Chapter 12 Flashcards
Chromosome theory of inheritance
genes have specific loci along chromosomes and chromosomes undergo segregation and independent assortment
Name two alleles located on Chromosome 11
Student choice
one example: ALD
If you crossed an F1 plant from pg. 241 with a plant that is recessive for both genes (rryy). what would be the phenotypic ratio?
1:1:1:1
Why did Thomas Hunt Morgan choose the fruit fly for his experiments?
prolific breeders, two-week generation, chromosomes could be seen with a light microscope
What is meant by wild type?
the character most commonly observed in natural populations.
ex. red eyes
In contrast, a mutant phenotype would be white eyes.
Why did Morgan see males who were white-eyed in the F2 generation?
White is recessive. He discovered this in the F1 generation.
There is no corresponding allele on the Y chromosome so if the white allele is on the X, cannot be masked.
What is a sex-linked gene?
Located on either X or Y chromosome.
If X- linked, on X.
If Y-linked, on Y
What does the SRY gene control? Where is it located?
SRY stands for sex-determining region of Y is required for the development of testes.
If absent, ovaries will develop in an XY individual*.
*Assuming the WNT4 gene is active.
Why are X linked diseases more common in males?
Males inherit a Y from their father and an X from their mother. If mom passes a recessive allele for hemophilia, for example, there is no corresponding allele to mask the recessive allele.
Females need to inherit 2 recessive alleles for hemophilia to be affected by the disease.
If a carrier female has children with a colorblind male, what is the chance that their sons have the disorder?
50%
Hint: look at the boys only. 1/2 of the boys are colorblind.
What is a Barr body?
The inactive X in each cell of a female.
Females have 2 X. If both were active, there would be twice as many of the proteins encoded by the one X in males.
In early development, almost all of one X chromosome in each cell in females becomes inactivated.
How do you think this happens?
Hint: What can you add to DNA to make it inactive? Take a look at page 245.
Is it possible to have a tortoiseshell cat? Why or why not?
No. not usually. It would have to be a Klinefelter Male!
Males only have on X. There are no Barr Bodies. If males inherit a black allele on the X, then they will only have black patches.
What are linked genes?
genes located near each other on a chromosome
Which other gene do you see linked to BRCA1?
How are parental offspring different from recombinant offspring?
Take a look at page 248.
Parental types = inherit a phenotype that matches either of the parents
Recombinants: new combinations of seed shape and color.
What is the null hypothesis of the cross?
GgNn X ggnn?
1:1:1:1
This is the expected ratio for the test cross.
See pg. 247.
Is this what happened? Why or why not?
Take a look at the chromosome. Which type of alteration is shown?
Translocation
What does this Karyotype show?
What would be the symptoms?
47 XXX
healthy, no unusual symptoms other than being slightly taller than average.
Fertile. unlike with 45 X
