Genetics 1

Start Studying!

Terms

undefined, object

copy deck

How many strands of DNA are copied into mRNA at a time?: only one
What's the central dogma of molecular biology?: DNA (transcription) to RNA (translation) to protein
True/False: Genes can be located on DNA in either orientation.: true
Some genes are interrupted by ________. This occurs mostly in __________ genes.: introns
eukaryotes
True/False: Only one strand of DNA codes for the mRNA.: FALSE! The orientation of the gene determines which strand of DNA codes for the mRNA.
Which are copied into RNA, exons or introns?: BOTH!! The introns are later spliced out before translation.
What is the adaptor that translates a triplet codon in the mRNA into an aa in the protein?: transfer RNA (tRNA)
The amino acids are attached to the tRNA at the ______ end.: 3' -OH end
The triplet codons in mRNA are translated into protein on ___________.: ribosomes
The genetic code is universal, non-overlapping, and commaless. It's also __________, meaning that several codons code for the same aa.: degenerate
The ______ codon is used to initiate translation.: met (AUG)
What are the 3 stop/nonsense codons?: UGA, UAG, UAA
What are Chargaff's rules?: equal amounts of A=T, G=C.
What is different about mRNA?: no introns. it all codes.
The backbone of DNA has the sugar _________ and phosphate linked by ________________.: deoxyribose
phosphodiester bond
Name the purines.: adenine
guanosine
Name the pyrimidines.: Cytosine
Thymine
Uracil
______(base) is only in RNA. ______ is found in DNA.: U
T
The 2 strands in the Watson-Crick DNA double helix are ___________.: antiparallel
It's a right-handed double helix
Base pairing uses what kind of bond?: hydrogen
The hydrophobic _________ are located on the inside of the double helix, the hydrophilic ______________ on the outside.: bases

phosphate and deoxyribose residues
Name 2 forces that hold the double helix together.: 1) H bonds
2) pi-electron interactions between the bases (base stacking)
How do you denature DNA? 2 ways. What is renaturing called?: alkali or heat
annealing/hybridization
What happens if you denature circular DNA?: tangled mesh of strands that can't come apart
What is hyperchromicity effect of DNA upon denaturation?: melting temp of DNA: A=T melts at a lower temp b/c the bonds aren't as strong.
Bases can absorb more light
The cohesive ends of bacteriophage lambda DNA allow ______________.: circularization
Usually, you have ________ base pairs per turn of DNA. If you have + supercoil, you get ______ (more or less?): 10
less b/c it's overwound, get fewer bp's/turn
How do you fix a supercoil? When do supercoils happen?: topoisomerase
during replication
What can produce a supercoil?: intercalation of aromatic compounds into DNA
What is the enzyme that makes the peptide bond?: ribozyme
What are SnRPs? What's a disease involving them?: small RNA nuclear proteins (spliced out of preRNA before mRNA is made)

Lupus is an autoimmune dz against snRPs.
What's required to identify mutant alleles producing a monogenic pattern of inheritance?: a genetic discriminant
What are the 4 subspecialties of medical genetics?: 1) cytogenetics (chromosomes)
2) molecular (DNA and mutations)
3) biochemical (analates and sm. molec.)
4) clinical (for MD's)
All diseases have both ______ and __________ mechanisms.: genetic and environmental
Mendelian traits are __________.: discontinuous
Who did x-ray diffraction on DNA to get the structure?: Rosalind Frankin
Mutations are transmitted in families if the __________ is affected.: germline
This effect states that a mutation might be common in a population.: founder effect
How many chromosomes in a normal karyotype?: 46
(23 pairs)
What's the location of a gene?: locus
somatic chromosomes are also called __________.: autosomal
what is a hemizygote?: inherited one allele on either the X or Y
Who's the person who brought the pedigree to your attention? Does he have to be affected?: proband
no
Cystic fibrosis is an ____________ inherited dz.: AR
Clues of autosomal recessive (AR):: 1) occurs in siblings, parents unaffected
2) males = females
3) parents of affected kid are carriers
4) parents may be consanguinous
5) recurrence risk for each sib in 25% (independent risk)
If both parents are 1/2 normal (heterozygous) for an enzyme, kid will be very low (homozygous). This type of inheritance is..: AR
The Cot value is directly proportional to the ________________.: complexity of the genome.
renaturation kinetics - the more complex, the longer it takes to anneal
The ___________ of the genome does NOT determine its complexity, but rather the ____________________.: size
% of unique sequences
Highly repetitive sequences (satellite DNA) are located in ____________.: centromeres
What is satellite DNA?: highly repetitive DNA
What's the repeat sequence unique for human DNA?: Alu sequence
endonuclease site in introns
What's a processed pseudogene?: intermediate repetitive DNA
NONFUNCTIONAL COPIES OF A NORMAL GENE
contain mutations, are reverse transcribed
usually still have the polyA signal (not normally encoded)
DNA is wrapped around a ______________ core like beads on a string.: nucleosome
What is Lyon's hypothesis?: one of the X's inherited in girls gets inactivation/condensation (Barr body), randomly at first, then is set later in progeny
What's Turner syndrome?: 45, X
(no barr body)
What's Kleinfelter's syndrome?: YXXXX (3 Barr bodies) infertile
Gene regulation is at the ______________ level.: chromatin
How do you inactivate a gene?: methylation
What does it mean to be "nuclease sensitive"?: in euchromatin, where it's not condensed, nuclease can get in easier for transcription
How many base pairs per turn of DNA?: 10
Where is the highest concentration of DNA found?: sperm heads
Give 2 common mutations: 1) deamination of C (methylated)
2) depurination (AP sites) hot spots
What's Werner syndrome?: AR premature aging
can't fix mutations with the usual helicase/exonuclease activity
What is associated w/ all cancers?: ANEUPLOIDY
different # of chromosomes
DNA replication is _______________.: semi-conservative
Replication of circular DNA gives you 2 circles. So now you need ___________, which makes double-stranded cuts.: topoisomerase II
Bacteria and viruses with circular DNA replicate as _____ structures or "__________________.": theta
rolling circles
In cell cycle, DNA synthesis is restricted to the ____ phase.: S
In prokaryotes, DNA synthesis occurs _________.: at all times
T/F: There's only one site for replication in eukaryotes.: false
there are many simultaneous sites
(replication bubbles)
DNA polymerase elongates the _______ end of a DNA strand. _________________ are the substrates for DNA polymerase.: 3'
deoxyribonucleoside triphosphates
DNA polymerase needs a template and a _________.: primer
E.coli DNA polymerase I has 2 exonuclease activities:: 1) 5' to 3' removes RNA primers from Okazaki fragments
2) 3' to 5' proofreads
DNA synthesis at the __________ strand is discontinuous. Synthesis at the __________ strand is continuous. ______________, or short strands of DNA, occur on the ___________ strands.: lagging
leading
Okazaki, lagging
RNA is later removed and replaced by DNA bases with the help of ____________.: polymerase I
links the Okazaki pieces: DNA ligase
_____________ relieves the tension so replication can begin. ______________ unwinds the helix (needs ATP to break H bonds).: topoisomerase I
helicase
____________ removes primer and proofreads ____________ seals fragments: DNA polymerase I
DNA ligase
During each round of replication, bases are lost at the ends. Need _____________. Put on by ___________.: telomeres
telomerase
telomerase contains ______ which codes for the telomeric repeat.: RNA
How do repair enzymes know which strand to fix?: The real (parent) strand gets methylated. DNA restriction endonucleases cut the one that's not methylated.
Name 2 repair deficiencies.: xeroderma pigmentosum

Cockayne syndrome (transcription-coupled repair)
A to G is example of _______ mutation.: transition
A to C is example of _________ mutation.: transversion
tautomeric form of adenine pairs with?: Cytosine
deamination of cytosine produces _________. this causes a ______ mutation.: Uracil
transition
Name 2 types of DNA repair mechanisms.: 1) direct repair
2) excision repair
Methyl-directed mismatch repair by ______________.: dam methylase methylates adenine residues
Give a disorder due to defective mismatch repair.: hereditary nonpolyposis colorectal cancer (NPCC or Lynch syndrome)
What may lead to gene duplication?: unequal crossing over
What happens when both strands of DNA are damaged?: error-prone DNA repair
inducible system
SOS enzymes put in whatever bases it can find
but since only 3% of DNA codes for proteins, it's ok.
How did gene families come about?: crossing over
Branch migration is catalyzed by _______ protein, which allows crossing over.: recA
Phage lambda integration into e.coli is an example of ______________.: site-specific recombination
Recombination of Ig genes to generate antibody diversity is example of _____________.: site-specific recombination
bacterial sex is called ____________: conjugation
What are conjugative plasmids and what role do they play in hospitalism?: conjugation move from one bacterium to another, transferring antibiotic resistance. R- to R+ plasmid.
What are the simplest mobile genetic elements?: jumping genes or insertion sequences (IS)
When you insert a transposon, you generate ____________.: direct repeats in the target sequence
Eukaryotic cells have a special transposon called a ______________. It's infectious.: retrotransposon
What are the 3 clues for autosomal recessive (AR)?: 1) consanguinity parents
2) siblings affected (not parents)
3) males = females
What are 2 AR diseases?: cystic fibrosis
sickle cell anemia
What are the 6 clues for autosomal dominant (AD)?: 1) males = females
2) every generation
3) affected parent-->offspring
4) heterozygotes are AFFECTED. No such thing as a "carrier."
5) Homozygotes die.
6) isolated cases mean a new mutation
Give 2 examples of AD diseases.: achondroplasia
NF1
Which inheritance pattern shows male to child transmission (besides Y-linked)?: AD
Which inheritance pattern do you get variable expression?: AD (like NF1; some have cafe' au lait spots, some have neurofibromas)
How do you explain an AD trait skipping generation?: lack of penetrance
Give an example of a sex-limited dz.: male-limited precocious puberty
(familial testotoxicosis)
Give the products of an unaffected female (XX) and an affected male (X*Y) for an X-linked recessive disease.: all daughters will be carriers.
no males will be affected.
X X
X* X*X X*X
Y XY XY
For X-linked recessive, can a male be a carrier?: no. he's either affected or not.
Give 3 X-linked recessive (XLR) clues.: 1) no male to male transmission
2) mom's brother is also affected (inherited from mom's mom).
3) due to new mutations sometimes
What's Lyon's hypothesis?: inactivated X in females.
which one gets inactivated is random at first, then subsequently fixed.
According to Lyon's hypoth, 50/50 mosaicism is predicted unless there is _______________.: skewed X inactivation
Give an example of a disease where mosaicism can determine phenotype.: Duchenne Muscular Dystrophy in female carriers
skewed x inactivation determines phenotype of XLR disorders
(and calico cats are all female)
Give an example of an X-linked dominant (XLD) disease.: hemophilia (usually lethal if homozygous)
no such thing as "carriers."
Give the 3 XLD clues.: 1) affected fathers-->only affect daughters
2) females more than males
3) males usually die if affected (hemizygous)
Give an example of XLD disease.: Rett syndrome (girls)
What does the poisonous death cap mushroom Amanita phalloides do?: inhibit eukaryotic RNA polymerase
(can't synthesize RNA) very deadly
RNA chains are synthesized in the _____________ direction.: 5' to 3'
During transcription, the RNA template strand is read in the ___________ direction.: 3' to 5'
Does RNA polymerase require a primer?: no
What goes on the 5' end of new mRNA?: PPP
(triphosphate group)
mRNA has to be copied from the ____________ strand in the ____________ direction. RNA is synthesized in the _________ direction.: ANTISENSE
3' to 5'
5' to 3'
Which RNA polymerase subunit recognizes start sequences (promoters) for transcription?: sigma factor
In the promoter regions, there are usually more _______ base pairs. Why?: A-T b/c it's a weaker bond than G-C
What's a recognition site for initiation of transcription (promoters)?: TATA box
What stimulates transcription upstream from the promoters?: positive regulatory elements (enhancers)
What tells RNA polymerase to fall off and stop RNA synthesis (transcription termination)?: Rho-factor
What acts as a transcription terminator and cancer therapeutic? Give an example.: aromatic compounds that intercalate in DNA

actinomycin D and Rifampicin
What makes mRNA and is inhibited by the mushroom poison?: RNA polymerase II
Eukaryotic transcription initiation requires ___________.: enhancers
DNA-binding proteins can have 3 motifs, which are?: 1) helix-turn-helix (phage lambda, CRP)
2) zinc-finger
3) leucine zipper
DNA binding proteins have 2 domains. Name them.: 1) DNA binding domain
2) activating domain
Eukaryotic mRNA has a ___________ at its 5' end, and a _______ at its 3' end.: guanosine triphosphate CAP at 5' (which ribosomes require for initiation of translation)

polyA tail at 3' end
How is transcription terminated?: endonuclease cleaves pre mRNA,
mRNA is polyAdenylated at 3' end.
Transcription of rRNA genes is done by _____________ in the ____________.: RNA polymerase I
in the nucleOlus
Stable RNAs are made from precursors, then processed into smaller fragments in the ________.: nucleus
Polio virus is ___RNA. Would it infect?: + (like mRNA).
yes
Rabies virus is ___RNA. Would it infect?: -. no.
It would infect if it packaged RNA polymerase and changed itself to +
Reo virus is ____RNA. Would it infect?: +-. No.
Needs RNA polymerase
HIV is ___RNA. Does it infect?: +. yes.
it carries reverse transcriptase.
RNA-->ssDNA-->dsDNA-->rearrangement
How can we account for many people with HIV not getting AIDS?: human endogenous retroviruses
What 4 things are needed to synthesize RNA?: 1) RNA polymerase
2) promoters (TATA box) w/ sigma factor
3) enhancers
4) Rho-factor for termination
What does eukaryotic RNA polymerase need that prokaryotic doesn't?: enhancers
What's a common prokaryotic promoter sequence?: TATA box
TTGACA
Which e.coli RNA polymerase subunit dissociates after transcription initiation?: sigma factor
Explain enhancer/UAS.: upstream activating sequences
required for transcription upstream from promoters.
tissue-specific
Name 3 methods of prokaryotic transcription termination.: 1) rho-factor
2) hairpin turns
3) intercalation by rifampicin
What's the difference b/t prokary. and eukary. mRNA's?: both have 5' GTP cap
but eukary. have 3' polyA tail
How is eukary. mRNA synthesis terminated?: polyA tail at 3' end
Describe transcription of rRNA and tRNA in prok and eukary.: prok: genes occur in multiple copies on precursor molecules that must be processed.
It's a ribozyme: contains RNA instead of polypeptide. Need RNA polymerase to make all cellular RNAs.

euk: rRNA is transcribed by RNA polymerase I in the nucleOlus.
tRNA transcribed by RNA polymerase III, processed by ribunuclease III.
How does the mushroom poison work?: it contains alpha-amanitin, which inhibits RNA polymerase II.
treated with aucubin
What's lupus (SLE)?: autoimmune dz against SnRNPs
malar butterfly rash
What causes beta thalassemia? What selective advantage do they have?: incorrectly spliced mRNA
malaria
(RBC's do not have DNA; just proteins for carrying oxygen)
mRNA is more stabile in humans or e.coli?: humans (10 hrs. vs. 5 minutes)
it's stabile RNA (like tRNA and rRNA)
Where do you splice mRNA?: donor and acceptor splice sites
they have consensus sequences
like "GU" and "AG"
___________ in _____________ catalyze the splicing of mRNA. How?: SnRNP's in spliceosomes
-bind to 5' splice site
-lariat formation (branched RNA)
-5' cleavage, release, broken down
-mature RNA remains
How can abnormal processing in the beta globin gene cause beta thalassemia?: RNA mutations in INTRONS can cause mutations because of incorrect splice sites
How do you get more than one protein from the same gene?: alternate splicing
all tRNA have ______ at 3' end.: CCA
Introns in mitochondrial genes are self-splicing, that is, they function as ___________.: ribozymes
polyA tails play a role in ?: translation regulation
Describe 3 regions of type II introns (mRNA) that are highly conserved/required for splicing.: 1) donor splice site at 5' end
2) acceptor splice site at 3' end
3) branch site at intron/exon boundaries AG:GU
What is RNA editing?: 2 forms of apo-B
liver: apo-B100
intesting: apo-B48 b/c has UAA (a stop codon) instead of CAA
posttranscriptional editing
so you get a shorter version in the gut.

Start Studying!

Deck Info

Number of cards 164