All alleles that an organism contains, sets limits within which characteristics of individuals may vary
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What is co-dominant
2 Alleles both contribute to phenotype- blend of both or both
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What Monohybrid
inheritance of a single gene
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How do you set out cross
Parents phenotype, parents genotype, gametes , punnet square, F1 genotype, F1 phenotype, ratio
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What is CF?
Recessive
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What is polydactyl ?
Dominant allele
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When does co-dominant occur?
where instead of 1 allele being dominant and the other recessive , both alleles are dominant to some extent
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What is expresses in the phenotype?
Both alleles
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so the 2 alleles both contribute to?
Phenotype -
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How
blend of both features or both features represented
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eg
roan cows
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How many chromosomes in a homologous pair? so?
2 so 2/total allele can be present in a single organism
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If 2< allelic forms
multiple alleles for the characteristic
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When is there multiple alleles
because sometimes gene has more than 2, that is, multiple alleles of a single gene
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eg
ABO blood group= 3 alleles- diff antigens only 2/3 alleless can be present In individuals 2 homologous chromosomes= 2 gene loci
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What is Ia and Ib
co dominant
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what is Io
recessive
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What is Dihydrid
Inheritance of 2 characteristics controlled by 2 separate genes inherited independently
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Why can they pass into gametes in any combination
As a result of meiosis
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Steps
1. Work out parent genotypes 2. Work out possible gametes (understand independent segregation) 3. work out outcome of all possible fertilisations- any male gamete can combine with any female gamete
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4.
Translate genotype into phenotypes and work out ratio/ probabilities
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What type of cross
In which alleles of 2 diff genes involved
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eg
YyPp= YP, Yp, yP, yp = eg YYPP
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What is Sex linkage
when Many genes occurring on X chromosome (larger) don't appear on the Y as no equivalent homologous portion of Y chromosome
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So
Recessive on X more frequent as no homologous portion of Y
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eg
Colour blind, haemophilia ,Xh y (males xy, females **)
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Genotype
Genetic constitution of an organism
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Phenotype
Expression of this genetic constitution and its interaction with the environment
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What does it mean with autosomal linkage
linked= genes whose loci are located on the same chromosome
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define
Set of genes at diff loci on same chromosome except for crossing over will be inherited together
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What are alleles inherited?
are of parent type
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How check?
look at offspring- greater number of offspring have same phenotypes as their parents and fewer are phenotypically different
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What is recombination
In meiosis when genetic material move from one chromosome to another results in having offspring not identical to parental chromosomes
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what is the P of genes close together being separated during crossing over less than?
Than that of genes that are further apart
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How to detect linkage
If know how many recombinant offspring( without parental type chromosome) you can work out how far apart genes are from each other
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Formula
100xrecombinant offspring/ total no. offspring
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What is Epistasis
When expression of one gene depends on expression of another gene
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EG
coat colour in dogs
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3 colours
brown, black, golden
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What does first gene control
Fur pigment
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B= b=
black, brown
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What does second control
gene present pigment not attached to fur and if no pigment= yellow colour
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