biochem nucleutides, nucleic acids and heredity Flashcards by Joshua Cardenas

that the transmission of hereditary information took place in the nucleus, more specifically in structures called

chromosomes.

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Chemical analysis of nuclei showed chromosomes are made up largely of proteins called

histones and nucleic acids.

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The hereditary information was thought to reside in genes within the

chromosomes

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By the 1940s, it became clear that ____carry the hereditary information

deoxyribonucleic acids (DNA

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There are two kinds of nucleic acids in cells:

ribonucleic acids (RNA)
deoxyribonucleic acids (DNA)

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*Purine

-Adenine (A)
-Guanine (G)

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Both RNA and DNA are polymers built from monomers called

nucleotides.

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There are two kinds of nucleic acids in cells:

ribonucleic acids (RNA)
deoxyribonucleic acids (DNA)

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*Pyrimidine

-Cytosine (C)
-Thymine (T)
-Uracil (U)

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A nucleotide is composed of

: a base, a monosaccharide, and a phosphate.

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Nucleosides: composed of

base and monosaccharide

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: a compound that consists of D-ribose or 2-deoxy-D-ribose bonded to a purine or pyrimidine base by a B-N glycosidic bond.

Nucleoside:

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is esterified with an -OH of the monosaccharide

a nucleoside in which a molecule of phosphoric

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a nucleoside in which a molecule of phosphoric

esterified with an -OH of the monosaccharide

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-a nucleoside in which a molecule of phosphoric acid is esterified with an -OH of the monosaccharide, most commonly either the

3’ or the 5’-OH.

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base sequence is read from the

5’ end to the 3’ end

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serves as a common currency into which energy gained from food is converted and stored.

adenosine 5’-triphosphate (ATP)

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: the ordered arrangement of nucleic acid strands.

Secondary structure

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a type of 2° structure of DNA in which two polynucleotide strands are coiled around each other in a screw-like fashion.

Double helix:

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DNA is coiled around proteins called

histones.

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Histones are rich in these basic amino acids

Lys and Arg

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Lys and Arg

whose side chains have a positive charge.

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The negatively-charged DNA molecules and positively-charged histones attract each other and form units called

nucleosomes

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Nucleosomes are further condensed into

chromatin.

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a core of eight histone molecules around which the DNA helix is wrapped

Nucleosome

Chromatin fibers are organized into

loops

DNA bases are

A, G, C,

. Chromatin fibers are organized into loops, and the loops into the bands that provide the superstructure of

chromosomes.

The sugar in DNA is

2-deoxy-D-ribose

T; the RNA bases are

A, G, C, and U

* The three differences in structure between DNA and RNA are:

* The three differences in structure between DNA and RNA are: - DNA bases are A, G, C, and T; the RNA bases are A, G, C, and U. - The sugar in DNA is 2-deoxy-D-ribose; in RNA it is D-ribose. - DNA is always double stranded; there are several kinds of RNA, all of which are single-stranded.

The sugar in RNA is

D-ribose.

DNA is always _____ stranded

double

Small Transports amino acids

Transfer RNA (tRNA)

RNA is always _____ stranded

single

Directs amino sequence of proteins

Messenger RNA(mRNA)-

Combines with proteins to form ribosomes, the site of protein synthesis.

Ribosomal RNA(rRNA)

Pocesses intitial mRNA to its mature form in eukaryotes.

Small Nuclear RNA(snRNA)

Affects gene expression; used by scientists to knock out gene being studied.

Small Inefering RNA(siRNA)

Affects gene expressions; important in growth and development

Micro RNA (miRNA)

a section of DNA that, when transcribed, codes for a protein or RNA.

* Exon

catalyze cleavage of part of their own sequences in mRNA and tRNA

Ribozymes (catalytic RNA)

: a section of DNA or mRNA that does not code for a protein.

Intron

a segment of DNA that carries a base sequence that directs the synthesis of a particular protein, tRNA, or mRNA

Gene:

In bacteria the gene is

continuous

. In higher organisms the gene is

discontinuous.

. DNA double helix unwinds at a specific point called an

origin of replication

______chains are synthesized in both directions from the origin of replication

* Polynucleotide

At each origin of replication, there are

two replication forks

At each origin of replication, there are two replication forks, points at which new _______ strands are formed.

polynucleotide

* DNA is synthesized from its

5' > 3' end (from the 3' -> 5' direction of the template).

* The leading strand is synthesized continuously in the

5' ->

The lagging strand is synthesized semidiscontinuously as a series of

Okazaki fragments

Okazaki fragments of the lagging strand are joined by the

enzyme DNA ligase.

___-direction toward the replication fork.

Unwinds the DNA double helix/ unzips enzyme

Helicase-

During replication, the very condensed superstructure of chromosomes is opened by a

signal transduction mechanism

(also called gyrases) facilitate the relaxation of supercoiled DNA by introducing either single strand or double strand breaks in the DNA.

Tropoisomerases

- are assemblies of "enzyme factories".

Replisomes

Replication is ______

semiconservative

Replication is semiconservative

each daughter strand contains one template strand and one newly synthesized strand

Joins assembled nucleotides

DNA Polymerase

Threads leading strand

Clamp Proteins-

removes a positive charge and thus weakens the DNA-histone interactions.

Acetylation

Synthesizes primers

Primase

Joins Okazaki fragments in lagging strand

Ligase

Replication of DNA starts with unwinding of the

double helix.

signal transduction mechanism. * One step of this mechanism involves

acetylation and deacetylation of key lysine residues

Unwinding proteins called _______attach themselves to one DNA strand and cause separation of the double helix.

helicases

are placed at about every 50 nucleotides in the lagging strand synthesis.

Primases

are enzymes that catalyze the synthesis of primers

* Primases

one of the most common repair mechanisms.

Base excision repair (BER)

An ______ liberates the sugar-phosphate unit of the damaged site

exonuclease

are key enzymes in replication.

* DNA polymerases

seals the backbone to complete the repair

DNA ligase

an _______ catalyzes the hydrolysis of the backbone

endonuclease

It catalyzes the hydrolysis of the -N-glycosidic bond between the incorrect base and its deoxyribose.

DNA glycosylase

inserts the correct nucleotide

* DNA polymerase

removes and repairs up to 24-32 units by a similar mechanism involving a number of repair enzymes

NER (nucleotide excision repair

a genetically identical population.

Clone

a process whereby DNA is amplified by inserting it into a host and having the host replicate it along with the host's own DNA.

* Cloning

an automated technique for amplifying DNA using a heat-stable DNA polymerase from a thermophilic bacterium.

Polymerase chain reaction (PCR)