Chapter 14: Mendel and the Gene Idea
Inheritance:
-when ________________ are passed down from parents to offspring
-involves:
-_______________________ (DNA and proteins)
-___________ (segments of DNA functional product)
-unit of ___________________
-each gene has a specific ___________ on the chromosome
-______________: different version of same gene
-arise from __________________ in DNA sequence of gene
-contain information for organism development
Early thoughts about inheritance
-both __________________ contributed to the characteristics of the offspring
-the favored _______________________ of how this occurred was the blending theory of heredity
The Blending Theory of Heredity
-the offspring’s traits are some _____________________ between the parental types
-unable to explain why characteristics ______________________ in one generation and _________________ in the next
-if this was true population would reach a _____________________ appearance
Gregor Mendel
-“_________________ of Modern Genetics”
-a monk who was trained in science at the University of Vienna
-determined how organisms pass on _______________________ traits to their offspring
-Mendel developed his theory from the study of the variation of ________________________
-Why peas?
-many different _____________ (clear-cut characteristics)
-____________ to work with (short generation time many generations studied)
-can ________-fertilize or ___________ fertilized
-in nature, pea plants _______-fertilize
-pollens fertilize eggs from _________ flower
-Mendel _________-fertilized pea plants
-pollen from one plant fertilized egg from different plant
-focused on __________________ traits
-observed _______________ generations
Terms to know:
-_____________________ is an organism’s expressed traits
-what it looks like
-_____________________ is an organism’s genetic makeup
-_____________________ is the condition in which both the alleles are the same of a given trait
-all _________________ carry that trait
-homozygotes are ________-breeding or _________ breeding
-_____________________ is the condition in which the two alleles are different for a given trait
-half the gametes carry one allele and half the carry the other allele
-heterozygotes are _________________ (not ________-breeding)
Mendel’s Experiment
-Mendel started his experiments with true-breeding plant varieties (of ____________________ trait) which he hybridized (cross-fertilized)
-___ (parental) generation: white flower X purple flower (both true-breeding) -___ (first filial) generation: all purple flower
-he found that in the F1 generation these character traits did not _______________ as predicted
-Mendel hypothesized that the loss of the white color meant the plants had lost that allele and when he crossed the F1 plants he would get only _____________flowered plants
-F1 generation _______-fertilized: F1 X F1
-____ (second filial) generation: ¾ purple flowers and ¼ white
(3:1 ratio)
-the white allele was not ______ but was ___________ by the presence of the purple allele
-Mendel had found that the trait for purple flowers was a
________________ trait and the trait for white flowers was a
________________ trait
-______________ allele: the allele that is expressed in a heterozygote
-______________ allele: the allele that is masked in a heterozygote
Mendel repeated these experiments with the six other characters and found similar _________ ratios in the F2 generations Mendel’s Model based on four concepts:
First: alternative versions (________________) of genes account for variations in inherited characters
Second: for each character, an organism inherits ________ alleles (can be the same or different), one from each parent Third: if the two alleles at a locus differ, then one (the dominant allele) determines the organism’s
_____________________, and the other (the recessive allele) has _________________________ effect on appearance Fourth (Mendel’s first law or Law of ____________________): the two
