BIOL 3600 - CH.8 HW

In the fruit fly a known deletion on the X chromosome removes both a gene involved in the fly's development and the gene for eye color. The deletion is lethal when homo/hemizygous. Flies heterozygous for the mutation are viable but have indentations at the wing margin, so the deletion is named the Notch mutation. The allele for wild types is dominant over the allele for white eyes. Predict the phenotypic ratio of the offpsring from a cross between a white eyes notched female and a wild type male.

1 wild type female: 1 notched female: 1 white eyed male

Familial Down syndrome is similar to primary Down syndrome since it's caused by trisomy 21. However, in familial Down syndrome, all or part of the 3d 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 doesn't have Down syndrome because he/she has a total of 2 copies of chromosome 21. Suppose a woman is a translocation carrier of chromosome 21 on chromosome 14. She conceives 6 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. 1. viable normal or translocation carrier 2. viable with Down syndrome 3. inviable

1. 2 normal copies of 21 and 2 normal copies of 14 + 1 normal copy of 21, 1 21 to 14 translocation, and 1 normal copy of 14 2. 1 normal copy of 14, 2 normal copies of 21, and 1 21 to 14 translocation 3. 2 normal copies of 21 and 1 normal copy of 14 + 2 normal copies of 14 and 1 normal copy of 21 + 1 21 to 14 translocation, 1 normal copy of 21, and 2 normal copies of 14

Frank Castle has Klinefelter syndrome (47, XXY). His mother has normal skin, but his father has anhidrotic ectodermal dysplasia (X linked condition where the skin doesn't have sweat glands). Frank has patches of normal skin and skin without sweat glands. Complete the sentences, some answers may be used more than once or not at all. Frank received the mutant chromosome from his (1). Nondisjunction occurred in his (2) during the (3) meiotic division.

1. Father 2. Father 3. First

Place the type of translocation and sequence/s translocated next to each set of chromosomes. Nonhomologous chromosomes: AB*CDEFG, RS*TUVWX 1. AB*CD, RS*TUVWXEFG 2. AUVB*CDEFG, RS*TWX 3. AB*TUVFG, RS*CDEWX 4. AB*CWG, RS*TUVDEFX

1. nonreciprocal translocation of EFG 2. nonreciprocal translocation of UV 3. reciprocal translocation of CDE and TUV 4. reciprocal translocation of DEF and W

Place the type of chromosomal mutation next to each set of chromosomes. The * represents the centromere. wild type chromosome: AB*CDEFG 1. chromosomal mutation: AB*CDEFDEFG 2. AB*DEFCDEFG 3. AB*CDE 4. AB*CGFED 5. AEDC*BFG

1. tandem duplication of DEF 2. displaced duplication of DEF 3. deletion of FG 4. paracentric inversion that includes DEFG 5. pericentric inversion of BCDE

Define tetrasomic

2 extra copies of a specific chromosome

Assume the autotriploid cell in the image has 3n=30 chromosomes. For each of the gametes made by this cell, what would the chromosome number of the resulting zygote be if the gamete fused with a normal haploid gamete?

2n: 30 1n: 20 1n: 20 2n: 30 3n: 40 Chromosomes absent: 10

Define tetraploid

4 homologues of each chromosome

Some people with Turner syndrome are 45,X/46,XY mosaics. How could this mosaicism arise?

A cell loses a Y chromosome soon after fertilization in an XY embryo.

Describe mosaicism.

A child with the phenotypic features characteristic of Turner syndrome has a mixture of normal cells and cells with 1 copy of the X chromosome. A cancerous tumor develops in a woman's ovary. A tortoiseshell cat has patches of orange and black fur.

The Notch mutation is a deletion on the X chromosome of Drosophila melanogaster. Female flies heterozygous for Notch have an indentation on the margins of their wings. Notch is lethal in the homozygous and hemizygous conditions. The Notch deletion covers the region of the X chromosome that contains the locus for white eyes, an X‑linked recessive trait. Determine the phenotypes and proportions of progeny produced by the crosses listed in the table below. Cross - Parental Phenotypes A - red eyed Notch female × white eyed male B - white eyed Notch female × red eyed male C - white eyed Notch female × white eyed male

A only: 1/3 wild type males B only: 1/3 red eyed Notch females C only: 1/3 white eyed females A&B only: 1/3 wild type females A&C only: 1/3 white eyed Notch females B&C only: 1/3 white eyed males

Species A has 2n=8 chromosomes and Species B has 2n=14 chromosomes. Calculate all possible chromosome numbers for the following individuals, not all answers will be used.

Allotiploid AB offpsring: 15 and 18 Autotetraploid A offspring: 16 Allotetraploid AB offspring: 19, 22, and 25 Monosomic B: 13 Uniparentaldisomic A: 8 Tetrasomic A: 10

Red/green color blindness ia a human X linked recessive trait. The normal allele X^B is dominant to the mutant allele X^b. Marlene has normal color vision but her father is color blind. Marlene marries Guillermo who also has normal color vision. Marlene and Guillermo have a daughter who has Turner syndrome and is color blind. How and whom did the daughter inherit color blindness?

An ovum with X^b followed by fertilization by sperm from a paternal nondisjunction event

Barney and Clair are parents of child A. Marshal and Lily are parents of child B. Robin and Ted are parents of child C. All children have Down syndrome. A Southern blot is used to analyze the restriction fragment length polymorphisms (RFLPs) of the parents and their children. Since trisomy 21 is the major cause of Down syndrome, a probe complementary to a sequence of chromosome 21 is used for RFLP detection. Thicker bands on the blot indicate the presence of 2 RFLPs os the same fragment length. Label each child with the nondisjunction event that made her/his RFLP pattern.

Barney/Clair/Child A: meiosis I in mother Lily/Marshal/Child B: meiosis II in father Robin/Ted/Child C: undetermined

~0.3% of human live births are trisomic, while only 0.02% are monosomic. What's the best explanation for why the occurrence of monosomics is less than trisomics?

Deleterious recessive alleles are always expressed on the monosomic chromosome but not on the trisomic chromosomes

The variety of bananas typically eaten in N.America and Europe don't contain seeds, so cannot reproduce. The plants that grow these bananas are clones of a single parent plant that have been derived through natural selection and selective breeding. In the 1950s, the Gros Michel banana was the most common banana and was nearly eradicated by disease. As a result, the most common variety today is the Cavendish banana. Due to increasingly devastating diseases that attack the cloned Cavendish bananas, researchers in Belgium have created banana cultivars that are resistant to disease. However, many countries do not wish to use these resistant bananas because they are genetically modified organisms, also called GMOs. Select the arguments for GMO bananas. Select the arguments against GMO bananas.

For: Banana clones are infertile and can't readily hybridize with resistant cultivars. Iinserting the resistance gene is more precise than hybridization. Against: GMO bananas can be patented and can outcompete local varieties. Little is known regarding human health and GMO bananas

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 multigene families, changes in gene function can occur when random fixed mutations are introduced into a new chromosomal environment, and duplicated genes provide extra copies of DNA that aren't constrained by an essential function.

Using breeding techniques, A. Dylan and V.S. Baranov created trisomic mice for each of the different mouse chromosomes and found only mice with trisomy 19 developed fully. Mice trisomic for all other chromosomes died during development. For some of these trisomics, they compared the length of development before the embryo died as a function of the size of the chromosomes present in 3 copies. What best describes the findings based on the graph? What's the best explanation for the results?

Mice trisomic at small chromosomes survived longer than mice trisomic at larger chromosomes, and there is an inverse relationship between size of the trisomic chromosome and the length of embryonic development. Being trisomic for larger chromosomes affects the dosage of more genes and is more detrimental, causing development to cease at an earlier stage.

Suppose species 1 in the figure has 2n=10 and species 2 has 2n=12. How many chromosomes would be present in the allotetraploid in the figure?

Number of chromosomes: 22

Describe the effectof copy number variation on human phenotypes.

Oncogene overexpression due to a gain in copy number can cause cancer. Increase in the copy number of genes involved in starch digestion allows for a high starch diet. Copy number variations are associated with polygenic disorders like schizophrenia.

Suppose 6 populations of sharks from 6 different geographic locations were genetically analyzed. It was determined each of the 6 populations had a different arrangement of chromosome 7. The banding pattern of the ancestral chromosome was numbered 98765432. Variant 1: Order A=98755432, B=53549732, C=97855432, D=53549732 Variant 2: A=97855432, B=853549732, C=98755432, D=85549732 Variant 3: A=85549732, B=85549732, C=853549732, D=853549732 Variant 4: A=853549732, B=97855432, C=85549732, D=97855432 Variant 5: A=53549732, B=98755432, C=53549732, D=98755432 What order did the other 5 variants of chromosome 7 most likely arise? Suppose the banding pattern variation for chromosome 2 in sharks arose in the given order. The ancestral chromosome is numbered 7654321. Identify which chromosomal modifications are responsible for the banding pattern changes seen in each of the novel chromosomes. 76543210 —(1)—> 74563210 —(2)—> 74563211 —(3)—> 745563211 —(4)—> 732145561 —(5)—> 73214556

Order A 1. Inversion 2. Mutation 3. Duplication 4. Translocation 5. Deletion

Lesch‑Nyhan syndrome is an X‑linked/recessive condition caused by mutation of the HPRT1 gene responsible for purine metabolism. The syndrome's characterized by juvenile‑onset gout/involuntary muscle movements/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. Select all the descriptions that could explain how their daughter inherited Lesch‑Nyhan syndrome.

The father didn't contribute a sex chromosome to his daughter by nondisjunction of the sex chromosomes, the daughter is XO and her only X chromosome came from her mother who was a carrier. The mother's X chromosomes failed to separate during meiosis and the daughter inherited 2 X chromosomes with the Lesch-Nyhan mutation while the father didn't contribute sex chromosomes.

Progeny of triploid tomato plants often have parts of an extra chromosome with the normal complement of 24 chromosomes. Mutants with a part of an extra chromosome are referred to as secondaries. James and Margaret Lesley observed secondaries arise from triploid (3n), trisomic (3n + 1), and double trisomic (3n + 1 + 1) parents, but never from diploids (2n). What is a possible reason secondaries arise from parents with unpaired chromosomes but not from parents with normal diploids?

The trivalent chromosomes would still be able to associate through chiasma prior to segregation during meiosis

Define polyploidy

a chromosomal complement with at least 3 complete sets of homologous chromosomes

Define n=4

a genome composed of 4 unique chromosomes

Give examples of how fragile sites can be responsible for phenotypic abnormalities.

decreased gene dosage from damage induced copy loss, disruption of tumor suppressor genes causes tumor formation, and loss of gene function due to centromere loss

2 brothers have X‑linked red-green colorblind vision, and their parents have normal color vision. The 1st brother's karyotype is 47,XXY (Klinefelter syndrome), and the 2nd brother's karyotype is 46,XY. What parent and in what cell division phase did the first brother's chromosomal nondisjunction occur? Assume no recombination.

in the mother in meiosis II

Aneuploidy is an umbrella term referring to multiple kinds of conditions where an individual has an abnormal number of chromosomes for their species. Some of the patients on the abnormal tab of the karyotype virtual interactive suffer from different types of aneuploidy. Use the interactive to determine from which form of aneuploidy patient 367 suffers.

monosomy

Crossing over in a pericentric inversion makes chromosomes have extra copies of some genes and no copies of other genes. The fertilization of gametes with these duplication/deficient chromosomes often results in children with syndromes characterized by developmental delay/mental retardation/abnormal development of organ systems/early death. 1 study examined individual sperm cells of a male heterozygous for a pericentric inversion on chromosome 8 and determined crossing over took place within the pericentric inversion in 26% of the meiotic divisions. Assume a man and woman are phenotypically normal, but the woman is heterozygous for a pericentric inversion on chromosome 8. The man is karyotypically normal. What's the probability this couple's child will inherit a duplicated/deficient chromosome 8 that results from crossing over in this pericentric inversion?

probability: 13%

A man has a large inversion on 1 of his chromosomes. How might this impact his offspring?

severe phenotypic abnormalities caused by unbalanced chromatids

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

translocation

The image is part of a virtual karyotype of a tumor from a leukemia patient. What specific chromosomal changes can be detected based on this karyotype?

trisomy 12 and heterozygous deletion in half of chromosome 11