These are full comprehensive notes on the entire Module of Gene Expression for the AQA A-level specification. They are written using a mixture of my own research, class learning and the specification. They include diagrams, step by steps and everything I needed to get an A* in A-level Biology.
Punnett Square used to calculate
probability of offspring genotypes .
eg .
parent genotypes
:
Ff ✗ Ff
F f
F FF Ff
Cross :
f Ff ff
offspring genotypes
:
FF , Ff , Ff , ff
offspring phenotypes :
no CF : CF =3 :/ chance of getting CF :
25%
Autosomal Disorder A disorder caused mutation chromosome that i s not chromosome cystic fibrosis
by genetic on a a s ex
eg .
Sex Linked Disorder If the allele is found on the lower portion of the ✗ chromosome where there i s no
corresponding portion of Y .
eg . red -
green colour blindness , haemophilia Duchenne's ,
muscular Distrophy .
Huntington's Disease
An autosomal dominant disorder . When the allele is expressed , the protein Huntingtin is produced which affects the ner vous system
by breaking down ner vous tissue over many years Patients
. will die around 10-15 years following developing symptoms .
Dominant, Recessive & Codomirart Alleles
dominant I for
9
Only copy of allele needed trait to be expressed in the
phenotype .
eg .
Hurtington s
recessive
only expressed of cystic fibrosis
> allele is in t h e absence dominant allele .
eg .
.
codomirar t 9 Alleles a re expressed equally in the phenotype in a
heterozygous organism Both .
t r a i ts expressed -
eg . colour in
c ows .
Blood Groups .
A B C D red blood
cells
^z
s ^ >
←
a
°
u
r s
us
Antibodies made in plasma
A B C D
'
un co u
?
no
anti -
B anti -
A antibodies Anti A & Anti B
-
-
0 the universal donor because it doesn't
is has no
antigens so
trigger an immune response .
AB blood can have
any blood donated because t h e re a re no antibodies in t h e blood so no blood type will trigger on immune
response .
1^-1 " 1 BIB IBI IA IB
°
A 1^-10 B AB > 0 9 101°
Genotypes : > or S or codominant recessive
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