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4-1 Reading Guide: Foundations of Genetics (p. 172 – 179)
Name ___________________
Early Ideas About Heredity
 Combined ____________________ _____________________ from a sperm and an egg determines the
_____________________ or features of an offspring.
 Heredity is the passing of _________________________________ from parents to offspring.
 The idea of ____________________________________ inheritance is offspring are a blend of genetic material
from both parents.
o The genetic material ___________________________________ or blended like colors of paint.
o Over many generations, populations would eventually look __________________________________.
o Blending traits CANNOT explain why some traits _________________________________ a
generation.
Gregor Mendel and His Experiments
 Gregor Mendel was the first to record evidence that ______________________ are determined by factors
passed from ____________________ to offspring.
 Mendel established the basic __________________________________ of ___________________________.
 Genetics is the study of how __________________________________ of organisms are passed from parent to
offspring.
Mendel’s Experimental Methods
 Mendel conducted breeding experiments by studying seven traits of _____________________ plants and each
trait had only __________________ variations.
Controlled Experiments
 Mendel controlled _____________________________ in pea plants, allowing him to see how traits pass from
one generation to another.
 Mendel allowed some flowers to ___________________________.
 He also performed ______________________________________ by transferring pollen from one pea flower
to another.
Mendel’s Unique Methods
 Used __________________________ plants for each trait – plants that always produce offspring with that trait
when they ___________________________.
 Recorded the inheritance of traits for several ____________________________________.
 Used a ______________________________________ approach.
Mendel’s Experimental Results
 Mendel concluded that _____________________ _____________________ control each inherited trait.
 When organisms reproduce, each gamete – sperm or egg – contributes ________________________________
factor for each trait.
Dominant Factors
 A genetic factor that ____________________ another genetic factor is called __________________________.
 A dominant trait is observed when offspring have _____________________ or ________________________
dominant factors.
Recessive Factors
 A genetic factor that is ________________________________ by the presence of a dominant factor is
_________________________________.
 A recessive trait can be observed only when ______________________________________ recessive genetic
factors are present in offspring.
Mendel’s Laws of Heredity
 Law of segregation: the two factors for each trait segregate - _________________ from each other – during
_______________ when gametes form.
 Law of independent assortment: the factors for one trait separate _____________________ of how factors
for other traits separate.
Modern Definitions of Mendel’s Ideas
 Mendel did not know about _____________________________ or how cells reproduce, but his ideas about
_________________________ are still true today.
Genes and Alleles
 A gene is a __________________________________ of __________________________________ that has
information about a trait in an organism.
 Each form of a gene with different information is called an _______________________________.
Phenotype and Genotype
 The ______________ traits and all characteristics of an organism make up the organism’s ________________.
 The __________________ that make up an organism is the organism’s _____________________________.
 The alleles of a particular _____________________ is that gene’s genotype.
Homozygous and Heterozygous Genotypes
 Because eukaryotes have pairs of chromosomes, a genotype for a gene has _____________________ alleles.
 If the two alleles have the _____________________ information, the genotype is _____________________.
 If the two alleles have _______________________ information, the genotype is ________________________.
Law of Segregation Explained
 The movement of chromosomes during __________________________ explains Mendel’s law of segregation.
o Each set of _________________________________ separate into different ______________________
during meiosis II.
o Each gamete receives only ________________________________ allele.
Law of Independent Assortment Explained
 The daughter cells produced by meiosis receive one ____________________________________ from each
pair of homologous chromosomes.
o A daughter cell might receive the A or a chromosome from pair 1 and the B or b chromosome from pair
2.
o This results in ____________________________________ possible allele combinations for two
homologous pairs of chromosomes.
Importance of Mendel’s Genetic Studies
 In the 1860’s, no one knew about _____________________ or _____________________ so it was hard to
understand Mendel’s discoveries.
 All the research of modern genetics is based on _____________________ conclusions from his work with
__________________ ____________________.