Genetic crosses
- Created by: vezting
- Created on: 22-03-16 11:06
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- genetic crosses
- Genotype and phenotype
- genotype is genetic make up of an organism
- organism with two identical alleles for one gene is homozygous, and two different alleles is heterozygous
- genes code for proteins that are part of structure or code for enzyme. there are no genes coding for genetic disease. its altered alleles that produce altered proteins.
- phenotype is characteristics that are expressed
- phenotype is determined by genotype and environment
- dominant, recessive, codominant
- allele is dominant if it is always expressed in phenotype
- recessive is only expressed in phenotype when 2 identical copies of the allele are present
- or in absence of a dominant allele
- 2 alleles are codominant if they are both expressed in the phenotype of a hetrozygote
- Linkage and sex linkage
- linkage refers to two or more genes that are located on the same chromosome
- the linked alleles of these genes are usually inherited together because they don't segregate independently at meisois
- unless chiasmata have formed between them
- at cross over the allels from one chromatid become linked to alleles on other chromatid, reducing number of phenotypes
- characteristics are sex linked if the gene that codes for them is on one of the sex chromosomes.
- Y chromosomes has fewer genes so most sex linked genes are likely to be found on X chromosome
- in linkage alleles are shown together EG PLPL
- Genotype and phenotype
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