Patterns of Inheritance - ScienceGonnaGetYou

Whether a person has curly hair or a cow has large muscles may seem random so scientists started keeping track of heritable traits with pedigree charts.

MEET JIM & ZENA

Jim & Zena have a lot of PHENOTYPES which are also known as observable characteristics.
In order to figure out if each of these traits is heritable or acquired, we can make a pedigree chart.

Has horns
Mostly white with some black fur
Huge muscles

No horns
Even mix of black and white fur
Typical muscles

WHAT IS A PEDIGREE CHART?

PEDIGREE CHARTS help scientists to follow phenotypes (trait variations) of one trait through several generations to find patterns of inheritance.
Males and females are represented with squares and circles respectively.
The shading of the shapes denotes what trait each individual has.

PEDIGREES TRACK PATTERNS IN FAMILIES

What patterns do we see when we look at Jim’s family pedigree?

While there does appear to be a slight pattern that traits don’t just come from nowhere, let’s analyze some more family examples to really figure out what is going on with this cow musculature!

Patterns in Cow Pedigrees

Big Muscled Cows

have at least one big muscle parent
can have offspring with big or medium muscles
never have parent or offspring with typical muscles

Medium Muscled Cows

Can have any muscled parents or offspring

Typical Cows

have at least one typical parent
can have offspring with typical or medium muscles
never have parent or offspring with big muscles

FACTORS OF INHERITANCE

After years of collecting data on inheritance, scientists realized that there are two versions of cow muscle information that can be inherited.

ALLELES are different versions of a trait that can be inherited.
Every cow gets one allele from each parent and we represent the different forms with capital and lowercase letters.
For cow muscles:
- Capital E represents big muscles
- Lowercase e represents typical muscles

SO HOW DO COWS GET THEIR MUSCLES?

Using these letters, the patterns become clear!
- Jim got one E from each parent giving him EE for big muscles.
- Zena got one e from each parent giving her ee for typical muscles.
- Greyboy got his E from Jim and his e from Zena giving him Ee for medium muscles.

HUMAN HAIR TYPE

While a simplified explanation, this pedigree shows how hair types can be inherited.

Notice that Curly haired HH parents only have H to give so their child will always have at least one H.
- If a child gets another H from parent 2, they will have curly hair. If they get h from parent 2 they will have wavy hair.