Genetics exam 2

what must be true about the location of linked genes?

must be on same chromosome

when does crossing over occur?

prophase I

when genes are completely linked, what will progeny phenotypic ratio be?

1:1 looks like mom: looks like dad

what is the formula to determine recombination frequency?

number of recombinants/total x 100

if the recombination frequency is > 50%, genes are linked or unlinked?

unlinked

what are the three units that mean genetic distance between alleles

recombination frequency (%), map units (m.u.), centiMorgans (cM)

no crossing over

nonrecombinant

crossing over occurs

recombinant

AB/ab is what kind of arrangement?

coupling arrangement

Ab/aB is what kind of arrangement?

repulsion arrangement

how does a genetic map differ from a physical map?

genetic maps are based on recombination rates instead of physical distance

as genes get further apart, how does the recombination frequency appear compared to expected and why?

appears less, double crossing over

what is the difference between ribose and deoxyribose?

ribose has H-OH group on 2’ carbon, deoxyribose has H-H

what did Griffith’s experiment with bacteria in mice discover?

bacteria can inherit traits from other bacteria through a transforming principle

what did Avery, MacLeod, and McCarty’s experiment with adding enzymes to the transforming principle discover?

the transforming principle is DNA

what did Hershey and Chase’s experiment with bacteriophage discover?

DNA, not protein is the genetic material

what is Chargaff’s rule?

A=T, G=C

which bases are purines?

A, G

which bases are pyrimidines?

T, C, U

how many rings in purines?

2

how many rings in pyrimidines?

1

what base is this?

A

what base is this?

G

what base is this?

C

what base is this?

U

what base is this?

T

what is the bond called that connects the nucleoside to the base?

glycosidic bond

what is the bond called that links nucleosides together via phosphates

phosphodiester linkage

what is the bond called that links 2 bases together

hydrogen bond

how many hydrogen bonds between G and C?

3

how many hydrogen bonds between A and T?

2

would a DNA sequence with a lot of A-T or G-C have a higher Tm?

G-C

what are similar but not identical copies of unique DNA sequences that arose from duplication of an existing gene called?

gene families

would a repetitive sequence or a single copy sequence be a single strand for longer and why?

single copy sequence, it is more unique so harder to find a partner

what makes up a histone octamer?

2 of each of the core histone proteins: H2A, H2B, H3, H4

what histone proteins are linker histones?

H1

what is a nucleosome?

repeating unit of chromatin

what makes up a nucleosome?

histone octamer, DNA wrapped around 1.65 times, a linker histone, linker DNA

what are the levels of organization of chromatin (6)

double stranded helix, nucleosome, fiber, loop, thicker fiber, chromatid

why do histones and DNA bind?

histones are positively charged and DNA is negatively charged

what do spindle microtubules attach to?

centromeres

what would happen if a chromosome was missing its centromere?

it would get lost

what are the repeated sequences of nucleotides at the ends of chromosomes called

telomeres

true or false, there is some single stranded DNA at the telomeres

true

what happens if a chromosome lacks a telomere

it will be unstable and degrade

what is eukaryotic DNA and proteins called?

chromatin

what is densely packed chromatin called?

heterochromatin

where is heterochromatin located (4)?

centromeres, telomeres, inactive x chromosome, most of y chromosome

what is loosely packed chromatin called?

euchromatin

which type of chromatin is where transcription occurs?

euchromatin

what theory proposes that mitochondria and chloroplasts in eukaryotic cells arose from bacteria?

endosymbiotic theory

how are bacterial chromosomes packgaged?

supercoiled

what enzymes add or reduce supercoiling in prokaryotic DNA?

topoisomerases

is prokaryotic DNA linear or circular?

circular

is eukaryotic DNA linear or circular?

linear

what DNA replication model is this, and is it the right one?

conservative, no

what DNA replication model is this, and is it the right one?

dispersive, no

what DNA replication model is this, and is it the right one?

semiconservative, yes

what did Meselson & Stahl’s experiments with centrifuged DNA and isotopes of nitrogen discover?

DNA replicates semiconservatively

what enzyme copies DNA, and what end does it add nucleotides to?

DNA polymerase, 3’

what is the direction of DNA synthesis always?

5’ to 3’

how does the leading strand replicate in the theta model (2)?

continuously in the same direction as unwinding

how does the lagging strand replicate in the theta model (2)?

discontinuously in the opposite direction of unwinding

why does the lagging strand replicate discontinuously in the theta model?

antiparallel nucleotide strands

what are fragments of lagging strands called?

Okazaki fragments

what component of replication binds to the origin and separates strands of DNA to initiate replication?

initiator protein

what component of replication unwinds DNA at the replication fork?

helicase

what component of replication protects the single nucleotide strands and prevents secondary structures

single-strand-binding proteins

what component of replication removes strain ahead of the fork?

DNA gyrase/topoisomerase

what component of replication adds an OH group to the 3’ end so DNA can attach?

primase

what component of replication synthesizes the leading and lagging strands?

DNA polymerase

what DNA polymerase removes the RNA primer and replaces it with DNA in prokaryotes?

DNA polymerase I

what DNA polymerase carries out elongation from the 3’ end in prokaryotes?

DNA polymerase III

what component of replication connects the nicks of Okazaki fragments after RNA primers are removed?

DNA ligase

what is the primer with a 3’ OH group that is needed to begin DNA synthesis made of?

small piece of RNA

how does DNA polymerase proofread?

by detecting the overall shape

what is how fast DNA polymerases work called?

speed

what is the accuracy of DNA polymerases called?

fidelity

what is how long of a stretch DNA polymerases can make called?

processivity

what drives the processivity of DNA replication?

clamps

how many origins of replication in prokaryotes vs eukaryotes?

1, many

what DNA polymerase of eukaryotes initiates DNA synthesis and has primase activity?

DNA polymerase alpha

what DNA polymerase synthesizes the lagging strand in eukaryotes?

DNA polymerase delta

what DNA polymerase synthesizes the leading strand in eukaryotes?

DNA polymerase epsilon

what prevents multiple rounds of synthesis from the same origin in eukaryotes?

licensing, once and only once

what happens to nucleosomes after replication?

added back

what lengthens telomeres and how does it do it?

telomerase, RNA template

what mutations occur under normal conditions?

spontaneous mutations

what mutations are triggered by environmental conditions?

induced mutations

what is it called when the tautomer form of a base occurs and causes it to pair wrong?

tautomeric shift

what is it called when a wrong base pair is added during synthesis or repair?

incorporation error

what is it called when an incorporation error is not repaired and becomes permanent (passed onto daughter cell)?

replication error

what is it called when one nucleotide is exchanged for another?

base substitution

what is it called when a nucleotide is added?

insertion

what is it called when a nucleotide is removed?

deletion

what mutations can alter the reading frame?

insertions and deletions

purine —> purine or pyrimidine —> pyrimidine is what?

transition

purine ←→ pyrimidine is what?

transversion

are transitions or transversions more common?

transitions

what kind of mutation causes something to occur?

gain of function