Chapter 15 Flashcards
chromosome theory of inheritance
- mendelian genes have specific loci (positions) on chromosomes
- chromosomes undergo segregation and independent assortment
who had the first solid evidence associating a specific gene with a specific chromosome
thomas hunt morgan
–experimented with fruit flies provided convincing evidence that chromosomes are the location of mendel’s heritable factors
morgan noted wild type which is really…
normal phenotypes that were common in the fly populations
traits alternative to the wild type/ normal phenotypes are called
mutant phenotypes
what did morgan’s experiment deal with and how did he figure out it had to do with chromosomes?
Correlating Behavior of a Gene’s Alleles
with Behavior of a Chromosome Pair
• In one experiment, Morgan mated male flies with white eyes (mutant) with female flies with red eyes (wild type)
– The F1 generation all had red eyes
– The F2 generation showed the 3:1 red:white eye ratio, but only males had white eyes
• Morgan determined that the white-eyed mutant allele must be located on the X chromosome
• Morgan’s finding supported the chromosome
theory of inheritance
—sex linked genes
are x and y chromosomes homologous?
technically yes but only the ends of y chromosome have regions that are homologous to regions of the x chromosome
true or false:
eggs can have either x or y and sperm can have either x or y
FALSE;
eggs are only x and sperm can be x or y
sex linked gene
a gene that is located on either sex chromosome
_ chromosome have genes for many characters unrelated to sex, whereas the _ chromosome mainly encodes genes related to sex determination
- x
- y
for a recessive x-linked trait to be expressed in a girl what has to happen?
-what about a boy?
- a girl needs two recessive x chromosomes
- a boy only needs one
True or false: x-linked recessive disorders are much more common in males than in females
true
what are some disorders caused by recessive alleles on the x chromosome in humans
- colorblindness
- duchenne muscular dystrophy
- hemophilia
what is the Barr body
when one of the x chromosome in mammalian females condenses and does not work anymore.
*
if a female is heterozygous for a particular gene located on the x chromosome she will be a _____ for that character
mosaic- a picture or pattern produced by arranging together small colored pieces of hard material, such as stone, tile, or glass.
linked genes
genes located on the same chromosome that tend to be inherited together
who crossed flies with different traits to see how linkage affects inheritance
thomas hunt morgan
wild type is recognized with….
wild type is normal
it is recognized with a plus +
what would be the ratio if genes are located on different chromosomes?
1:1:1:1