nucleosomes to form a supercoil
11DNA histones ? form nucleosomes (help to
super coil DNA)
12Making Chromosomes
- Occurs right before cell division (mitosis)
- Steps
- DNA copies itself through DNA Replication
- The DNA coils (wraps) around proteins called
histone proteins. - Chromosomes are made.
13The DNA molecules in a cellAre packaged into
chromosomes
14Chromosome Structure
- Two shapes of chromosomes
- Single chromosome (1 copy of DNA) V shaped
- Double Chromosome (2 copies of DNA) X shaped
a.k.a-duplicated chromosome
Occurs right before cell division (mitosis)
15Chromosomes and Cell Division
- In preparation for cell division (mitosis)
- DNA is replicated (single ? double chromosome)
- V shape ? X shape
16Each duplicated chromosomehas two sister
chromatids, which separate during cell division
17Double Chromosome Structure
Kinetochore attaches to spindle fibers
Sister
18Another view
19Draw and Label the Pieces of a Duplicated
Chromosome
20Chromosomes
- Every eukaryotic species has a characteristic,
unique of chromosomes in EACH cell nucleus - Ex Humans have 46 chromosomes
- of chromosomes does NOT necessarily equal
complexity
21Different Types of Cells
- There are 2 types of cells in the human body
- Somatic cells all body cells
- 2. Gametes reproductive cells (sperm and egg)
22Different cell types ? different cell divisions
- Eukaryotic cell division consists of
- Mitosis, division of the nucleus
- Cytokinesis,division of cytoplasm
- Occurs in somatic cells
- In meiosis
- Gamete cells are produced after a reduction in
chromosome number
23Chromosome Number
- Gametes (sperm/egg) have 1 copy of each
chromosome and are called haploid. - Somatic (body) human cells have 2 copies of each
chromosomes and are called diploid. - Human somatic cells have 23 PAIRS of chromosomes
(total 46 chromosomes). - All pairs of chromosomes differ in size, shapes,
and set of genes.
24Haploid vs. Diploid
- Haploid when a cell has 1 copy of each
chromosome. - Expressed as n 23
- Diploid when a cell has 2 copy of each
chromosome. (a.k.a TOTAL of Cs in organisms) - Expressed as 2n 46
Haploid sperm cell
n
Haploid egg cell
n
Fertilization
2n
Diploid Zygote cell
25Set of Chromosomes
- Each chromosome set contain 2 homologues.
- Chromosomes have a twin or matching pair.
- Homologous Chromosomes chromosomes that are
similar in shape, size, and genes. - Each homologue in a pair comes from each parent!