CHROMOSOMES

1
CHROMOSOMES

• CHAPTER 8

2
CHROMOSOMES

• Rod shaped structures composed of DNA and
  proteins
• Visible only when cell begins to reproduce
• Formed from the coiling of chromatin
• Located in nucleoplasm

3
CHROMOSOME structure

• Chromatids
• Centromere
• Occur in pairs
• Number of chromosomes does not indicate organism
  complexity
• p. 152

4
CHROMOSOME structure

• Chromatin coils into chromosomes
• Chromosomes composed of genes
• Humans have 30 000 genes
• Genes composed of DNA
• DNA structure is double helix

5
(No Transcript)
6
HISTONES

• Proteins that DNA wraps around
• Maintain the shape of DNA

7
NONHISTONES

• Proteins involved in controlling specific
  activity regions of DNA

8
CHROMOSOME structure

• DNA composed of nucleotides
• Nucleotides composed of
• deoxyribose (5 C sugar)
• phosphate group
• nitrogenous base
• 4 types
• adenine thymine
• cytosine guanine

9
CHROMOSOME structure

• Nucleotides occur in pairs
• Humans have 3 000 000 000 base pairs
• This is known as a GENOME
• all of the base pairs of an organism

10
Diploid

• Normal number of chromosomes
• 2N 2n
• Humans have 46 CHROMOSOMES
• Chimpanzees have 48 CHROMOSOMES

11
Haploid

• Half the normal number of chromosomes
• 1N n
• Human haploid number is 23
• Chimpanzees haploid number is 24
• Found in egg and sperm

12
Two types of chromosomes

• AUTOSOMES
• SEX CHROMOSOMES

13
AUTOSOMES

• CHROMOSOMES OTHER THAN SEX CHROMOSOMES
• Humans have 22 pairs of autosomes
• 44 autosomes
• Chimpanzees have 23 pairs of autosomes
• 46 autosomes

14
SEX CHROMSOMES

• Determines gender of organism
• always last pair of chromosomes
• Only one pair of chromosomes determines gender
• Humans pair number 23
• Chimpanzee pair number 24

15
SEX CHROMSOMES

• female chromosomal condition
• XX
• Male chromosomal condition
• XY

16
KARYOTYPE

• Chromosomal map depicting matching chromosomes in
  pairs
• Longest chromosomes are first pair
• Shortest pair is second to last
• Sex chromosomes are always the last pair

17
To match chromosomes

• Alleles matching chromosome
• Length
• Gene locations
• Centromeres location

18
CELL DIVISION

• CELL REPRODUCTION
• CHAPTER 8

19
Cell division

• Process by which cells produce offspring cells
• Differs in prokaryotic and eukaryotic cells

20
Cell division in prokaryotic cellsp. 154

• Bacterial cell have cell wall NOT made of
  cellulose
• Possess circular chromosome (DNA) known as
  PLASMID

21
BINARY FISSION

• DNA (plasmid) is copied
• New cell membrane begins to form
• Cell grows to 2x original size
• Cell membrane pinches inward in center
• New cell wall forms
• Cell splits into two independent cells

22
CELL CYCLE

• CHAPTER 8

23
OVERVIEW

• CELL CYCLE
• I. Interphase
• II. Mitosis
• III. Cytokinesis

24
I. Interphase

• A. G1 phase
• B. S phase
• C. G2 phase
• G0 phase

25
Interphase

• Time between cell division
• Divided into 3 phases

26
Interphase G1

• G1 stands for time gap
• Cell grows and develops
• Longest phase of interphase

27
Interphase S

• Synthesis
• DNA is copied (synthesized)
• Shortest interphase stage

28
Interphase G2

• Time gap between S phase and mitosis
• Organelles are replicated
• More cytoplasm is formed

29
Interphase G0

• Can occur when cell leaves G1
• These cells do not divide
• Examples
• Brain cells
• Nerve cells

30
MITOSIS

• Division of the nucleus
• Continuous process

31
II. MITOSIS M phase

• A. Prophase
• B. Metaphase
• C. Anaphase
• D. Telophase

32
Prophase

• First phase of mitosis
• Longest phase taking 50-60 of the time
• Chromatin begins to coil into visible chromosomes
• Centrioles begin to move to the poles

33
Prophase

• Nucleolus disappears
• Nuclear envelope breakdown
• MITOTIC SPINDLE begins to forms
• 2 types of spindle fibers

34
kinetochore fibers

• kinetochore disk shaped protein on
  centromere
• Extends from kinetochore of each chromatid to one
  of centrosomes

35
polar fibers

• Extend from centrosome to centrosome

36
METAPHASE

• SECOND PHASE OF MITOSIS
• SHORTEST PHASE OF MITOSIS
• Chromosomes line up at the equator
• Centrosomes have reached the poles
• Each chromosome is held in place by kinetochore
  fibers

37
ANAPHASE

• Third phase of mitosis
• Spindle fibers shorten pulling chromatids to
  poles
• Chromatids separate and move towards pole
• Ends when chromatids reach poles
• ATP supplies energy for this action

38
TELOPHASE

• Last phase of mitosis
• Spindle fibers disassemble
• Nucleolus reappears (2)
• Nuclear envelope reforms (2)
• Chromosomes uncoil into chromatin

39
III. CYTOKINESIS

• Division of cytoplasm and organelles

40
III. CYTOKINESIS

• A. Cleavage furrow formation
• B. Organelles are divided between cells
• When finished 2 new cells are formed

41
Cytokinesis in plant cell

• Cell plate begins to form
• Cell plate will become the cell wall