EQ1: How do we inherit traits from our parents?

EQ2: Is inheritance predictable?

What is Genetics?Genetics is the scientific study of heredity

What are Genes?Genes are the sequence of DNA (A, T, C, G) that codes for a protein and thus determines a trait.

Ex. Hair color

What is a Trait?A trait is a specific characteristic

that varies from one individual to another, one of several options for a gene.Examples:

Brown hairTongue rollingFree earlobes

What is an Allele?Alleles are the different possibilities for a

given trait. Scientists give them a letter to represent the possibilities (1 letter represents 1 whole gene- a loooong piece of DNA ex. Your eye color). The letter chosen doesn’t matter Capital or lowercase DOES matter [make sure they look

different!]

Every trait has two alleles (one from the mother and one from the father)

Example: Can roll tongue = RrMom’s egg gave you a R allele (Can roll) and

Dad’s sperm gave you a r allele (Can’t roll) so you probably have “Rr” (Can roll- R wins over r)

Examples of Alleles:B = Brown Hairb = Blonde Hair

If my dad has brown eyes, why do I have blue eyes?

Practice: Gene, Trait or Allele?r = can’t roll tongue

Allele!

Practice: Gene, Trait or Allele?Eye color

Gene!

Practice: Gene, Trait or Allele?F = free earlobes

Allele!

Practice: Gene, Trait or Allele?Blue eyes

Trait!

Practice: Gene, Trait or Allele?B = Brown eyes

Allele!

Gregor MendelFather of Genetics1st important studies of

heredityIdentified specific traits in the

garden pea and studied them from one generation to another

Mendel’s Conclusions

1.Law of Segregation – Two alleles for each trait separate when gametes form; Parents pass only one allele for each trait to each offspring

2.Law of Independent Assortment – Genes for different traits are inherited independently of each other Just because you got your mom’s hair doesn’t mean you have to

get all the traits of mother

Dominant vs. RecessiveDominant – Masks (covers) the other

trait; the trait that shows if present. Usually more commonRepresented by a capital letter

Recessive – Less common. An organism with a recessive allele for a particular trait will only exhibit that trait when the dominant allele is not present; Will only show if both recessive alleles are inheritedRepresented by a lower case letter

R

r

Dominant & Recessive Example

TT - Represent offspring with straight hair

Tt - Represent offspring with straight hair *T still wins, but your children could get curly

hair!tt - Represents offspring with curly hair

T – straight hairt - curly hair

Genotype vs. PhenotypeGenotype – The genetic makeup of an

organism; The gene (or allele) combination an organism has. Example: Tt, ss, GG, Ww

Phenotype – The physical characteristics of an organism; The way an organism looksExample: Curly hair,

straight hair, blue eyes, tall, green peas

Genotype vs. PhenotypeGenotype: The allele combination inherited

from the parents.Ex: Genotype (Genetics say) = Bb

Phenotype: The observable characteristics of the genotype inherited. The organism’s appearance or trait expressed.Ex: Phenotype (PHysical appearance for Bb)=

Brown hair

Practice: Genotype or Phenotype?Brown hair

Phenotype!

Practice: Genotype or Phenotype?Rr

Genotype!

Practice: Genotype or Phenotype?bb

Genotype!

Practice: Genotype or Phenotype?Hitchhiker’s thumb

Phenotype!

Practice: Genotype or Phenotype?Straight hair

Phenotype!

Practice: Genotype or Phenotype?Tt

Genotype!

Homozygous vs. HeterozygousHomozygous (purebred) –

Term used to refer to an organism that has two identical alleles for a particular trait (TT or tt)

Heterozygous (hybrid) - Term used to refer to an organism that has two different alleles for the same trait (Tt)

RR

Rr

rr

Homozygous vs. HeterozygousHomozygous Dominant:

Homozygous Recessive:

Heterozygous:

RR

Rrrr

Practice: Homozygous dominant, homozygous recessive, or Heterozygous?HH

Homozygous dominant!

Practice: Homozygous dominant, homozygous recessive, or Heterozygous?

EeHeterozygous (one dominant & one recessive allele)!

Practice: Homozygous dominant, homozygous recessive, or Heterozygous?

bb Homozygous recessive!

Practice: Homozygous dominant, homozygous recessive, or Heterozygous?Uu

Heterozygous (one dominant & one recessive)!

Allele Practice WS pg. 12Let’s make sure you get how the genetic code

works before we get into using the code!