unit 6 - gene expression and regulation

DNA is primary source of

DNA is primary source of

hereditary material

genetic info is stored as

sequence of bases in DNA and RNA

DNA is packaged into

chromosomes before genetic info is passed from parent to daughter cells

nucleotide bases in DNA

adenine, thymine, cytosine, and guanine

nucleotide bases in RNA

adenine, uracil, cytosine, guanine

pyrimidines

single ring structure

which bases are pyrimidines

uracil, cytosine, and thymine

pruines

double ring structure

what bases are purines

adenine and guanine

prokaryotic organisms have ___ chromosomes

circular

eukaryotic organisms have ___ chromosomes

linear

genetic info is copied during

DNA replication

when does DNA replication occur?

before cell division

why is DNA replication semiconservative

DNA molecule contains one original strand and newly synthesized strand

directional in DNA molecule influences

replication process

each DNA strand has ___ on one end and ___ on the other end

terminal phosphate group, terminal hydroxyl group

phosphate terminus

5-prime end

hydroxyl terminus

3-prime end

leading strand

nucleotides can only be added to growing strand in 5’ to 3’ direction (strand in synthesized continuously)

lagging strand

one strand will always be synthesized discontinuously, in fragment

helicase

unwinds DNA strands

topoisomerase

relaxes supercoil at replication fork

DNA polymerase

synthesizes new strands

where is DNA polymerase attached?

to 3’ end of template strand

ligase

joins DNA fragments on laggin strand

genetic information flows from

DNA to RNA to protein

RNA molecules are used to

facilitate protein synthesis using RNA information

ribosomes

contain RNA and assemble proteins

transcription

process in which enzyme directs formation of mRNA molecule + DNA strands are separated

template strand

noncoding strand

non-template strand

coding strand

gene targeted for transcription is located on

coding strand

RNA polymerase reads

DNA sequences + aligns correct nucleic acid with complementary base + adds new nucleotides to assemble mRNA

messenger RNA (mRNA)

carries genetic info from RNA to ribosomes

transfer RNA (tRNA)

recruited by ribosomes to create polypeptide sequence as directed by mRNA

anticodon

3-base sequence of tRNA

ribosomal RNA (rRNA)

functional units of ribosomes responsible for protein assembly

introns

sequences of mRNA that do not code for amino acids

exons

sequences of mRNA transcript that code for amino acids

alternative splicing

process of splicing introns + connection retained exons in mature mRNA transcript

different mRNA transcripts lead to

different proteins

translation of mRNA generates

polypeptides

translation

process by which mRNA sequence is used to generate polypeptide

initiation

rRNA in ribosome interacts with mRNA at first start codon, mRNA nucleotides are grouped together (codons)

elongation

each newly arrived tRNA brings another amino acid to be added to polypeptide chain, rRNA adds amino acids as tRNA brings them

termination

amino acids continue to be added until STOP codon is reached, translation ends

translation mechanisms are

similar in nearly all organisms

translation is the ___ process in flow of info from DNA to RNA to protein

final

gene expression

process by which instructions in DNA are transcribed and translated into function protein

regulatory sequences

stretches of DNA that can be used to promote or inhibit protein synthesis

epigenetic changes

involve reversible modification of DNA or histones

histones

proteins used to wrap DNA around

slight chemical modification of DNA and histones causes

tight packing or loose packing of DNA

packing and unpacking of DNA regulates

gene expression

cell differentiation

cells within same organism having different phenotypes

transcription factors

proteins that promote or inhibit transcription of gene

operons

closely linked genes that produce single mRNA molecules during transcription

what does the operon inclue?

genes to be transcribed, regulatory sequences, and operator

operator

sequence that either inhibits or promotes transcription by binding with regulatory proteins

lac operon

example of inducible gene

when regulatory protein is bound to operator

RNA polymerase cannot bind to regulatory sequence

inducers

molecules that bind to regulatory protein + cause it to change shape

when the regulatory protein is released from operator

RNA polymerase is able to transcribe operon’s genes

promoters

DNA sequences upstream of transcription start site where RNA polymerase and transcription factors bind to initiate transcription

negative regulatory molecules

inhibit gene expression by blocking transcription

only certain tissues have ___ proteins that turn on regulatory genes

activator

mutations

change in genome of an organism

disruptions in genes and gene products can result in

new phenotype

gene mutations

changes in nucleotide sequence of a particular gene

frame shift

when base is added or removed from sequence

nonsense

mutation creates stop codon, preventing production of protein

missense

when one amino acid is substituted for another

changes in chromosomes number often result in

new phenotypes

triploidy

having 3 copies chromosomes (results in sterility)

polyploidy

having multiple sets of homologous chromosomes (can result in increased vigor in plants)

horizontal transfer of genetic info

exchange of genetic info between different genomes or unrelated organisms

transformation

refers to uptake of naked DNA

transduction

transmission of foreign DNA into cell where viral genome integrates with host genome

conjugation

cell to cell transfer of DNA

transposition

movement of DNA segments within and between DNA molecules