Transcript Pedigrees and genetic disorders PP

 Humans have 23 pairs of chromosomes,
containing 3 billion letters of DNA code and
24,000 genes.
 One set comes from MOM and one set comes from
DAD. There are 22 pairs of autosomes and 1 pair of sex
chromosomes, X and Y.
 XX = female
 XY = male
X
X
Dad
Y
Mom
X
XX
XX
Girl
Girl
XY
XY
Boy
Boy
 Patterns of inheritance:
 We receive one of each
chromosome from mom and
one from dad.
Geneticists study how genes are
inherited in offspring.
 Autosomal Dominant
 Autosomal Recessive
 Sex-linked
 A pedigree is a chart of the genetic history of family over
several generations.
 Scientists or a genetic counselor would find out about
your family history and make this chart to analyze.
 Female
 Male
Examples of connected symbols:
 Married Couple
 Siblings
 What does a pedigree chart look like?
 Affected
 Autosomal carrier
 Deceased
1.
Determine if the pedigree chart shows an autosomal
or X-linked disease.
 If most of the males in the pedigree are
affected the disorder is X-linked
 If it is a 50/50 ratio between men and
women the disorder is autosomal.
 Is it Autosomal or X-linked?
 Autosomal
2.
Determine whether the disorder is dominant or
recessive.
 If the disorder is dominant, one of the
parents must have the disorder.
 If the disorder is recessive, neither parent
has to have the disorder because they can
be heterozygous.
 Dominant or Recessive?
 Dominant
 Dominant or Recessive?
 Recessive
Autosomal Dominant
 Achondraplasia
 Dwarfism
 Huntington’s Disease
 brain disorder that affects a person's ability to think,
talk, and move.
Cystic Fibrosis
•Lung infections
•Mutation stops production of a protein found in the cells
of lungs and other organs – leads to thick mucus and
bacterial infections of the lungs.
 PKU
 Smaller than normal head, epilepsy, mental retardation
 Mutation in gene that breaks down phenylalanine (an
amino acid found in the body and in some foods like
proteins and diet drinks)
 In the US, babies are screened at birth b/c it can be
treated with diet
 Maple Syrup Urine Disease
 Can’t break down certain amino acids. Build up causes
brain damage.
 Treated with restricted diet (no protein!)
 Hemophilia
 Bleeding disease
Women = XX
Men = XY
 Mutation in clotting factor gene
 Sex linked disorder
 1 in 4,000 males, rare in females
Gene is found on the X chromasome.
How does this affect men and women
differently?
 Not all genes have dominant and recessive alleles.
Some have alleles that are both expressed together in
the heterozygote individuals.
 Co-dominant alleles have three phenotypes, one for
each genotype.
 Sickle Cell Disease
 Normal -- two normal hemoglobin alleles
 Sickle cell trait -- heterozygotes, having one of each allele: a mild condition
where 50% of the red blood cells are affected.
 Sickle cell anemia -- two sickle cell alleles in their genotype: a severe form
where all the red blood cells are affected.
 In your textbook:
 Chapter 14 p. 363
 Answer # 1, 2, 5, 6, 7, 8, 14, and 15