Chapter 15: The Chromosomal Basis of Inheritance!
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Overview: Locating Genes on Chromosomes
Genes are located on ____________
–Can be ___________ using certain techniques(fluorescent dye)
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Concept 15.1: Mendelian inheritance has its physical basis in the behavior of
chromosomes
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Several researchers proposed in the early 1900s that genes are located on
chromosomes
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The behavior of chromosomes during meiosis was said to account for Mendel’s
laws of ___________ and ________________________
–The chromosomal basis of Mendel’s laws
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Morgan worked with ____________ because they breed at a _____ rate
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Morgan first observed and noted
Thomas Hunt ____________ provided convincing evidence that
___________________ are the location of Mendel’s heritable factors
–A new generation can be bred every two _______
–They have only ______ pairs of chromosomes
–Wild type, or ____________, phenotypes that were common in the fly populations
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Traits alternative to the wild type are called _________ phenotypes
In one experiment Morgan mated male flies with _______ eyes (mutant) with
female flies with _______eyes (wild type)
–The F generation all had red eyes
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The F generation showed the ______ red:white eye ratio, but only ________ had
white eyes
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Morgan determined that the white-eye mutant allele must be located on the
______ chromosome
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Morgan’s discovery that transmission of the X chromosome in fruit flies
correlates with inheritance of the eye-color trait
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Was the first solid evidence indicating that a specific _______ is associated with a
specific ____________
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Concept 15.2: Linked genes tend to be inherited together because they are located
______ each other on the ______ chromosome
Each chromosome has hundreds or thousands of genes!
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Morgan did other experiments with fruit flies to see how linkage affects the
inheritance of two different characters
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Morgan crossed flies that differed in traits of two different characters
Morgan determined that
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Genes that are ______ together on the same chromosome are linked and do not
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Unlinked genes are either on ________ chromosomes of are _____ apart on the
same chromosome and _____________________
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When Mendel followed the inheritance of two characters
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When 50% of all offspring are recombinants
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He observed that some offspring have combinations of traits that do not match
either parent in the P generation
____________ offspring are those that show new ___________ of the parental
traits
–Geneticists say that there is a ______ frequency of recombination
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Morgan proposed that some process must occasionally _________ the physical
connection between genes on the _______ chromosome
–________________ of ______________ chromosomes was the mechanism
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_________ genes
–Exhibit recombination frequencies less than _______
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A genetic ___________ is an ordered _________ of the genetic _______ along a
particular chromosome
–Can be developed using ______________ frequencies
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A linkage map is the actual map of a chromosome based on recombination
frequencies
The ________ apart genes are on a chromosome
–The more likely they are to be ___________ during crossing over
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Many fruit fly genes were mapped initially using recombination frequencies
Concept 15.3: ______________ genes exhibit unique patterns of inheritance
An organism’s ___________
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Is an inherited ___________ character determined by the presence or absence of
certain chromosomes
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In humans and other mammals there are two varieties of sex chromosomes, _____
and _____
Different systems of sex determination are found in other organisms
The _____ chromosomes have genes for many characters unrelated to sex
A gene located on either sex chromosome is called a ______________ gene
Some ____________ alleles found on the X chromosome in humans cause certain
types of disorders
–________ blindness
–Duchenne muscular dystrophy
–______________
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In mammalian females
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One of the two ______ chromosomes in each cell is randomly ___________ during
embryonic development
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If a female is ___________ for a particular gene located on the ____ chromosome
–She will be a _______ for that character
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Concept 15.4: Alterations of chromosome ________ or structure cause some
genetic disorders
Large-scale chromosomal alterations often lead to spontaneous __________ or
cause a variety of _________________ disorders
When _____________ occurs pairs of ____________ chromosomes do not
____________ normally during meiosis
–Gametes contain _____ copies or _____ copies of a particular chromosome
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______________
–Results from the ___________ of gametes in which nondisjunction occurred
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Is a condition in which offspring have an __________ number of a particular
chromosome
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If a zygote is trisomic it has _______ copies of a particular chromosome
If a zygote is monosomic it has only _______ copy of a particular chromosome
Polyploidy is a condition in which there are more than _______ complete sets of
chromosomes in an organism
____________ of a chromosome can lead to four types of changes in chromosome
structure
–Deletion
–______________
–Inversion
–________________
–Alterations of chromosome structure
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Alterations of chromosome number and structure
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Down syndrome
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Nondisjunction of sex chromosomes
–Are associated with a number of serious human disorders
–Is usually the result of an extra chromosome 21, ________ 21
–Produces a variety of _________ conditions
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Klinefelter syndrome is the result of an extra chromosome in a male, producing
__________ individuals
Turner syndrome is the result of monosomy X, producing an ______karyotype
Cri du chat is a disorder caused by a __________ in a chromosome
Certain _________ are caused by _____________ of chromosomes
Concept 15.5: Some inheritance patterns are exceptions to the standard
chromosome theory
Two normal exceptions to Mendelian genetics include
–Genes located in the nucleus
–Genes located _________ the nucleus
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In mammals
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______________ genes
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The phenotypic effects of certain genes depend on which ________ is inherited
from the mother and which is inherited from the father
Genomic _______________ involves the silencing of certain genes that are
“stamped” with an imprint during ________ production
–Are genes found in ___________ in the cytoplasm
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The inheritance of traits controlled by genes present in the chloroplasts or
___________
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Depends solely on the ___________ parent because the zygote’s cytoplasm comes
from the ______
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Some diseases affecting the _____________ and nervous systems are caused by
defects in mitochondrial genes that prevent cells from making enough _______
Hurry and write a few sentences to summarize what you learned, or found
interesting, before you forget it !
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