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DNA, Chromosomes, and Protein Synthesis
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DNA, Chromosomes, and Protein Synthesis
DNA, Chromosomes, and Protein Synthesis
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1
Question
How does chromatin become organized into a chromosome?
Page 1
Answer
Histones cluster into groups of eight to form nucleosomes. DNA wraps around nucleosomes, forming chromatin fibers that twist into supercoiled structures, chromatids, and ultimately chromosomes.
2
Question
How do complementary base pairs allow one DNA strand to specify another?
Page 1
Answer
A pairs with T, and C pairs with G. Each base on one strand therefore determines its complementary base on the other strand.
3
Question
How does transcription differ from translation in protein synthesis?
Page 2
Answer
Transcription copies genetic instructions from DNA into RNA in the nucleus. Translation occurs at ribosomes, where the nucleotide sequence guides amino-acid assembly into a polypeptide.
4
Question
How does mitosis preserve chromosome information in daughter cells?
Page 5
Answer
DNA is replicated before cell division. During mitosis, sister chromatids separate so that two daughter cells receive identical copies of the cell’s DNA.
5
Question
How does a change in a gene’s alleles affect an inherited trait?
Page 7
Answer
Alleles are alternative forms of a gene. Their combination contributes to genotype, and the expressed genotype—together with environmental influences—contributes to phenotype.
6
Question
What does cytogenetics examine, and which techniques does it use?
Page 1
Answer
Cytogenetics studies chromosomes and their relationship to hereditary traits using cytology and microscopy techniques.
7
Question
How does molecular genetics investigate DNA?
Page 1
Answer
Molecular genetics uses biochemical techniques to study DNA structure and function.
8
Question
What roles do histone proteins play in chromatin?
Page 1
Answer
Histones protect and organize DNA. Groups of eight histones cluster to form a nucleosome around which DNA wraps.
9
Question
How do nonhistone proteins contribute to chromatin function?
Page 1
Answer
Nonhistone proteins provide structural support for chromatin and regulate gene activity.
10
Question
How does DNA packaging proceed from nucleosomes to chromatids?
Page 1
Answer
DNA wraps around nucleosomes, then twists into a chromatin fiber. Further twisting produces a supercoiled structure and chromatids; two chromatids form a chromosome.
11
Question
What measurements are given for DNA molecules in a human cell?
Page 1
Answer
The notes describe 46 DNA molecules, each averaging 44 mm in length and 2 nm in diameter.
12
Question
How wide is the supercoiled DNA structure described here?
Page 1
Answer
The supercoiled structure is 200 nm wide.
13
Question
How does chromatin-fiber diameter differ between its untwisted and twisted forms?
Page 1
Answer
The untwisted chromatin fiber is 10 nm in diameter; the twisted form is 30 nm in diameter.
14
Question
What components make up a nucleotide?
Page 1
Answer
A nucleotide consists of a sugar, a phosphate group, and a single- or double-ringed nitrogenous base. The sugar identified for DNA is deoxyribose.
15
Question
How do pyrimidines differ structurally from purines?
Page 1
Answer
Pyrimidines have a single C–N ring; purines have a double C–N ring.
16
Question
Which nitrogenous bases are classified as pyrimidines?
Page 1
Answer
Cytosine, thymine, and uracil are pyrimidines.
17
Question
Which nitrogenous bases are classified as purines?
Page 1
Answer
Adenine and guanine are purines.
18
Question
Which four bases are listed for DNA?
Page 1
Answer
DNA contains C, T, A, and G: cytosine, thymine, adenine, and guanine.
19
Question
Which four bases are listed for RNA?
Page 1
Answer
RNA contains C, U, A, and G: cytosine, uracil, adenine, and guanine.
20
Question
How does the DNA double helix arrange its backbone and bases?
Page 1
Answer
DNA forms a double helix. Its sugar-phosphate backbones lie outside, while nitrogenous bases face inward and pair with complementary bases.
21
Question
Which bases pair in DNA according to the complementary-pairing rules?
Page 1
Answer
In DNA, T pairs with A, and C pairs with G.
22
Question
Which bases pair in RNA according to the complementary-pairing rules?
Page 1
Answer
In RNA, U pairs with A, and C pairs with G.
23
Question
How can a complementary DNA sequence be predicted from one strand?
Page 1
Answer
Apply the pairing rules position by position: replace each T with A, each A with T, each C with G, and each G with C.
24
Question
What is the stated location of DNA in the cell?
Page 1
Answer
DNA is located in the nucleus.
25
Question
What is the stated function of DNA in relation to polypeptides?
Page 2
Answer
DNA serves as a code for the structure of polypeptides synthesized by a cell.
26
Question
What does a gene encode in the definition given here?
Page 2
Answer
A gene is a DNA nucleotide sequence that codes for one polypeptide.
27
Question
How is a genome defined in these notes?
Page 2
Answer
A genome is all of the genes of one person.
28
Question
What proportions of human DNA are described as coding and noncoding?
Page 2
Answer
The notes state that approximately 3% of human DNA codes and 97% does not code.
29
Question
What roles are assigned to noncoding DNA in these notes?
Page 2
Answer
The notes associate noncoding DNA with organizing chromatin and describe it as “junk” DNA.
30
Question
How does RNA generally differ from DNA in strand structure?
Page 2
Answer
RNA generally consists of one nucleotide chain with a single backbone and unpaired bases. The notes identify tRNA as an exception that folds onto itself.