AP Biology : Understanding Autosomal and Sex-Linked Inheritance

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #1661 : Ap Biology

Color blindness is determined by a sex-linked recessive allele found on the X chromosome. A family has a daughter that sees normally, but a son that is color blind. The mother and father both have normal vision. The maternal grandfather also has normal vision.

Based on this family history, which statement is true?

Possible Answers:

The daughter is a carrier for color blindness.

The grandmother is colorblind.

The grandmother must carry at least one allele for colorblindness.

The father is a carrier for color blindness.

Correct answer:

The grandmother must carry at least one allele for colorblindness.

Explanation:

In order to solve the problem, trace the colorblind allele all the way to the grandparent's alleles. It is possible that the daughter is a carrier, but this is not a guarantee. Males can not be carriers, as they only have one X chromosome; they either have the allele or they do not. Finally, the maternal grandmother may be colorblind, but this is not guaranteed.

All that we know is that at least one of the maternal grandmother's alleles codes for colorblindness. The maternal grandmother passed this allele to the mother. The color blind son inherits his Y chromosome from his father, and his only X chromosome from his mother; thus, the mother must be a carrier to pass down a color blind X chromosome to the son.

Example Question #1662 : Ap Biology

What is the name for a genome that contains an abnormal number of chromosomes?

Possible Answers:

Translocation

Duplication

Inversion

Aneuploid

Euploid

Correct answer:

Aneuploid

Explanation:

If cell division occurs incorrectly, and the resulting cell contains an abnormal number of chromosomes, that cell is considered to be aneuploid. Polyploidy is the presence of an entire extra copy of the genome in a cell. Euploid (true ploid) refers to a cell with the correct number of chromosomes.

Example Question #1663 : Ap Biology

Genes that are on the same chromosome are called __________.

Possible Answers:

codominant genes

epistatic genes

diploid genes

alleles

linked genes

Correct answer:

linked genes

Explanation:

Linked genes are found on the same chromosome, and do not always separate according to independent assortment. Alleles are different versions of a gene. Codominance is a mode of inheritance in which both alleles, if present, are fully expressed.

Example Question #1664 : Ap Biology

A man has a copy of an X-linked dominant trait. Is it possible for his son to also possess the trait?

Possible Answers:

None of these

No

Yes, but only if he inherits it from his father

Yes, he can inherit it from his mother or his father

Yes, but only if he inherits it from his mother

Correct answer:

Yes, but only if he inherits it from his mother

Explanation:

Although X-linked dominant traits tend to be rare, it is certainly possible that the boy would inherit it from an affected mother. A father only gives a Y chromosome to his sons. This means that the boy could not inherit the X-linked dominant trait from his father.

Example Question #1665 : Ap Biology

A human cell has 22 chromosomes in addition to a Y chromosome.  It is __________.

Possible Answers:

a male somatic cell

an ovum

a female sex cell

a female somtic cell

a sperm

Correct answer:

a sperm

Explanation:

Since the cell has a total of 23 chromosomes it must be a gamete. Recall that the diploid number for humas is 2n=46. The presence of a Y chromosome means that it corresponds to a male gamete so it must be a sperm cell.  

Example Question #11 : Inheritance

What is an autosome?

Possible Answers:

The Y chromosome

The X chromosome

Both the X and Y chromosomes

A non-sex chromosomes

Correct answer:

A non-sex chromosomes

Explanation:

Autosomes are all the chromosomes that do not determine an individual's sex. X and Y chromosomes both determine sex, and are sex chromosomes. The other 22 pairs of chromosomes are autosomes. 

Example Question #12 : Inheritance

Fertilization results in __________.

Possible Answers:

an autosome

a zygote

a haploid cell

a gamete

Correct answer:

a zygote

Explanation:

The union of two gametes is called fertilization, which results in a zygote. The zygote is a diploid cell that will grow into the entire organism.

Example Question #13 : Inheritance

A human haploid cell will have how many chromosomes?

Possible Answers:

Correct answer:

Explanation:

A haploid cell has only one set of chromosomes as compared to the two sets normally found in diploid cells. In a haploid cell there are 22 autosomes and 1 sex chromosome for a total of 23 chromosomes.   

Example Question #14 : Inheritance

When two human haploid cells fuse together the resulting cell will have how many chromosomes? 

Possible Answers:

Correct answer:

Explanation:

Haploid cells have 23 chromosomes each (22 autosomes and 1 sex chromosome) so when they fuse the resulting cell will have 46 chromosomes (44 autosomes and 2 sex chromosomes). This idea is demonstrated during fertilization, where two haploid cells (gametes) fuse to form the zygote, which is diploid.

Example Question #15 : Inheritance

A human somatic cell has how many chromosomes?

Possible Answers:

44

Correct answer:

Explanation:

A somatic cell is a diploid cell so it will have 22 pairs of autosomes and one pair of sex chromosomes for a total of 46 chromosomes.  

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