2 Multiple AllelesMany genes have more than two alleles.This does NOT mean that an individual can HAVE more than two alleles.This simply means that more than two alleles for a trait exist in a population.
3 Multiple Alleles: Example Human blood type is controlled by multiple alleles: A, B, O.O is recessive, while A and B are codominant, so if both alleles are present, both are expressed.There are four possible blood types: A, AB, B, and O.
11 Sex-Linked Traits and Chromosomes Autosomes are the “normal” or body chromosomesSex chromosomes (X or Y) contain sex-linked genes
12 Sex-Linked Traits and Chromosomes Specific pairs of these sex chromosomes are what determine our sex. The genes on each chromosome code for proteins that help us develop biologically into males or females.Males have the sex chromosomes XY .Females have the chromosomes XX.
15 Sex-Linked Traits and Chromosomes We get 1 X from mom, and either 1 X or 1 Y from dad, so there is ALWAYS a chance of being a boy or girl. Which parent determines the gender of the offspring?The dad.
16 X-Linked Traits and Disorders X-linked traits are inherited through genes on the X chromosome.
17 X-Linked Traits and Disorders X-linked disorders are more common in males than in females. Why?Males have only one X chromosome.If the X chromosome carries a defective allele for a gene, the Y chromosome does not have a normal allele that is able to balance it out.This results in a genetic disorder.
18 X-Linked Traits and Disorders If the X chromosome carries a defective allele for a gene, the Y chromosome does not have a normal allele that is able to balance it out.
19 X-Linked Traits and Disorders X-linked traits are usually passed down through the mom. Why?Mothers can pass the genes to daughters AND sonsFathers can pass genes to daughters BUT NOT to sons
20 Examples of X-Linked Disorders ColorblindnessDecreased ability to see or distinguish between certain colorsRed-green colorblindness, blue-yellow colorblindness
21 Examples of X-Linked Disorders ColorblindnessDecreased ability to see or distinguish between certain colorsRed-green colorblindness, blue-yellow colorblindness
22 Examples of X-Linked Disorders HemophiliaA bleeding disorder that prevents blood from clotting properlyThe person bleeds more than someone without hemophilia
23 Examples of X-Linked Disorders Duchenne Muscular DystrophyA disorder that involves rapidly increasing muscle weakness and loss of muscle tissue
25 PedigreesA diagram that shows the inheritance pattern of a trait over many generations is called a pedigree.
26 I II III How To Read A Pedigree Pedigree Symbols Male Female Children/ Marriage SiblingsIII
27 How To Read a PedigreeLooking at a family pedigree, we observe how certain traits have been passed down from parents to offspring and also how certain traits and genetic disorders are expressed.
28 Tips for interpreting pedigree 1. How many males vs. females are affected?Equal = autosomalMore males = sex-linked2. Does it skip generations?Yes = recessive, No = dominant3. Who is a carrier (unaffected)?females only = sex-linkedeither sex = usually autosomal
29 Autosomal Recessive Inheritance 1. Males and females are equally affected2. May skip generations or appear to be an isolated event3. Chance of offspring having trait is ¼ if two parents are heterozygous carriers
30 Autosomal dominant Inheritance 1. Males and females are equally affected2. Every affected person has an affected biological parent (no skipping generations)3. Normal siblings do not pass trait on to their offspring
31 X-Linked Recessive Inheritance 1. Males affected more than females2. May skip generations (ex. grandfather to grandson), but all affected males inherit trait from carrier mothers3. The disease is never passed father to son– mothers are carriers.