Answer Key
Section 6.4
Study Guide
1. genes code for proteins
2. any of the alternative forms
of a gene that may occur at
a specific locus
3. homozygous; heterozygous
4. Homologous chromosomes
are two chromosomes, one
from the mother and one
from the father, that have
the same length, overall
appearance, and genes,
although the alleles may
differ.
8. Yes, it has to be
homozygous recessive.
9. environment, such as
nutrients and sunshine
10. homozygous dominant
11. allele
12. heterozygous; recessive
Copyright by McDougal Littell, a division of Houghton Mifflin Company
Homologous
Chromosomes: Images
should be similar to the
Visual Vocab on page 180
in the textbook. Students
will label Gene A, Gene A,
gene B, and Gene b.
5. Answers will vary. Sample
answer: Genotype is the
underlying genetics of an
organism, which could be
compared to someone’s
thoughts that you can’t
read. Phenotype is the
observable traits, which
could be compared to
someone’s words that tell
you what they’re thinking
about.
6. as letters, uppercase for
dominant alleles and
lowercase for recessive
alleles
7. Genotype: homozygous
dominant; homozygous
recessive; heterozygous.
Phenotype: dominant;
recessive; dominant.
Alleles: TT; tt; Tt
Answer Key
1