In mouse, genes X, Y and Z are on chromosome 2. The map of genes X, Y and Z is: XYZ 20 m. u. 20 m. u. You cross an individual with genotype XXYYZZ to an individual with genotype xxyyzz, and F1 progeny are collected. Assume interference between regions (X-Y and Y-Z) is 100%. When an F1 individual produces gametes, what proportion of its gametes would have xyz genotype

28%

i hope i'm right

Explanation:

In F1 we will get 100% XxYyZz

each of these organism has two chromosomes that look like this

X20Y30Z

x20y30z

Those two chromosomes are homologous

we want a gamete that contains the second chromosome where crossing-over didn't occur. The distance between the genes of the chromosomes in map units is equal to the frequency of recombination in percentage. Therefore there is a 20% that x and y will recombine and a 30% chance that y and z will recombine. We want a chromosome that is not recombined.

The possible gametes are

XYZ XYz XyZ Xyz xYZ xYz xyZ xyz if the genes were on different chromosomes xyz would be 1/8 or 12,5%

Since there is a 20% that the genes x and y will recombine that means there is a 80% chance that they won't and since there is a 30% chance that the genes y and z will recombine that means there is a 70% chance that they won't.

80%*70%=56% chances that the genes won't recombine. But, there are two non-recombinant gametes:XYZ and xyz therefore the chances for xyz is 56/2=28%

c. earths continental crust is thicker than its lithosphere.

because, the lithosphere is the outermost layer of the earth/ 100 km thick and is defined by its machanical properties.the lithosphere contains oceanic and continental crust that varies in age and thickness across locations and geologic time. the lithosphere is the coolest layer of the earth in terms of temperature. the term lithosphere should not be confused with the use of "geosphere" which is used to indicate all of earth systems, including the atmosphere, hydrosphere   and biosphere. the surface of the earth can be divided into the continental crust and the oceanic crust.   the continental crust is made mostly of granite while the oceanic crust is made of basalt. the average thickness of the continental crust is 25 miles and the average thickness of the oceanic crust is 5 miles.   three types of rock, igneous, sedimentary, and metamorphic, make up the surface of the earth. that's why 3 option is preferable.