Heredity

Review of Traits

A trait is a characteristic of something

Traits can be both behavioral or physical

Inherited traits are coded in the DNA of the organism

All organisms contain DNA, so all organisms pass on traits

Examples of inherited traits

hitchhiker thumb

Is this a physical trait or a behavioral trait?

Examples of inherited traits

widow’s peak hairline

Is this an inherited trait or an acquired trait?

Examples of inherited traits

attached earlobes

How many people in the class have this inherited trait?

Examples of inherited traits

tongue rolling

Is this a physical trait or a behavioral trait?

Examples of inherited traits

hand clasping

Is this a physical trait or a behavioral trait?

What determines traits? Traits are written

on chromosomes

Chromosomes come in pairs

One chromosome comes from mom

One chromosome comes from dad

What determines traits?Is this a plant or animal cell?

What evidence suggests your inference?

Each particular section of a

chromosome codes for a gene

Humans have about 25,000 genes – we are still discovering!

What determines traits? Each gene codes for a

protein that will help determine a trait

The different versions of a trait are called alleles.

For instance, the same spot on matching chromosomes could contain an allele for straight thumb or an allele for hitchhiker thumb.

What determines traits?

Alleles are kinda like different stitching on the pockets of different brands of jeans

They perform the same function, but are slightly different

Allele for “flying bird”

Allele for “w”

What determines traits?

Your unique alleles determine your many unique traits

No two humans could be identical, because there are almost an infinite number of gene combinations

How do we read the code? The genotype is

the code written on the DNA

The phenotype is the resulting appearance

(pheno is like photo)

How do 2 alleles make 1 trait?

Dominant alleles are like class clowns – you always know if they are in the room.

Recessive alleles are like shy people – you don’t know they are there unless they are alone

How do 2 alleles make 1 trait?

If a dominant allele is present in the genotype, that allele’s phenotype will show outwardly.

Example, Straight Thumb is dominant over hitchhiker’s Thumb

H h

How do 2 alleles make 1 trait?

The only way a hitchhiker’s thumb shows up in the phenotype is if 2 recessive traits are inherited in the genotype.

H + H =

H + h =

h + h =