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Summary AQA ALEVEL BIOLOGY NOTES ON DNA AND GENES

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ALEVEL NOTES ON DNA AND GENES TEST ADJUSTED TO THE AQA SPECIFICATION AND MADE FROM MARKSCHEMES

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=
DNA
HeVAstodyo


In the nucleus of eukaryotic cells DNA molecules are
long linear and associated with
proteins called histones
.
very , , .






Histone proteins help to support the DNA .




In
eukaryotic cells DNA and histone proteins coil
tightly to make compact chromosome

a
,
up very .




of of
The mitochondria and
chloroplasts eukaryotic cells also contain DNA which like the DNA prokaryotes is


, , ,




short ,
circular and not associated with histone proteins .




Centromere




Iih
me


→ ,
DNA
around
[
wound
histone proteins pna


fAeHs ?
Chromosome



In DNA molecules short circular and not associated histone proteins
prokaryotic cells, with

.


are ,




if
DNA Double Helix -




hihA .


8 →
Gb
Circular Coiled super coiled
chromosome to fit in the cell


Chromosome




A base of DNA that for of



gene is
a sequence codes the amino acid
sequence a polypeptide or a


functional RNA (
including ribosomal RNA and tRNAs )

The complete set of in cell is known and the full of proteins that the
genes a as the cell 's range



genome
cell is able to
produce is known as its proteome .




In lot of doesn't code for polypeptides for functional RNA)
eukaryotes the nuclear DNA
they code

a .

,



Even that do code for polypeptides contains sections that don't code for amino acids these sections
genes
-





are called introns .





All the bits of gene that do code for amino acids are called exons .





Alleles are different forms of a
gene .




DNA sequence
The order of bases allele different
in each is
slightly
.




-
,




for different of the
so
they code
slightly versions same


polypeptide .

Leg .
different
eye
colour ,
blood type . . .
)
GC6A 'T G A T G A C6C T A G C C IT 6
I I
1
whatarehomologouschromosome.se?--- c GC TIA C T A C T G1C G A T C G G A C
-
EX0N IN TR0N EX0W INTRON ,




Humans have 23 pairs of chromosomes 46 ,
in total .




← ( e. g. the Is )
Pairs of matching chromosomes are called
homologous pairs .




In
homologous pair both chromosomes the size

a are same


have the different
and same
genes ,
although they could have alleles .




for characteristic be found fixed Hocus)
.
Alleles
coding the same will at the same
position on each

chromosome in a
homologous pain .

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