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Who was Morgan and what did he do??

http://www.columbia.edu/cu/alumni/Magazine/Legacies/Morgan/

Using fly notation cross a female red eyed fly with a male white eyed fly! (what do you rememeber?)

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Figure 12.4

ExperimentP

Generation

Results

F1

Generation

F2

Generation

All offspringhad red eyes.

Eggs

Eggs

ww

w

w

w

w

w

w w

Sperm

Sperm

XY

XX

ww w

w

w

w ww

Conclusion

F1

Generation

F2

Generation

PGeneration

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EX. Calico cats (One of the genes for hair color is on X chromosome)

Two alleles (orange or black)

Why are females patchy??Each patch has a different X turned on (orange or black)

Orange patch=bunch of cells there with the X with the orange allele turned on. Black patch=bunch of cells with the black X on.

Why are males not patchy like females? Single X and so either the orange or the black hair color gene on in entire body.

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X = orangeX = black

MALES:• XY = orange• XY = black

FEMALES:• XX = orange• X X = black• X X = orange or black patches

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Figure 12.8

Early embryo:

Two cellpopulationsin adult cat:

X chromosomes

Cell division andX chromosomeinactivation

Allele fororange fur

Allele forblack fur

Active X

Orange furBlack fur

InactiveXActive X

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https://smartsite.ucdavis.edu/access/content/user/00002950/bis10v/media/ch10/x_inactivation.html

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Anhydrotic dysplasia X-linked sweat gland problem

X = normal sweat glands X' = absence of sweat glands.XY….would be?Normal maleX’Y…would be?No sweat glands male

XX…..Normal femaleX'X' do not have sweat glands

XX' …..Heterozygous females have patches of skin with sweat glands and patches of skin without sweat glands. So swaths or populations of cells that have one X turned on and other patches with a different X on.

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What do you know about colorblindness?

X linked

Given X inactivation …….should heterozygous females for colorblindness be able to see color?

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What do you know about colorblindness?Suppose: X = color vision               X’ = color blind The retina of a heterozygous (XX’) female will have some cells with the X inactivated and other cells with the X’ inactivated.

A heterozygous female has some color blind cells in her retina.

The non-color blind cells enable her to see color.

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Figure 12.10a

P generation (homozygous)

Wild type(gray body,normal wings)

Wild-type F1 dihybrid(gray body,normal wings)

b vg+

Double mutant(black body,vestigial wings)

b vg+

b vg+

b vg

b vg

b vg

Term!

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Figure 12.10b

b vg+

b vg

b vg+

b vg+

b vg

b vg

b vg+

b vg

b vg

b vg

b vg

b vgb vg

b vg

b vg

b vg

Meiosis I

Meiosis I and II

Meiosis II

Eggsb vg b vgb vg+b+ vgb+ vg+

Sperm

Wild-type F1

dihybrid(gray body,normal wings)

F1 dihybrid testcross

Recombinantchromosomes

Homozygousrecessive(black body,vestigial wings)

Gametes??

How many different kinds of gametes from male?

How many different gametes from female?

If no recombination?

With recombination?

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Figure 12.10c

b vg+ b vg b vgb vg

Recombinantchromosomes

Eggs

185Black-normal

206Gray-

vestigial

944Black-

vestigial

965Wild type

(gray-normal)

Testcrossoffspring

Sperm

b vg

b vg

b vgb vg

b vgb vgb vg

b vg b vg

Parental-type offspring Recombinant offspring

Recombinationfrequency

100 17%2,300 total offspring

391 recombinants

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Figure 12.12

Shortaristae

Blackbody

Cinnabareyes

Vestigialwings

Browneyes

Redeyes

Normalwings

Redeyes

Graybody

Long aristae(appendageson head)

Wild-type phenotypes

0 48.5 57.5 67.0 104.5

Mutant phenotypes

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1. What kind of sex determination did our ancestors have and when did the y chrosome evolve?

2. What do they mean SRY evolved from a related gene??

3. The chapter talks about SRY, what does it stand for?

4. Why do you think the Y lost its ability to recombine (other than at the tips)??

5. Why would the Y lose genes? What kinds of genes would it be unlikely to lose and why?

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6. Chimps have lost some genes as well but there seems to be many duplicated genes on the chimp Y, what might these genes be doing?

7. To review…What is the debate about in the article?

8. What are the “dying gasps of the Y chromosome”?

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Sex Determination patterns

Chromosomal determination

Remember…..we have autosomes as well as sex chromosomes

1.XX/XY -humans and drosophila

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2. ZW –birdsreversed compared to the XY system:

females are heterogametic-females have two different kinds of chromosomes (ZW)

males have two of the same kind of chromosomes (ZZ) So they are…….

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3. Haplodiploidy-insect such as ants and bees

Unfertilized eggs develop into haploid individuals, which are the males.

Diploid individuals are generally female

Males cannot have sons or fathers.

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3. Haplodiploidy-insect such as ants and bees

Unfertilized eggs develop into haploid individuals, which are the males.

Diploid individuals are generally female

Males cannot have sons or fathers.

Many females can decide the sex of their offspring by storing received sperm and either releasing it for fertilization or not.

This allows them to create more workers (who are male), depending on the status of the colony

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Environmental Sex Determination

Temperature at which egg is incubated- alligators, turtles, sex

Sometimes one sex hatches out when it is hot and the other when it is cool. Males are cool in turtles.

For others, the extreme temperatures are one sex and the middle temperature is the other. Males hatch out of middle temps in alligators.