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
