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338 Cards in this Set

  • Front
  • Back
chrom's are made up of many ______
what is the haploid # of chrom's in humans?
________ genes are distributed among human chrom's
_______ megabases (over 3 billion nucleotides) in human chrom's
what is mendels 4th postulate?
during gamete formation, segregating pairs of unit factors assort independently of eachother
in 1903 _________ discovered that there must be more unit factors than chromosomes
Sutton and Boreri
t/f Certain genes are transmitted according to the law of independent assortment-
F- certain genes are NOT transmitted according to the law of independent assortment
describe independent assortment-
2 genes on 2 different homologous pairs of chromosomes form 4 genetically distinct gametes
when 2 nonallelic genes are on the same chrom, that tend to be inherited together
when 2 genes are so close to one another that no crossover occurs and parental gametes are produced
complete linkage
this type of crossover takes place during prophase I
crossover of 2 linked genes
________ are 2 new allele combinations generated by crossover b/t 2 linked genes
recombinant/ crossover gametes
t/f it's more likely that crosses involving genes on the same chrom will result in a percentage of offspring from recombinant gametes
the % of offspring from recombinant gametes is variable, depends on the _______ b/t 2 genes
these 2 men first explained crossover events-
Morgan and Sturtervant
Morgan discovered ______ in __________ (where the inheritance pattern of genes is located on the X-chromosome)
X-linkage, Drosophila
during meisosi, these are the pts of genetic exchange-
chiasmata- synapsed homologous chrom's
these are synapsed homologous chrom's and the pts of genetic exchange during meiosis
t/f if 2 genes are located relatively close to eachother along a chromosome they are MORE likely to have a chiasma form b/t them and undergo genetic exchange-
FALSE, the closer 2 genes are located to eachother the LESS likely they are to form a chiasma and undergo genetic exchange, the FARTHER apart they are, the more likely to undergo genetic exchange
physical exchange of chromosomal material during meiosis
cross over
t/f in drosophila, crossover occurs in females, in humans it occurs in BOTH sexes
who came up w/ the idea of chrom mapping?
who came up with the idea of x-linkage
thomas morgan, by study of the drosophila
this involves the data based on recombination events b/t genes that could be used to map a sequence of genes on the chrom
chromosomal mapping
the frequency of exchange can be taken as an estimate of _________ b/t 2 genes or loci along a chrom
relative distance
if you have 24 map units you have how many centimorgans (cM's)
__________ represent points of genetic exchange
the physical exchange leading to recombination
crossing over
the % of recombinants can be used to determine-
relative distance of genes to one another
t/f in flies crossover only occurs in females
t/f crossover events occur on autosomal and sex chromosomes
T (however in flies, crossover only occurs in females)
Sturtevant and Morgans data strongly supports the idea that chrom's contain genes organized in a __________, and that genes are equivalent to Mendel's 'unit factors'
linear order
who discovered that genes are equivalent to Mendel's theorized unit factors
Sturtevant and Morgan
t/f crossing over can go undetected
T, if the linkage b/t 2 the alleles is unchanged after cross-over
this type of crossover involves 3 gene pair's in the exchange
double crossover
what are the 3 requirements of mapping 3 or more genes-
1)the genotype of the organism producing the gametes must be heterozygous for the genes of interest
2)genotypes can be accurately determined by observing phenotype
3)a sufficient # of offspring must be produced
this is the crossover event in one region of the chrom that inhibits a second event in nearby regions-
what is the coefficient of coincidence (c)?
c= observed DCO/expected DCO
what is the equation for interference-
I= 1.0- c
t/f interference decreases as the genes in question are located farther apart-
as the ______ b/t 2 genes increases, mapping experiments become more inaccurate
_______ can be obscured when studying genes of interest on the same chrom
a statistical method used to determine if 2 genes are linked or unlinked
LOD score method
this method was important for assigning genes to chrom's and in constructing human chrom. maps-
LOD score method
describe somatic cell hybridization as a way to assign human genes to a chrom-
1) 2 cells in a culture can be induced to fuse, producing a heterokaryon
2) the cell contains 2 nuclei in a single cytoplasm
3) the nuclei fuse, creating a synkaryon
4)as cells are cultured, the human chrom's are gradually lost
human deletion syndrom, in which it gets its name from the 'crying like a cat' symptom of the genetic disease-
cru du chat
identified in 1963
this chromosomal abberation involves 2n + or - a number, X
chromosomal abberations involving multiples of n-
euploidy; polyploidy
chromosomal abberation in which multiples of the same genome are present-
chromosomal abberation in which multiples of different genomes are present
the loss of one chromosome (2n-1)
in humans this is the name of the disease caused by the loss of one chrom (monosomy)-
turner syndrome (45, X)
-monosomy of autosomes, will die during development
this syndrome involves the monosomy of autosomes, and death during development occurs
turner syndrome
in Drosophila this is the syndrom caused by the loss of 1 chrom (2n-1)
Haplo IV, where a loss of Chrom IV occurs and results in reduced body size and low viability
this is the syndrome in Drosophila caused bye the loss of 1 chrom (monosomy, 2n-1) in which the loss of chrom IV occurs and results in reduced body size and low viability
Haplo IV
t/f plants can tolerate the loss of one chrom-
_________ is the partial loss of 1 chrom
segmental deletion
this syndrome is an example of segmental deletion (loss of 1 part of a chrom as opposed to the whole chrom)
cru du chat (crying like a cat)
what is the designation for cru du chat syndrome?
46, -5p (where -5p indicates the loss of part of the small arm of chrom 5)
what chrom is missing in cru du chat syndrome?
the p arm of chrom 5
__________ births result in cru du chat syndrome (____% die during the 1st year of life)
1 in 50,000 and 90% die during the 1st year of life
list the problems accompanying the cru du chat syndrome-
1) anatomic malformation
2) gastrointestinal and cardiac complications
3) mental retardation
4) abnormal development of larynx
t/f in cru du chat the deleted portion of chrom 5 is paternal in origin in most of the cases
TRUE, 80% of the cases of cru du chat the deleted portion of chrom 5 is paternal in origin
the addition of a chrom to a diploid genome (2n+1)
what syndrome is commonly associate with trisomy in which the designation is 47, XXY
Kleinfilder syndrome
t/f the addition of an autosome is usually lethal during development
the only human autosomal trisomy in which a significant # of individuals survive longer than a year past birth
down syndrome
what is the designation for down syndrome?
trisomy 21
47, 21+
an extra chrom, called chromosome 21
how many births result in down syndrome
approximately 1 in 800 live births (6,000 children a year)
what are some phenotypical results of down syndrome (trisomy 21)
1)fold in corner of each eye
2)flat face
3)round head
5)protruding tongues
6)short hands
7)physical psychomotor and mental retardation
8)short life expectancy
9)prone to respiratory disease
10)heart malformations
___% of people affected by down syndrome are expected to live to the age of 50
50%, over 50 they teend to develop many problems
what would be the designation of a BOY with down syndrome?
(47, XY, 21+)
what would be the designation of a girl with down syndrome?
(47, XX, +21)
the _______ is the source of the extra chromosome in 95% of down syndrome cases
t/f the female is more than likely responsible for the extra chromosome present in down syndrome children
t/f the female is more than likely responsible for the deleted portion of chrom 5 in the cru du chat syndrome-
FALSE, 80% of the cases, the deleted chrom 5 portion is paternal in origin
at the age of 30 how many births would likely be affected by down syndrome?
1 in 1,000
at the age of 40 how many births would likely be affected by down syndrome?
1 in 100
why are older women more likely to have a child w/ DS?
the primary oocytes that undergo complete meiosis I and enter into meiosis II in a 40 yr old woman are older than the oocyte that went through the same process 10 years ago
what is the mean maternal age for those giving birth to down syndrome children
t/f maternal nondisjunction during the 2nd meiotic division is the cause of trisomy 21
F, nondisjunction during the 1st meiotic division is the most common cause of DS
what is the most common cause of DS?
maternal nondisjunction of the 1st meiotic division
what is the designation of Patau Syndrome?
(47, +13)
___ in _______ live births result in Patau Syndrome
1 in 19,000
what is the avg survival rate of someone w/ Patau syndrome
3 months (1 in 20 will live longer than 6 months)
this syndrome is addition of a chromosome to the 13th genome, results in death due to cardiopulmonary arres, congenital heart disease and pneumonia
Patau Syndrome
this syndrome is related to partial monosomy
Cru du chat
this syndrome is trisomy 13
Patau syndrome
this syndrome is trisomy 18
Edwards Syndrome
this syndrome is trisomy 21
Downs Syndrome
this is a test used to detect partial monosomy
fluorescent in situ hybridization (FISH)
it is estimated that ______% of all conceptions are terminated by spontaneous abortion
t/f a significant number of spontaneous abortuses are trisomic
t/f trisomies for every chromosome have been detected
_________ aberrations for every chromosome have been detected
_____ abberations are rarely found
what 3 organisms have been commonly used to study modes of sexual differentiation by studying the lifecycle
1)Clamaydomonas (green algae)
2) Zea Mays (corn)
3) C. elegans (nematodes)
C elegans have ___ autosomal chrom's
what are the genotypes of female and male nematodes?
female XX
male XO (they lack the Y chromosome)
how do you determine the sex of a nematode?
the ratio of X chromosomes to the number of autosomal chromosomes
a ratio of ____ in nematodes results in hermaphrodites, and a ratio of ____ results in males-
1, 0.5
who used the hermipteran insect Lugaeus turicus to study XX/XY mode of sex determination
Edmund Wilson
females produce similar gametes and are referred to as being the ________ sex
t/f females are the heterogametic sex
F, homogametic (XX)
t/f males are the heterogametic sex
T, (XY)
Edmund Wilson used _______ to begin to understand how sex is determined
in 1920 ______ discovered the Y chromosome
Painter discovered the Y chromosome
what did Painter discover?
Y chromosome
when was it determined that the diploid number is 46
this syndrome involves abnormal sexual development such as male genitalia and internal ducts, but testes fail to produce sperm, enlargment of breasts and rounded hips, below normal intelligence
Klinefelter syndrome
what are some symptoms of Klinefelter syndrome?
1) male genitalia and internal ducts, but failure to produce sperm
2) enlargement of breasts and rounded hips
3) below avg intelligence
4) long arms, legs, large feet and hands
what is the designation for Klinefelter syndrome?
(47, XXY) 44 autosomes and the XXY chromosomes

can also be 48,XXXY; 48,XXYY; 49,XXXXY; 49,XXXYY
how many males will have the klinefelter syndrome?
2 in every 1,000
what are treatment options for klinefelter syndrome?
1) testosterone replacement for correction of the androgen deficiency
2) tailoring school curricula to address learning difficulties
syndrome involving female external genitalia and internal ducts, but the ovaries are rudimentary
turner syndrome
this phenotype would indicate what genetic disorder?
short stature, skin flaps on the back of neck, underdeveloped breasts, but normal intelligence-
turner syndrome
t/f someone with turners syndrome would be LESS susceptible to disorders such as osteoperosis, hypothyroidism, and diabetes
FALSE, they would be MORE susceptible
what is a viable treatment for turners syndrome?
hormone treatment (estrogen)
what is the designation of turners syndrome?
(45, X) 44 autosomes and one X chromosome
how many females will develop turner syndrome?
1 in 2,000 (most 45,X embryos die in utero)
when a mitotic error during development occurs such as (45,X)/(46,XY) and (45,X)/(46,XX)
t/f turner syndrome is an example of a mosaic genetic disorder
T, mosaic is a mitotic error during early development
which syndrome is a good example of a mosaic disorder?
Turner Syndrome
term for an error during cell division in which the homologous chrom's fail to seperate and migrate to opposite poles
this syndrome is a result of nondisjunction that results in monosomic gametes
Turner syndrome
this syndrome is a result of nondisjunction where trisomic gametes form
this designation occurs 1 in 1200 births, can appear normal or can have underdeveloped secondary sex characteristics, sterility and mental retardation
this sex linked disorder will result in above avg height and subnormal intelligence
no consistent correlation b/t the extra Y chrom and the predisposition of males to behavioral problems
region of the human Y chrom that contains genes
region of the human Y chrom that lacks genes
region of the Y chrom that has some genes that are homologous to the X and some that aren't
NRY-non recombining region
region of the human Y chrom that shares homology w/ the X chrom
PAR (psuedoautosomal region)
region of the human Y chrom that encodes a gene product that signals undifferentiated gonadal tissue of the embryo to form testes (the testis determining factor)
SRY region (sex determining region Y)
this region of the Y chromosome is NOT in female chromosomes
SRY (sex determining region Y) region
t/f the SRY region is present in ALL male mammals
how can a human male have the sexual genotype XX?
if the SRY region is present on one of the X chrom's
how can human females have the sexual genotype XY?
if the SRY region is missing from the Y chromsome
explain the transgenic mice experiment-
eggs that are XX are injected with SRY DNA and the offspring develop into males thus proving that SRY gene is the primary signal for male development
t/f because females have 2 X chromosomes more genes are expressed in females
F, only a SINLGE active X chromosome exists in each cell, no more genes are expressed in females than males
this is a term to describe a mechanism that regulates the level of gene products at a certain loci on the X chrom such that the males nad females have equal amnts of gene product
dosage compensation
the dark staining body in interphase cells of females is referred to as-
barr bodies
t/f the study of sex chromosome syndromes have shown that regardless of how many X chromosomes exist, all but one is inactivated
TRUE, no matter how many X chromosomes exist, all but one is inactivated
if all but one X chrom is inactivated why aren't individuals w/ Turner or Kleinfelder syndrome 'normal'?
-perhaps inactivation doesn't occur during early stages of development
-maybe not ALL of the genes are inactive
this is the idea that inactivation of the X chrom occurs randomly-
Lyon Hypothesis (Mary Lyon and Liane Russell)
the mosaic pattern of orange or black in Calico cats is an example of -
the Lyon Hypothesis
-in rare cases there are male calicos (1 in 3,000)
Pigmentation gene on the ______ chromosome allows calico cats to have one allele that will give rise to black color and another allele that gives rise to the orange color
X chromosome
the allelic forms of Glucose-6-Phosphate dehydrogenase in which fibroblasts taken from females and G6PD isoforms were analyzed is evidence for -
Lyon Hypothesis
give an example of a phenotype of an X-linked disorder in females-
the retinas of female carriers are composed of mosaic patches of colorblind and normal areas
how are almost all genes on an entire X chrom inactivated?
there is a region on the X chrom, called the X Inactivation Center (XiC) 1Mb or 10^6 base prs
this is the region of the X chromosome that is responsible for the inactivation of almost all genes on an entire X chrom
X Inactivation Center (XiC)
in the X inactivation center what gene is transcribed (RNA made) that is involved in inactivating the X chrom
Xist gene
what experiment proved that the XIC region inactivated the genes on the extra X chromosome
an experiment that deleted that region resulted in the X chromosome no longer being inactivated thus proving that the XIC region was responsible for inactivating the genes on the extra X chrom
who first showed in 1916 that in flies the Y chrom doesn't determine maleness?
Calvin Bridges
what did Calvin bridges propose about the drosophila sex determination?
he proposed that both the X chrom's and the autosomes play a role in sex determination
t/f if a fly displays the sex genotype XXY it will be male-
F, XXY flies were normal females, thus proving that Y chromosomes did not cause maleness
what is the genotype of sterile drosophila males?
what is the role of the Y chromosome in flies-
the Y chromosome in flies lacks male determining factors, but Y does contain some genes important for male fertility
what determines sex in flies?
the ratio of X chroms to the number of haploid sets of autosomes
what characteristics would indicate a triploid female drosophila?
heavy set bodies, course bristles, course eyes, and they may be fertile
how do triploid drosophila females originate?
from diploid eggs fertilized by normal haploid sperm
what kind of gametes are produced by triploid drosophila females?
gametes that display a wide range of chrom complements, thus giving rise to offspring w/ a variety of abnormal chromosomal constituents
this involves the sex-determining system of flies in which sexual phenotype is controlled by a balance b/t genes on the X chrom and genes on the autosomes
Genic Balance Theory
this sex determining factor of flies involves the X:A ratio at 1:2, where the presence of an additional X chrom alters the balance and results in female differentiation
threshold for maleness
t/f mutants have been identified that are involved w/ sex determination in flies
this is the autosomal gene causing maleness even if the sex genotype is XX
transomer (tra) tra/tra
XX tra/tra are male
this X linked gene is known as the 'master switch' in which if females of XX have it they will die, but if XY males with the gene have it, they are fine-
Sex lethal (sxl)
XX sxl/sxl-females die
XY sxl males- are fine
t/f in both mammals and flies x-linked genes are transcribed at twice the level of the genes in females
FALSE, only in drosophila (flies)
term that describes the expression of a recessive allele on one homolog as caused by the deletion of the dominant allele on the other homolog
describe psuedodominance
expression of a recessive allele on one homolog as caused by the deletion of the dominant allele on the other homolog
what is the inheritance pattern of chrom duplication?
how do new genes arise?
duplications of an essential genes and an extra copy of the gene can get mutations and thus give rise to a new gene
t/f in general an essential gene doesn't accumulate mutations
TRUE, duplications of essential genes, and extra copies can get mutations
this describes a segment of the chrom that is turned around 180 degrees
t/f the inverted sequence may or may not include the centromere
TRUE, doesn't necessarily involve the centromere
in this type of inversion the arm ratio remains unchanged
paracentric inversion
in this type of inverstion the arm ratio is changed
pericentric inversion
what are the consequences of inversions during gamete formation?
normal linear synapsis during meiosis is not possible
an inversion loop will form and crossing over doesn't occur
in this type of inversion the centromere is not part of the rearranged chromosome segment
paracentric inversion
what happens when a single crossover occurs w/i an inversion loop?
the inversion loop can produce abnormal chromatids
when a single crossover occurs, this type of inversion doesn't involve centromere's as part of the rearranged chrom segment
when a single crossover occurs, this type of inversion involves the centromere as part of the rearranged chrom segment
pericentric inversion
this is the movement of a chromosomal segment to a new location in the genome
the exchange that occurs in translocation occurs b/t 2 ___________ chromosomes
breaks occur w/i the ___________ region on 2 nonhomologous chromosomes
this syndrome involves sensitive sites along chrom X, results in mental retardation
Fragile X syndrome
fragile X syndrome affects ___________ males and ___________ females
1 in 4000 males and 1 in 8000 females
what gene on the X chromosome accounts for the Fragile X syndrome?
FMR1 gene encodes an RNA binding protein, and thus a trinucleotide repeat of CGG occurs
what reasons are bacteria good research organisms?
1) short reproductive cycles
2) grow fast
3) haploid
4) spontaneous mutations
this is considered the primary source of genetic variation
spontaneous mutation
why is it advantageous for bacteria to be haploid-
b/c all mutations will be expressed DIRECTLY in the descendants of mutant cells
type of medium where the nutrient components of the growth medium are very simple and consist only of an organic carbon source-
minimal medium
wild type bacteria for all growth reuqirements and can grow on minimal medium
a bacterium that is unable to synthesize one or more organic compounds-
an auxotroph that loses its ability to make histidine would be disignated as-
what 2 bacteriologists were involved in conjugation studies
lederburg, tatum
process where the genetic info from one bacterium is transferred and recombined w/ that another bacterium
genetic info is transferred from one chrom to another, resulting in an altered genotype
genetic recombination
describe tatum and lederburgs experiment that implied genetic recombination-
they plate 2 auxotrophic strains (A and B) on minimal medium and discovered NO GROWTH, but after mixing the 2 (both containing components the other didn't have) they found that plating would produce prototrophs, and growth occurred on the minimal medium through genetic recombination
cells that serve as donors of parts of their chrom's
F+ cells (f for fertility)
recipient bacteria that receive the donor chrom material (DNA) and recombine it w/ part of their own chrom
F- cells
who designed the U tube in which to grow F+ and F- cells
physcial interaction is the initial stage of the process of conjugation and is mediated through a conjugation tubed called the ______
F or sex pilus
F+ cells contain a __________ that confers the ability to donate part of their chrom during conjugation
F factor (fertility factor)
following conjugation and genetic recombination- recipient cells always become ___
a gene of the F factor that is involved in the transfer of genetic info
tra genes
t/f the F factor has been shown to consist of a circular dbl stranded DNA mx, making up about 2% of the bacterial chrom
t/f the F factor is AKA a plasmid
process in which a separation of 2 strands of the dbl helix of DNA occurs, one moving by way of a sex pilus into a recipient cell (F-) and the other remaining in the donor cell (F+), both replicating which results in both cells becoming F+
cells that behave as chrom donors, a special calls of F+ cells that demonstrate an elevated frequency of recombination
Hfr (high frequency recombination)
t/f when Hfr comes into contact with F- cells, the F-cells become Hfr
FALSE, they remain F- cells
t/f when F+ cells come into contact w/ F- cells, the recipient becomes F+
technique in which Hfr and F- cells come into contact but are put in a blender to separate conjugation, then grown on medium containing the antibiotic to ensure recovery of only recipient F- cells
interrupted mating technique
what experiment proved that Hfr bacterium was transferred linearly and gene order and distance between genes, as measure in minutes could be predicted
interrupted mating technique- by interrupting the conjugation of Hfr and F- cells at different pts in time, one could see which genes were transferred at a faster rate and before others
t/f minutes are equivalent in bacterium to mu's in eukaryotes
t/f E.coli chrom is circular (no free ends) w/ a point of origin (O) that varies from strain to strain
What determines the O site of E.coli Chrom-
the F factor intergrates into the chrom at different pts and its position determies the O site
the use of _________________ w/ different Hfr strains allowed researchers to map the entire E. coli chrom
interrupted mating technique
Hfr underwent a comination at a rate of ______ times more frequently than F+ strain
Alderberg discovered that the F factor could lose its integrated status, causing the cell to revert to the F+ state known as
F'-> Hfr
F' cells initiate conjugation w/ F- cells, much like F+ cells do; the f factor is transferred to the F- cell, and then duplicate w/i the recipient cell, b/c the recipient still has a complete chrom- this creates a partially diploid calle called a
t/f the transfer of DNA b/t bacteria is unidirectional
this is an enzyme consisting of polypeptide subunits encoded by 3 rec genes (recb, recc, and recd)
RecBCD protein
extrachromosomal, circular piece of dsDNA that replicates independent of the chromosome
what are the 2 components of R plasmids
1)RTF-resistance transfer factor
2) r-determinants
this component of the R plasmid encodes genetic info essential to transfer the plasmid b/t bacteria
RTF factor
this component of the R plasmid are genes conferring resistance to antibiotics
what would happen if a bacteria contained r-determinant plasmids but not RTF plasmids?
the bacterial cell would still be resistant however it would not be able to transfer the genetic material for resistance to recipient cells
_______ derived from E.coli, encodes for one or more proteins that are highly toxic to bacterial strains that don't harbor the same plasmid
Col plasmid- not usually transmissable to other cells, whereas the R plasmid is easily trasmissable
proteins, called ______, encoded for by the Col plasmid kill neighboring bacteria
process in which small peices of extracellular DNA are taken up by a living bacterium, leading to a stable genetic change in the recipient cell
what are the 2 main categories of transformation
1)entry of DNA into a recipient cell
2)recombination of the donor DNA w/ its homologous region in the recipient chrom
t/f only competent bacterial cells will take up DNA in transformation
the recombinant region in transformation that contains one host strand and one mutant strand
after the first round of cell division following transformation what is produced-
1 cell containing the original nontransformed chrom and the other containing the transformed chrom.
these are referred to as bacterial viruses
these are viruses that have bacteria as their host
bacteriophage that includes an icosahedral head filled w/ DNA, a tail consisting of a collar, tube, sheath, base plate and tail fibers-
bacteriophage T4
what are the 3 processes in assembly of a mature virus structure-
1)DNA packaging as viral heads are assembled
2)tail assembly
3)tail fiber assembly
a cleared area where bacteria is absent
______ occur wherever a single virus has intially infected one bacterium in the lawn that as grown up during incubation
virally mediated gene transfer from one bacterium to another
when approximately _____ viruses are constructed w/i a bacteria, the cell lyses and the mature phages are released to infect other bacterial cells
~200 viruses
process in which viral DNA enters a bacterial cell and instead of replicating in the bacterial cytoplasm, its integrated into the bacterial chrom
t/f in lysogeny- no new viruses are produced and no lysis of the bacterial cell will occur
TRUE, unless introduced to certain stimuli that would induce viral DNA to lose its integrated status and initiate replication, phage reproduction, and lysis of the bacterium
viral DNA integrated into the bacterial chromosome
ciruses that can either lyse the cell or behave as a prophage
viruses that can only lyse the call are referred to as-
bacterium harboring a prophage has been ___________ and is said to be ________
lysogneized, lysogenic
bacterium that is capable of being lysed as a result of induced viral reproduction
viral DNA, that can replicate either in the bacterial cytoplasm or as part of the bacterial chrom is classified as an-
virus mediate bacterial DNA transfer
who discovered transduction
Zinder and Lederberg
describe the Zinder-Lederberg experiment using Salmonella-
using the Davis U tube, they placed 2 auxotrophic strains of Salmonell LA-2 and LA 22 on either side of the filter, when plated independently the LA 22 side produced prototrophs
this type of inheritance is exhibites when intermeidate phenoypic expression fo a trait occurs in an organism that is heterozygours for 2 alleles
incomplete dominance
inheritance where 2 distinctive effects of 2 alleles occur simultaneously in a heterozygous organism
chromosomes consist of very lg numbers of genes that are part of the same chrom and are said to be __________
the _________ is the unit of transmission during meiosis
chromosome (NOT THE GENE)
-the reshuffling or recombination of the alleles b/t homologs
-a physical breaking and rejoining process that occurs during meiosis
crossing over
the degree of crossing over b/t any 2 loci on a single chrom is proportional to the distance b/t them known as-
interlocus distance
these indicate the relative locations of genes on the chrom
chromosome maps
type of linkage resulting in only parental or noncrossover gametes
complete linkage (seldom occurs)
t/f the frequency w/ which crossing over occurs b/t any 2 linked genes is proportional to the distance seperating the respecitve loci along the chrom-
as the distance b/t 2 genes increases the proportion of _______ gametes increases and that of __________ gametes decreases
recombinant, parental
t/f the number of recombinant gametes approaches but will not exceed 50%
what ratio is characteristic of complete linkage?
_________ is observed only when 2 genes are located very close together and the # of progeny is relativiely small
complete linkage
who was the first to discover X-linkage
these are known as points of genetic exchange
t/f if linked genes exist in a linear order along the chrom, then a variable amount of exchange occurs b/t any 2 genes
the physical exchange of genetic info leading to recombination
crossing over
t/f linkage and crossing over are restricted to X-linked genes
F, thy could also be demonstrated w/ autosomal genes
in flies crossing over only occurs in-
what is the chromosomal theory of inheritance-
chromosomes contain genes in a linear order and these genes are equivalent to Mendel's unit factors
the closer 2 loci reside on the axis of the chrom, the less likely that any ____________ event will occur b/t them
single crossover
when 2 loci are far apart, crossover will occur in an area of the chrom b/t them, this seperates them, yielding-
recombinant gametes
the chromatids that are not involved in the exchange of material during cross over
non cross over gametes
in a single crossover-the %age of tetrads involved in an exchange b/t 2 genes is twice as great as the percentage of __________
recombinant gametes produced
what is the theoretical limit of recombination due to crossing over?
double exchanges of genetic material result from -
DCOs (double cross overs)
in the case of a ____________, 2 seperate and independant events or exchanges must occur simultaneously
double crossover
if 3 genes are relatively close together along one chrom, the expected frequency of dbl crossover gametes is
a)extremely high
b)extremely low
extremely LOW
the 3 criteria for a successful mapping cross-
1) genotype of the organism producing the crossoer games must be heterozygoes at all loci under consideration
2)crross must be constructed so that genotypes of all gametes can be accurately determined by observing the phenotypes of offspring
3)a sufficient # of offspring must be produced in the mapping experiment to recover a representative sample of all crossover classes
phenotypes that complement one another (i.e. one wild, other mutant)
reciprocal classes
these phenotypes generally occur in the greateast proportion of offspring
noncrossover phenotype
phenotype, because of their probability of occurence, must be present in the least numbers
double crossover phenotype
when a crossover event in one region of the chrom inhibits a 2nd event in nearby regions
_________ decreases as the genes in question are located father apart
this type of exchange of genetic material takes place in Drosophila as well as certain Fungi
mitotic recombination
a statistical method used to determine if 2 genes are linked or unlinked
LOD score method
technique that aids in assigning human genes to their respective chrom's that relies on the fact that 2 cells in culture can be induced to fuse into a single hybrid cell
somatic cell hybridization
when 2 cells from different organisms are induced to fuse together they produce a__________, containing 2 nuclei in a common cytoplasm-
when the 2 nuclei of a heterokaryon eventually fuse together they form a-
result of fragments of a particular chrom become transferred to another chrom
_______ ensures genetic constancy within members of the same species
chromosomes such as XY, often characterize one sex or the other
heteromorphic chrom's/ sex chrom's
_______ rather than _________ ultimately serve as the underlying basis of sex determination
genes rather than chrom's
differentiation involving the gonads where gametes are produced
primary sexual differentiation
differention that involves the overall appearance of the organism, IE differences in such organs as mammary glands, external genetalia
secondary sexual differentiation
an individual containing ONLY male or ONLY female reproductive organs-
unisexual, dioecious, gonochoric
individuals containing both male AND female reproductive organs
bisexual, monoecious, hermaphroditic
individuals of intermediate sexual differentiation, who are most often sterile
green alga Chalmydomonas spend most of their lives in the _______ phase, asexually producing daughter cells by mitotic division
this organism spends most of its life in the haploid phase, reproducing asexually
this organism has an alternating life cycle b/t the diploid sporophyte stage and the haploid gametophyte stage, that are linked by the processes of meiosis and fertilization
Zea mays
what are the 2 sexual phenotypes of C. elegans-
hermaphroditic-both testes and ovaries and males with only testes
approximately how many male C. elegans would be produced after self fertilization?
less than 1%, the rest hermaphrodite
what percentage of male vs hermaphrodite would result in the cross fertilization of a male and a hermaphrodite C. elegans
50% male, 50% hermaphrodite
t/f C. elegans lacks a Y chromosome completely
T, maleness is determined by genes located on both the X chrom and autosomes
what determines the sex of C. elegans?
the ratio of X chromosomes to the number of sets of autosomes
who demonstrated that females have 2 X chromosomes whereas males only have 1, by examining Protenor (with 14 chrom's)
fertilization by X bearing sperm resultes in ______ offspring, and fertilization by X deficient sperm results in ________ offspring
female, male
ratio of offspring depending on the random distribution of the X chrom into 1/2 male gamets during segregation
XX/XO sex determination or Protenor mode of sex determination
what 2 organisms did Wilson study to better understand sex determining chromosomes
Protenor and Lygaeus turicus
Wilson discovered that males of the Lygaeus turicus species have a single X and a smaller heterochromosome called a
Y chrom
mode of sex determination following random fertilization, equal numbers of male and female progeny will be produced w/ distinct chrom complements-
XX/XY sex determination
In Protenor and Lygaeus insects, males produce unlike gametes and are thus described as-
heterogametic sex
females who have 'like' sex chroms are the________ producing uniform gametes w/ regard to chrom numbers and types
homogametic sex
t/f the male is always the heterogametic sex
who discovered the Y chrom in human males
when was the diploid number of human chromosomes finally clarified?
t/f the Y chrom determines maleness in humans
syndrome where genetalia and internal ducts are usually male, but testes are rudimentary and fail to produce sperm
Klinefelter syndrom
syndrome where affected individ'l has female external genetalia and internal ducts, but ovaries are rudimentary
Turner syndrome
t/f in Klinefelter syndrome intelligence is not affected
FALSE, its usually below normal
t/f in Turner syndrome intelligence is not affected
what is the designation of Klinefelter syndrome?
(47, XXY)
what is the designation of Turner syndrome?
both turner and klinefelter syndrome result from __________, the failure of the X chrom to segregate properly during meiosis
individuals called _____ whose somatic cells display 2 different genetic cell lines, each exhibiting a different karyoype
(IE 45,X/46,XY or 45,X/46,XX)
t/f most 45,X fetuses die in utero and are aborted spontaneously
TRUE, making Klinefelters more frequent than Turner syndrome
syndrome that occurs every 1 in 1200 births, varies highly in expression, some women are normal and other are underdeveloped secondary sex charactersitcs, sterility, retardation
47, XXX syndrome
present on both ends of the Y chrom are ______ that share homology w/ the X chrom and synampse and recombine during meiosis
gene that controls male sexual development, encodes a gene product that triggers the undifferentiated gonadal tissue of an embryo to form testes-
SRY (sex determining region Y)
t/f the SRY gene on the Y chrom provides the primary signal for male development
the critical factor in determining sex of drosophila is the ratio of X chrom's to the number of haploid sets of _________