+COUPLE+

**Sometimes happy**

**Sometimes...not**

P/S : It bored me to death when the "fighting season" came. Maybe it is better if I go solo again... Or should I step back and go far away from here??? Eager for some signs now. Sighs.....

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+NO MORE CRIES+

"Hapuskanlah air mata di pipi dan hilangkan lara di hati... Terimalah semua sebagai sebahagian dari perjalanan hidup ini dengan kebesaran hati dan jiwa... Dirimu akan menemukan apa rahsia di sebalik titian kehidupan yang telah dijalani dan diduga ALLAH... Sehingga kelak akan engkau rasakan tiada lagi riak kegelisahan dan keresahan saat bersendiri..."

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+FRUSTRATED+

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+VARIATION IN CHROMOSOME STRUCTURE PART 1+

NATURAL VARIATION IN CHROMOSOME STRUCTURE

• A cytogeneticist studies variations in chromosome structure and number.
• The chromosomes for a given species vary in both size and shape.
• Chromosomes are named according to the location of their centromere.
• Based on the location of the centromere, the chromosome is either called metacentric, submetacentric, acrocentric, or telocentric.

1. All chromosomes have long arm(q) and short arm(p).

• A karyotype is a micrograph that arranges the chromosomes with the short arm at the top and then in descending order by size.
• Cytogeneticists use stains to further identify the chromosomes.

1. The use of Giemsa stain produces a G banding pattern which is used as a standard identification pattern for chromosomes.
2. Banding patterns may also be used to identify changes in chromosome structure.
   

MUTATIONS AND CHROMOSOME STRUCTURE

• Changes in chromosome structure may either change:

1. Total amount of genetic material within the chromosome (increase or decrease).
2. Rearrange the genetic material within a chromosome or between 2 chromosomes.

• Changes to chromosome include:

1. Deficiencies and deletions = Changes the total genetic content (missing region) of the chromosome.
2. Duplications = Changes the total genetic content (repeating segment) of the chromosome.
3. Inversions = Changes the arrangement of the chromosome.
4. Translocations = May be either simple translocations or reciprocal translocations. These typically change both the arrangement of chromosome and total genetic content.
   

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+VARIATION IN CHROMOSOME NUMBER PART 2+

NATURAL AND EXPERIMENTAL WAYS TO PRODUCE VARIATION IN CHROMOSOME NUMBER

• Variations in chromosome numbers are due to nondisjunction of the chromosomes.
• Meiotic nondisjunction produces haploid cells with extra or fewer chromosomes.
• Mitotic nondisjunction produces patches of tissues that have an altered chromosome numbers.
• Interspecies crosses can create allopolyploids.
  

MITOTIC NONDISJUNCTION

• Occurs after fertilization has occurred.

1. The result is an organism which contains a group of cells genetically different from one another.
2. This is called mosaicsm.

• The size and location of mosaic region depend on when and where the event occurred.
• If event occurs in first mitotic division, result is a bilateral gynandromorphy.
  

CHANGES IN EUPLOIDY

• An autopolyploid = increase in the numbers of chromosome sets in a single species.
• Alloploidy is the result of an interspecies cross.
• Allodiploids have one set of chromosomes from each parent.
• Allopolyploid contains a combination of interspecies chromosome sets.
• An allotetraploid has 2 complete sets of chromosomes from 2 species.
  

FERTILITY AND EUPLOIDY

• Allodiploid are usually sterile, unless the species is closely related.
• Evolutionary related chromosomes from 2 different species are called homologous.
• Allotetraploids are usually fertile because they possess 2 complete sets of the chromosomes (including sex chromosomes) from each species.
  

EXPERIMENTAL TREATMENTS AND POLYPLOIDY

• Polyploid and alloploid plants are important in agriculture.

1. Several mechanisms have been developed to generate these chromosome combinations.
2. e.g. drug colchicines binds to tubulin and interferes with normal chromosome segregation, thus promoting nondisjunction.
   

CELL FUSION AND HYBRID PLANTS

• In cell fusion, individual calls are mixed together and made to fuse, thus allowing the crossing of 2 species that would not naturally occur.

1. This requires the removal of cell wall, creating a protoplast.
2. Once fused, cell contains 2 nuclei, called a heterokaryon.
3. This cell will then undergo nuclear fusion to produce a hybrid cell with a single nucleus.
   

MONOPLOIDS AND AGRICULTURE

• A monoploid allows researchers to generate a strain of a crop that is homozygous for all of its genes.
• These true-breeding strains may then be crossed to produce plants that are heterozygous for many genes.
• These plants are usually more vigorous called hybrid vigour or heterosis.
• The use of anther culture can produce diploid strains of crops that are homozygous for all genes.
• Animal species may be produced by parthenogenesis, which involves inducing them to begin development without fertilization.

1. The haploid zygote usually only lives for a short period before dying, but this provides useful information for developmental biologists.
   

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+VARIATION IN CHROMOSOME NUMBER PART 1+

VARIATION IN CHROMOSOME NUMBER

May be result of:

• Change in numbers of sets of chromosomes.
• Variation in numbers of chromosomes within a set.

TERMINOLOGY FOR VARIATION IN CHROMOSOME NUMBER

• Euploid = organism that have chromosome numbers that is an exact multiple of the chromosome set.
• Triploid = organism with three multiples of the chromosome set.
• Polyploidy = organism with three or more sets of chromosomes.

ANEUPLOIDY AND GENE EXPRESSION

• Aneuploidy = change in numbers of a specific chromosome:

1. Trisomic (2n+1) = an extra copy of one chromosome.
2. Monosomic (2n-1) = a missing copy of one chromosome
   

• Aneuploidy commonly causes an abnormal phenotype usually due to change in production of gene product.

ANEUPLOIDY AND HUMANS

• Approximately 5-10% of fertilized human eggs have abnormal chromosome numbers.

1. Almost 50% of spontaneous abortions are due to to aneuploidy.
2. Changes in numbers of X chromosomes are usually non-lethal due to formation of inactive Barr bodies.
3. May be phenotypic consequences due to the expression of genes early in embryonic development (prior to X activation).
   

• Age of parents may also influence formation of aneuploid condition.
• An example is Down Syndrome in which chromosomes do not separate correctly during anaphase.
• May be due to age of the oocyte, but other factors may also contribute.
  

VARIATIONS IN EUPLOIDY IN ANIMALS

• Most animals are diploid and changes in numbers of chromosome sets are not tolerated.
• Exceptions are:

1. Male bees which are monoploid. Some vertebrate animals such as amphibians and reptiles are polyploid.
   

VARIATIONS IN EUPLOIDY IN ANIMAL TISSUES

• Tissues of body may have abnormal variations in the numbers of chromosome sets.

1. Liver cells in humans are triploid, tetraploid or octoploid – called endopolyploidy.
   

• Polytene chromosomes in the salivary glands of Drosophila consist of bundled replications of chromosome that lie together in a parallel fashion.

1. Can contain up to 9 sets of chromosomes.
2. The central location of aggregation is called chromocenter.
3. Polytene chromosomes consist of dark bands called chromomeres. About 95% of DNA is found in chromomeres.
   

VARIATIONS IN EUPLOIDY IN PLANTS

• Unlike animals, plants commonly exhibit euploidy.

1. Polyploidy plants often have outstanding agricultural characteristics or produce large flowers.

• Polyploids with an odd numbers of chromosome sets are usually sterile due to production of aneuploid gametes.

1. Sterility is often selected for in modern agriculture.
   

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+MENGIDAM LORH...+

Suddenly I'm craving for choco ice cream. Aiyo... Lame sudah x makan. Terpaksela meninggalkan laptp dan pergi ke 7 Eleven di depan. Nak g Baskin n Robin jauh sangat. Huhu... Jum suma makan, yum2....

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+APAKAH MAKSUD KEJAYAAN NEGARA?+

Menurut pendapat saya, kejayaan negara bergantung pada perpaduan rakyat negara tersebut. Melalui perpaduan, sesebuah negara akan bertambah kuat dan tidak mampu ditindas oleh negara lain. Konsep 1 Malaysia yang diperkenalkan oleh kerajaan membuktikan perpaduan penting terutamanya kepada negara berbilang kaum seperti Malaysia. Hal ini disebabkan kurangnya persefahaman antara beberapa kaum di Malaysia baru-baru ini. Perpaduan dapat dipupuk dengan menyemai sikap saling menghormati dan bantu-membantu tanpa membezakan agama, bangsa dan warna kulit. Melalui perpaduan, rakyat dapat memperoleh manfaat kerana negara yang aman mampu menarik minat pelabur asing menjalin urus niaga di Malaysia. Kita sebagai rakyat Malaysia yang bertanggungjawab haruslah memastikan keamanan dan kestabilan negara sentiasa terjaga.


**Karangan 1 perenggan di atas ditulis semasa kelas Bahasa Melayu. Tiada kesalahan penggunaan ayat, bangge2, haha... Tapi rasenye karangan ni tak kuat pun. Ape-apepun selamat menyambut hari kemerdekaan ke-52. Bangga jua jadi rakyat Malaysia. Hee~**

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