biology 10

The arrangement of parts within D N A affects

The arrangement of parts within D N A affects

its actions within a cell, e.g. → relationship of structure to function.

DNA & RNA are

nucleic acids

polynucleotide

DNA & RNA are nucleic acids that consist of long chains polymers

monomers

nucleotides

sugar-phosphate backbone

repeating pattern of sugar-phosphate-sugarphosphate

monomers are nucleotides that are joined together by

covalent bonds between the sugar of one and the phosphate of the next

Each nucleotide consists of three components

a nitrogenous base

a sugar

a phosphate group

DNA- deoxyribose sugar

missing an oxygen atom

RNA

ribose sugar

thymine (T) and cytosine (C)

single-ring structures

adenine (A) and guanine (G)

larger, double-ring structures

double helix sides

sugar-phosphate backbones connected by phosphodiester bonds

each rung of double helix

a pair of bases connected by hydrogen bonds

double helix base pairing rings

dictate the combos of bases

During cell reproduction

DNA must duplicate

one copy to the new offspring cell while keeping one copy for itself

Each strand of DNA serves as a template to

guide reproduction of the other strand

DNA Replication: The players

ENZYME

helicase

unzipping the DNA helix

primase

Synthesizing an RNA primer

DNA polymerase III

adding bases to a new DNA chain
proofreading the chain for mistakes

DNA polymerase I

Removing RNA primers replacing gaps between ozakai fragments with correct nucleotides, repairing mismatched bases

Ligase

final binding of nicks DNA during synthesis and repair

gyrase

supercoiling

origins of replication

DNA replication begins on a double helix at specific sites & proceeds in both directions, creating what are called replication “bubbles”

DNA provides instructions to

a cell and the organism as a whole

An organism’s genotype= its genetic makeup

is the heritable information contained in the sequence of nucleotide bases in its DNA.

The phenotype,= the organism’s physical traits

arises from the actions of a wide variety of proteins

Information flow

DNA specifies the synthesis of proteins

How does an Organism’s Genotype Determines Its Phenotype

information flow

transcription

translation

transcription

the transfer of genetic information from DN A into an RNA molecule

translation

conversion between the nucleic acid language to the protein language

DNA is linear sequence of

nucleotide bases

When a gene is transcribed, the result is

a RNA molcule

DNA is simply rewritten (transcribed) as a

sequence of bases of RNA

The sequence of nucleotides of the RNA molecule dictates

the sequence of amino acids of the polypeptide

gene to protein is based on

a triplet code

codons

Triplet code: three base series

codons are transcribed (copied) as

a complement to the RNA

RNA codons are translated into

amino acids that together form a polypeptide

genetic code

is the set of rules that convert a nucleotide sequence in RNA to an amino acid sequence

how many triplet codons

64

61 code for amino acids

one specifying start

3 are stop codons

instructing the ribosomes to end the polypeptide

A given RNA triplet always

specifies a given amino acid

Wobble base

triplet codons allow for error in the code

Allows for some mistakes

The genetic code is

nearly universal

the genetic code is shared

by organisms from the simplest bacteria to the most complex plants and animals

Genetic engineering

because diverse organisms share a common genetic code, we can program one species to produce a protein from another species by transplanting DNA

Genetic engineering allows scientists

to mix & match genes from various species, with many useful genetic engineering applications in agriculture, medicine, and research

Nucleotides added to the new RNA molecule

take their place one at a time by forming hydrogen bonds with the nucleotide bases there

process of transcription

two DNA strands must first separate at the place where the process will start

only one of the DNA strands serves as a

template for the newly forming RNA molecule; the other strand is unused

RNA nucleotides linked by

RNA polymerase

hydrogen bonds with the nucleotide base

U, with T, rather than A.

promoter

“Start transcribing” signal is at the

Initiation & Elongation

located in the DNA code at the beginning of the gene and specifies where RNA polymerase attaches

Initiation

the attachment of RNA polymerase to the promoter and the start of RNA synthesis

Elongation

the RNA grows longer and the RNA strand peels away from its DNA template

the DNA strands rejoin

Termination

RNA polymerase reaches a terminator, signaling the end of the gene

polymerase detaches from the RNA & the gene

the DNA strands rejoin completely

transcriptions stages

1.initiation

2.elongation

3.termination

Prokaryotes

RNA transcribed from a gene immediately functions as messenger RNA (mRNA), the molecule translated into protein.

Eukaryotic cell

localizes transcription in the nucleus and processes the RNA transcripts before they move to the cytoplasm for translation

RNA processing

1. adding nucleotides: the cap & tail, that marking the mRNA for export from the nucleus & recognition by ribosomes

2. RNA splicing

RNA splicing

taking out non-coding regions (introns) leaving only exons (coding regions- the parts that are expressed)

mRNA produced by transcription requires

Ribosomes

tRNA- transfer RNA as an interpreter to match codons to amino acids to form the appropriate polypeptide

ATP to be translated

To perform this task, tRNA molecules must carry out two distinct functions:

1. pick up the appropriate amino acids

2. recognize the appropriate codons in the mRNA

The unique structure of tRNA molecules enables them to perform both tasks

Ribosomes

organelles in the cytoplasm that coordinate the functioning of mRNA and tRNA & make polypeptides.

ribosomes consists of

two subunits, each is made up of proteins & ribosomal RNA (rRNA)

ribosomes has

a binding site for mRNA on its small subunit and binding sites for tRNA on its large subunit

Translation: The Process

divided into the same three phases as transcription: 1. initiation, 2. elongation, and 3. termination.

Initiation: translation

1. An mRNA molecule binds to a small ribosomal subunit, then a special initiator tRNA binds to the start codon, where translation is to begin on the mRNA.

2. A large ribosomal subunit binds to the small one, creating a functional ribosome

After initiation is complete in translation

amino acids are added one by one to the first amino acid during elongation

Three-step elongation process: translation

1.Codon recognition

2. Peptide bond formation

3. Translocation

Termination: translation

1. a stop codon reaches the ribosome’s A site

2. the completed polypeptide is freed,

3. the ribosome splits back into its subunits.

Mutation

Any change in the nucleotide sequence of a cell’s DNA

mutation can

involve large regions of a chromosome or just a single nucleotide pair

within a gene can be divided into two general categories:

nucleotide substitutions & nucleotide insertions or deletions

Missense mutations

a single nucleotide & change the AA coding

Nonsense mutations

change of a normal codon into a stop codon

Deletions or insertions

of one or more nucleotides in a gene cause frameshift mutations

Deletions/ insertions

often have disastrous effects

may alter the triplet grouping of the genetic message

most often produces a nonfunctioning polypeptide

Mutations can occur

in a number of ways

Spontaneous mutations result from

random errors during DNA replication or recombination

spontaneous mutations result from

random errors during DNA replication or recombination

mutagens

physical & chemical agents

most common physical mutagen is

high-energy radiation

many mutagens can act as

carcinogens, agents that cause cancer, you should avoid them as much as possible.

Mutations are one source of the

rich diversity of genes in the living world; diversity that makes evolution by natural selection possible

virus

simple infectious particle consisting of a bit of nucleic acid wrapped in a protein coat and an envelope of membrane

a virus share some

of the characteristics of living organisms

virus in the form of

nucleic acid packaged within a highly organized structure

virus is not considered

alive because it is not cellular and cannot reproduce on its own

A viral genome may consist of

DNA or RNA, and may be single or double-stranded

Bacteriophages

viruses that attack bacteria (“bacteria-eaters”), or phages for short

bacteriophages consist of

a molecule of DNA enclosed within an elaborate structure made of proteins

once they infect a bacterium

phages enter a reproductive cycle called the lytic cycle- using host to manufacture more virus

lysogenic cycle

viral DNA incorporation of the viral genome into the host cell genome, infecting it from within

Plant Viruses

infect plant cells can stunt plant growth and diminish crop yields

Most have RNA rather than DNA as their genetic material.

Animal Viruses

infect animal cells are common causes of disease

AIDS

caused by HIV (human immunodeficiency virus), an RNA virus with some nasty twists