a sequence of bases on DNA that codes for a specific protein which results in a characteristic.
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what is an allele?
different versions of the same gene.
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what is a genotype?
the alleles an organism has e.g. Bb
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what is a penotype?
the characteristics the alleles produce e.g. brown eyes
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what is dominant?
an alleles whos characteristic appears in the phenotype with only one copy.
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what is resssesive?
an alleles whos characteristic appears in the phenotype if there are 2 copies.
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what is codominant?
alleles that are both expressed in the phenotype
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what is a locus?
the fixed position of a gene on a chromosome.
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what is homozygote?
an organism that carried 2 copies of the same allele.
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what is heterozygote?
an organism that carries 2 different alleles.
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what are the 3 types of cross (e.g. crossing over of genes)?
monogenic, dihybrid, codominant.
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what is monogenic?
3:1
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what is dihybrid?
9:3:3:1
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what is codominant?
1:2:1
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what is sex linked?
whenwhenan allele that codes for a characteistic is on a sex chromosome.
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why does the Y chromosome carry fewer genes than the X chromosome?
this is because the Y chromosome is smaller than the X chromosome.
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which chromosome are most of the genes carried on?
X
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what is this called?
X-linked genes
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why do males only have one allele for sex-linked genes?
this is because they only have 1 X chromosome and there for only have one copy of it, so they express the characteristic of this allele even if its recessive.
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what is an example of X-linked disorders?
colourblindness and haemophilia.
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what is an autosome?
any chromosome that isnt a sex chromosome.
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what are genes on the same autosome said to be?
linked
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what does this mean?
they will stay togther during indepentant assortment and crossing over.
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what is an epistatic gene?
A gene that masks the expression of another gene.
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recessive epistatic allele dihybrid cross ratio?
9:3:4
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dominant epistatic allele dihybrid cross ratio?
12:3:1
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what data do you need to work out the value of chi-squared?
the expected and observed value, critical value
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how do you work it out?
observed-expected value, then square the answer, then divide it by the expected value, add all the number together
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what is the rule for chi-squared?
the value of chi-squared has to be higher or equal to the critical value for the results to be significant.
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