Topic 3: Protein synthesis, Cell function and reproduction

DNA is composed of

(1) phosphoric acid

(2) a sugar called deoxyribose; and

(3) four nitrogenous bases (two purines, adenine and guanine, and two pyrimidines, thymine and cytosine)

The total number of different proteins produced by the various cell types in

humans is estimated to be at least _____

100,000

the human body has approximately________ different genes that code for proteins in each cell

20,000 to 25,000

forms the two helical strands that are the backbone of the DNA molecule

phosphoric acid and deoxyribose

it lies between the two helical strands in the DNA structure and connect them

nitrogenous bases

Controls the formation of RNA, which controls the formation of specific proteins

DNA

Refers to the entire process starting from TRANSCRIPTION to TRANSLATION

Gene expression

the building blocks of nucleic acids

nucleotides

What is the first stage of DNA formation?

1 phosphoric acid + 1 molecule of deoxyribose + 1 base

What are the four nucleotides formed during initial stage of DNA formation?

○ Deoxyadenylic acid

○ Deoxythymidylic acid

○ Deoxyguanylic acid

○ Deoxycytidylic acid

The code triplets in the DNA result in the formation of in the RNA

complementary code triplets (codons)

difference between RNA from DNA

• sugar in RNA is ribose, which contains an extra hydroxyl ion appended to the ribose ring structure

• Thymine is replaced by another pyrimidine, uracil

How does RNA polymerase activates the synthesis of RNA?

by adding two extra phosphate radicals to each nucleotide to form triphosphates

the last two phosphates in the RNA are combined by __________________ derived from ATP in the cell

high-energy phosphate bonds

In the DNA strand immediately ahead of the gene to be transcribed is a sequence of nucleotides called

promoter

it causes unwinding of about two turns of the DNA helix and separation of the unwound portions of the two strands.

RNA polymerase binding to the promoter

a process wherein the RNA polymerase moves along the DNA strand. At each step, it temporarily unwinds the DNA and adds a new RNA nucleotide to the growing RNA strand

elongation

what is the the DNA nucleotide that causes the polymerase and the newly formed RNA chain to break away from the DNA strand? what process is this?

chain-terminating sequence termination

a large, immature, single strand of RNA that is processed in the nucleus to form mature messenger RNA (mRNA)

Precursor messenger RNA (pre-mRNA)

directs the splicing of pre-mRNA to form mRNA

Small nuclear RNA (snRNA)

carries the genetic code to the cytoplasm for controlling the type of protein formed

Messenger RNA (mRNA)

transports activated amino acids to the ribosomes to be used in assembling the

protein molecule

Transfer RNA (tRNA)

_______, along with about ____________, forms ribosomes, the physical and chemical structures on which protein molecules are actually assembled

Ribosomal RNA

75 different proteins

What are the single-stranded RNA molecules of___________ that can regulate gene transcription and translation?

21 to 23 nucleotides

MicroRNAs (miRNAs)

long single RNA strands that are suspended in the cytoplasm

Messenger RNA molecules

mRNA are composed of several hundred to several thousand RNA nucleotides in _________, and they contain codons that are exactly complementary to the code triplets of the DNA genes

unpaired strands

start codon

AUG

stop codons

UAA UAG UGA

amino acid for codons GGU GGC GGA GGG

Glycine

amino acid for RNA codons

AUU AUC AUA

amino acids for codons

CCU CCC CCA CCG

amino acids for

UGG

amino acid for CGU CGC CGA CGG AGA AGG

Arginine

Each type of tRNA combines specifically with ________ that are to be incorporated into proteins

1 of the 20 amino acids

how may nucleotides are in the tRNA?

80

what does the tRNA look like

cloverleaf like

in tRNA, At one end of the molecule there is always an ________ to

which the transported amino acid attaches at a ________ of the ribose in the adenylic acid

adenylic acid

hydroxyl group

The specific code in the tRNA that allows it to recognize a specific codon is again

a triplet of nucleotide bases and is called

anticodon

ribosomal RNA, which constitutes about ___ of the ribosome

60%

site of proteins are formed in the cell

cytoplasm

miRNA are short (____________) single-stranded RNA fragments that regulate gene expression

21 to 23 nucleotides

acts to decrease gene expression and is processed by the cell into molecules that

are complementary to mRNA

miRNA

the primary transcripts of the gene

pri-miRNA

The pri-miRNAs are then processed in the ________ by the __________ to pre-miRNAs, which are _______, stem loop structures

nucleus

microprocessor complex

70-nucleotide

pre-miRNAs are processed in the _______by a specific ____ enzyme that helps assemble an __________________ and generates miRNAs.

cytoplasm

dicer

RNA-induced silencing complex (RISC)

how does the miRNA regulate gene expression?

by binding to the complementary region of the RNA and promoting repression

of translation or degradation of the mRNA before it can be translated by the ribosome

alterations in the function of this RNA have been associated with diseases such as cancer and heart disease

miRNA function

siRNA are comprised of ____________ and can be administered to silence

expression of specific genes

20 - 25 nucleotides

can be tailored for any specific sequence in the gene, can be used to block translation of anymmRNA and therefore expression by any gene for whichnthe nucleotide sequence is known

siRNAs

why can A single mRNA molecule can form protein molecules in several ribosomes at the same time

because the initial end of the RNA strand can pass to a successive ribosome as it leaves the first

when the amino acid is activated and the when the ATP (energy molecule) combines with the amino acid it forms the

amino acid - adenosine monophosphate complex

two methods whereby the biochemical activities in the cell are controlled

(1) genetic regulation, in which the degree of activation of the genes and

the formation of gene products are themselves controlled, and

(2) enzyme regulation, in which the activity levels of already formed enzymes in the cell are controlled

It is estimated that there are___________ enhancer sequences in the human genome.

more than 100,000 gene

connects the DNA and RNA polymerase II, helping start transcription

Transcription factor IIB

DNA regions that increase transcription by binding transcription factors

enahncers

provides another layer of precise control over gene expression

enahncers

mammalian cell cycle may be as little as 10 to 30 hours when

not inhibited and are reproducing as rapidly as they can,

actual stage of mitosis, lasts for only about

30 minute

DNA begins to be duplicated________ before mitosis, and the duplication is completed in _______

5 to 10 hours

4 to 8 hours

DNA polymerase attaches to and moves along the DNA template strand, adding nucleotides in the ________ direction

5′ to 3′

causes bonding of successive DNA nucleotides to one another, using high-energy

phosphate bonds to energize these attachments

DNA ligase

DNA helixes in each chromosome are approximately _______ in length

6 centimeters

enzymes that break the hydrogen bonding between the base pairs of the DNA, permitting the two strands to separate

DNA helicase

a Y shape where the area that will be the template for replication to begin.

replication fork

Replication progresses only in what direction

5′ to 3′ direction

At the replication fork, the strand oriented in the 3′ to 5′ direction, toward the replication fork is __________ while oriented 5′ to 3′, away from the replication

fork is ______

leading strand

lagging strand

always bind as the starting point for DNA replication

primer

replication proceeds in the ________ direction on the _______ strand

5′ to 3’

leading

joins the Okazaki fragments together by forming covalent bonds, creating one continuous strand

DNA ligase

short segments of DNA that are synthesized on the lagging strand during DNA replication

okazaki fragments

removes the RNA primers from the original strands, after the continuous and discontinuous strands are both formed during elongation

exonuclease

“proofreads” the newly formed DNA, checking and clipping off any mismatched or unpaired residues

exonuclease

transiently break the phosphodiester bond in the backbone of the DNA strand to prevent the DNA in front of the replication fork from being overwound

topoisomerase (reversible nis sya na process)

duplicated but still attached chromosomes are called

chromatids

chromosomes are attached together at the center called

centromere

mitosis follows automatically within _______ after DNA replication

1 or 2 hours

Each centriole is a small cylindrical body about _______ and

about___________ in diameter, consisting mainly of _________ structures arranged in the form of a ______

0.4 micrometer long

0.15 micrometer

nine parallel tubular

cylinder

Each pair of centrioles, along with attached pericentriolar material, is called a

centrosome

complex of microtubules extending between the two new centriole pairs is called

spindle

the entire set of microtubules plus the two pairs of centrioles is called the

mitotic apparatus

it extends between the respective spines and, using a stepping action as in muscle, actively slide the spines in a reverse direction along each other

molecular motors

cells that do not reproduce during the entire life of a person, except during the original period of fetal life

neurons and some striated muscle cells

Each time a cell divides, an average person loses _________ from the ends of that cell’s telomeres

30 to 200 base pairs

blood cells, the length of telomeres ranges from __________ at birth to as low as _____in older people.

8000 base pairs

1500

How can telomerase activity enhance proliferation of cancer cells

In cancer cells, telomerase activity is abnormally activated so that telomere length is maintained, making it possible for the cells to replicate over and over again uncontrollably

it allows to prevent formation of the mitotic spindle and therefore

prevent mitosis, even though replication of the DNA continues

colchicine

mature human cells each produce a maximum of about __________ proteins

8000 to 10,000

the potential number of proteins that would be produced if all genes were

active

20,000 to 25,000 or more

cells that die as a result of an acute injury usually swell and burst due to loss

of cell membrane integrity is called

necrosis

difference between necrosis and apoptosis

Necrotic cells may spill their contents, causing inflammation and injury to neighboring cells. Apoptosis, however, is an orderly cell death that results in disassembly and phagocytosis of the cell before any leakage of its contents occurs, and neighboring cells usually remain healthy.

Apoptosis is initiated by activation of a family of proteases called

caspases (inactive: procaspases)

Alzheimer disease is a neurodegenerative diseases that may be due to

Abnormalities of apoptosis

normal genes that code for various proteins that control cell adhesion,

growth and division wherein if mutated or excessively activated can cause cancer

Proto-oncogenes

how many oncogenes have been discovered in human cancers

100 different oncogenes

suppress the activation of specific oncogenes

tumor suppressor genes

examples of viruses associated with cancers in humans

human papilloma virus (HPV)

hepatitis B and hepatitis C virus

Epstein-Barr virus

human immunodeficiency virus (HIV)

human T-cell leukemia virus

Kaposi sarcoma–associated herpes virus (KSHV)

Merkel cell

polyomavirus

how do DNA viruses cause cancer?

the DNA strand of the virus can insert itself directly into one of the chromosomes,

thereby causing a mutation that leads to cancer

how do RNA viruses cause cancer?

RNA viruses carry reverse transcriptase that causes DNA to be transcribed from the RNA, the transcribed DNA then inserts itself into the animal

cell genome, leading to cancer

cancer cells supply these which are nutrients required for cancer growth, causing many new blood vessels to grow into the cancer

angionenic factors