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GCSE Biology Paper 2
Inheritance
Alleles
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Created by
Sophia Robinson
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Cards (23)
What should you be able to describe by the end of the video?
Dominant
and
recessive alleles
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What do homozygous and heterozygous refer to?
Types of genotypes based on
alleles
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What is a key fact about human chromosomes?
Normal human cells contain
23
pairs of chromosomes
Each pair consists of one chromosome from the
father
and one from the
mother
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What are genes?
Sections
of DNA on a
chromosome
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How many copies of every gene do humans have?
Two
copies of every gene
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What is the gene that controls earwax?
The earwax gene
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What are alleles?
Versions of a
gene
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What does the allele for wet earwax symbolize?
Capital E
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What does the allele for dry earwax symbolize?
Lowercase e
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What is the genotype of a person with two copies of the allele for dry earwax?
Lowercase e lowercase e
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What does homozygous mean?
Having two copies of the same
allele
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What does phenotype refer to?
Characteristics caused by
alleles
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What is the phenotype of a person with two alleles for dry earwax?
Dry
earwax
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What is the genotype of a person with two alleles for wet earwax?
Capital E
capital E
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What is the phenotype of a person with two alleles for wet earwax?
Wet
earwax
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What is the genotype of a person with one allele for wet earwax and one for dry earwax?
Capital E
lowercase e
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What does heterozygous mean?
Having two different
alleles
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What phenotype does a heterozygous person for earwax have?
Wet
earwax
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What is a dominant allele?
Shows in
phenotype
with one copy
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What is a recessive allele?
Shows in
phenotype
only with two
copies
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How are most characteristics controlled?
Most characteristics result from many
genes
acting together
Example:
Height
is influenced by multiple genes
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What will the next video cover?
Genetic
crosses
and allele inheritance
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Where can you find questions on this topic?
In the
vision workbook
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