BIO 272W Sapling Ch. 10 & 11 HW

Place the steps of the Hershey-Chase experiment in order from first to last.

1) Radiolabel phage DNA and phage protein 2) Mix each type of phage with separate bacteria 3) Agitate to separate cells from phage bodies 4) Centrifuge to separate bacteria into a pellet 5) Measure pellet and liquid for radioactivity

Enter the complementary sequence to the following DNA strand. 5'-CGATGAGCC-3'

3'-GCTACTCGG-5'

If DNA is the transforming factor, match the expected results of each experiment by placing the appropriate mouse image.

A -> R strain (nonvirulent) = mouse alive B -> S strain (virulent) = mouse dead C -> heat-treated S strain = mouse alive D -> R strain & heat-treated S strain = mouse dead E -> R strain & heat-treated S strain with polysaccharides, lipids, RNA, and proteins destroyed = mouse dead F -> R strain & heat-treated S strain with polysaccharides, lipids, RNA, proteins, and DNA destroyed = mouse alive

Classify each feature as describing euchromatin, heterochromatin, or both.

Euchromatin: loosely packed, high level of transcription, found in prokaryotes, major state of most genes Both: state of DNA organization Heterochromatin: tightly packed, low level of transcription, major state of the inactive X chromosome

If the C content of a DNA molecule is 22%, what are the percentages of the remaining bases?

G = 22% T = 28% A = 28%

Match each description to the term it defines.

Gene: a short segment of a chromosome that codes for an RNA molecule, a functional unit of heredity Allele: one of the different forms of a gene that exists at a single locus Chromosome: threadlike DNA molecules that are visible during mitosis, large genetic element that carries genes essential to cellular function

James Watson and Francis Crick used the X-ray diffraction image taken by Rosalind Franklin shown below to deduce structural properties of B-form DNA. What findings did Watson and Crick make from this image?

Has a consistent diameter Includes 10 base pairs per repeat Shaped like a helix

Select each of the characteristics that are key features of genetic material.

It must encode the blueprint to form proteins and other structures It must periodically mutate to generate variation It must be able to replicate and transmit to progeny

Classify each feature as describing prokaryotic DNA structure or eukaryotic DNA structure.

Prokaryotic: condensed only by DNA supercoiling, does not have telomere region, arranged in a single looped structure, DNA is circular Eukaryotic: condensed around histone proteins, has repeating telomere region, arranged in multiple chromosomes, DNA is linear

Which of the following statements describes purines and pyrimidines in DNA molecules?

Pyrimidines form hydrogen bonds with purines Pyrimidines consist of a one-ring structure

Suppose that a hapless graduate student has forgotten to label four different sample tubes that contained thermophilic archaea, bacteria, single-stranded DNA viruses, and double-stranded RNA viruses. The table below shows the nucleotide content of each sample, except for the nucleotide uracil, which is excluded. Label each unknown sample with the appropriate sample name.

Sample 1: 33% guanine, 33% cytosine, 17% adenine, 17% thymine = thermophilic archaea Sample 2: 23% guanine, 23% cytosine, 27% adenine, 27% thymine = bacteria Sample 3: 19% guanine, 31% cytosine, 17% adenine, 33% thymine = single-stranded DNA virus Sample 4: 27% guanine, 27% cytosine, 23% adenine, 0% thymine = double-stranded RNA virus

Identify the key structural features of a DNA molecule.

The backbone of DNA is made of a sugar and a phosphate molecule DNA bases are always paired using Watson-Crick base pairing DNA strands are antiparallel and include a 5' end and a 3' end

Identify the statements that describe the structure of DNA.

The five-carbon sugar of DNA is called deoxyribose Adenine is paired with thymine, and guanine is paired with cytosine A DNA double helix contains two sugar-phosphate backbones oriented in opposite directions

You have performed an analysis to determine the proportions of each of the four nucleotide bases in the DNA of several tissue samples from various species. The results appear in the following table. Which conclusions can you draw from this data?

The proportion of T is roughly equal to the proportion of A. The proportion of purines is roughly equal to the proportion of pyrimidines. The proportion of C is roughly equal to the proportion of G.

Erwin Chargaff's experiments on the composition of DNA provided clues about the structure of DNA. Select the statements that describe what Chargaff discovered about the base pair composition of DNA.

The proportions of A:T base pairs and C:G base pairs are similar for members of the same species and vary between species DNA molecules contain similar numbers of A and T bases and similar numbers of G and C bases

Identify the pieces of evidence describing the features of DNA that Watson and Crick used to determine the structure of DNA.

The sugar-phosphate backbones of each DNA helix run antiparallel to one another The nitrogenous bases on each DNA helix are arranged perpendicularly to the central axis A purine base forms hydrogen bonds to pair with a pyrimidine base located on the opposite DNA strand. Specifically, A pairs with T, and C pairs with G The diameter of the DNA double helix is 2 nanometers, with each purine-pyrimidine base pair spanning an equivalent distance between the two chains