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Biology
Inheritance, Variation & Evolution
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GCSE🔥 > Biology > Inheritance, Variation & Evolution
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4.6.2–Variation & evolution
GCSE🔥 > Biology > Inheritance, Variation & Evolution
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4.6.1-Reproduction
GCSE🔥 > Biology > Inheritance, Variation & Evolution
25 cards
Cards (69)
Give 2 examples of inherited disorders?
Polydactyly
(homozygous dominant allele)
Cystic fibrosis
(homozygous recessive allele)
What is
inherited
disorder?

Disorder
that is caused by the
inheritance
of certain
alleles
What are
alleles
?

Different
forms of
gene
What is
genotype
?

The
alleles
What is
phenotype
?

Physical characteristics
What is
homozygous
?

Both alleles
of an
organism
are the
same
What is
heterozygous
?

The
alleles
of an
organism
are
different
Some
characteristics
are controlled by a
single gene.
Fur colour
in
mice
Red-green colour blindness
in
humans
A
dominant allele
is always
expressed
, even if only
one
copy is present (
75
%)
A
recessive allele
is only
expressed
if
two
(
both
)
copies
are
present
(
no dominant
,
25
%)
Most
characteristics
are a result of
multiple genes interacting,
rather than a
single gene
What the name of the diagram to determine the expected percentages of different genotypes in the offspring of two parents?
Punnett square
How many chromosomes do ordinary human body cells contain?
46
(
23 pairs)
22
pairs of chromosomes control characteristics only but one of the pairs carries the genes that determine sex
Female:
XX
(same chromosome)
Male:
XY
(different chromosome)
What is
variation
?

The
difference
in the
characteristics
of
individuals
in a
population
What cause variation in individuals?
The
genes
they have
inherited
(
genetic
causes)
The
conditions
in which they have
developed
(
environmental
causes)
A
combination
of
genes
and the
environment
—>There is usually
extensive
genetic
variation
within a population of a species
All variants arise from
mutations
, which
most have
no effect
on the
phenotype
some
influence
phenotype
very
few
determine
phenotype
Mutations
occur
continuously
in the genome, but very rarely a
mutation
will lead to a new
phenotype
If the new
phenotype
is suited to an
environmental change
, it can lead to a relatively
rapid
change in the
species
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