Biology - CARNES AP BIO © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings...

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

PowerPoint® Lecture Presentations for

Biology

Eighth Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp

BIG IDEA III Living systems store, retrieve, transmit and

respond to information essential to life processes.

Enduring Understanding 3.C

The processing of genetic information is

imperfect and is a source of genetic variation.

Essential Knowledge 3.C.1

Changes in genotype can result in changes in phenotype.


Essential Knowledge 3.C.1: Changes in genotype can result in changes in phenotype.

• Learning Objectives:

– (3.24) The student is able to predict how a change in

genotype, when expressed as a phenotype, provides a

variation that can be subject to natural selection.

– (3.25) The student is able to create a visual

representation to illustrate how changes in a DNA

nucleotide sequence can result in a change in the

polypeptide produced.

– (3.26) The student is able to explain the connection

between genetic variations in organisms and

phenotype variations in populations.


Alterations in a DNA sequence can lead to changes in the type of amount of the protein produced and the consequent phenotype.

• A mutation is any change in the genetic information of a

cell (or virus). Mutations are the primary source of genetic

variation.

• Mutations may involve large portions of a chromosome or

affect just one base pair of nucleotides.

• DNA mutations can be positive, negative or neutral based

on the effect or the lack of effect they have on the resulting

nucleic acid or protein and the phenotypes that are

conferred by the protein.

• If the mutation is in a cell that gives rise to a gamete, it may

be passed on to offspring.


Types of DNA Mutations

• Point mutations can are chemical changes in just one base

pair of a gene.

• The change of a single nucleotide in a DNA template strand can

lead to the production of an abnormal protein.


Types of Point Mutations

• Point mutations within a gene can be divided

into two general categories:

– Base-pair substitutions

– Base-pair insertions or deletions

Fig. 17-23

http://highered.mcgraw-

hill.com/sites/0072556781/

student_view0/chapter11/

animation_quiz_4.html

Wild-type

3 DNA template strand

5

5

5

3

3

Stop

Carboxyl end Amino end

Protein

mRNA

3

3

3

5

5

5

A instead of G

U instead of C

Silent (no effect on amino acid sequence)

Stop

T instead of C

3

3

3

5

5

5

A instead of G

Stop

Missense

A instead of T

U instead of A

3

3

3

5

5

5

Stop

Nonsense No frameshift, but one amino acid missing (3 base-pair deletion)

Frameshift causing extensive missense (1 base-pair deletion)

Frameshift causing immediate nonsense (1 base-pair insertion)

5

5

5 3

3

3

Stop

missing

missing

3

3

3

5

5

5

missing

missing

Stop

5

5

5 3

3

3

Extra U

Extra A

(a) Base-pair substitution (b) Base-pair insertion or deletion

http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter11/animation_quiz_4.html






Errors in DNA replication or repair mechanisms and external factors can cause random changes (mutations) in the DNA.

• Mutations can occur in a number of ways.

• Spontaneous mutations include base-pair substitutions,

insertions, deletions and longer mutations that occur during

DNA replication, repair, or recombination.

• Physical agents, such as X-rays and UV light, and various

chemical agents that cause mutations are called

mutagens.

• Whether or not a mutation is detrimental, beneficial or

neutral depends on the environmental context.


Errors in mitosis or meiosis can result in changes in phenotype.

• Nondisjunction occurs when a pair of homologous chromosomes

does not separate properly in meiosis I or sister chromatids do not

separate in meiosis II.

• As a result, a gamete receives either two or no copies of that

chromosome.

• A zygote formed with one of these aberrant gametes has a

chromosomal alteration known as aneuploidy, a non-typical number of

a particular chromosome. This can include trisomy (2n+1) or

monosomy (2n-1).

– Changes in chromosome number often result in new phenotypes,

including sterility caused by triploidy and increased vigor of other

polyploids.

– Changes in chromosome number often result in human disorders with

developmental limitations, including Trisomy 21 (Down syndrome) and

XO (Turner syndrome).

Fig. 15-13-3

Meiosis I

Nondisjunction

(a) Nondisjunction of homologous chromosomes in meiosis I

(b) Nondisjunction of sister chromatids in meiosis II

Meiosis II

Nondisjunction

Gametes

Number of chromosomes

n + 1 n + 1 n + 1 n – 1 n – 1 n – 1 n n


• Polyploidy is a condition in which an organism

has more than two complete sets of

chromosomes

– Triploidy (3n) is three sets of chromosomes

– Tetraploidy (4n) is four sets of chromosomes

• Polyploidy is common in plants, but not animals

• Polyploids are more normal in appearance than

aneuploids

Alterations of Chromosome Number


New Phenotypes Can Arise from Changes in Chromosome Number

• Sterility can be caused by triploidy:

– An extra X chromosome in a male (XXY) produces a

disorder known as Klinefelter. These individuals have

male sex organs, but the testes are abnormally small

and the man is sterile.

• Increased vigor can be seen in some polyploids:

– A common example in plants is the observation of

hybrid vigor whereby the polyploid offspring of two

diploid individuals is more vigorous and healthy than

either of the two diploid parents.


Human Disorders Due to Chromosomal Alterations

• Alterations of chromosome number and

structure are associated with some serious

disorders.

• Some types of aneuploidy appear to upset the

genetic balance less than others, resulting in

individuals surviving to birth and beyond.

• These surviving individuals have a set of

symptoms, or syndrome, characteristic of the

type of aneuploidy.

Fig. 15-16


Aneuploidy of Sex Chromosomes

• Nondisjunction of sex chromosomes produces

a variety of aneuploid conditions:

– Klinefelter syndrome is the result of an extra

chromosome in a male, producing XXY

individuals.

– Monosomy X, called Turner syndrome,

produces X0 females, who are sterile; it is

the only known viable monosomy in

humans.


Monosomy X – Turner Syndrome

XO individuals are phenotypically female, but their sex organs do not

mature at adolescence, and they are sterile. Most have normal

intelligence.


Alterations of Chromosome Structure http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter15/changes_in_chromosome_structure.html

• Breakage of a chromosome can lead to four types of

changes in chromosome structure:

http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter15/changes_in_chromosome_structure.html




Disorders Caused by Structurally Altered Chromosomes

• The syndrome cri du chat (“cry of the cat”),

results from a specific deletion in chromosome

5:

– A child born with this syndrome is mentally

retarded and has a catlike cry; individuals

usually die in infancy or early childhood.


Normal chromosome 9

Normal chromosome 22

Reciprocal translocation Translocated chromosome 9

Translocated chromosome 22 (Philadelphia chromosome)

Translocation Associated with Chronic Myelogenous Leukemia (CML)


Changes in genotype may affect phenotypes that are subject to natural selection.

• Genetic changes that enhance survival and reproduction

can be selected by environmental conditions.

• Selection results in evolutionary change.

• Illustrative examples include:

– Antibiotic Resistance Mutations

– Pesticide Resistance Mutations

– Sickle Cell Disorder and Heterozygous Advantage

– Bozeman #33:

http://www.bozemanscience.com/ap-biology/






Biology

Eighth Edition









Biological systems have multiple

processes that increase genetic variation.


Essential Knowledge 3.C.2: Biological systems have multiple processes that increase genetic variation.


– (3.27) The student is able to compare and contrast

processes by which genetic variation is produced and

maintained in organisms from multiple domains.

– (3.28) The student is able to construct an explanation

of the multiple processes that increase variation within

a population.


The imperfect nature of DNA replication and repair increases variation.

• Initial pairing errors in nucleotide placement may occur as often as 1

per 100,000 base pairs.

• The amazing accuracy of DNA replication (one error in ten billion

nucleotides) is achieved as DNA polymerases check each newly

added nucleotide against its template and remove incorrect

nucleotides.

• While the DNA proofreading and repair mechanisms are highly

accurate, sometimes errors in DNA replication are not detected. These

errors (mutations) can increase variation among individuals of the

same species and, in some cases, can be selected for among

individuals in a population.

• In Darwin’s theory of evolution by natural selection, genetic variations

present in a population result in adaptation as the individuals with the

variations best suited to an environment produce the most offspring.


The methods of horizontal acquisition of genetic information in prokaryotes increase variation.

1. Transformation (the uptake of foreign DNA from

the surrounding environment).

2. Conjugation (the direct transfer of genes from

one prokaryote to another).

3. Transduction (the transfer of genes from one

prokaryote to another via a viral vector).

4. Transposition (movement of DNA segments

within and between DNA molecules).


Transformation | Transduction | Conjugation


• R plasmids carry genes for antibiotic resistance.

• Antibiotics select for bacteria with genes that are

resistant to the antibiotics.

• Antibiotic resistant strains of bacteria are

becoming more common.

• Exposing a bacterial population to a specific

antibiotic, will kill antibiotic-sensitive bacteria but

not those that happen to have R plasmids with

genes that confer antibiotic resistance.

R Plasmids and Antibiotic Resistance


Antibiotic Resistance and the R Plasmid


Transposons http://www.youtube.com/watch?v=6vWrxt1ZCUY

• Stretches of DNA that can move about within a

genome through a process called transposition

are called transposable genetic elements, or

transposable elements.

• Transposons move about a genome as a DNA

intermediate, either by a “cut-and-paste” or a

“copy-and-paste” mechanism.

• Read Article: Barbara McClintock & Mobile

Genetic Elements

http://www.youtube.com/watch?v=6vWrxt1ZCUY


Sexual reproduction mechanisms involving gamete formation in eukaryotes serve to increase genetic variation.

• Reproduction processes that increase genetic variation are

evolutionarily conserved and are shared by various

organisms. These processes include:

– Crossing over during meiosis

– Random assortment of chromosomes during meiosis.

– Fertilization



Biology

Eighth Edition









Viral replication results in genetic variation, and

viral infection can introduce genetic variation into the hosts.


Essential Knowledge 3.C.3: Viral replication results in genetic

variation, and viral infection can introduce genetic variation into the hosts.


– (3.29) The student is able to construct an explanation

of how viruses introduce genetic variation in host

organisms.

– (3.30) The student is able to use representations and

models to describe how viral replication introduces

genetic variation in the viral population.


The basic structure of viruses includes a protein capsid that surrounds and protects the genetic information (DNA or RNA).

• Viruses are not cells.

• Viruses are very small infectious particles

consisting of nucleic acid enclosed in a protein

coat and, in some cases, a membranous envelope.

• Viral genomes may consist of either:

– Double- or single-stranded DNA, or

– Double- or single-stranded RNA

• Depending on its type of nucleic acid, a virus is

called a DNA virus or an RNA virus.


Fig. 19-3

RNA

Capsomere

Capsomere of capsid

DNA

Glycoprotein

18 250 nm 70–90 nm (diameter)

Glycoproteins

80–200 nm (diameter) 80 225 nm

Membranous envelope RNA

Capsid

Head

DNA

Tail sheath

Tail fiber

50 nm 50 nm 50 nm 20 nm

(a) Tobacco mosaic virus

(b) Adenoviruses (c) Influenza viruses (d) Bacteriophage T4


Viral replication differs from other reproductive strategies and generates variation via various mechanisms.

• Viruses have highly efficient replicative capabilities

that allow for rapid evolution and acquisition of

new phenotypes:

– They replicate via a component assembly model allowing one

virus to produce many progeny (lytic cycle).

– Viral replication allows for mutations to occur through usual host

pathways.

– Some viruses lack replication error-checking mechanisms, and

thus have higher rates of mutation.

– Related viruses can combine/recombine if they infect the same

host cell.

– Some viruses can integrate into host DNA and establish latent

(lysogenic) infection – can result in new properties for host cell.

Transcription

and manufacture of capsid proteins

Self-assembly of

new virus particles

and their exit from the cell

Entry and

uncoating

Fig. 19-4 VIRUS 1

2

3

DNA

Capsid

4

Replication

HOST CELL

Viral DNA

mRNA

Capsid proteins

Viral DNA

Reproductive Cycles of Phages

Fig. 19-5-5

Phage assembly

Head Tail Tail fibers

Assembly

Release

Synthesis of viral

genomes and

proteins

Entry of phage

DNA and

degradation of

host DNA

Attachment 1

2

4

5

3

Fig. 19-6

Phage DNA

Phage

The phage injects its DNA.

Bacterial chromosome

Phage DNA circularizes.

Daughter cell with prophage

Occasionally, a prophage exits the bacterial chromosome, initiating a lytic cycle.

Cell divisions produce population of bacteria infected with the prophage.

The cell lyses, releasing phages.

Lytic cycle

Lytic cycle

is induced or

Lysogenic cycle

is entered

Lysogenic cycle

Prophage

The bacterium reproduces, copying the prophage and transmitting it to daughter cells.

Phage DNA integrates into the bacterial chromosome, becoming a prophage.

New phage DNA and proteins are synthesized and assembled into phages.


The reproductive cycles of viruses facilitate transfer of genetic information.

• During infection, some viruses introduce variation into the

host genome in the form of DNA or RNA.

• When the host cell is bacterial, it is referred to as

lysogenesis; whereas in eukaryotic cells, this is referred to

as transformation.

• Since viruses use the host metabolic pathways, they

experience the same potential as the host for genetic

variation that results from DNA metabolism.

• Illustrative examples include:

– Transduction in Bacteria

– Transposons present in incoming DNA


Generating Genetic Variation via Lysogenic Infections

• Viral replication often allows for mutations to

occur through usual host mechanisms.

• While many prophage genes are silenced

as a viral genome “hides” in the host cell

during a latent infection, other prophage

genes may be expressed during lysogeny.

• Expression of these genes may alter the

host’s phenotype.


RNA Viruses

• Often times, the viruses that infect animals are

RNA viruses (retroviruses).

• Retroviruses are RNA viruses that are

equipped with an enzyme called reverse

transcriptase, which transcribes an RNA

template into DNA, providing an RNADNA

information flow, the opposite of the usual

direction.

• RNA viruses lack replication error-checking

mechanisms, and thus have higher rates of

mutation.

Fig. 19-8

https://highered.mcgraw-

hill.com/sites/0072495855/

student_view0/chapter24/

animation__hiv_replication

.html

Glycoprotein Viral envelope

Capsid

RNA (two identical strands) Reverse

transcriptase HIV

HIV Membrane of

white blood cell

HIV entering a cell

0.25 µm

Viral RNA

RNA-DNA hybrid

HOST CELL

Reverse transcriptase

DNA

NUCLEUS

Provirus

Chromosomal DNA

RNA genome for the next viral generation

mRNA

New virus

New HIV leaving a cell

https://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter24/animation__hiv_replication.html







Emerging Viruses

• Emerging viruses are those that appear

suddenly or suddenly come to the attention of

scientists

• Severe acute respiratory syndrome (SARS)

recently appeared in China

• Outbreaks of “new” viral diseases in humans

are usually caused by existing viruses that

expand their host territory


Absence of Replication Error-Checking Mechanisms

• RNA viruses lack replication error-checking mechanisms, and thus have higher rates of mutation.

• This often leads to emerging viruses and epidemics within populations.

– An error in replicating the genome of an RNA virus is not corrected by proofreading.

– Some mutations change existing viruses into new genetic varieties that can cause disease.


Emerging Viruses


Fig. 19-UN1

Phage

DNA

Bacterial

chromosome

The phage attaches to a

host cell and injects its DNA

Prophage

Lysogenic cycle • Temperate phage only • Genome integrates into bacterial chromosome as prophage, which (1) is replicated and passed on to daughter cells and (2) can be induced to leave the chromosome and initiate a lytic cycle

Lytic cycle • Virulent or temperate phage • Destruction of host DNA • Production of new phages • Lysis of host cell causes release of progeny phages

Biology - CARNES AP BIO © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings...

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Transcript of Biology - CARNES AP BIO © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings...