Chapter 15- The Chromosomal Basis Of Inheritance Flashcards
The chromosome theory of inheritance states:
Mendelian genetics have specific loci on chromosomes
Chromosomes undergo segregation and independent assortment
Fruit flies have how many pairs of chromosomes?
4
Morgan determine that the white eyed mutant allele must be located on the…
X chromosome
Gene On the Y chromosome codes for a protein that directs the development of male anatomical features
SRY gene
sperm either contains an ____ or _____ chromosome
X, Y
A gene that is located on either sex chromosome is called a
Sex-linked gene
_____ chromosomes have genes for many characters unrelated to sex, where as the ______ chromosome mainly encodes genes related to sex determination
X, Y
For A recessive X linked trait to be expressed, a female needs……
And a male needs……
Two copies of the allele
One copy (hemizygous)
X linked recessive genedisorders are much more common in
Males
If a female is heterozygous for a particular gene located on the X chromosome she will be a ________ for that character
Mosaic
In mammalian females, one of the two X chromosomes in each cell is randomly inactivated during embryonic development, the inactive X condenses into a….
Barr Body
Each chromosome has ___________ genes (except theY chromosome)
Hundreds or thousands of genes
What ratios do you see for traits on the same chromosome vs. different chromosomes?
Different chromosomes 1:1:1:1
Same chromosome 1:1:0:0
What did Morgan find that was usually inherited together? (Parental phenotypes)
They did not sort independently because they were
Body color and Wing size
On the same chromosome
Offsprings with a phenotype matching one of the parental phenotypes are called
Parental types
A ______% Frequency of recombination is observed for any two genes on different chromosomes
50
If the number of recombinations is below 50% it is….
One the same chromosome (linked)
Who created the genetic map?
One of Morgan’s students, Alfred Sturtevant
What is an ordered list of the genetic loci along a particular chromosome
Genetic map
A genetic map of a chromosome based on recombination frequencies
Linkage map
Distance between genes can be expressed as what units?
Map units
One map unit Represents a 1% recombination frequency
How do you calculate map distance?
Number of recombinants
Divided by
Total number of offspring
x100
- pairs of homologous chromosomes do not separate normally during meiosis
- as a result, one gamete received two of the same type of chromosome and the other game he receives no copy
Nondisjunction
This results from the fertilization of gametes in which non-disjunction occurred
Offspring has an abnormal number of a particular chromosome
Aneuploidy
Monosomic- zygote has one copy of a particular chromosome
Trisomic- zygote has three copies of a particular chromosome
Is a condition in which an organism has more than two complete sets of chromosomes
Polyploidy
This is common in plants
What causes “cry of the cat”?
Deletion in chromosome 5
CML leukemia is caused by what?
Translocations of chromosomes
What is it called when the phenotype depends on which parent passed along the alleles for those traits?
Involves the silencing of certain genes that are “stamped” with an imprint during gamete production
Genomic imprinting
They can have the same genotype but the phenotype is different
Methylation makes it inactive
