Chromosome n DNA rearrangement Fatch

  Fatchiyah, Ph.D. Lab. Molecular Biology Brawijaya University

Chromosome & DNA?

• Chromosomes, threadlike structures, first observed by Nageli in 1842.
• Walter Flemming was the first to follow the process of mitosis and replication of chromosomes.
• Thomas Morgan, in his experiments with fruit flies, described genetic recombination, and demonstrated that traits were to inherited together to varying degrees.
• Alfred Sturtevant extended Morgan’s ideas, used observed recombination rates to produce the first genetic maps.

• Surrounded by a nuclear envelope
• Perinuclear s
• Communicates with cytoplasm

  through nuclear pores The nucleus is the center of cellular operations

  The Nucleus Content of nucleus:

• A supportive nuclear matrix
• One or more nuclei
• Chromosomes
• Chromatin
• DNA bound to histones _{Figure 3.13}

  What Are Chromosomes?

• Cytogenetics is the study of

  chromosomes and the related disease states caused by abnormal chromosome number and/or structure.

• Chromosomes are complex structures

  located in the cell nucleus, they are composed of DNA, histone and non- histone proteins, RNA , and polysaccharides.

• They are basically the "packages" that contain the DNA.

  

What Are Chromosomes?

• Normally chromosomes can't be seen with a

  light microscope but during cell division they become condensed enough to be easily analyzed at 1000X.

• To collect cells with their chromosomes in

  

this condensed state they are exposed to a

mitotic inhibitor which blocks formation of the spindle and arrests cell division at the metaphase stage Type of chromosome structure

  1. The short arm is designated as p and the long arm as q .

  2. The centromere is the location of spindle attachment and is an integral part of the

  Metacentric Submetacentric Acrocentric chromosome .

  Chrom. 1 Chrom. 9 Chrom. 14

  3. It is essential for the The ideogram is basically a "chromosome map" normal movement and showing the relationship between the short and segregation of long arms, centromere (cen), and in the case of chromosomes during acrocentric chromosomes the stalks (st) and satellites (sa). The specific banding patterns are cell division.

Figure 3.14 Chromosome Structure

  Organization of Genes on Human Chromosome

  Structural Organization of the Nucleosome

  Structural Organization of the Nucleosome

  Nucleosome Disruption

_{disrupt and re-form nucleosomes, although, in principle, the same complex might catalyze both reactions. The DNA-binding proteins could function in}

Figure 4-34. A cyclic mechanism for nucleosome disruption and re-formation. According to this model, different chromatin remodeling complexes

  Chromosome Facts

• • number of chromosomes: 22 pairs + 1 pair

  sex-determining chromosomes = 46

• – one chromosome of each pair donated from

  each parent’s egg or sperm
• – sex chromosomes: X,Y for males; X,X for females

• – largest chromosome #1 = ~263 million base

  pairs (bp)

  Chromosomes can be “painted” for easy identification. By technique of multiplex fluorescence in situ hybridization (M-FISH)

  Mitotic chromosomes

G1 chromosomes

  Gene Facts

• size of human genome: 3.4 billion base pairs (bp)
• number of human genes: ~100,000
• genes vary in length and can cover thousands of bases
• – avg. size: ~3,000 bp
• only about 5% of the human genome contains genes

  

Chromosomes come in pairs

• Humans have 23 pairs of chromosomes
• –Total of 46 chromosomes
• Fruit flies have 4 pairs of chromosomes
• –Total of 8 chromosomes

  

Normal Chromosomes

Normal human somatic cells have 46 chromosomes: 22

   pairs, or homologs, of autosomes (chromosomes 1-22)

and two sex chromosomes. This is called the diploid

number. Females carry two X chromosomes (46,XX)

while males have an X and a Y (46,XY).

  Germ cells (egg and sperm) have 23 chromosomes: one

   copy of each autosome plus a single sex chromosome. This is referred to as the haploid number.

  

One chromosome from each autosomal pair plus one

   sex chromosome is inherited from each parent.

  Mothers can contribute only an X chromosome to

   their children while fathers can contribute either an X or a Y.

  Chromosomes of human Male

  Female Y-chrom

  

Members of a chromosome pair

• Cells with PAIRS of chromosomes are

  diploid

• – di – means “two”, “double”, “twice”
• – oid – “appearance”

• • The two members of any chromosome pair are

  called homologues, or a homologous pair
• Ex:
>– The two “number 1” chromosomes are homologues
• – The two “number 21” chromosomes are homologues.

  

In sexual reproduction

• new organisms (zygotes) are formed by the joining together of two sex cells (gametes):
• – a sperm cell from a male and
• –an egg cell from a female

  What would happen if…….

• a human egg cell had 46 chromosomes AND

• • a human sperm cell had 46 chromosomes?

  46 chromosomes

• 46 chromosomes 92 chromosomes

  Too many for a human!

  

Diploid organisms need….

• A way to produce sex cells (eggs and

  sperm) that only have ONE member of

  each chromosome pair
• In humans, sex cells each have 23 chromosomes
• – ONE member of each homologous pair

• – Half of amount of chromosome is named

  genome (haploid)

  Just right for a human!

  23 chromosomes

• 23 chromosomes 46 chromosomes

The different possibilities of the way chromosomes will separate into gametes helps create genetic diversity OR

Effect of Crossing Over

  Crossing over occurs when homologous chromosomes pair with

  Chromatids cross over one each other before the another, and the crossed first meiotic division sections of the chromatids are exchanged.

  

Chromosomes

Figure 4-14. Two closely related species of deer with very different chromosome numbers. In the evolution of the Indian muntjac, initially separate chromosomes fused, without having a major effect on the animal. These two

species have roughly the same number of genes. (Adapted from M.W. Strickberger,

Evolution, 3rd edition, 2000, Sudbury, MA: Jones & Bartlett Publishers

  Arabidopsis 25, 498 genes Missing Missing Missing Different Missing

  The emphasis in the human

genome

Human 26,588 genes

• The nervous system
• The immune system
• The blood system
• Signaling and cell-cell communication
• Programmed cell death

  Structure of Chromosome - NORs

Structure of Chromosome - NORs

  Interphase nucleus of onion root tip through light microscope nucleolus

  

Structure of Chromosome - NORs

Structure of Chromosome - NORs electron micrograph of interphase cell from bat pancreas nucleolus Polytene Chomosome of Drosophila as Giant chromosome

Polytene chromosome

  Phase-contrast image of Drosophila melanogaster polytene cromosomes.

  A. The end of the X-chromosome is marked with an arrow. Chromocentre is in the upper right corner.

  B. Shows a magnification of chromomere and interchromomere bands W-chromosome Yeast Artificial Chromosome

  

Bacterial Artificial Chromosome Manipulation

by Homologous Recombinant

  Metaphase: Chromosome in middle cell

  Antibodies of a person with an autoimmune disease stain centromers