Pedigrees & Genetic Disorders 6C Pedigrees, Family Traits Tracking Genetic Disorders through Generations

Pedigrees Simple way to model inheritance of characters over generations Often used to track genetic disorders in families Any disease or disorder that is inherited

Pedigrees In tracking the inheritance of recessive genetic disorders, individuals can carry the genetic information for a genetic disorder but not show the trait They are called carriers How can a parent carry the genetics for a recessive disorder without showing the trait?

Pedigrees To use a pedigree, you must understand the symbols: Square = male Circle = female Shaded = trait

Pedigrees If the trait is recessive, what are the genotypes of these individuals?

Pedigrees If the trait is dominant, what are the genotypes of these individuals?

More Pedigree Symbols

Where is the P generation? I Where is F1 gen? II Where is F2 gen? III IN EACH GENERATION, YOU LABEL INDIVIDUALS BY BIRTH ORDER – II-3, III-5 What is the name of ___ individual? What color are the ind that show the trait?

Determining If The Trait Is Dominant or Recessive First question to ask….. Expressed in every generation? Dominant Skip generations? Recessive

Dominant Trait Additional Checks If you think it is DOMINANT, double check: 1) Every affected individual has at least one affected parent 2) Affected individuals who mate with unaffected individuals have a 50% chance of transmitting the trait to each child 3) Two affected individuals may have unaffected children. RECESSIVE

Recessive Trait Additional Checks If you think it is RECESSIVE, double check: 1) An individual who is affected may have two parents who are not affected 2) All the children of two affected individuals are affected

Where is the P generation? Where is F1 gen? Where is F2 gen? IN EACH GENERATION, YOU LABEL INDIVIDUALS BY BIRTH ORDER – II-3, III-5 What is the name of ___ individual? What color are the ind that show the trait? Is this dominant or recessive? DOMINANT

RECESSIVE

DOMINANT

RECESSIVE

RECESSIVE

Autosomal dominant

Auto Dom 19

Auto Dom 20

Autosomal Recessive 21

Auto Dom 22

Auto Rec 23

Autosomal Recessive 24

Auto Dom 25

Human Chromosomes In humans, we have 46 chromosomes 23 homologous pairs Homologous pairs are the same shape and size and code for the same traits

Human Chromosomes Locate the 23rd pair X and Y XX = female XY = male

Human Chromosomes 22 pairs of AUTOSOMES 1 pair SEX-LINKED chromosomes (otherwise known as Somatic) Non sex-linked 1 pair SEX-LINKED chromosomes Used to determine gender

Gender Chromosomes The X and Y chromosomes not only determine our gender but they also code for other traits as well Some genetic information can be affected by our gender chromosomes Presence of XX or XY

Gender Chromosomes If a genetic disorder is linked specifically to the X or Y chromosome then depending if you are male (XY) or female (XX), you may have a higher or lower probability of inheriting the disorder

Examples of X-linked Traits Color Blindness 2. Hemophilia: lacking the ability to clot blood 3. Muscular Dystrophy: weakening or loss of muscles

Analyzing X-Linked and Y-Linked Traits Are only males affected? Y-Linked If the alleles for a trait are on the Y chromosome, then only males can have it Only males have a Y chromosome

Y Linked 33

Y-Linked Traits If a male shows the trait for a y-linked disorder… All of his sons will also show the trait All of his sons must inherit the Y from dad, so if dad’s Y carries a disorder, all subsequent males will also have the disorder

Y Linked 35

Y-Linked Only males are affected? Is the trait expressed in males and females? Sex-Linked

X-Linked Inheritance Sex-Linked traits are expressed unequally in males and females In sex-linked traits, if any females are affected it must be x-linked X-linked dominant and x-linked recessive

X-Linked Disorders X-Linked disorders are more difficult Unaffected male X (Y) Affected male X+ (Y) Unaffected female XX Affected if dominant XX+ Not affected if recessive Affected female X+X+

X-Linked Inheritance Pedigrees of x-linked traits show special patterns that differentiate it from autosomal disorders On x-linked pedigrees, I will tell you that it is x-linked, otherwise assume autosomal or y-linked

X-Linked Dominant Affected male  all females affected Affected male  no sons Homozygous female  all children Heterozygous female  some children

All daughters from affected male are affected

X Dominant Add II-3 Homozygous mother Without heterozygous mother 42

X-Linked Recessive Affected female  all sons affected Carrier female  not all sons affected

X Rec 44

X Recessive 45

Affected male  All sons affected