Cell Biology

what is the central dogma?

DNA transcribed into RNA which is then translated into proteins.

genetic information are copied into another chemical forms known as ____

RNA

what is a major structural difference between RNA and DNA (from quiz)

1. RNA uses uracil bases instead of thymine (for DNA)

2. RNA uses ribose while DNA uses deoxyribose

3. RNA is single stranded while DNA is not

can RNA fold onto itself? True or false

si

what enzyme makes the RNA transcripts

RNA polymerase

the DNA in genes is used as a template to create ____?

RNA that is complimentary to DNA

where does DNA reform at after the transciption process?

at the double helix

during rna transcript formation,is there a need for a primer?

No. there is no need for it.

what do the following kinds of RNA function as?

mRNA

rRNA

miRNA

tRNA

a. Messanger rna code for proteins

b. ribosomal rna catalyze protein synthesis & form the core of the ribosome structure

c. micro rnas regulate gene expression

d. transfer rnas sever as “adaptors” between mRNA and amino acids during protein synthesis.

how does transcription begin?

by guiding RNA polymerase to the transcription start size of the gene

sequences near transcription start size that bind are called ___

promoter

in bacteria, promoters are bound by what?

sigma factors associated with the RNA polymerase

what disassociates RNA polymerase?

terminator sequence

which is more highly regulated; eukaryotic transcription or bacterial transcription?

eukaryotic but bacteria is also tightly regulated

what are the 3 types of RNA polymerase in eukaryotes?

RNA pol I

RNA pol II

RNA pol III

what genes are transcribed at different types of polymerase?

RNA pol I-most rRNA genes

RNA pol II-all protein-coding genes, miRNAs and splicesome genes

RNA pol III-tRNA genes, 5s rRNA genes etc

what starts the assembly of protein complex?

TATA binding protein

assembly of protein complex leads to ____

RNA pol II binding

what other organelle has to be moved in the process of transcription?

nucleosomes

mRNAs are modified at the 5’ end by addition of what?

addition of methylated GTP in a 5’ to 5’ linkage

the 3’ end of the mRNA is modified by what?

by the addition of 200-250 As bound to proteins that eventually stabilize the 3’ end of the message

differentiate between introns vs exons

introns-intervening sequence that eventually get lost

exons-expressed sequences that are encoded

what recognizes which part of the gene needs to be spliced?

the spliceosome

where does RNA processing (splicing, capping & tailing) take place?

nucleus

explain the splicing reaction.

it occurs by 2 reactions that form a “lariet” structure from the introns and ligates the exons

what ribonucleoprotein complexes recognize splicing branch points?

U1 and U2

function of U4, U5 & U6

they assemble to catalyze the splicing reaction

what percent of genes are alternatively spliced in humans?

95%

how do mRNAs move to the cytoplasm after processing is over in the nuclues?

they are moved via the nuclear pore complex

mRNA’s encode proteins using a ___

triplet code

the triplet code in the mRNA base pairs with ____?

tRNAS which then fold to structures exposing a sequence, its anticodon as well

how are amino acids linked to tRNAS

through covalent linkage

how many aminoacyl-tRNA synthetases are there?

20

a large subunit and a small one come together to form ------

a ribosome which are enzymes that catalyze the formation of polypeptides

what are the 3 binding sites for tRNAS?

E site (exit), P site (peptidyl-tRNA) & A site (aminoacyl-tRNA)

at what site does the first tRNA bind at?

at the A site beginning the start of elongation

what catalyzes the addition of a new amino acid on the growing polypeptide?

ribosome

what site does binding occur when the stop codon is reached?

A site

what is a polysome?

clusters of multiple ribosomes often bound to a single mRNA producing multiple proteins

what balances protein synthesis?

protein degradation

whats a proteasome?

a large protein complex that degrades protein in the cell

what libase adds ubiquitin?

ubiquitin ligase

proteins are targeted for degradation by addition of ___, a small protein?

ubiquitin.

what switches the transcription of genes?

transcription regulators

what can trigger the formation of specialized cell type

a master transcription factor

define organismal cloning?

the ability of a cell from an organism to make a new organism proving the hypothesis that cells keep their intact genome

at what phase is transcription controlled?

at the INITIATION stage due to it being highly processive

what controls the formation of the transcriptional regulatory complex?

Regulatory DNA sequences.

transcription factors are often _____

dimers

for bacteria, a single transcript can encode proteins to form ____

operons

is the trypophan repressor an allosteric protein? true or false

true

transcription regulators activate gene expression while repressors do ___

repress gene expression

what is “looping DNA”

it brings enhancer and promoter sequences close to each other to interact

what is the mediator in the cell?

it is a large transcriptional regulatory complex that stabilizes transcription factors

transcription regulators promote the assembly of ____

chromatin-modifying proteins

transcription activators recruit __ while transcription repressors recruit ___

activators recruit histone acetyltransferases

repressors recruit histone deacetylases

during development of cells, are they specialized or unspecialized?

they are unspecialized initially but become more specialized as they become mature

how many transcription factors are present in humans?

around 1000

can a small number of transcription regulators change the cell function?

yes. it can even dedifferentiate the cell into a stem cell

what is the positive feedback loop of the cell?

a continuous expression of cell characteristics alongside its progeny.

what is used to reinforce the positive feedback loop allowing for memory to be retained even in daughter cells?

epigenetic memory

what regulates mRNA translation and stability?

small non coding RNAs called miRNA (micro RNA)

what makes miRNA

RNA pol II

miRNA can be packaged into ____

RNA induced silencing complex (RISC). RISC then end up binding with mRNA

how many miRNA are present in humans

500 and they function to regulate critical cellular processes

how are genetic changes that dont increase fitness elimated?

through natural selection

what is gene duplication?

formation of 2 different genes to diversify

repeated rounds of gene duplication leads to ___

large gene families

how many nucleotide pairs can be found in chromosomes

3.2 * 10^9 nucleotide pairs

what must happen to germ-line cells for mutations to be passed down?

germ line cells must be altered for mutations to be passed down

do mutations of somatic cells transfer? T or F

false

what are point mutations?

changes to a single nucleotide pair that occur from faulty DNA copying or repair

what are transposons?

they are mobile genetic elements that move

how do genes and genomes evolve?

they evolve thru the production of genetic variation either by mutation or gene transfer

what are the 6 kinds of ways to create genetic variation

1. mutation within a gene

2. mutation within regulatory DNA

3. exon shuffling

4. horizontal gene transfer

5. gene duplication

6. movement of genetic elements (transposition)

what is an example of gene families that were created through the process of duplication?

globin genes

duplication and movement of exons is a process known as __?

exon shuffling

proteins are composed of exon types that encode a ____

protein domain. these domains can then be placed together in various combinations

what kind of genetic variation produces insertional mutations?

transposition of the gene. (the mobile genetic elements)

can mutations or changes be retained if they have selective advantages? true or false

true. it is a process known as selection

explain a phylogenetic tree

a tree showing relationshops between species that can be traced to a common ancestor and compares genes of those species

whole genome comparisons show that the human genome shows __ %conversion with other mammals?

95.5%

what are transposons?

mobile genetic elements in the cell that move or “transpose”

what are the two major families of transposable sequences?

retrotransposons: L1 element

alu sequence