Genetics Terms You’ve Gotta Know
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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