biology 121 chapt.10-14

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Which one of the following lists the four bases
contained in DNA?

adenine, guanine, cytosine, thymine

Which one of the following lists the four bases
contained in RNA?

adenine, guanine, cytosine, Uracil

Which one of the following describes a nucleotide most completely?

nitrogen base, a sugar, and a phosphate group

What technique was most helpful to Watson and Crick?

X-ray crystallography


the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1

One strand of a DNA molecule has the base sequence ATAGGT. The complementary base sequence on the other strand of DNA will be _


A particular _____ contains the information for making a specific polypeptide, but _____ can be used to make any polypeptide.

gene and mRNA ... a ribosome and tRNA

Which one of the following statements correctly describes mRNA processing in eukaryotes?

Introns are cut out, and the resulting exons are spliced together.

In a eukaryotic cell, transcription takes place

in the nucleus

The two sugar-phosphate strands with their associated nitrogenous bases of a DNA molecule are joined to each other by __

hydrogen bonds between nucleotide bases

A geneticist found that a particular mutation had no effect on the polypeptide encoded by a gene. This mutation probably involved _

substitution of one nucleotide

A gene is usually __

the information for making a polypeptide

The number of nucleotide bases on the mRNA that together designate an amino acid is _____; this unit is called a(n) _____.

three ... codon

A mutagen causes

a change in the base sequence of DNA

Which one of the following lists the chemical components of a nucleotide?

a nitrogenous base, a sugar, and a phosphate group

Which of the following is an "emerging virus" that has a direct impact on human health?


What is the proper order of the following events in the expression of a eukaryotic gene?
1. translation
2. RNA processing

3, 2, 1

During the replication of DNA molecules,

both strands of a molecule act/serve as templates

Which of the following processes occurs in the
cytoplasm of a eukaryotic cell?


The information carried by a DNA molecule is in __

the order of the nucleotides in the molecule

Genetic information is transferred from the nucleus to the cytoplasm of eukaryotic cells in the form of _


A uracil nucleotide is a _____ nitrogenous base attached to the _____, with the 5′ carbon of the sugar attached to a phosphate group.

one-ringed ... carbon of a sugar that has an OH group at the 2′ carbon

Before a DNA virus is assembled and leaves the cell, a number of processes occur. Place these steps into the order in which they occur:
1. Viral DNA is replicated using host cell enzymes.
2. Viral receptors bind to host glycoproteins on the cell membrane.
3. Viral RNA is translated.

2, 1, 3

HIV and phage lambda both __

integrate their DNA into the host's chromosome

During translation, amino acid chain elongation occurs until

the ribosome encounters stop codons in the mRNA

The anticodon of an incoming _____ molecule, carrying its amino acid, pairs with the mRNA _____ at the ribosome

tRNA ... codon

When messenger RNA (mRNA) is being made, the RNA base _____ always pairs with the base _____ in DNA.

U ... A

After an RNA molecule is transcribed from a eukaryotic gene, portions called _____ are removed and the remaining _____ are spliced together to produce an mRNA molecule with a continuous coding sequence.

introns ... exons

The genetic information in DNA is contained in _

the sequence of nucleotides along the length of one strand of the DNA molecule

What do DNA and RNA have in common?

Both are composed of nucleotides

The flow of information in a cell proceeds ______

from DNA to RNA to protein

How does RNA polymerase know where to start transcribing a gene into mRNA?

RNA polymerase starts when the enzyme attaches to a certain nucleotide sequence called a promoter at the beginning of a gene

What type of infectious agent causes Creutzfeldt-Jakob disease in humans?

a prion

How do retroviruses, such as HIV, differ from other viruses?

They contain the enzyme reverse transcriptase.

The function of tRNA during protein synthesis is to _

deliver amino acids to the growing polypeptide chain

During translation in a eukaryotic cell

polypeptides are synthesized at ribosomes, according to instructions carried by mRNA

The process by which cells become specialized is called


Gene expression involves the flow of information from genes to proteins, which is accomplished via _____ and _____


Why, of all cell types, do embryonic stem cells (ES cells) have the greatest potential for use in the treatment of disease?

They are undifferentiated cells that have the potential to differentiate into all of the different specialized cells of the body.

The second-leading cause of death in most developed countries (following heart disease) is _____


It is possible for a cell to make proteins that last for months; hemoglobin in red blood cells is a good example. However, many proteins are not this long-lasting. They may be degraded in days or even hours. What is the advantage of short-lived proteins?

Short-lived proteins enable the cells to adjust (control) gene expression when this is critical to their well-being.

How many active X chromosomes are there in each cell of a female mammal?


Which of the following will bind to the operator of a bacterial gene?

a repressor

Tumor-suppressor genes are important in the prevention of cancer because they _

produces gene products that prevent uncontrolled cell growth

All your cells contain proto-oncogenes, which can change into cancer-causing genes. Why do cells possess such potential time bombs?

Proto-oncogenes are necessary for normal control of cell division

The lac operon of Escherichia coli, a bacterium, is composed of

three genes and two control sequences, the promoter and the operator

A breakthrough in animal cloning in the late 1990s came with the development of nuclear transplantation. Nuclear transplantation is a process whereby __

a nucleus from an adult donor is placed into a cell without a nucleus, put in culture to produce an early embryo, and implanted into a surrogate mother

Using a cell taken from a multicellular organism to grow a genetically identical new organism is called


Although all of the cells in your body contain a complete set of DNA, different types of cells arise because___

different genes are switched on and off in each type of cell

What kinds of somatic cell gene mutations can frequently lead to the first stages of cancer?

mutations in genes that regulate cell division

who determined the structure of DNA?

Watson and Crick

DNA synthesis can be described as __________meaning it is a half old and half new replicated strand.


who first pictured DNA and determined it is a double helix structure?


what is the 3 steps of transcription?

1.Initiation-RNA polymerase attaches to the promoter.first few RNA bases are added
2.Elongation-more RNA is added.RNA detaches from DNA,DNA reattaches.
3. Termination-RNA polymerase reaches terminator sequence.RNA &RNA polymerase detaches from DNA. DNA reattaches

what is the 3 steps of translation?

1Initiation-rRNA makes up the ribosome. mRNA carries the genetic code. tRNA brings first amino acid
2.Elongation-additional amino acids are added
codon recognition-(anti-codon) tRNA base pairs with mRNA (codon). Peptide bond formation-joins amino acids translocation-ribosomes moves to the next codon
3. Termination-ribosome reaches a stop codon. no corresponding tRNA. ribosome and polypeptide are released. ribosome and mRNA can be re-used


sequence of amino acids


coiling or folding of chain


3d shape.

Proper __ is needed for proper __

structure and function

proteins control____


P site

holds tRNA and growing amino acid chain

A site

holds incoming tRNAs

major component of ribosome


during S phase of interphase what occurs

DNA replication

function of DNA

each gene is responsible for the production of one polypeptide


DNA serves as a template for the synthesis of RNA

where does transcription occur in


in transcription RNA moves into



RNA directs the assembly of amino acids to form proteins

where does translation occur in


DNA---------------- RNA --------------Protein
transcription translation

steps from DNA to Proteins


single stranded nucleic acid

the two important nucleic acids



carries protein-building instructions


major component of ribosomes


delivers amino acids of ribosomes

all 3 are produced by


all 3 are needed for


Prokaryotic is different from Eukaryotic because

no nucleus, RNA is available for translation immediately

Eukaryotic is different from Prokaryotic because

transcription occurs in the nucleus. most be transported to cytoplasm to interact with ribosomes. Allow for additional processing prior to translation


addition of 5'cap


addition of ~250 As to 3' end of mRNA


removal of introns, join of exons

the genetic code is

carried on the mRNA

mRNa bases are read

in 3s

each three base sequence

one codon

each codon specifies

one amino acid

there are total of how many genetic code


specify amino acids


3 are stop codons; they

stop translation

gene mutations

change in the nucleotide sequence of DNA

mutations in the DNA of germ cells can be passed on

next generation

point mutation

change of a single base


doesn't change the amino acid sequence


changes a single amino acid

which is the most common mutations


which is the less common mutations

silent mutant





an example of gene mutation


sickle cell anemia is trait in

heterozygous,normal phenotype

noncellular infectious agents



no cytoplasm,ribosomes,organelles,metabolism


viruses that infect bacteria

virus attaches to

cell membrane

viral RNA is translated into viral proteins

by host cell machinery

viral proteins assemble into viral particles and

leave the cell

in HIV life cyle: virus enter the


viral RNA is used

make DNA

viral DNA enters the nucleus and inserts itself into the

host chromosome

viral DNA is transcribed into

viral RNA

Viral RNA is translated into

viral protein

proteins assemble into new

viral particles

Prions:proteinaceous infective particles

attract and cause misfolding of similar proteins

diseases for prions

mad cow disease-cow

the small circular RNA~300 to 400 nucleotides
infect plant cells . don't code for any protein



abnormally folded proteins found on the surface of neurons

cell differentiation

transcription control
mRNA processing and transport
Tanslational control
Postranslational control


groups of genes that have related functions and are controlled by the same promoter

the lactose operon

three genes needed for metabolism of lactose
not needed when there is no lactose,or when glucose is abundant

DNA packaging

more tightly packaged DNA is less accessible to transcription machinery
condensed chromosomes are turned off

X chromosome Inactivation

Barr Bodies

in mammalian females

one X is shut down

randomly occurs at the __
*indendepently in each cell

200 cell stage

in x chromosome inactivation: Dosage Compensation-

prevents over expression of genes
*females and males have similar expression of X-linked traits

in x chromosome inactivation:Mosaic-

different tissues exhibit different gene expression(maternal X or parternal X)

transcription factors

proteins that bind to enhances and promoters to recruit RNA polymerase


proteins that bind to silencare to inhibit transcription

mRNA processing

must be completed BEFORE leaving nucleus
delaying processing delays translation
alternative splicing leads to alternative proteins

mRNA stability

more stable,more expression


small RNA molecules that decrease gene expression
target mRNA for degradation
inhibit translation destroy or die

initiation of translation

primary means of controlling gene expression
regulatory proteins bind to either enhance or inhibit translation

posttranslational control


protein modification

after synthesis,modifications are required

every cell contains all of the genes needed for the

entire organism

cells can_____to make different types of cells



only mechanism for commerical production

orchids are used to

reproduce plants with desirable trait
*high yields
*disease resistance

Animal Cloning

Cloning adult cells results in offspring that are NEARLY identical to donor. Maternal Twins are natural clones.Mitochondrial DNA is inherited from egg donor

Preserve valuable genetics

Scamper, Second Chance
Produce identical animals for research purposes
Producing transgenic offspring

Undifferentiated cells

can develop into many cell types. in adults.

Make up human embryos

Embryonic stem cells can develop into 300 different cell types

stem cells: Sources

From spare embryos left over from fertility treatments / informed consent.From cloned human embryos developed in the laboratory

Possible uses of stem cells

To repair / replace damaged human tissue.
Treat / cure diseases and injuries

examples of use of stem cells

Parkinson's, stroke, diabetes


genes that cause cancer.Often growth factors

Tumor suppressor genes

prevent uncontrolled cell growth

Result of several mutations in DNA

Step 1: Uncontrolled cell growth
Oncogenes turned on
Step 2: Tumor formation
Tumor supressor genes turned off
Step 3: Metastasis
More tumor supressor genes turned off

____ of certain alleles increase a person's risk of developing cancer


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