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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
④
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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