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26 Cards in this Set
- Front
- Back
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What isa Gene? |
A sequnce of bases on a DNA that code for a protein (polypeptide) which results in a characteristic (e.g. the gene for eye colour) |
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What isanAllele? |
- One or more alternative forms of a gene - Most plants and animals have 2 alleles for each gene, one from each parent, however there can be more |
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What is aGenotype? |
The geneticconstitution fora characteristic(e.g. BB foreye colour) |
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What is aPhenotype? |
- The expression of the genetic constitution and its interaction with the environment - The organisms physical characteristic determined by a genotype (e.g. the phenotype for the genotype BB is brown eyes) |
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What ismeant byDominant? |
An allele whose characteristics alwaysappear in the phenotypewhen present, evenwhen there is only 1present - They mask thephenotype of recessivealleles |
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What ismeant byRecessive? |
An Allele whosecharacteristicsonly appear in thephenotype when 2copies of it arepresent |
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What is meantbyCodominance? |
Alleles that are both dominant so both expressed in the phenotype (e.g. alleles for haemoglobin) |
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What ismeant bylocus? |
- The fixed position pfa gene on achromosome - Allelesof a gene are foundat the same locus oneach chromosomepair |
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What is meantbyHeterozygous? |
When a geneis coded forby 2 differentalleles (Bb) |
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What ismeant byHomozygous |
When a geneis coded for by2 of the samealleles (BB orbb) |
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What are the 2 equations needed for the hardy-weinberg principle? |
p+q=1 p2+2pq+q2=1 |
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What 2 thingscan occur withco-dominance? |
The phenotype iseither a blend of thetwo dominant allelesor both are present,some showing oneallele and someshowing the other |
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How can you find out the geneotype of a heterozygous gene? |
- Test Cross - you mustcross the unknownheterozygous organismwith an organismpresenting a recessivephenotype for the samecharacteristic - from that you can work it out |
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Whatchromosomeare sex-linkeddiseases usuallyassociated with? |
The XChromosomeas it is bigger |
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Why may menbe more likelyto getsex-linkeddiseases? |
Males have XY and so ifthe sex-linkedchromosome is on the Xchromosome, they onlyneed one recessive alleleto show the diseasewhilst women wouldneed 2 |
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What ismeant bymultiplealleles? |
When a genehas more than2 alleles (e.g.blood groups) |
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Name asex-linkeddisease |
- Haemophilia - Blood clots really slowly and can lead to severe internal bleeding - it is almost completely confined to males and affects around 1 in every 20,000 people |
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In which crossesdo parentgenotypes needto be combined? |
Dihybridcrosses |
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What sort of chartis used to tracethe inheritance ofsex-linkedcharacteristics? |
Pedigreecharts |
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How arepedigreechartspresented? |
Males are squares,Females are circles,Shading in either shapeindicates the presence ofthe character in question, adot within a circle meansthey have a normalphenotype but is a carrier |
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Sex linked diseases can be passed on from father to son. True or false? Explain your answer |
Offspring get their X chromosome from their mother and their Y chromosome from their father; Most sex-linkages are on the X chromosome, which a son gets from their mother - The father plays no part |
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From a Pedigree chart, how can you tell a certain charatceristic is recessive? |
Parents withoutdisease are shown tohave children with thedisease, If thedisease wasdominant none of thechildren could have it |
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What is aGenePool? |
the term for allthe alleles ofall the genes ina population |
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What ismeant byAllelicFrequency? |
AllelicFrequency |
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What is aMutation? |
A change tothe genotypeas a result of achange to theDNA |
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What 5 things areneeded for theHardy-WeinbergyPrinciple to betrue? |
- No mutations -Population is isolated(no movement in orout of population) -No selection - Largepopulation - Mating israndom |
