KEY
Note Taking Guide
Topic # 3033
Genotype and Phenotype
Anna Blight
Genetic terminology
The creation of genetic material goes from __________(DNA) to _____________(RNA)
to _____________ (protein).
_______________ (Proteins) code for ___________ (genes), which code for
_______________ (traits).
Each pair of _______________ (chromosomes) carries a pair of ___________ (genes).
_____________ (Alleles) are genes that occupy different loci on each
____________(chromosome) and affect the same trait.
There are ______ (two) alleles, one on each chromosome of a _____________
(homologous pair).
The alleles may correspond, which makes the animal ____________ (homozygous), or
contrast, which makes the animal ___________ (heterozygous). Example: whether
cattle are horned or polled is controlled by one or the other locus for horns.
During gametogenesis, ________________ (homologous chromosomes) segregate and
each new gamete gets one of the ___________ (alleles).
A ___________ (dominant) allele overpowers the expression of its __________
(recessive) allele and is represented by a _________ (capital) letter.
A recessive allele is represented by a _______ (lower case) letter, and is masked by a
__________ (dominant) allele, unless the animal is _______ (homozygous recessive).
In this case, the animal will have the appearance expressed by the recessive trait.
Heterozygous animals (Aa) pass on _____ (A) to one gamete and ______ (a) to the
other gamete. Homozygous animals (AA or aa) pass on ______ and ______ (either A
and A or a and a) to each gamete.
When male and female gametes combine to form a ________ (zygote) chances are
_________ (equal) that one or the other allele of each parent will be passed on.
Traits like coat color are determined by a ________________ (dominant allele) or
homozygosity of ____________ (recessive) alleles.
Females carry two ________ (XX) chromosomes and males carry ________(X and Y)
chromosomes. Males therefore determine the _______ (sex) of the offspring by passing
on either the ________ (X or Y).
____________ (Bird species) are opposite where females are _______ (XY) and
________________ (determine the sex) of the offspring.
Compared to humans, who have ______ (23) pairs of chromosomes, most farm animals
have more, and only swine have less with _____(19) pairs of chromosomes.
____________ (Genotype) is the genetic make up of an animal.
____________ (Phenotype) is the outward appearance of an animal, due to its genetic
make up.
For any pair of alleles, _______ (three) genotypes are possible, _____, ______, and
_____. (AA, Aa, and aa).
In sheep, ________ (black) wool is a recessive trait and both parents must carry the
recessive _______ (allele), since the sheep must be ___________ (homozygous
recessive) to show the trait.
The _________ (Punnett) square is a table used to calculate the genotype and phenotype
of an animal.
A
a
A
AA
Aa
a
Aa
aa
If you cross two heterozygous parents, Aa and Aa, where A=white wool and a=black
wool, you get a genotypic ratio of _________ (1:2:1 or 1 AA : 2 Aa : 1 aa) and a
phenotypic ratio of _________ (3:1 or 3 white : 1 black).
A
A
A
AA
AA
a
Aa
Aa
Cross one homozygous dominant, AA, with a heterozygous, Aa. The genotypic ratio is
___________ (1:1 or 50% homozygous, 50% heterozygous). The phenotypic ratio is
________ (100% white wool).
A
a
a
Aa
aa
a
Aa
aa
Cross a homozygous recessive with a heterozygous animal. The result is 1:1 __________
(genotypic) ratio, and 50% __________ (white) to 50% ________ (black).