Mendel and human disorders

Question 1

reasons why genetic disorders are recessive

Answer 1

1. 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.
2. 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.

Question 2

cystic fibrosis
Tay-Sachs disease
Phenylketonuria (PKU)

Answer 2

excess mucus production.
lipid accumulation in brain cells
accumulation of phenylalanine (type of amino acid)

Question 3

Disorders associated with dominant
alleles

Answer 3

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)

Question 4

Frequency of alleles
causing disease early in life (common to rare)

Answer 4

Dominant/recessive: common
Incomplete dominance: rare
Dominant/recessive: very rare

Question 5

Independent assortment of alleles (include examples and when it occurs)

Answer 5

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

Question 6

what is linked genes and why is it important to study

Answer 6

Genes found on the same chromosome

Studying linked genes allows us to find the location of genes on chromosomes.

Question 7

The rate at which gene are separated
depends…

Answer 7

on how far apart they are from one another.

Question 8

if genes are on the same chromosome
(linked), then:

Answer 8

the phenotypic combination in the parents will be the most common combination in the offspring

and ratios different

Question 9

The proportion of recombinants can be
used to…

Answer 9

determine how far apart the genes are, and map them onto chromosomes

Question 10

How do we find the location of genes ?

Answer 10

Some chromosomal mutations are associated
with phenotypes, and can be used to map
genes onto chromosomes