Transcript Genetics Terms You’ve Gotta Know

BASIC GENETICS TERMS
Terms you’ve gotta know
GENE
A section of DNA that
has information about a
specific trait of an
organism
 A chromosome is a
chunk of DNA and
genes are parts of
chromosomes

ALLELE
Each form of a gene OR each option for each gene
 Example: attached or unattached earlobes are
the alleles for the gene for earlobe shape

DOMINANT/RECESSIVE
Dominant: a genetic factor that blocks another
genetic factor
 Recessive: a genetic factor that is hidden by the
presence of a dominant factor
 Question: Using pea plants, how did Mendel
figure out that genes are either dominant or
recessive?

HOMOZYGOUS/HETEROZYGOUS
Homozygous: two alleles for a gene that are the
SAME
 Heterozygous: two alleles for a gene that are
DIFFERENT
 You get one allele from your mom and one from
your dad.
 If you get the same from your mom and dad, you
are homozygous for that trait.
 If your mom gave you a different allele than your
dad, you are heterozygous for that trait

GENOTYPE
Tt
Alleles that make up an organism. Your
genotype is which genes you have!
 Genotype is written in letters
 It is usually the first letter of the dominant trait
to make it easier
 Choose a letter for each of these traits. Write
both the dominant and the recessive genotype
allele letters

Free Earlobes
 Freckles
 Dimples
 Tongue-roller

GENOTYPE
Now, using your letters from before write a
genotype for a person without freckles
 Write a genotype for a person with freckles

GENOTYPE-HETEROZYGOUS AND
HOMOZYGOUS
A Heterozygous genotype means an organism
has both the dominant and the recessive allele
 Homozygous recessive means an organism has
2 recessive alleles
 Homozygous dominant means an organism
has 2 dominant alleles
 Write a heterozygous genotype for handedness
 Write a homozygous dominant and a homozygous
recessive genotype for handedness

PHENOTYPE
Observable traits and all characteristics of an
organism
 What you look like (your phenotype) is based on
what your genotype is (your genes)
 What will the phenotype of these genotypes be:

PP, Pp, pp (Dominant is purple flowers, recessive is white
flowers)
 RR, Rr, rr (Round peas are dominant to wrinkled peas)
 YY, Yy, yy (Yellow peas are dominant to green peas)

GENOTYPE/PHENOTYPE PRACTICE
What is the genotype for white flowers?
 What are the genotypes for purple flowers?
 What phenotypes will result from these genotype:
PP, Pp, pp

You’ve got it!! Now you are a genetics super star 