Chapter 13 Chromosomal Basis of Inheritence Flashcards
What is the Chromosomal Theory of Inheritance
genes occupy specific loci (positions) on chromosomes
chromosomes undergo segregation and independent assortment during meiosis.
What is the law of segregation
states that pairs of alleles separate from each other during gamete formation via meiosis
What is the law of independent assortment
states that each pair of alleles sorts independently of other pairs of alleles during gamete formation
The first solid evidence associating a specific gene with a specific chromosome came from the work of
Thomas Hunt Morgan in the early 1900s
Why did Morgan choose fruit flies for his experiment
They produce many offspring
A generation can be bred every two weeks
They have only four pairs of chromosomes
In one experiment, Morgan mated male flies with white eyes (mutant) with female flies with red eyes (wild-type)
What did the F1 generation have?
The F1 generation all had red eyes
What did morgans F2 generation have?
parental was mutant male and red wild type female.
The F2 generation showed the classical 3:1 red:white ratio, but only males had white eyes
What did Morgans test cross reveal?
That white eyed females are viable; eye color is linked to the x chromosome and absent from the y chromosome.
Y chromosome characteristics
highly condensed.
default for humans is female - SRY gene on Y is for “maleness”
In some animals environmental temperature determines sex
For some species of reptiles, the temperature at which the eggs are incubated during a specific period of embryonic development determines whether the embryo will develop into a male or female.
Global climate change may therefore impact the sex ratio of such species.
In mammalian females how is the x chromosome chosen to be inactivated
randomly chosen to inactive and form a bar body
why are females mosaic
if a female is heterozygous for a gene located on the x chromosome she will be a mosaic for that character - think of calico cat fur colors.
What is hemophilia
excessive bleeding because one or more proteins are lacking that are required for blood clotting.
what is red green colorblindness?
a malfunction of light sensitive cells in the eyes
what is Duchenne muscular dystrophy
a condition characterized by a progressive weakening of the muscles and loss of coordination.
what is gene linkage
assortment of some genes is not independent because they are linked together on a chromosome
when does genetic recombination occur
when genes are further apart recombination occurs more frequently. Less often between nearby genes.
what did Sturtevent use for linkage maps of fruit flies
recombination frequencies
