Genetics Terms
Target #10- I can define gene
 Gene: a piece of DNA that provides a…
 Each gene has a
(location) on a chromosome
Target #11- I can define allele
 Allele:
 Cells have
for each gene
Target #12- I can differentiate between homozygous & heterozygous
 Homozygous:
 Ex: If B = tall in size, then a homozygous allele is BB
 Heterozygous:
 Ex: if B = tall b= short, then a heterozygous allele is Bb
Target #13- I can differentiate between genotype & phenotype
 Genotype:
 Trait not seen outwardly
 Phenotype:
 What is expressed physically
Target #14- I can differentiate between dominant and recessive alleles
 Dominant:
 Ex: if B = tall and b = short, an organism with Bb or BB will be tall because the capital letter represents
the dominant trait
 Recessive:
 Ex: if B = tall and b= short, an organism will only be short with a bb because the lower case letters
represent the recessive trait
Punnett Squares & Monohybrid Crosses
Target #15- I can explain what a Punnett Square is used for
 Punnett Square:
 The axis represent the
of each parent
 Show the
 By counting the number of squares of each offspring genotype, the ratio of genotypes can be
determined
 The ratio of phenotypes can be determined also
Target #16- I can determine the ratio of genotype and phenotype of offspring produced in a monohybrid cross
 Monohybrid cross: a cross that examines
 Example:
Suppose you cross a pea plant that is homozygous dominant (_________ ) for purple flowers with a pea plant
that is homozygous recessive for white flowers (_________)
 F1 generation
 Genotype: Pp
 Heterozygous
 Phenotype
 Purple Flowers
 A homozygous tall plant (
) is crossed with a heterozygous plant (
 What are the genotypes of the offspring? What is the ratio of genotypes?
 What are the phenotypes of the offspring? What is the ratio of phenotypes?
).
 A man with hitchhiker’s thumb (
expecting a child.
) and his wife who also has hitchhiker’s thumb (
 What are the genotypes of the offspring? What is the ratio of genotypes?
 What are the phenotypes of the offspring? What is the ratio of phenotypes?
 What is the probability that the child will also have hitchhiker’s thumb?
) are
Dihybrid Crosses
Target #17- I can determine the ratio of genotype and phenotype of offspring in a dihybrid cross
 Dihybrid Cross:
 The grid for dihybrid crosses is similar to monohybrid
 Example: Supposed you cross two plants with yellow, round peas that are heterozygous for both traits
 Genotype for both parents is: _________________________
 F2 Generation
 Genotypes?
 Phenotypes?
 A woman has the genotype eegg (no hitchhikers thumb and no widow’s peak. A man has the genotype EeGg
(hitchhikers thumb and widow’s peak)
 What are the genotypes and phenotypes
 A man has the genotype BbDd (brown hair and brown eyes). His wife has blonde hair and blue eyes (bbdd).
 What are the genotypes and phenotypes of the offspring?