Gentetics Chapter 8 HW:

Select the statements that explain why duplication is a driving force for evolution and the generation of new genes.

-Genes duplicate and then diverge from the original sequence to create novel genes. -Duplicated genes provide extra copies of DNA that are not constrained by an essential function. -Changes in gene function can occur when random fixed mutations are introduced into a new chromosomal environment.

Lesch‑Nyhan syndrome is an X‑linked, recessive condition caused by mutation of the HPRT1 gene responsible for purine metabolism. The syndrome is characterized by juvenile‑onset gout, involuntary muscle movements, and behavioral disorders. A mother and father have a young daughter who was diagnosed with Lesch‑Nyhan syndrome. No one in the father's family was ever diagnosed with the syndrome. The mother's maternal grandfather was diagnosed with Lesch‑Nyhan syndrome, but neither one of her parents was diagnosed with the condition.

-The daughter inherited two X chromosomes with the Lesch‑Nyhan mutation. Nondisjunction of the mother's X chromosomes occurred during meiosis, and the daughter inherited no X chromosome from her father. -The father did not contribute a sex chromosome to his daughter due to nondisjunction of the sex chromosomes. The daughter is XO and her only X chromosome came from her mother, who was a carrier.

Red‑green color blindness is a human X‑linked recessive disorder. The normal allele, XB, is dominant to the mutant allele, Xb. Jill has normal color vision, but her father is color blind. Jill marries Tom, who also has normal color vision. Jill and Tom have a daughter who has Turner syndrome and is color blind.

A. an ovum carrying Xb followed by fertilization by sperm from a paternal nondisjunction event (none from father) -Option A is the right answer. As in Turner's syndrome, 80% cases are due to parental nondisjunction. And in female there will be only one X so the gene which is normally recessive will express itself for color blindness.

Match the definitions to the appropriate terms that describe the number of chromosomes.

Tetraploid: 4 homologues of each chromosomes Tetrasomic: 2 EXTRA copies of of a SPECIFIC chromosome 𝑛=4: a genome composed of 4 UNIQUE chromosomes (X) PLOIDY: number of sets of homologous chromosomes TetraSOMY: is an aneuploidy condition, so it will have 2 extra single chrom. per chromosome whole therefore 4 chromatids in a chromosome rather than 2 N=X: number of chromosomes in one set is X, then the ploidy of the cell can be represented as n=X,

Familial Down syndrome is similar to primary Down syndrome in that it is caused by trisomy 21. However, in familial Down syndrome, all or part of the third copy of chromosome 21 has translocated onto another autosome, typically chromosome 14. In cases of familial Down syndrome, one of the parents of the affected child is often a carrier of a translocated chromosome. The translocation carrier parent does not have Down syndrome because he or she has a total of two copies of chromosome 21. Suppose that a woman is a translocation carrier of chromosome 21 on chromosome 14. She conceives six zygotes with a normal man who carries no aneuploidies. Match the description of the chromosomes inherited by each zygote with the viability of the zygote.

VIABLE NORMAL/TRANSLOCATION CARRIER: -two normal copies of 14, two normal copies of 21 -one normal copy of 14, one normal copy of 21, one 21 to 14 translocation VIABLE WITH DOWN SYNDROME: -one 21 to 14 translocation, two normal copies of 21, one normal copy of 14 INVIABLE: -one normal copy of 14, two normal copies of 21 -one normal copy of 21, two normal copies of 14 -two normal copies of 14, one normal copy of 21, one 21 to 14 translocation

Select the definition of polyploidy.

a chromosomal complement with at least three complete sets of homologous chromosomes

polypoidy

a chromosomal complement with at least three complete sets of homologous chromosomes

Select the definition of euploidy.

a complete chromosome set or an exact multiple of the haploid chromosome set

euploidy

a complete chromosome set or an exact multiple of the haploid chromosome set

During meiosis, errors can occur during chromosome replication. Which term describes the addition of genetic material to a chromosome through extra replication of a chromosomal section?

duplication

Two brothers have X‑linked red-green colorblind vision, and their parents have normal color vision. The first brother's karyotype is 47,XXY (Klinefelter syndrome), and the second brother's karyotype is 46,XY. In which parent and in what cell division phase did the first brother's chromosomal nondisjunction occur? Assume no recombination.

in the mother in meiosis II

During meiosis, errors can be made during chromosome replication. Which term describes a mutation where a chromosome breaks, and its genetic material is reinsterted in a different orientation?

inversion

Many errors can occur during meiosis. Which term describes the process of sister chromatids not separating at the centromere during cell division?

nondisjunction

A man has a large inversion on one of his chromosomes. How might this impact his offspring?

severe phenotypic abnormalities caused by unbalanced chromosomes (since inversion results from missing copies of genetic info)

Select the definition of aneuploidy.

the addition or loss of less than a full set of chromosomes or chromosome pairs

During meiosis, errors occur during chromosome replication. Which term describes the rearranging of genetic material between nonhomologous chromosomes without a net loss or gain of genetic material?

translocation