Biology Chapter 12 Study Guide
Mrs. Sistarenik
1. What is genetics? STUDY OF HEREDITY
2. What is the relationship between genetics and heredity? PASSING OF TRAITS
FROM ONE GENERATION TO THE NEXT
3. Who is Gregor Mendel? FATHER OF GENETICS, OBSERVED & QUANTIFIED
PATTERNS OF INHERITANCE IN PEA PLANTS
4. What are some reasons why peas make a great specimen for breeding? MATURE
QUICKLY, SELF-POLLINATING, **HAVE SEVERAL TRAITS THAT CAN
EASILY BE DISTINGUISHED BETWEEN
5. How did Mendel carry out his experiments? (What are the three steps?)
P GENERATION – SELF-POLLINATED TO MAKE SURE PURE FOR TRAITS
(EXAMPLE FLOWER COLOR – PURPLE VS WHITE)
CROSSED P GENERATION TO PRODUCE F1 GENERATION – ALL PURPLE
OFFSPRING
ALLOWED F1 GENERATION TO SELF-POLLINATE AND PRODUCE F2
OFFSPRING, 75% PURPLE OFFSPRING & 25% WHITE OFFSPRING
6. Explain the difference between the P generation, F1 generation, and F2 generation.
P GENERATION – PARENTAL GENERATION
F1 GENERATION – OFFSPRING OF P GENERATION
F2 GENERATION – OFFSPRING OF F1 GENERATION
7. What is true breeding and how was it important to Mendel?
WHEN PEA PLANTS WERE ALLOWED TO SELF-POLLINATE TO PRODUCE
PURE P GENERATION PEA PLANTS
8. What is the difference between self-pollination and cross-pollination?
SELF-POLLINATE – PLANT USES ITS OWN SPERM (POLLEN) AND EGG
CROSS-POLLINATE – SPERM (POLLEN) FROM A DIFFERENT PLANT IS USED
TO FERTILIZE THE EGG OF THE FIRST PLANT
9. What was Mendel’s common ratio (results) for the F2 generation in a monohybrid
cross?
75% DOMINANT TRAIT & 25% RECESSIVE TRAIT (3:1 RATIO)
10. What are Mendel’s 2 laws?
LAW OF SEGRAGATION – WHEN GAMETES (SEX CELLS) ARE PRODUCED, A
PAIR OF ALLELES IS SEPARATED INTO EACH GAMETE
LAW OF INDEPENT ASSORTMENT – DURING GAMETE (SEX CELL)
FORMATION, THE ALLELES OF EACH GENE SEPARATE INDEPENDENTLY OF
EACH OTHER
11. How do you write alleles?
WITH LETTERS, CAPITAL LETTERS = DOMINANT TRAITS,
lower case letters = recessive traits
12. What is the difference between dominant and recessive alleles/traits (explain both)?
ALLELES ARE FORMS OF A TRAIT, THE ALLELES FOR SKIN PIGMENTATION
ARE NORMAL(DOMINANT) AND ALBINISM (RECESSIVE)
TRAITS ARE LIKE HAIR COLOR, EYE COLOR, SKIN PIGMENTATION
13. What is the difference between homozygous vs. heterozygous? What are the
different types of homozygous? Why is their only one type of heterozygous?
HOMOZYGOUS DOMINANT – 2 DOMINANT ALLELES (DD)
HOMOZYGOUS RECESSIVE – 2 RECESSIVE ALLELES (dd)
HETEROZYGOUS DOMINANT – 1 DOMINANT ALLELE & 1 RECESSIVE
ALLELE (Dd)
14. What is the difference between genotypes and phenotypes?
GENOTYPE – ALLELE COMBINATION
PHENOTYPE – THE WAY THE TRAIT IS SHOWN
15. What are some of the major differences between monohybrid cross and dihybrid
crosses (Punnett squares)?
MONOHYBRID CROSS – 1 TRAIT, 4 BOX PUNNETT SQUARE
DIHYBRID CROSS – 2 TRAITS, 16 BOX PUNNETT SQUARE
16. How do you complete a monohybrid cross? Dihybrid cross?
MONOHYBRID – CROSS 2 PARENTS GENOTYPES AND MATCH ALLELES IN
PUNNETT SQUARE (2 ALLELES PER BOX)
DIHYBRID – CROSS 2 PARENTS GENOTYPES AND MATCH ALLELES IN 16
BOX PUNNETT SQUARE (4 ALLELES PER BOX)
17. What is the difference between Punnett squares and pedigrees?
PUNNETT SQUARES SHOW THE PROBABILITY THAT AN OFFSPRING WILL
HAVE A TRAIT, PEDIGREES TRACE A TRAIT THROUGH MANY
GENERATIONS
18. What are the 3 pieces of information that can be determined by examining a
pedigree?
SEX-LINKED OR AUTOSOMAL, GENDER, GENOTYPE OF INDIVIDUAL
19. What is a test cross and what is its purpose?
THE PURPOSE IS TO DETERMINE IF A DOMINANT PHENOTYPE IS MOST
LIKELY HOMOZYGOUS OR HETEROZYGOUS
20. What are 6 exceptions to the “rules” of heredity?
MULTIPLE ALLELES, CO-DOMINANCE, INCOMPLETE DOMINANCE, SEXLIBNKED TRAITS, ENVIRONMENTAL INFLUENCES, AND POLYGENIC
TRAITS