Chromosomal Genetics Flashcards
What is the chromosome theory of inheritance?
Genes have specific locations on chromosomes
What did Thomas Hunt Morgan work on? (early 1900s)
Fruit flys.
What does W+ mean?
Wildtype (the phenotype most commonly found in nature)
What does W mean?
Mutant (variation from the wildtype)
Do bees and ants have sex chromosomes?
No. Females are diploid and males are haploid
What did Morgan conclude when he bred the F1 female wildtype and an F1 wildtype male resulting in a 3:1 ratio with no females having white eyes?
Eye colour is a sex-linked trait
Hemizygous
Having only one copy of a gene or chromosome segment instead of the usual two
If the genes are on the X-chromosome only, they are_______?
X-linked
If the genes are on the Y chromosome only, they are______?
Y-linked
What is a barr body?
An inavtivated X chromosome in females
Barr bodies are reactivated in____?
Ovarian cells
Do females have two functioning X chromosomes?
No. Only one.
Is it random which X chromosome gets deactivated?
Yes, it results in genetic mosaics
Are tortoiseshell cats usually female?
Yes, because the pattern is related to both X chromosomes
Linked genes
Genes near each other on the same chromosome
If genes are separated, will crossovers occur?
Yes
What are map units?
The number of recombinant chromosomes
In Morgan’s experiment, why weren’t the flys perfectly linked?
Because there were recombinants present due to crossing over between the two genes in the F1 female
How to calculate recombination frequency?
Recombinants/Total # offspring
What is the difference between a genetic map and a linkage map?
A genetic map allows us to see the order of genes and which ones are on the same chromosomes
A linkage map is based on recombinant frequency (how far apart genes are)
When does nondisjunction occur?
Anaphase l, ll, or after fertilization (the diploid cell can have an extra copy of a chromosome = trisomy) (only having one copy = monosomy
What is trisomy?
Having an extra set of chromosome 21 chromosomes
What is the genotype of klinefelter syndrome?
XXY
What is the genotype of Jacobs syndrome?
XXYY
What is the genotype of Triple X syndrome?
X0 or XX(partial)
What does a deletion do?
Removes a chromosomal segment
What does duplication do?
Repeats a segment
What does inversion do?
Reverses a segment
What does a translocation do?
Moves a segment from one chromosome to a non homologous chromosome
Which organelles genes are maternally inherited?
Mitochondrial and Chloroplast
