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Flashcards in Exam 2: Other Things Deck (31)

when exactly does an inversion loop form?

prophase of meiosis I during bivalent formation


what is a pachytene cross

a structure that forms from 2 homologous pairs of chromosomes during bivalent formation in meiosis if there is a balanced reciprocal translocation

all 4 chromosomes come together in a cross


what is the ori

single origin of replication site in the circular chromosome of a bacterium like E. coli


what does primase do, during what process

makes an RNA primer on ssDNA during replication


example of post-translational processing

removing initial methionine

modifying aa side chains

guided protein folding


why is colinearity not true in most eukaryote genes?

b/c coding sequences in transcription units are likely to be interrupted by introns

also exons with coding sequences btwn introns may not be included in mRNA


what is colinearity

when aa sequences in the formed protein correspond to the order of codons on mRNA


what feature of DNA is found at the beginning of a transcription unit?

promotor region


what does lac operon do, and why

single transcription unit that codes for 3 proteins used in the processing and breaking down of lactose


what is a sigma factor

transcription factors in bacteria that participate in the transcription complex

each sigma factor enables specific groups (modules) of operons to be turned on simultaneously in bacteria

half a dozen or more different ones depending on species


when lac repressor binds to allolactose why can't it bind to the promotor?

repressor undergoes a conformational change when found to allolactose


how can you change a weak promotor to a strong one?

change base sequence to increase its affinity to the transcription complex


what is a nick and what fixes it

broken covalent bond on a single strand of dsDNA between the sugar's 3' carbon and adjacent phosphate

no material is missing

ligase fixes


difference between 3' and 5' ends of an Okazaki fragment

5' end has original RNA primer and the rest of the fragment out to the 3' end is made of DNA

5' end has attached phosphate


how could a mutation outside a transcription unit affect the expression of a gene

change a cis regulatory site so a TF that binds to the site doesn't bind as strongly or binds too strongly


why do eukaryote genes need to have many different ways of being turned on?

single genes need to be turned on and off in different places in the body, or at different times, or under different conditions

for each new case, a separate CRM may be needed


what is combinatorial control in gene regulation

when a CRM can only be activated by a specific combination of TFs at the right time and sequence


difference between trisomy and triploidy

trisomy is 3 copies of an individual chromosome

triploidy is 3 copies of every chromosome at the same time


what causes triploidy?

dispermy-fertilization of one egg with two sperms


how to diagnose Klinefelter in a male

if he has a Barr body



phenotype of a person with a ring chromosome

retarded growth and short


in a G2 chromosome how many generations of DNA are represented



how can a eukaryote replicate its DNA in a short time when movement of replication forks is faster in bacteria?

eukaryotes have thousands of replicon origins


how are separate Okazaki fragments joined

3' (DNA) end meets 5' (RNA) end and DNA polymerase I rips out RNA nucleotides 1 at a time and replaces with DNA nucleotides 1 at a time

nick migrates forward 1 nt until only nick is left and is fixed by ligase


why are telomeres needed

protect ends of chromosomes from fusing to other chromosomes

b/c chromosomes get shorter with every replication

found at ends of linear chromosomes made of many copies of the same short non-coding repeat sequence


why do chromosomes get shorter after every replication?

3' end of ssDNA can't be copied to the very end


how does telomere system work

allows some of the repeat units to be lost every replication without the loss of essential genetic info


whats the trend in introns as you go from simple to complex organisms

introns per gene increases


where is start codon located, what does it start

mRNA 1st codon of ORF at 5' end

starts process of translation, coding for 1st aa methionine


how many protein coding genes in human genome



during transcription does RNA polymerase use coding or antisense strand as a template?