ABABO WHAT’S YOUR BLOOD TYPE?. Many genes have more than two alleles. This does NOT mean that an...

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A B AB O

WHAT’S YOUR BLOOD TYPE?

Many 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.

MULTIPLE ALLELES

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.

MULTIPLE ALLELES: EXAMPLE

MULTIPLE ALLELES

WHAT HAPPENS IF WE GET THE WRONG BLOOD FROM A BLOOD

DONOR?

Autosomes are the “normal” or body chromosomes

Sex chromosomes (X or Y) contain sex-linked genes

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.

We get 1 X from mom, and either 1 X or 1 Y from dad, so there is ALWAYS a 50-50 chance of being a boy or girl. Which parent determines the gender of the offspring? The dad.

X-linked traits are inherited through genes on the X chromosome.

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.

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.

X-linked traits are usually passed down through the mom. Why?

Mothers can pass the genes to daughters AND sons

Fathers can pass genes to daughters BUT NOT to sons

ColorblindnessDecreased ability to see or distinguish between

certain colors Red-green colorblindness, blue-yellow colorblindness

EXAMPLES OF X-LINKED DISORDERS

ColorblindnessDecreased ability to see or distinguish between

certain colors Red-green colorblindness, blue-yellow colorblindness

HemophiliaA bleeding disorder that prevents

blood from clotting properly The person bleeds more than

someone without hemophilia

Duchenne Muscular Dystrophy A disorder that involves rapidly

increasing muscle weakness and loss of muscle tissue

BLOOD TYPE/MULTIPLE ALLELE PRACTICE PROBLEMS…

A diagram that shows the inheritance pattern of a trait over many generations is called a pedigree.

PEDIGREES

HOW TO READ A PEDIGREE

Male Female

Pedigree Symbols

Children/ Marriage Siblings

Looking 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.

HOW TO READ A PEDIGREE

1. How many males vs. females are aff ected?Equal = autosomalMore males = sex-linked

2. Does it skip generations? Yes = recessive, No = dominant

3. Who is a carrier (unaff ected)?females only = sex-linkedeither sex = usually autosomal

TIPS FOR INTERPRETING PEDIGREE

1. Males and females are equally aff ected2. May skip generations or appear to be an isolated event3. Chance of off spring having trait is ¼ if two parents are heterozygous carriers

AUTOSOMAL RECESSIVE INHERITANCE

1. Males and females are equally aff ected2. Every aff ected person has an aff ected biological parent (no skipping generations)3. Normal siblings do not pass trait on to their off spring

AUTOSOMAL DOMINANT INHERITANCE

1. Males aff ected more than females2. May skip generations (ex. grandfather to grandson), but all aff ected males inherit trait from carrier mothers3. The disease is never passed father to son– mothers are carriers.

X-LINKED RECESSIVE INHERITANCE

X-LINKED INHERITANCE: A CASE STUDY

ABABO WHAT’S YOUR BLOOD TYPE?. Many genes have more than two alleles. This does NOT mean that an...

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