genetic (notes)

assalamualaikum w.b.t...


lagi few days dah nak exam! >.<

so bear with me..saja nak share notes..

if bermanfaat untuk siapa2 silakan ambik :)

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genes ade dua jenis :

constitutive - "housekeeping genes" --> simple structure (constant)
controllable - expressed only when needed --> complex structure (only in certain condition)

gene regulation in prokaryotes :
-a set of gene which is regulated or controlled by ONE PROMOTER

structure :
-cistrons (code for specific protein)
-promoter region
-operator region
-regulatory region

function :
-catabolic (lac operon)
-anabolic (ara operon)


LAC OPERON

how it works ?

--> in the absence of lactose,the repressor protein binds to d operator region..RNA polymerase (RNAP) cannot bind to d promoter region..there's no transcription occur..genes are not expressed..

-->in the presence of lactose,d lactose will bind to d repressor protein n change in shape..so dat d repressor protein cannot bind to the operator region coz of d change of shape..the RNAP can bind to d promoter region,transcription occur n mRNA produced ! ^_^

gene regulation in eukaryotes :

-transcription - level of regulation

-mencegah penggumpalan mRNA

-no translation when not needed

regulatory pathways :

-hormones

-DNA structures (histones n chromatin packaging)

-enhancers

-DNA-binding protein

-transcription factors

key : has David end D-boring talk ?

*the more the protein bounds to the DNA,the less the transcription (sebab lagi ketat)

GENE MUTATION

mutations :

- changes in nucleotide sequence in DNA

- MAY occur in SOMATIC CELL --> not passed to d offsprings

- MAY occur in GAMETES --> MAYbe passed to d offsprings

- jarang berlaku

- repaired by enzymes

chromosomal mutation :

- mungkin melibatkan perubahan struktur kromosom

- deletion a part of chromosome

jenis :

-deletion

-inversion

-translocation

-nondisjunction

-duplication

DELETION :  

                                          

-due to d breakage

-a piece of chromosome hilang

INVERSION :

-chromosome segment break off

-segment jadi upside-down then reattaches

DUPLICATION :

-berlaku bila gene sequence is repeated

TRANSLOCATION :

-melibatkan dua heterozygous chromosomes

-part of one chromosome is transfered to another chromosome

NONDISJUNCTION :

-kegagalan chromosomes untuk separate semasa mitosis

-menyebabkan gamete mempunyai lebih atau kurang chromosomes

disorder :

--> down syndromes (three 21st chromosomes)

--> turner's syndromes (single X chromosomes)

--> klinefelter's syndromes (XXY chromosomes)

CHROMOSOME MUTATION

--> virus that can affect DNA..the virus will inject the DNA and affect the code..for example,the original code is ABCDEFGHI but the affect code will be ABEGHICDF 

GENE MUTATION

-change in the nucleotide osequence of gene

-may only involve single nucleotide

-mungkin disebabkan copying error,virus kimia n etc

types :

-point mutation

-substitution

-insertion

-deletions

-frameshift

POINT MUTATION

-sicle cell disease - result of one nucleotide substitution

-berlaku kat haemoglobin gene

-example of point mutation-

FRAMESHIFT MUTATION

-inserting or deleting one or more nucleotides

-change the 'reading frame' like changing a sentence

-proteins built incorrectly

example : kalau code yang normal,mesti ada tiga,tiga kod kan..but kalau yang frameshift mutation,salah satu kod hilang..

RECOMBINANT DNA

-placing a relevant gene on an organism's DNA

-organism required a specific trait carried by exogenous DNA

-example : recombinant human insulin

 

okeh..setakat tu je dulu :*

 

xoxo,

yanie

dna replication

assalamualaikum w.b.t...

juz a simple note for my exam ..

dekat initiation,helicase break d hydrogen bond..then,akn ad 2strands yg t'hasil 

-leading,lagging..kt leading,utk bt proses elongation,juz need DNA polymerase,RNA primer wujud kejap je..sbb die continuous reaction..proses elongation kat leading akn continue without more RNA primer..but utk lagging,p'lukan dua2 utk continue elongation tu..bila smpai mse RNA primer abis,akn ad RNA primer len dtg..smpai hbs proses elongation tu n hasilkan okazaki fragment..sbb die non-continuous reaction..okazaki fragment dicantumkn oleh DNA ligase..after sume2 tu,akn ad 2 strands t'hasil iaitu leading ngan lagging..proses replication akn stop bila dua2 da smpai kt ujung strand (kwsn nme telomere)

--> in the DNA replication process,there's three steps involve,  

1)initiation

    - the enzyme helicase will break the hydrogen bonds between the base pairs..the unwinding process happen in the segments that rich in adenin and thymine (A & T)

    - then,the replication fork formed

 

2)elongation

    - there will involved two strands which is leading (5' - 3') and lagging (3' - 5'). in the leading strands,the its only need the DNA polymerase to complete the elongation process because it is a continuous reaction. 

    - but for the lagging strands, it will need both DNA polymerase and RNA primer to complete the elongation process because it is a non-continuous reaction..

    - after that,the Okazaki Fragment is formed. the DNA ligase is needed to bind the Okazaki Fragment together..

 

3)termination 

    - when the DNA polymerase reached the end of the strands,the termination occur at the telomere, the non-coding segments..termination is d last process of DNA replication..



xoxo,

yanie