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1. Autosomal or Sex-linked?
- equal ratio = focus on sex chromsome and subsequent steps to include gender (sex-linked)
- unequal ratio = males/females  has more mutation than other gender (e.g., 3:1) (not sex-linked)
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P: WT X DM
F1: Heterozygous (carriers)
F2: 3:1 / 1:1 (depending on scenario)

2. (If not sex-linked) Choose shortest autosome
- 9:3:3:1 achieved --> unlinked
- 9:3:3:1 NOT achieved --> linked
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P: WT X DM
F1: Heterozygous
F2: 9:3:3:1 (unlinked) / NOT 9:3:3:1 (linked)
*Often linked, would result in recombinants to be lower in number

3. Test cross
> unknown X homozygous recessive parent (DM)
> determine if phenotype is heterozygous/homozygous
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F1: X x DM
F2: 1:1:1:1 (unlinked) / NOT 1:1:1:1 (linked)
*Location of gene
Formula: Recombinants/Total x 100 = ____cM

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Linked genes: A set of genes that are in close proximity with one another.
- Likely to be inherited togetehr during cross over
Uninked genes: Genes located on different chromosomes

Usage
> Able to locate novel mutation through linkage analysis by knowming location of mutation & associated phenotype
> Genetic inkage map

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Depending on the distribution pattern of F2 phenotypes, we can use the number we attain to find the corressponding rows on the Pascal Triangle

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Trait is controlled by independantly assorting gene loci

` Individual polygenes segrgate & independantly assort according to Mendelian principles

Each gene locus or an inactive allele that does not contributes to the phenotype

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Discontinuous Variation (Qualitative)
- Characteristics fall into distinct groups
- Sometimes there is only 2 forsm of a characteristic

Continuous Variation (Quantitative)
- Charateristics which do not show clear cut differences (show a range of differences)

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Polygenic (quantitative) traits: Influenced by 2 or more genes residing at different loci on same/different chromosome

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*1 gene, many effects
> A trait <-- many interactions between multipe genes (>1 gene is responsible for the phenotype of the trait)
> The protein "trait" produced by 1 gene affects the expression of another

Epistasis - an interaction at the phenotypic level
~ genes involved may still show independant assortmnet (genotypic level)
--> however,  phenotypic ratios may deviate from those expected from independant assortment
Occurs in:
` when ≥2 loci interact to create new phenotypes
` when an allele at 1 locus masks the effects of alleles at ≥1 other loci
` when an allele at 1 locus modifies the effects of alleles at ≥1 other loci

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> Allele of phenotypic ratio --> causes death of an organism
> Can be dominant/recessive

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> Gene may exist in >2 allelic forms (vary in dominance)
> BUT can only have 2 alleles for a given gene, multiple alleles may exist at population level --> many cobinations of 2 alleles are observed

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> Gene may be in >2 allelic forms (vary in interactions)
> Alleles of a gene pair in a heterozygote are BOTH expressed partially --> offspring inherit "in-between" phenotype
> Neither dominant/ recessive
> F2 ratio = 1 : 2 : 1

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> 2 phenotypes for 1 trait - alleles of a gene pair in a heterozygous are BOTH fully expressed
` offspring phenotype is neither dominant/recessive
> Law of Dominance is X followed
> F2 phenotypic ration = 1 : 2 : 1
Example: Blood group (3 alleles; A, B, O)

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Linked genes

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Polygenic Inheritance