by ms. duko. what is genetics? genetics is the scientific study of heredity
TRANSCRIPT
By Ms. Duko
What is Genetics?Genetics is the scientific study of heredity
What is a Trait?A trait is a specific characteristic
that varies from one individual to another.Examples: Brown hair, blue eyes, tall,
curly
What is an Allele?Alleles are the
different possibilities for a given trait.Every trait has at least
two alleles (one from the mother and one from the father)
Example: Eye color – Brown, blue, green, hazel
Examples of Alleles:A = Brown Eyesa = Blue EyesB = Green Eyesb = Hazel Eyes
What are Genes?Genes are the sequence of DNA that codes for a protein and thus determines a trait.
Dominant vs. RecessiveDominant - Masks the other trait; the trait
that shows if presentRepresented by a capital letter
Recessive – 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 alleles are presentRepresented by a lower case letter
R
r
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
Homozygous vs. HeterozygousHomozygous – Term used
to refer to an organism that has two identical alleles for a particular trait (TT or tt)
Heterozygous - Term used to refer to an organism that has two different alleles for the same trait (Tt)
Punnett SquaresPunnett Square – Diagram
showing the gene combinations that might result from a genetic cross
Used to calculate the probability of inheriting a particular traitProbability – The chance
that a given event will occur
Punnett SquareParent
Parent Offspring
How to Complete a Punnett Square
Y-Yellowy-white
Genotype:1:2:1
(YY:Yy:yy)
Phenotype:3 Yellow1 White
You Try It Now!Give the genotype and phenotype for the
following cross: TT x tt (T = Tall and t = Short)
TT x ttStep Two: Complete the Punnett Square
T T t t
Tt Tt
Tt Tt
TT x ttStep Three: Write the genotype and phenotype
T T t t
Tt Tt
Tt Tt
Genotype: 4 - Tt
Phenotype:100% Tall
Remember: Each box is 25%
You Try It Now!Give the genotype and phenotype for the
following cross: Tt x tt
Tt x ttStep One: Set Up Punnett Square (put one parent
on the top and the other along the side)
T t t t
Tt x ttStep Two: Complete the Punnett Square
T t t t
Tt tt
Tt tt