Key words and definitions- sort them out!
• Each gene has the code
to make a protein.
• Bases are grouped into
3’s.
• A sequence of 3 bases
codes for an amino acid.
• The order of bases
controls the order of
amino acid in the
protein.
Inheritance and genetic
disorders
Learning Objective:
In order to be successful in this lesson you must
be able to:
Explain that some genetic disorders are
caused by the inheritance of an abnormal
number of chromosomes
Inheritance and genetic
disorders
State that
some
disorders
are
inherited
Explain that
polydactyly is
caused by a
dominant
allele and
cystic fibrosis
by a
recessive
allele
PROGRESS
Explain that some
genetic disorders
are caused by the
inheritance of an
abnormal number of
chromosomes
Genetic diagrams- key words
recessive
allele
homozygous
heterozygous
dominant
Cystic fibrosis
• Cystic fibrosis is an inherited disorder of cell
membranes that mainly affects the lungs and
Causes the production of
pancreas.
thick sticky mucus
• It is caused by a recessive allele. In a genetic
diagram:
- the recessive allele can be shown as f
- the dominant allele can be shown as F
Someone who is homozygous (ff) for the recessive allele will develop cystic
fibrosis. Someone who is heterozygous (Ff) or homozygous for the dominant
allele (FF) will not develop cystic fibrosis.
Parent phenotype: heterozygous x heterozygous
Next draw out
Parent genotype:
a genetic cross
for a
Gametes:
homozygous
dominant
Punnett square:
mother and a
heterozygous
father
Outcome:
The chance of them producing a child with cystic fibrosis is
1 in 4, or 25%.
The parents are carriers of the disorder, as it is possible for them to produce a
child with cystic fibrosis, without having it themselves.
Polydactyly
Polydactyly is an inherited condition in which a
person has extra fingers or toes. It is caused by
a dominant allele of a gene. This means it can
be passed on by just one parent if they have
the disorder.
Polydactyly: Genetic cross
Mother has polydactyly and has and is heterozygous; father does not have
polydactyly
Parent phenotype:
Parent genotype:
Gametes:
Punnett square:
Outcome:
Down syndrome: a chromosomal
disorder
Down syndrome is a developmental disorder caused by an extra copy of
chromosome 21 (which is why the disorder is also called "trisomy 21").
Having an extra copy of this chromosome means that individuals have
three copies of each of its genes instead of two, making it difficult for
cells to properly control how much protein is made. Producing too much
or too little protein can have serious consequences.
http://learn.genetics.utah.edu/content/disorders/chromosomal/down/