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Biology Exam Study Guide, Introduction to Genetics
1. Know all the vocabulary (you have these written out, and we have had a quiz)
2. Who was Gregor Mendel? What organism did he work with?
3. Mendel concluded biological inheritance of traits is determined by chemical factors; today we
know these “factors” are genes; genes control traits; genes are passed from parents to their
offspring.
This law is called?
4. Genes occur in different forms called?
5. Mendel also concluded that for some traits, there is a dominant allele and a recessive allele;
the dominant is always expressed if present (dominant over the recessive; recessive alleles have to
be the only ones present to be expressed)
This law is called?
6. For Mendel’s pea plants, Dominant traits included: round seed, yellow seed, and tall plant,
what were some recessive traits?
7. What is Phenotype? Give some examples:
8. What is Genotype? Give some examples:
9. A capital letter represents______________= T or A or etc; a lowercase letter represents the
________________= t or a or etc.
 TT = ______________ dominant= will have dominant phenotype
 Tt = _______________ = will have dominant phenotype
 tt = _______________ recessive= will have recessive phenotype
 P = ____________ generation
 F1 = offspring from a cross between ____________
 F2 = offspring from a cross between ____________
10. For Mendel’s pea plants each trait was controlled by two alleles; he concluded these two
alleles segregate from each other during the production of a plant’s gametes (sex cells); thus a
recessive trait can seem to disappear in the F1 generation and then reappear in the F2 generation.
This law is called?
11. Principles of probability allow us to do what?
12. KNOW how to set up and fill in a single trait Punnett square such as on p. 268 of textbook;
be able to give the ratios for genotype (e.g. 1 TT: 2 Tt: 1 tt) and phenotype (3:1 = 3 dominant trait:
1 recessive trait).
Examples:
In a pea plant tall is dominant and short is recessive. Two tall F1 pea plants that are heterozygous
cross-fertilize each other.
 What is the genotypic ratio?
 What is the phenotypic ratio?
 Use a punnett square to explain your answer and to compare the probable genetic
variations in the F2 plants.
An F1 plant that is homozygous for shortness is crossed with a heterozygous F1 plant.
What is the probability that a seed from the cross will produce a tall plant?
 Use a punnett square to explain your answer and to compare the probable genetic
variations in the F2 plants.
13. Mendel also concluded that genes for different traits can segregate independently
during the formation of gametes.
This law is called?
We receive one copy of a gene from our “mother” and one copy from our “father”.
14. There are exceptions to the patterns that Mendel found since not all genes show the simple
patterns of dominant and recessive alleles.
 What is incomplete dominance? An example is when you cross a red and white flower
in four o’ clock plants and get pink flowers.
 What is codominance? An example occurs when a black and white chicken crossfertilize to produce checkered offspring.
 What are multiple alleles? An example occurs in the coat colors in a rabbit, it is
determined by a single gene that has four different alleles.
15. The patterns of genetics found in plants also apply to animals and other organisms (T. H.
Morgan was a major biologist in studying genetics of animals…specifically the fruit fly); of course
the genetic patterns above apply to humans also.
16. All of your traits (characteristics) are not 100% determined by genetics; there are also
environmental factors such as climate for a plant or nutrition for a human; our behavior has
genetic and environment (how we are raised) factors.