Genetics progress tests 3 and 4

Which of the following statements best describes a heterochromatic region of DNA?

a chromosome region with few expressed genes, repetetive DNA sequences, and darkly stained regions of G-banded chromosomes

Which of the following best describes the features of histones?

the five types of histone proteins in chromatin are basic proteins with a positive charge that allows them to bind to DNA as part of the chromatin structure

The compaction leading to a metaphase chromosome in eukaryotes involves which of the following?

all of these statements - five major types of histones (H1, H2A, H2B, H3, H4), the formation of the 30nm fiber, a structure with 6-8 nucleosomes per turn and histone H1 stabilizing the solenoid, anchoring and further compaction of the loops onto a scaffold

Which term describes a fruit fly that has a total of 7 chromosomes because it is missing one copy of chromosome 3?

aneuploid

If the haploid number for a plant species is 14, how many chromosomes are found in the somatic cell fo a member of the species that is diploid, monosomic, trisomic, and tetraploid respectively?

28, 27, 29, 56

A human germ cell experiences a meiotic disjunction of chromosome 21 in meiosis 1. Which of the following statements best describes the pattern you would expect to observe in the resulting gametocytes?

two cells will have 24 chromosomes, and two cell will have 22 chromosomes

A boy with Klinefelter syndrome (47,XXY) is born to a mother who is phenotypically normal and a father who has the X-linked skin condition called anhidrotic ectodermal dysplasia. The mother's skin is completely normal with no signs of the skin abnormality. In contrast, her son has patches of normal skin and patches of abnormal skin. Which parent contributed the abnormal gamete, when did the meiotic mistake occur, and explain the son's skin phenotype.

The father must have contributed the abnormal X-linked gene, nondisjunction must have occured during meiosis 1, and the son's mosaic phenotype is caused by X-chromosome inactivation (a form a dosage compensation in mammals)

Certain trees are known to occur with several different chromosome numbers. Individuals with the somatic chromosome numbers of 28, 56, 70, and 84 have been identified. With regard to chromosome number, what designation would be given to a tree with 56 chromosomes?

tetraploid

Which human condition can result from a chromosome 7 with a nonfunctional hybrid PMS-A PMS-B gene, and a deletion of the PMS-A, PMS-B, and the 17 genes between them?

Williams-Beuren syndrome

The figure shows the structure of a series of fruit fly deletion mutations. The gap in each line represents the segment of the chromosome that is deleted in each mutant. Strains that were heterozygous for each deletion mutation and a point mutation (A, B, C, D, E, F) were created and analyzed for wild-type (+) or mutant (-) phenotype. The results of the analyses are shown in the table. Which of the following is the correct order of the six point mutations on the chromosome?

E, D, C, A, F, B

A normal chromosome and its homolog carrying an inversion are given. The dash represents the centromere.

Normal: MN-OPQRST

Inversion: MQPO-NRST

What type of inversion is present and what is the name of the structure that will form during synapsis?

pericentric, inversion loop

A normal chromosome and its homolog carrying an inversion are given. The dash represents the centromere.

Normal: MN-OPQRST

Inversion: MQPO-NRST

If there is a crossover between P and Q, which of the following are the recombinant gametes?

MN-OPQM

TSRN-OPQRST

Which of the following sets of gametes would result from alternate segregation in reciprocal balanced translocation heterozygotes?

set 2

Individuals with familial Down syndrome have ___ chromosomes in their somatic cells, including a/an _____________

46, 14/21 Robertsonian translocation

How does RNA polymerase use DNA to synthesize an mRNA strand during transcription?

the polymerase uses one template strand of DNA to assemble a complementary, antiparallel strand of ribonucleotides

Where would you expect to observe coupling of transcription and translation?

in the cytoplasm of prokaryotes

There is a substantial difference between the number of genes and the number of proteins in many eukaryotic genomes, especially those of mammals. It is common for large eukaryotic genomes to express more proteins than there are genes in the genome. Which mechanism involves post-translational processing of identical pre-mRNAs leading to different mature mRNAs?

alternative intron splicing

What happens during the process of "scanning" in eukaryotic translation?

the small ribosomal subunit moves along the 5' UTR in search of the start codon

During _____, the RNA polymerase core enzyme and sigma subunit bind to the -10 censensus sequence (Pribnow box) double-stranded promoter in _____

transcription, prokaryotes

During _____, enhancers bind activator proteins to form a protein 'bridge' that bends DNA in _____

transcription, eukaryotes

During _____, mRNA is elongated by RNA polymerase adding ribonucleotides to 3' end in _____

transcription, both prokaryotes and eukaryotes

A tRNA contains the anticodon 5'-CAG-3'. This tRNA would pair with which mRNA codon and carry which amino acid?

5'-CUG-3', which corresponds to the amino acid leucine

Which enzyme initiates the 5' capping of the mRNA?

guanylyl transferase

Which DNA regulatory sequence interacts with activator proteins to increase the level of transcription?

enhancer

Using the codon table, which amino acid has the most possible synonymous codons?

leucine

In the presence of glucose, where is the lac repressor bound?

lacO

In partial diploid of the genotype I-P+O+Z-Y+/I+P-O+Z+Y+, synthesis of

beta-galactosidase will be uninducible and permease will be inducible

The following hypothetical genotypes have genes A, B, and C corresponding to lacI, lacO, and lacZ, but not necessarily in that order. Data in the table indicate whether beta-galactosidase is produced in the presence and absence of the inducer for each genotype. Use this data to identify the correspondence between A, B, C abd lacI, lacO, and lacZ genes.

A=lacO, B=lacZ, C=lacI

In positive control of several sugar-metabolism related operons, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. What causes and increase in CAP?

decrease in glucose and increase in cAMP

Typically, methylation of nucleosome N-terminal tails leads to

tighter packing of the chromatin and reduced transcription

You have identified a mutation in a gene that seems to decrease transcription of another gene 2000bp away from the mutation site. What regulatory sequence, which may be found within another gene, has likely been mutated in the instance?

enhancer sequence

When CpG islands are unmethylated

genes downstream of the CpG islands cannot be expressed, because the promoter region is blocked by histones

Prader-Willi syndrome is a genetic disorder involving a partial deletion of chromosome 15q on the paternal chromosome. When both copies of a gene (or chromosome) are functional but only one is expressed, this is an example of

genomic imprinting

During RNAi, what do miRNAs target for destruction?

mRNAs

5'-CTG___-3' is half of a palindromic restriction site. What is the complete sequence?

5'-CTGCAG-3'

Given the following plasmid, what are the sizes of the fragments you would expect from a NotI/EcoRI double digest?

1.5kb, 3kb, 5.5kb

Assume that a plasmid is 4000 base pairs in length and has restriction sites at the following location: 600, 1000, 2200, and 3800. Give the expected sizes of the restriction fragments following complete digestion.

400bp, 800bp, 1200bp, 1600bp

A DNA fragment is introduced into the lacZ gene of a plasmid, which also contains an ampicillin resistance gene. What is the appearance of bacteria transformed with this plasmid if they are spread on plates containing ampicillin and Xgal?

white colonies that are resistant to ampicillin

Which of the following is true of the sequences found in DNA libraries from human tissue?

those in a muscle cDNA library should all be present in a brain genomic library

You set up an EcoRI restriction digest for a sample of genomic DNA from an individual with a hemoglobin mutation. To your surprise, you notice a different pattern of bands in the affected individual - you have identified a new SNP! What can you conclude from the pattern of bands from the gel below?

The SNP resulted in the creation of a new EcoRI site

Which of the following is not an assumption of the Hardy-Weinberg equilibrium?

natural selection operates

DNA from 100 unrelated people was digested with the restriction enzyme BamHI, and the resulting fragments were seperated and probed with a sequence for a particular gene. Three fragment lengths that hybridized with the probe were observed - namely 4.0, 6.0, and 8.0kb - where each fragment defines a different restriction fragment allele. The accompanying illustration shows the gel patterns observed; the number of individuals with each gel pattern is shown across the top. What is the allel frequency of the 4.0kb allele?

0.25

The incidence of Tay Sachs, an autosomal recessive genetic disorder, is approximately 1 in 3,500 in a certain population of Ashkenazi Jews. Assuming Hardy-Weinberg equilibrium, what is the frequency fo carriers for the Tay Sachs allel in this population?

3.3%

The incidence of phenylketonuria (PKU), an autosomal recessive genetic disorder, is approximately 1 in 4,500 in Ireland. Assuming Hardy-Weinberg equilibrium, what is the probability that an Irish female, who is phenotypically normal with no family history of PKU, and an Irish male, who like his parents does not have PKU but has a sister who does, will have a child with PKU?

0.49%

The most common form of color blindness, known as red-green blindness, is an X-linked recessive trait affecting about 8% of the male population in the United States. What proportion of females would you expect to be carriers?

0.147

During a University of Reno Nevada blood donation campaign, the frequencies of alleles determining the ABO blood groups were determined to be 0.7 for IO, 0.2 for IA, and 0.1 for IB. Assuming random mating, what is expected to be the frequency of blood type A?

0.32

You are studying ABO blood groups and you know that 2.25% of the population has genotype IBIB and 30.25% of the population has type O blood. What is the expected frequency of blood type A?

42%

A researcher is studying a newly discovered gene that causes increased body weight in domesticated chickens. In a mainland population, the frequency of the A1 allele is 0.2, for this gene with two alleles. If 100 of these mainland chickens are transported to an isolated island with a population of 200 A1A1 chickens, 400 A1A2 chickens, and 400 A2A2 chickens, what would the frequency of the A1 allele be in the asmixed population?

0.382

In 1814, a few dozen British colonists founded a settlement on Tristan da Cunha. One of these individuals carried a recessive allele for retinitis pigmentosa. By the 1960s the frequency of this allele was ten times higher on Tristan da Cunha than in the original population. This is an example of which genetic effect?

genetic drift, specifically the founder effect

Use the Chi-square table to answer this question. A population of 1000 Jeffery Pines from Mt Rose have been genotyped at a gene involved in resistance to blister rust. The genotypes are: R1R1: 300, R1R2: 500. R2R2: 200. What is the Chi-squared value and do you reject your chance hypothesis?

0.10, fail to reject