Heredity 29 Flashcards
The Ectoderm forms
Neural Tissue
What is phenotype
The physical expression of the genotype
Dominant Trait
Expressed even if only one dominant allele is present (e.g., Jj or JJ).
Recessive Trait
Expressed only when both alleles are recessive (e.g., jj for tight thumb ligaments)
What are alleles?
Variants of a gene located at the same position (locus) on homologous chromosomes. An individual inherits two alleles for each gene, one from each parent
Autosomes
Non-sex chromosomes, identical in both sexes (22 pairs in humans).
Sex Chromosomes
Determine biological sex (XX for females, XY for males)
What is meant by a disease being sex-linked?
Associated with genes on the sex chromosomes, typically the X chromosome.
How is sex link disease transfered
o Males express the condition if they inherit a single recessive allele (e.g., X-linked hemophilia).
o Females must inherit two recessive alleles to express the condition
Incomplete Dominance:
A heterozygous genotype results in a phenotype that is a blend of the two alleles.
What is an example of incomplete dominance?
Sickle cell trait (Ss) shows some symptoms of sickle cell anemia, but less severe than ss
What is co-dominance? What is an example?
*Co-dominance: Both alleles are expressed equally in the phenotype.
*Example: ABO blood group system, where IA and IB alleles express both A and B antigens in AB blood type(
The Mesoderm forms
Muscle
By day 12 of embryonic development, mesoderm. Elgin’s to form through
Gastrulation
The Oval, three-layered sheet production by gastrulation is called the
Embryonic disc
