BIO 325 Chapter Notes - Chapter 3: Monosomy, X-Inactivation, Karyotype

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22 Dec 2016

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Bio 325 chapter 3 sex linked - the trait must be physically located on a sex chromosome x linked dominant - -a trait that is only found on the x chromosome. If this trait is present in females, it will be expressed whether it is found on both x chromosomes or only one. Sperm and eggs in humans are this diploid - -cells or organisms that have two copies of each chromosome type. Mammals are usually this triploid - some cells or organisms can have more than two copies of each chromosome type. In females, this trait must be found on both x chromosomes in order to be expressed. If the trait is found in a male, it will be expressed genic balance - the method for sex determination is the concentration of x chromosomes. Short, broad shoulders, widely spaced nipples, shield breasts, trouble with spatial relationships. Prenatally, nearly 98% of these individuals with spontaneously abort.

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Complete the following paragraph to learn about x-linked inheritance. expressed, men, sex-linked, ... Question: Complete the following paragraph to learn about X-linked inheritance. expressed, men, sex-linked,... Complete the following paragraph to learn about X-linked inheritance. expressed, men, sex-linked, repressed, X, Y, autosomal, two, one Sex-linked alleles have a different pattern of inheritance compared to those found on ____________ chromosomes. This is because on ____________ alleles, the allele is only carried on the X chromosome and not the Y chromosome. That means that females can pass down diseased alleles to offspring through ____________ ____________ chromosomes, while males can pass down alleles through ____________ ____________ chromosome. For this reason, it is more likely that ____________ are afflicted with sex-linked diseases, because whatever allele is carried on their ____________ ____________ chromosome is ____________ .

We have discussed how recessive phenotypes are more likely to be expressed in males if the corresponding gene is found on the X-chromosome. For example, one-type of colorblindness is caused by a recessive X linked allele, and this trait is much more common inmales than females. But we have also discussed how, in placental mammals, one copy of each X chromosome is randomly silenced in female cells (X inactivation). This raisessomewhat of a paradox. Why donât half of heterozygous females exhibit colorblindness just like hemizygous males that carry the recessive allele?

Based on your under standing of Xinactivation in placental mammals, provide an explanation for why heterozygous females generally do not exhibit colorblindness despite the random silencing of one X chromosome.

b.How would your answer change if we were talking about a marsupial mammal (inwhich the paternally inherited copy of the X chromosome is inactivated in every cell)? Would you expect half of heterozygous females in a marsupial species toexhibit color blindness? Why or why not?

According to the multiplication rule of probability, the chance of crossing two pea plants that are heterozygous for height and have none of four offspring showing the recessive short phenotype is:A. Â¼ Ã Â¼ Ã Â¼ Ã Â¼.

B. Â¾ Ã Â¾ Ã Â¾ Ã Â¾.

C. (Â¼ Ã Â¼ Ã Â¼ Ã Â¼) + (Â¾ Ã Â¾ Ã Â¾ Ã Â¾).

D. Â¼ + Â¼ + Â¼ + Â¼.

E. None of the above.

What characteristic is exhibited by an X-linked trait?

a) Only females have the trait.

Females inherit X-linked traits from their maternal parent only.

c) Females can inherit a gene for an X-linked trait from either parent.

d) Males inherit X-linked traits from their paternal parent only.

e) Males can inherit a gene for an X-linked trait from either parent but normally inherit it from their fathers.

What characteristic is exhibited by a Y-linked trait?

		a) Y-linked traits appear only in male offspring of men with the trait.
		b)Y-linked traits are only passed from father to son.
		c) Y-linked traits can be passed from mother to son.
		d) Both A and B are characteristics of Y-linked traits.
		e) Both A and C are characteristics of Y-linked traits.

Which of the following codes for a phenotypic human male?

		a) XO with a copy of SRY gene on an autosomal chromosome?
		b) XXYY with one copy of the SRY gene deleted?
		c) XX with a copy of SRY gene on an autosomal chromosome?
		d) All of the above sex compliments results in a person with a sex phenotype of male.
		e) XY with the SRY gene located on an autosomal chromosome?

In Drosophila, yellow body is due to an X-linked gene (X^y) that is recessive to the gene for gray body (X⁺). A homozygous gray female is crossed with a yellow male. What are the genotypes of the F₁ progeny?

In some goats, the presence of horns is produced by an autosomal gene that is dominant in males and recessive in females. A horned female is crossed with a hornless male. The F₁ offspring are intercrossed to produce the F₂. What proportion of the F₂ females will have horns?

		a)1/2
		b)3/4
		c)1/4
		d) All
		None

a)		Females are X⁺X⁺; males are X⁺Y.
		b)Females are X⁺X⁺; males are X^yX^y.
		c)Females are X⁺X⁺; males are X^yY.
		d) Females are X⁺X^y; males are X^yY.
		e) Females are X⁺X^y; males are X⁺Y.

	Females inherit X-linked traits from their maternal parent only.
		Females can inherit a gene for an X-linked trait from either parent.
		Males inherit X-linked traits from their paternal parent only.
		Males can inherit a gene for an X-linked trait from either parent but normally inherit it from their fathers.

Males can inherit a gene for an X-linked trait from either parent but normally inherit it from their fathers.

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BIO 325 Chapter Notes - Chapter 3: Monosomy, X-Inactivation, Karyotype

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