Chapter 15: The Chromosomal Basis of Inheritance Flashcards
What is a sex-linked gene?
Any gene located on either the X or the Y chromosome
Are males and females affected differently by sex-linked genes?
Yes
What is the notation for red green colourblindness? (X-linked recessive trait)
N = Normal vision n = colour blind
Females:
XN XN = normal
XN Xn = normal
Xn Xn = colourblind
Males:
XN Y = normal
Xn Y = colourblind
X-linked disorders are more common in ________?
Males
In terms of haploid and diploid:
Females are _____ for each X-linked trait.
Males are _____ for each X-linked trait.
Females are diploid
Males are haploid
What is X inactivation?
When one of the Xs in a female is inactivated and it’s genes cannot be read.
What are linked genes?
When two genes are on the same chromosome.
|R |
|y |
Rather than:
|R |y
| |
Drosophila have __ homologous pairs.
4
Describe the naming system for drosophila.
b+b+ = grey b+b = grey
bb = black
What does it mean when a fly is wildtype?
It displays the normal phenotype
What does it mean when a fly is mutant?
It displays the unusual phenotype.
How do you test whether two traits are linked or unlinked?
Do a testcross of the two parents.
If the results are 1:1, they are unlinked.
If the results vary, they are linked.
What are recombinant offspring?
Offspring that look nothing like the parent.
Recombinant offspring are ______ common.
Less
Recombinant offspring originate from ____________.
Crossing over
If the genes are close together on a chromosome, it is ______ likely that there will be a crossover.
Less
If the genes are far apart on a chromosome, it is ______ likely that there will be a crossover.
More
What is recombination frequency?
The frequency of which a single crossover takes place
How do you calculate recombination frequency?
recombinants
__________________ x 100
total offspring
The higher the recombination frequency, the ________ the genes are on the chromosome.
The higher the recombination frequency, the _______ crossing over there was.
Further
More
What is nondisjunction?
When chromosome fail to separate during Meiosis
What is aneuploidy?
The abnormal number of chromosomes at the end of nondisjunction Meiosis
What will happen if one of these nondisjunction eggs gets fertilized?
Genetic disorders (like Down syndrome)
What are the 4 other methods where genetic disorders can occur?
- Deletion
- piece of chromosome is lost
- Duplication
- piece of chromosome is copied x2
- Inversion
- piece of chromosome pops out and is put back in backwards
- Translocation
- two chromosome broken off at the same time and rejoined to the other one
