Genetics Exam 3

H-DNA

-DNA sequences that form three stranded (triplex) structures

autosomal aneuploidies

-most embryos with this are spontaneously aborted. -no mechanism of dose compensation in these types of chromosomes

familial Down syndrome

-not trisomic for a complete chromosome 21, instead they have 46 chromosomes, but an extra copy of part of chromosome 21 is attached to another chromosome through a translocation.

DNA to serve as its own template for replication

Complimentary base pairing allows for?

Robertsonian translocation 14 and 21: the long arm of 21 and the short arm of 14 exchange places

Familial Down syndrome arises in offspring whose parents are carriers of chromosomes that have undergone a _______ ______. most commonly between chromosome ___ and ___

measured the amount of the four bases in DNA from a variety of organisms, and they found that DNA from diff organisms varies greatly in base composition. This finding disproved the tetranucleotide hypothesis. found amount of adenine is always equal to Thymine and the amount of guanine is always equal to the amount of cytosine. These findings became known as CHargaff's rules however the cause of these ratios was unknown at the time

How did Erwin Chargaff contribute to the understanding of DNA

-discovered the transforming principle -isolated several different strains of S. pneumonia type 1 2 3 and so forth. Griffith observed that small amounts of living type 3 S bacteria injected into mice caused the mice to develop pneomonia and die: when he examined the dead mice, he found large amounts type 3S bacteria in their blood. -when he injected type 2R bacteria into the mice, the mice lived and no bacteria recovered form their blood. Griffith knew that boiling killed all bacteria and destroyed their virulence; when he injected large amounts of heat killed type 3S bacteria into the mice the lived and no type 3S were recovered form their blood. -results were normal, but he injected his mice with a small amount of living type 2R bacteria along with a large amount of heat-killed type 3S bacteria. because they were both non virulent he expected the mice to live but instead the mice developed pneumonia and died. When Griffith examined the dead mice he found live type 3S bacteria. Their virulence was also heritable he discovered -concluded the the type 2R bacteria had somehow been transformned, acquiring the genetic virulence of the dead type 3S bacteria and this transformation had produced a permanent, genetic change in the bacteria. called the substance the transferring principle

How did Fred Griffith contribute to the discovery of DNA as a genetic material

-study of the T2 bacteriophage designed experiments to determine whether the phage protein or the phage DNA is transmitted in phage reproduction -used radioactive forms of isotopes of phosphorus and sulfur- these can used as a tracer to identify the location of a specific molecule because any molecule containing the isotope will be radioactive and therefore easily detected. -used phosphorus for DNA -used sulfur for protein 1. grew one batch of E. coli in a media containing P32 and infected the bacteria with the T2 phage so that all the progeny phages would have DNA labeled with P32. 2. Grew a second batch of E. coli in a medium containing S35 and infected these bacteria with T2 phage so that all progeny phages would have proteins labeled with S35. 3. then infected separate batches on unlabeled E. coli with the S35 and P32 labeled progeny phages. after allowing time for the phages to infect the ECOLi cells, placed cells in blender and sheared off the now-empty phage protein coats from the cell walls. 4. separated out protein coats nd cultured the infected bacterial cells 5. In S35 most of the radioactivity was detected in the phage protein coats and little was detected in the cells. when new phages emerged form the cells almost no S35 was detected. 6. indicated that the protein component of a phage does not enter the cell and is not transmitted to progeny phages, In P32 the bacteria were radioactive. most of the progeny phages that emerged were also radioactive demonstrating that DNA from the infecting phages had been passed on to the progeny phages. CONFIRMED: DNA is the genetic material of phages

How did Hershey and Chase contribute?

the original chromosome is restored and no rearrangement results

IF the two broken ends of a chromosome are rejoined correctly then, .....

heat-killed type 3S mixed with living type 2R avirulent bacteria or living type 3S virulent bacteria

IN griffith's experiments, with Strep pneumonia, injection of which strains caused the mouse to die?

alternate segregation

N1 and N2 move toward one pole and T1 and T2 move toward the opposite pole

adjacent 2 segregation

N1 and T1 move toward one pole and T2 and N2 move toward the other

adjacent 1 segregation

N1 and T2 move toward one pole and T1 and N2 move toward the other pole

that have two copies of the long arms of chromosomes 14 and 21, apparently the short arms these chromosomes which ae lost carry no essential genetic information

People who are carriers of familial down syndrome although they posses only 45 chromosomes, their phenotypes are normal because

spontaneous nondisjunction in egg formation

Primary Down syndrome usually arises from ____________

fusion of two non-homologue afrocentric chromosomes to form one larger chromsomes

Robertsonian translocations involve?

Bacterial

_______ DNA is frequently methylated to distinguish it from foreign, unmethylated DNA that may be introduced by viruses:

heterchromatin

_______ is characterized by a general lack of transcription, the absence of crossing over, and replication late in the S phase

when an individual is heterozygous for inversion

________________________, the gene order of the two homologs differs, and the homologous sequences can align and pair only if the 2 chromosomes form and inversion loop

when an individual is homozygous for a particular inversion.

______________________________, no special problems arise in meiosis, and the two homologous sequences can align and separate normally

roberstsonian translocations

a cause of some cases of Down syndrome

homologous copies of each chromosome

a cell that is triploid contains three

aneuploidy

a change in the number of individual chromosomes

chromsome inversion

a chromsome segment is inverted-turned 180 degrees

fragile x syndrome

a disorder that includes intellectual disability, exhibits x-linked inheritance and arises with a frequency of about 1 in 5000 Male births, has been shown to result from an increase in the number of repeats of a CGG trinucleotide.

chromsome duplication

a mutation in which part of the chromosome has been double.

DNA Methylation

a process in which methyl groups (CH3) are added (by specific enzymes) to certain positions on the nitrogenous bases

pericentric inversion

a region of a chromosomes spanning the centromere is broken and reattached in the reverse direction. this is an example of which type of chromosomal defect?

euchromatin

active

autopolyploidy

all chromosome sets are from a. single species

constitutive heterochromatin

all chromosomes have permanent _______ also called_______ at the centromere and telomeres as well as the Y chromosome

chromosome rearragements

alter the structure of chromosomes

robertsonian translocation

although the most frequent forms of Down syndrome are caused by random non disjunction of chromosome 21, Down syndrome occasionally runs in families. this form of familial Down syndrome involves the fusion of most of chromosome 21 to the end of chromosome 14. what is this type of chromosomal rearrangement?

polyploidy

an increase in the number of chromosome sets

heterzygous

an individual that is _______ for a duplication has one normal chromosome and one chromosome with duplication

homozygous

an individual that is __________ for a duplication carries that duplication on both chromosomes

moving to a new location and destroying the function of that gene

an inversion may break a gene into two parts, with one part....

polyploid

any organism that has more than two sets of chromsomes

half

approximately _____ of the gametes from an individual heterozygous for a reciprocal translocation are expected to be functional

rare fragile sites

are found in few ppl and exhibit mendelian inheritance. often associated with genetic disorders, such as intellectual disability, most of them consist of expanding nucleotide repeats, in which the number of repeats of a set of nucleotides is increased.

no, bc some chromosome segments are present in two copies whereas others are missing

are gametes produced by adjacent 1 and 2 segregation viable? and if not why

Edward syndrome

arises with a frequency of approximately 1 in 8000 live births -have severe intellectual disability, low-set ears, a short neck, deformed feet, clenched fingers, heart problems, and other disabilities

uniparental disomy

both chromosomes are inherited from the same parent

yes

can locations in the chromosomes also lead to position effects?

Patau syndrome

characteristics of this condition include severe intellectual disability, a small head, sloping forehead, small eyes, clef lip and palate, extra fingers and toes, and numerous other problems

structural variants

chromosome rearrangements and copy number variations are collectively referred to as

euchromatin

constitutes the majority of the chromosomal material and is where most transcription takes place.

he discovered that DNA consists of a large number of linked, repeating units, called nucleotides, each containing a sugar, a phosphate and a base -incorrectly proposed that DNA consists of a series of four-nucleotide units, each containing all four bases- adenine, guanine, cytosine and thymine in a fixed sequence.

describe what Phoebus Aaron Levene discovered in 1905

a paracentric inversion heterozygote with a crossover within the inversion

dicentric chromosomes occur during meiosis from which of the following scenarios?

negative

do phosphate groups frequently carry a negative or positive charge?

true

does the frequency of aneuploidy increase with age T or F

copy-number variations (CNVs)

duplications and deleting that range in length from thousands of base pairs to several million base pairs and these are also the variations that are detected when using microarrays.

unequal crossing over

duplications and deletions often arise from _____ _______ ____, in which chromosomes misalign during crossover

segmental duplication

duplications greater than a thousand base pairs in length

phenotype

duplications have major effects on _____

100%

during gametogenesis, what percentage of gametes would be aneuploid if nondisjunction occurred during meiosis 1?

topoisonmerases

enzymes that add or remove rotations form the DNA helix by temporarily breaking the nucleotide strands, rotating the ends around each other and then redoing the broken ends. -can both induce and relieve supercoiling, although not all of them can do both

2

for an inversion to take place the chromosome must break in _____ places

Z-DNA

forms a left-handed helix, structure of the backbone zig-zags back and forth, giving rise to its name

hairpin

forms when sequences of nucleotides on the same strand are inverted complements: consists of a region of paired bases (the stem) and intervening unpaired bases (a loop)

relocated in or near heterchromatin

genes that are ______________________ can be transcriptionally inactivated, leading to a change in phenotype

non reciprocal translocation

genetic material moves form one chromes to another without any reciprocal exchange.

deoxyribose

has a hydrogen atom at the 2 prime carbon atom and therefore contains one oxygen atom fewer over all

ribose

has a hydroxyl group attached to the 2 prime carbon atom

may or may not exhibit phenotypic abnormalities may have reduced fertility due to complications during meiosis

heterozygous carriers of chromosome inversions or reciprocal translocations

1.a chromosome may be lost in the course of mitosis or meiosis, if the centromere is deleted 2. the small chromosome generated by a roberstonian translocation may be lost in mitosis or meiosis. 3. Aneuploidy may arise through nondisjunction, the failure of homologous chromosomes or sister chromatids to separate in meiosis or mitosis. nondisjunction leads to some gametes or cells that contain an extra chromosome and other gametes or cells that are missing a chromsome

how can anueoploidy occur (3 ways)

wrong ends are connected errors in crossing over crossing over occurs between repeated DNA sequences

how can chromosome rearrangement come about?

1. they can physically link genes that were formally located on different chromosomes 2. the chromosome breaks that bring about translocations may take place within a gene and disrupt its function.

how can translocation effect phenotypes?

-succeeded in isolating and partially purifying the transforming substance. -shoed that a chemical composition closely matching that of DNA and quite diff from that of proteins. -enzymes such as trypsin and chymotrypsin, known to break down proteins, had no effect on the transforming substance -Ribonuclease, an enzyme that destroys RNA, also had no effect. -Enzymes capable of destroying DNA, however, eliminated the biological activity of the DNA -they also discovered that the transforming substance precipitated at about the same rate as purified DNA and that it absorbed ultraviolet light at the same wavelengths as DNA. -results were published in 1944 provided compelling evidence that the transforming principle-and therefore genetic information- resides in DNA

how did Avery, Colin MacLeod and McCarty contribute tot he discovery of DNA as the genetic material

using x ray diffraction images and by applying the laws of structural chemistry they were able to limit the number of structures that DNA could assume. -Watson recognized that an adenine base could bond with a thymine base and that a guanine base could bond with a cytosine base: these base pairings accounted for the base ratios that Chargaff had discovered earlier.

how did Watson and crick come to the conclusion on the shape of DNA molecules?

reconnecting the broken ends of DNA

how do organisms repair breaks?

can result if the molecule contains particular base sequences, such as stretch of alternating C and G nucleotides.

how does Z-DNA appear?

due to imbalances in the amounts of gene products (abnormal gene dosage)

how does chromosome duplication alter the phenotype?

changes in overall size of a chromosome, alteration of banding patterns revealed by chromsome staining, or the behavior of chromosomes in meiosis

how does visual examination by a microscope identify chromosome rearrangements?

30%

if 20 percent of the nitrogenous bases in a sample of DNA from a particular organism is guanine, what percentage should be adenine

have monosomy 21 and will be spontaneously aborted

if a gamete lacking chromosome 21 fuses with a normal gamete, the resulting gamete will

supercoil

if energy is used to add or remove any turns, strain is placed on the molecule, causing the helix to _____

centromere

if the deletion includes the ________, then the chromosome will not segregate in meiosis or mitosis and will usually be lost

there will be more offspring with parental phenotypes than with recombinant phenotypes

if two genes are linked and a doubly heterozygous F1 is testcrossed

when an inversion moves a wild-type allele at the white locus to a chromosomal region that contains highly condensed and inactive chromatin, the wild type allele is not expressed

in Drosophilia how you get an eye consisting of red and white spots?

purines=50%

in chargaff's analysis of the nucleotide composiiston of double stranded DNA, which of the following would have always been true?

9

in fruit flies, n=4, A fly with a trisomy would have a total of _____ chromosomes in each of its somatic cells?

loop out

in individuals heterozygous for deletion, the normal chromosome must ____ ____ during the pairing of homologs in prophase 1 of meiosis to tallow the homologous regions of the two chromosomes to align and undergo synapsis.

abnormal gametes that do not give rise to viable offspring and thus no recombinant progeny are observed

in individuals heterozygous for inversion, crossing over within the inversion is not diminished, but when crossing over does take place, the outcome is

alternate segregation produces all viable gametes and adjacent produces none

in individuals who are heterozygous for a reciprocal translocation, which pattern of chromosome segregation produces viable gametes and progeny?

10

in this relaxed state a stretch of 100bp of DNA would assume about ___ complete turns

allopolyploidy

in which all chromosome sets are from two or more species

trisomy 8

intellectual disability, contracted fingers and toes, low set malformed ears, and a prominent forehead -most individuals with this condition are mosaics.

paracentric inversions

inversions that do not include the centromere

pericentric inversions

inversions that include the centromere

plasmids

many bacteria contain additional DNA in the form of small circular molecules called _______, which replicate independently of the chromsome

position effect

many genes are regulated in a position-dependent manner. If their positions are altered by an inversion their expression may be altered. what is this called?

5 million base pairs

microscopy, however can detect only large chromosome rearrangements, typically those that are ______ in length

positive supercoiling

molecules that are overrotated exhibit

genetic mosaicism

nondijunction in a mitotic division may generate patches of cells in which every cell has a chromosome abnormality and other patches in which every cell has a normal karyotype. this type of disjunction leads to regions of tissues with different chromosome constitutions, a condition known as ______

heterochromatin

often inactive

translocation carriers

people who have a certain type of translocation that can ultimately lead to conditions such as familial down syndrome

autopolyploidy

polyploidy in which all sets of chromosomes originate from the same species is called...

common fragile sites

present in all humans and are a normal feature of chromosomes, often the locations of chromosome breakage and rearrangements in cancer cells, leading to chromosome deletions, translocations, and other chromosome rearrangments

hetercrhomatin

remains in a highly condensed state throughout the cell cycle, even during interphase

B-DNA

right-handed helix, has a clockwise spiral

A-DNA

right-handed helix, shorter and wider than B-DNA, and its bases are tilted away from the main axis of the molecule

polynucleotide strand

series of nucleotides linked with phosphodiester linkages is called a __________ strand

fragile sites

sites that develop constructions or gaps when the cells are grown in culture and that are prone to breakage under certain conditions

histones

small, positively charged proteins of five major types H1, H2A, H2B, H3, and H4

phosphodiester linkages

strong covalent bonds; which join the 5 prime phosphate group of one nucleotide to the 3 prime hydroxyl group of the next nucleotide

diploid with 13 chromosomes

suppose that gametes from two related diploid species going to produce a hybrid species. IF the original parents had 12 and 14 chromosomes, respectively, the resulting hybrid would be?

Tetraploid with 24 chromosomes

suppose that gametes from two related diploid species join to produce a hybrid species, and the original diploid parents had 8 and 16 chromosomes respectively. there is a subsequent doubling of the chromosomes in this hybrid species to produce allopolyploid. this allopolyploid would be?

supercoiling

takes place when the DNA helix is subjected to strain by being overwound or underwound

pairing and synapsis

the ___ and ____ of homologous regions require that one or both chromosomes loop and twist so that these regions are able to line up

telocentric

the centromere is at or very near the end of the chromosomes

submetacentric

the centromere is displaced toward one end, creating a long arm and a short arm ( on humans chromosomes, the short arm is designated by the letter p and the long arm by the letter q

metacentric

the centromere is located approximately in the middle, so the chromosome had two arms of equal length

acrocentric

the centromere is near one end, producing a long arm and a knob, or satellite, at the other end

expansion of a trinucleotide repeat region on the x chromsome

the chromosomal abnormality that leads to fragile-x syndrome involves

karyotype

the complete set of chromosomes possessed by an organism

nucleosome

the core of protein and DNA produced by digestion with nuclease enzymes is the simplest level of chromatin structure

translocation

the effect of _____ on chromosome segregation in meiosis depend on the nature of the translocation

pseudodominance

the expression of a normally recessive mutation

give rise to a translocation carrier

the fusion of a translocation chromosome with no otherr copies of chromosomes 21 and 14 with a normal gamete will give rise to

trisomy

the gain of a single chromosome, represented as 2n+1. a human would have 47 chromosomes

tetrasomy

the gain of two homologous chromosomes represented as 2n+2, humans would have 48 chromsomes

roberstonian translocation

the long arms of two afrocentric chromosomes become joined to a common centromere through a translocation, generating a metacentric chromosomes with two long arms and another chromosomes with two very short arms. the smaller chromosome is often lost because very small chromosomes do not have enough mass to segregate properly during mitosis and meiosis. The result is an overall reduction in chromosome number

chromosome deletion

the loss of a chromosome segment

monosomy

the loss of a single chromosome, represented as 2n-1. a human would have 45

nullisomy

the loss of both members of a homologs pair of chromosomes. it is represented as 2n-2 where n refers to the haploid number of chromosomes : in humans the person would have 44 chromsomes

Sex-chromosome aneuploidies

the most common aneuploidies seen in living humans

down syndrome

the most common autosomal aneuploidy in humans

translocation

the movement of genetic material between non homologs chromosomes or within the same chromosome

which genes are located in the deleted region.

the phenotypic consequences of a deletion depend on....

is wider and does not have major and minor grooves

the structure of A-DNA differs from that of normal B-DNA in that A-DNA....

cytogenetics

the study of inheritance and aberrations of heredity at the level of the chromosome

inter chromosomal dupliacations

the two copies are found on different chromsomes

intrachromosomal duplications

the two copies are found on the same chromsome

have complimentary sequences when one is read from 5 to 3 and the other is read from 3 to 5

the two strands of a DNA molecule....

Short

true or False: the long chromosome is generally lost after several cell divisions in Familial Down syndrome carriers.

true

true or false? more than one aneuploid mutation may occur in the same individual?

reciprocal translocation

two way exchange of segments between the chromsomes

euchromatin

undegoes the normal process of condensation and decondensation in the cell

negative supercoiling

underrotated molecules exhibit

duplications, deletions, inversions, and translocations

what are the 4 different types of chromosome rearrangements

nullisomy monosomy trisomy tetrasomy

what are the four different types of aneuploidy?

1. the genetic material must contain complex information 2.the genetic material must replicate faithfully 3. the genetic material must encode the phenotype 4. the genetic material must have the capacity to vary

what are the four major characteristic that genetic material must posses?

1. separate from normal chromosomes 14 and 21 in Anaphase 1 of meiosis. -jalf of the gametes will have the translocation chromosome and no ther copies of chromosomes 21 and 14. the other half will be normal each with a. single copy of chromosomes 21 and 14 and will result in normal offspring 2. the translocation chromosome may separate from chromosome 14 and pass into the same cell with the normal chromosome 21. -produces abnormal gametes only -half will have tow functional copies of chromsome 21 and the other half will lack chromosome 21 3. the translocation chromosome and the normal copy of chromosome 14 segregate together -pattern is rare because the two centromeres are boy derive from chromosome 14 and usually separate from each other. -all gametes are abnormal -half will result in monosomy 14 and the other half trisomy 14. all are spontaneously aborted

what are the three different ways that a translocation chromosome segregates when a translocation carrier produces gametes?

cytosine thymine uracil

what are the three pyrimidines in nucleic acids

1. the heterozygous condition may produce imbalances in the amounts of gene products similar to those produced by extra gene copies. 2. normally recessive mutations on the homologous chromosome lacking the deletion may be expressed when the wild-type allele has been deleted ( and is no longer present to mask the recessive allele's expression) 3. some genes must be present in two copies for normal function

what are the three reasons that individuals heterozygous for deletion may have multiple defects

sugar phosphate group a nitrogen-containing base

what are the three repeating units of DNA

makes the separation of the tow strands of DNA easier during replication and transcription. -underrotated, so separation of the two strands during replication and transcription is more rapid and requires less energy -supercoiled can be packed into a smaller space than can relaxed DNA

what are the two advantages of Negative supercoiling over relaxed state?

euchromatin heterochromatin

what are the two basic types of chromatin

Adenine and guanine

what are the two examples of purine that DNA and RNA contain

C and T

what are they pyrimidine bases in DNA

net positive charge

what charge do histones have?

that RNA isolated from TMV is sufficient to infect tobacco plants and direct the production of new TMV particles. -This finding confirmed that RNA carries the genetic instruction in this virus

what did Alfred Geiger and Gerhard Schramm demonstrate?

cell death

what do double stranded breaks in DNA cause

reduced recombination among genes located in the inverted region

what do individuals heterozygous for inversion also exhibit?

maternal nondisjunction

what do most cases of downs syndrome and other types of aneuploidy in humans arise from?

six membered ring attached to a five-member ring

what does a purine consist of?

sugar phosphate and a base

what does each nucleotide contain?

six member ring only

what does pyrimidine consist of?

how many hydrogen bonds there are between the two strands

what does the melting temperature of a DNA molecule depend on?

1 prime carbon atom of the sugar

what does the nitrogenous base always form a covalent bond with

core particle consisting of DNA wrapped around two times around an octamer of eight histone proteins (two copies of each). much like thread wound around a spool.

what does the nucleosome consist of??

a genetic variant at the Polo-like Kinase 4 (PLK4) gene that increases the frequency of aneuploidy bc it drastically increases the probability of errors in early mitosis in her zygotes which often leads to aneuploidy -it regulates the centriole and disruption of this can lead to failure of the chromosomes to separate properly in mitosis.

what factor might help explain the high rate of aneuploidy in human conceptionS?

the enzyme cleaves the "string" between the "beads", leaving individual beads attached to about 200 bp of DNA -the enzyme chews up all the DNA between the beads and leaves a core of proteins attached to a fragment of DNAq

what happens if a small amount of nuclease is added to a chromatin that is isolated from the nucleus of a cell and viewed with an electron microscope? IF more is added?

chromsome rearrangement occurs

what happens if the wrong ends of broken DNA are connected?

Tetranucleotide hypothesis

what hypothesis states that the structure of DNA was not variable enough to make it the genetic material? -also contributed to the idea that protein is the genetic material because the structure of protein, with its 20 different amino acids, could be highly variable

deoxyribose

what is DNA's sugar called

ribose

what is RNA's sugar called

one or more individual chromosomes are added or deleted

what is an example of anueploidy

a piece of chromosome may be duplicated, deleted, or inverted

what is an example of chromosome rearrangements

3n, 4n, 5n, or more

what is an example of polyploid

a deletion of the short arm of chromosome 5

what is criteria-du-chat syndrome caused by?

a phosphorus atom bonded to four oxygen atoms

what is included in a phosphate group

eukaryotic chromosomes have many origins of replication, while bacteria have one origin of replication

what is one difference between DNA replication in bacteria vs eukaryotes?

RNA has a hydroxyl group attached to the 2 prime carbon of the sugar

what is one way that RNA differs from DNA

the appearance of a characteristic loop structure in meiosis

what is one way to detect duplications?

unequal crossing over

what is the frequent cause of red-green color blindness in humans?

suppressed recombination among genes which allows alleles adapted to a specific environment to remain together, unshuffled by recombination

what is the importance of inversions in evolution

5 prime carbon of the sugar

what is the phosphate group always bonded to?

makes it more reactive and less chemically stable from DNA , hence why DNA is better suited to serve as the long-term carrier of genetic information

what is the result of the additional oxygen atom in RNA molecules

bar mutation

what mutation in fruit flies causes a reduced number of facets in the eye resulting in a smaller eye that is not oval shaped.

4 percent

what percent of the human genome consists of segmental duplications?

2 percent

what percentage of all fetuses with a chromosome mutation survive to birth?

negative supercoiling

what state is DNA most likely to be found in?

1. hydrogen bonds-link the bases on opposite strands, relatively weak bonds so that separation of the two nucleotide strands can occur 2. interaction between the stacked base pairs in the interior of the molecule. stacking interactions stabilize the DNA molecule but do not require that any particular base follow another, thus the base sequence of the DNA molecule is free to vary, allowing DNA to carry genetic information

what two types of molecular forces hold together two strands of DNA?

trisomy 18

what type of aneuploidy is responsible for Edwards syndrome in humans?

phosphodiester bond

what type of bond is formed between the hydroxyl group of one nucleotide and the phosphate group of an adjacent nucleotide, forming the sugar-phosphate backbone of DNA?

displaced duplication

what type of duplication is this? -the duplicated segment is located some distance from the original segment,t either on the same chromosome or on a different one

reverse duplication

what type of duplication is this? -the duplication is inverted

fruit fly with an X chromosome but no y chromosome

what was one of the first aneuploids to be recognized?

-the pollen containing an extra chromosome was not as successful in fertilization -trisomic zygotes were less viable

what were the effects of the trisomy mutation to the Jason-weed plants?

nucleiod

when a bacterial cell is viewed with an electron microscope, its DNA frequently appears as a distinct clump called a

haploinsufficient

when a single copy of a gene is not sufficient to produce a wild-type phenotype

late in S phase

when are fragile sites often replicated?

prophase 1 because the two chromosomes are not homologous throughout their length

when do problems in chromosome pairing arise in heterozygotes and why?

plenty of water surrounds the molecule and their are no unusual base sequences in the DNA- conditions that are likely to be present in the cells

when does the B-DNA structure exist?

H_DNA

when some of the DNA unwinds and a single polynucleotide strand from one part of the molecule pairs with double-stranded DNA from another part of the molecule

primary Down syndrome

when you have 3 full copies of chromosome 21

when double-stranded breaks occur in the DNA molecule found within a chromosome

where do chromosome rearrangements originate from?

inversions and translocations and sometimes in deletions of new adjacencies of genes and gene parts

where is the position effect seen?

B-DNA

which DNA structure is the most stable?

RNA

which contains numerous hairpins RNA or DNA

Z-DNA

which form of DNA is a left handed double helix?

H1

which histone is not part of the octomer that forms the nucleosome core?

A-DNA

which of the DNA structures exists when there is less water present

eukaryotic chromosomes are linear and there is a problem with copying the ends

which of the following makes DNA replication more complex in eukaryotes than in prokaryotes?

adjacent 2 segregation bc the two homologous chromosomes usually separate in meiosis

which one of these is the most rare and why? -adjacent 2 segregation -adjacent 1 segregation -alternate segregation

DNA

which part of the T2 bacteriophage entered E.coli cells in the Hershey- chase experiment that confirmed the identity of the transforming principle?

tandem duplication

which type of duplication is this?- the duplicated segment is immediately adjacent to the original segment

Francis Blakeslee

who began breeding several Jimson-weed plants in 1913 and observed unusual ratios of progeny

William Astbury

who began studying the 3 dimensional structure of DNA in 1947

Heinz Fraenkel-Conrat and Bea Singer -worked with TMV (tobacco mosaic virus ) - TMV virus possesses a single molecule of RNA surrounded by a helically arranged cylinder of protein molecules. -found that after separating the RNA and the protein of TMV, he could remix the RNA and protein of different strains of TMV and obtain intact, infectious viral particles -results proved that RNA carried the genetic info in TMV

who demonstrated that a few viruses use RNA not DNA as their genetic material and how?

John Belling

who demonstrated that the Jimsonweed plants were in fact trisomies?

Calvin Bridges in 1913

who discovered the first example of aneuploidy in a fruit fly and in what year?

Watson and Crick in 1953

who discovered the three dimensional structure of DNA ? and in what year

Rosalind Franklin

who obtained strikingly better images of DNA molecules through x ray diffraction?

X-ray diffraction

x-rays beamed at a molecule are reflected in a specific patterns that reveal aspects of the structure of the molecule