Mendel and human disorders Flashcards
reasons why genetic disorders are recessive
- Recessive alleles produce non-
functional proteins
Many mutations can produce non-functional
versions of the same protein. Mutations
usually result in a loss of function. - Dominant alleles mask the effect of
recessive alleles.
Therefore:
-recessive alleles can be carried by
individuals and have no effect on their
phenotype.
-they are difficult to eliminate from a
population.
cystic fibrosis
Tay-Sachs disease
Phenylketonuria (PKU)
excess mucus production.
lipid accumulation in brain cells
accumulation of phenylalanine (type of amino acid)
Disorders associated with dominant
alleles
Every affected person should have a parent with the disorder. Dominant alleles causing disorders are usually very rare in a population.
Or
associated with conditions that occur late in life. (Alzheimer’s disease: Mental deterioration, especially memory. Huntington’s disease: mental deterioration, especially muscle control)
Frequency of alleles
causing disease early in life (common to rare)
Dominant/recessive: common
Incomplete dominance: rare
Dominant/recessive: very rare
Independent assortment of alleles (include examples and when it occurs)
Pairs of alleles for a gene separate independently of other alleles for other genes during gamete formation.
ex: gametes produced in GgHh
only
occurs when the genes are on different
chromosomes
what is linked genes and why is it important to study
Genes found on the same chromosome
Studying linked genes allows us to find the location of genes on chromosomes.
The rate at which gene are separated
depends…
on how far apart they are from one another.
if genes are on the same chromosome
(linked), then:
the phenotypic combination in the parents will be the most common combination in the offspring
and ratios different
The proportion of recombinants can be
used to…
determine how far apart the genes are, and map them onto chromosomes
How do we find the location of genes ?
Some chromosomal mutations are associated
with phenotypes, and can be used to map
genes onto chromosomes