Fundamentals 5 Flashcards
(15 cards)
What gene causes red hair ?
Two copies of the red-haired version of MC1R
What are Mendelian traits ? What are examples of some ?
A trait encoded by a single gene with dominant and recessive alleles
1. Cleft chin
2. Dimples
3. Freckles
4. Albinism
What is oculocutaneous albinism (OCA) ?
Lack of melanin synthesis
There are 7 subtypes
Autosomal recessive
Describe classic OCA
OCA1
Caused by a deficiency of tyrosinase (TYR gene) leading to reduced melanin
Located with chromosome 11q14-11q21
What is non-Mendelian inheritance ? What are examples of it ?
Pattern of inheritance does not follow Mendels laws and does not produce Mendelian rations among the progeny of various crosses
1. Polygenic traits
2. Co-dominance
3. Incomplete dominance
4. Sex-linked
What are polygenic traits ?
Traits that are controlled by multiple genes, leading to continuous variation
What is co-dominance ?
When both alleles in a heterozygote are equally expressed, resulting in a phenotype that is neither dominant nor recessive
Eg. Blood types- the AB blood group is a result of co-dominance
What is incomplete dominance ?
A form of inheritance where neither allele is completely dominant over the other. The phenotype of the heterozygote is in intermediate between the two homozygous phenotypes.
What is sex-linked ?
Traits that are controlled by genes located on sex chromosomes
What is haplo-sufficient ?
Where one copy of the gene is enough to produce a normal functioning wild type phenotype
What are continuous traits ?
Traits that show a range of variation, rather than falling into distinct categories, influenced by many genes.
Eg. Height
What is autosomal dominant ?
Appears in both sexes with equal frequency, doesn’t skip generations.
One copy of the mutated gene causes the disorder.
Eg. Huntington’s disease
What is autosomal recessive ?
Appears in both sexes with equal frequency, frequently skips generations.
Parents can be unaffected and just carry the gene.
Eg. Cystic fibrosis
What is X-linked recessive ?
Caused by a mutation on the X chromosome, where the recessive allele only causes the phenotype when no normal allele is present.
Appears in males more frequently than females.
Fathers don’t transmit the trait to their sons.
Often skips a generation.
Eg. Red-green colourblindness
What is X-linked dominant ?
Appears in females more than males.
A dominant allele only causes the X chromosome causes the disorder.
Fathers pass the trait onto daughters, but not sons.
Doesn’t skip generations.
Eg. Familial vitamin D-resistant rickets.
