Only one copy of gene e.g. X linked
What is it when two alleles of a gene are both expressed neither being dominant or recessive to other?
If something is rare in exam question can assume it is
Can you be homozygous dominant
Can be but unlikely, normally assume in exam that its heterozygous
Define genotype, phenotype, inheritance (exam Q)
Geno - genetic makeup of an organism, with reference to a gene or the whole genome
Pheno - Observational characteristics of an individual defined by genotype and environment
Inheritance - Genetic characteristics transmitted from parents to offspring via alleles.
What is it called if one gene is responsible for a phenotype? 2 genes? Given an example of a polygenic disease
How is albinism inherited? What does this mean for 2 albinos offspring? What is this phenomena called
2 genes 2 alleles, recessive manner
Means their offspring less likely to get albinism as two types of gene ‘compliment’ each other so you get normal phenotype
If two genes are on the same chromosome they are said to be _______
Do linked genes independently sort at meiosis? What if they are really far apart?
No. If really far apart then yes almost behave like separate genes (i.e more likely to cross-over to separate chromosomes, genes that are close together are more likely to stay on same chromosome, or both go to other chromosome).
Why does polygenic inheritance not lead to 1:1:1:1 offspring if the 2 genes are on the same chromosome?
Because it depends how much cross-over occurs at meiosis to how much 2 of the 4 allele combinations occur.
Are X-Linked dominant and recessive males both phenotypic?
Yes as only one X chromosome so no difference. Difference is when they pass on to daughters as X linked dominant males will give condition to all daughters, X linked recessive won’t necessarily.
If you have a pedigree of two genes that are linked, and it shows a low rate of recombination ~10% of genes for example what could you say about the 2 genes?
They are closely linked therefore less likely to independently assort, more likely to travel together in meiosis and therefore less recombination.
Child of a gamete that has undergone recombination of genes
When does crossing over occur in meiosis? When does random assortment occur?
Crossing over - prophase I
Random assortment - metaphase I