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Biology . DNA RNA Thymine Guanine Cytosine Hydrogen bond Adenine Uracil Replication Protein synthesis. mRNA tRNA rRNA Transcription Translation Amino acids Ribosome Peptide bond Watson & Crick Chromatin histones. Vocabulary. 12–1 DNA.

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Biology l.jpg
Biology

Copyright Pearson Prentice Hall


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DNA

RNA

Thymine

Guanine

Cytosine

Hydrogen bond

Adenine

Uracil

Replication

Protein synthesis

mRNA

tRNA

rRNA

Transcription

Translation

Amino acids

Ribosome

Peptide bond

Watson & Crick

Chromatin

histones

Vocabulary


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12–1 DNA

  • Scientists discovered that the nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next.

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The Components and Structure of DNA

The Components and Structure of DNA

DNA is made up of nucleotides.

A nucleotide is a monomer of nucleic acids made up of:

  • Deoxyribose – 5-carbon Sugar

  • Phosphate Group

  • Nitrogenous Base

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The Components and Structure of DNA

There are four kinds of bases in in DNA:

  • adenine

  • guanine

  • cytosine

  • thymine

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The Components and Structure of DNA

Chargaff's Rules

Erwin Chargaff discovered that:

  • The percentages of guanine [G] and cytosine [C] bases are almost equal in any sample of DNA.

  • The percentages of adenine [A] and thymine [T] bases are almost equal in any sample of DNA.

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The Components and Structure of DNA

X-Ray Evidence 

Rosalind Franklin used X-ray diffraction to get information about the structure of DNA.

She aimed an X-ray beam at concentrated DNA samples and recorded the scattering pattern of the X-rays on film.

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The Components and Structure of DNA

The Double Helix 

Using clues from Franklin’s pattern, James Watson and Francis Crick built a model that explained how DNA carried information and could be copied.

Watson and Crick's model of DNA was a double helix, in which two strands were wound around each other.

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The Components and Structure of DNA

DNA Double Helix

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The Components and Structure of DNA

Watson and Crick discovered that hydrogen bonds can form only between certain base pairs—adenine and thymine, and guanine and cytosine.

This principle is called base pairing.

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12–1

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12–1

Avery and other scientists discovered that

  • DNA is found in a protein coat.

  • DNA stores and transmits genetic information from one generation to the next.

  • transformation does not affect bacteria.

  • proteins transmit genetic information from one generation to the next.

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12–1

The Hershey-Chase experiment was based on the fact that

  • DNA has both sulfur and phosphorus in its structure.

  • protein has both sulfur and phosphorus in its structure.

  • both DNA and protein have no phosphorus or sulfur in their structure.

  • DNA has only phosphorus, while protein has only sulfur in its structure.

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12–1

DNA is a long molecule made of monomers called

  • nucleotides.

  • purines.

  • pyrimidines.

  • sugars.

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12–1

Chargaff's rules state that the number of guanine nucleotides must equal the number of

  • cytosine nucleotides.

  • adenine nucleotides.

  • thymine nucleotides.

  • thymine plus adenine nucleotides.

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12–1

In DNA, the following base pairs occur:

  • A with C, and G with T.

  • A with T, and C with G.

  • A with G, and C with T.

  • A with T, and C with T.

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12-2 Chromosomes and DNA Replication

12–2 Chromosomes and DNA Replication

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DNA and Chromosomes

Many eukaryotes have 1000 times the amount of DNA as prokaryotes.

Eukaryotic DNA is located in the cell nucleus inside chromosomes.

The number of chromosomes varies widely from one species to the next.

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DNA and Chromosomes

Chromosome Structure

Eukaryotic chromosomes contain DNA and protein, tightly packed together to form chromatin.

Chromatin consists of DNA tightly coiled around proteins called histones.

DNA and histone molecules form nucleosomes.

Nucleosomes pack together, forming a thick fiber.

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DNA and Chromosomes

Eukaryotic Chromosome Structure

Chromosome

Nucleosome

DNA double helix

Coils

Supercoils

Histones

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DNA Replication

Duplicating DNA 

Before a cell divides, it duplicates its DNA in a process called replication.

Replication ensures that each resulting cell will have a complete set of DNA.

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DNA Replication

During DNA replication, the DNA molecule separates into two strands, then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template for the new strand.

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DNA Replication

New Strand

Original strand

Nitrogen Bases

Growth

Growth

Replication Fork

Replication Fork

DNA Polymerase

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DNA Replication

How Replication Occurs

DNA replication is carried out by enzymes that “unzip” a molecule of DNA.

Hydrogen bonds between base pairs are broken and the two strands of DNA unwind.

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12–2

In prokaryotic cells, DNA is found in the

cytoplasm.

nucleus.

ribosome.

cell membrane.

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12–2

The first step in DNA replication is

producing two new strands.

separating the strands.

producing DNA polymerase.

correctly pairing bases.

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12–2

A DNA molecule separates, and the sequence GCGAATTCG occurs in one strand. What is the base sequence on the other strand?

GCGAATTCG

CGCTTAAGC

TATCCGGAT

GATGGCCAG

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12-3 RNA and Protein Synthesis

12–3 RNA and Protein Synthesis

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12–3 RNA and Protein Synthesis

Genes are coded DNA instructions that control the production of proteins.

Genetic messages can be decoded by copying part of the nucleotide sequence from DNA into RNA.

RNA contains coded information for making proteins.

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The Structure of RNA

The Structure of RNA

There are three main differences between RNA and DNA:

The sugar in RNA is ribose instead of deoxyribose.

RNA is generally single-stranded.

RNA contains uracil in place of thymine.

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Types of RNA

Types of RNA

There are three main types of RNA:

messenger RNA

ribosomal RNA

transfer RNA

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Types of RNA

Messenger RNA (mRNA)carries copies of instructions for assembling amino acids into proteins.

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Types of RNA

Ribosomes are made up of proteins and ribosomal RNA (rRNA).

Ribosome

Ribosomal RNA

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Types of RNA

During protein construction, transfer RNA (tRNA) transfers each amino acid to the ribosome.

Amino acid

Transfer RNA

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Protein Synthesis

DNA

molecule

DNA strand

(template)

TRANSCRIPTION

mRNA

Codon

TRANSLATION

Protein

Amino acid


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Transcription

Transcription

DNA is copied in the form of RNA

This first process is called transcription.

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Transcription

RNA

RNA polymerase

DNA

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The Genetic Code

The Genetic Code

The genetic code is the “language” of mRNA instructions.

The code is written using four “letters” (the bases: A, U, C, and G).

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The Genetic Code

A codon consists of three consecutive nucleotides on mRNA that specify a particular amino acid.

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The Genetic Code

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Translation

Translation

Translation is the decoding of an mRNA message into a polypeptide chain (protein).

Translation takes place on ribosomes.

During translation, the cell uses information from messenger RNA to produce proteins.

Nucleus

mRNA

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Translation

The ribosome binds new tRNA molecules and amino acids as it moves along the mRNA.

Lysine

Phenylalanine

tRNA

Methionine

Ribosome

mRNA

Start codon

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Translation

Protein Synthesis

Lysine

tRNA

Translation direction

mRNA

Ribosome

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Translation

The process continues until the ribosome reaches a stop codon.

Polypeptide

Ribosome

tRNA

mRNA

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Genes and Proteins

DNA

mRNA

Protein

Codon

Codon

Codon

Single strand of DNA

Codon

Codon

Codon

mRNA

Alanine

Leucine

Arginine

Amino acids within a polypeptide

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12–3

The role of a master plan in a building is similar to the role of which molecule?

messenger RNA

DNA

transfer RNA

ribosomal RNA

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12–3

A base that is present in RNA but NOT in DNA is

thymine.

uracil.

cytosine.

adenine.

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12–3

The nucleic acid responsible for bringing individual amino acids to the ribosome is

transfer RNA.

DNA.

messenger RNA.

ribosomal RNA.

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12–3

A region of a DNA molecule that indicates to an enzyme where to bind to make RNA is the

intron.

exon.

promoter.

codon.

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A codon typically carries sufficient information to specify a(an)

single base pair in RNA.

single amino acid.

entire protein.

single base pair in DNA.

12–3

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12-4 Mutations a(an)

12–4 Mutations

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12-4 Mutations a(an)

Mutations are changes in the genetic material.

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Kinds of Mutations a(an)

Kinds of Mutations

Mutations that produce changes in a single gene are known as gene mutations.

Mutations that produce changes in whole chromosomes are known as chromosomal mutations.

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Kinds of Mutations a(an)

Gene Mutations 

Gene mutations involving a change in one or a few nucleotides are known as point mutations because they occur at a single point in the DNA sequence.

Point mutations include substitutions, insertions, and deletions.

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Kinds of Mutations a(an)

Substitutions usually affect no more than a single amino acid.

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Kinds of Mutations a(an)

The effects of insertions or deletions are more dramatic.

The addition or deletion of a nucleotide causes a shift in the grouping of codons.

Changes like these are called frameshift mutations.

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Kinds of Mutations a(an)

In an insertion, an extra base is inserted into a base sequence.

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Kinds of Mutations a(an)

In a deletion, the loss of a single base is deleted and the reading frame is shifted.

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Kinds of Mutations a(an)

Chromosomal Mutations 

Chromosomal mutations involve changes in the number or structure of chromosomes.

Chromosomal mutations include deletions, duplications, inversions, and translocations.

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Kinds of Mutations a(an)

Deletions involve the loss of all or part of a chromosome.

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Kinds of Mutations a(an)

Duplications produce extra copies of parts of a chromosome.

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Kinds of Mutations a(an)

Inversions reverse the direction of parts of chromosomes.

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Kinds of Mutations a(an)

Translocations occurs when part of one chromosome breaks off and attaches to another.

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Significance of Mutations a(an)

Significance of Mutations

Many mutations have little or no effect on gene expression.

Some mutations are the cause of genetic disorders.

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12–4 a(an)

A mutation in which all or part of a chromosome is lost is called a(an)

duplication.

deletion.

inversion.

point mutation.

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12–4 a(an)

A mutation that affects every amino acid following an insertion or deletion is called a(an)

frameshift mutation.

point mutation.

chromosomal mutation.

inversion.

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12–4 a(an)

A mutation in which a segment of a chromosome is repeated is called a(an)

deletion.

inversion.

duplication.

point mutation.

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12–4 a(an)

The type of point mutation that usually affects only a single amino acid is called

a deletion.

a frameshift mutation.

an insertion.

a substitution.

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12–4 a(an)

When two different chromosomes exchange some of their material, the mutation is called a(an)

inversion.

deletion.

substitution.

translocation.

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