X-Y system
males are XY and females XX
X-O system
insects
only one type of sex chromosome, females: XX , males :X
Z-W system
males ZZ and females ZW
haplo diploid system
females are diploid, males are haploid (bees and ants)
female
in humans absence of y makes the person
male
presence of y in humans makes person
XX, XY, XO
3 genotypes in Drosophila
XO or XY
male Drosophila flies
Hermann Henking
firebug, discovery of the X chromosome
Nettie Stevens and Edmund Wilson
differences in types of sex chromosomes, discovery of Y chromosome (Tenebrio=mealworm)
female
XX or XO is biologically what in humanns
male
XX or XXY in humans is biologically
organisms cannot survive without an X chromosome
why is OY lethal?
error in meiosis
absence or addition of "X" id due to (well-tolerated0
no because they do not contain the same genetic info
are X and Y strictly homologous
yes (homologous pair)
do X and X pair during meiotic cell division
no because they do not have shared sequence homology
do x and y crossover?
X chromosome
contains many types of essential genes in humans (this is why lack of this chromosome is lethal)
tolerated but not lethal
an extra X chromosome in humans is
Y chromosome
chromosome that contain genes associated w/ sperm production and drives male sexual differentiation
NR0B1 gene
gene on X chromosome that produces DAX protein
DAX protein
produces ovary tissue
SRY gene
the sex determining region of the Y chromosome in males. Encodes the testis-determining factor, which turns the primordial gonads into the testes
TDF protein
inactivates DAX protein; testes determining factor; triggers testes to develop
XO
sterile male in flies; Y still needed for sperm production, but sex would still be male
no so they produce twice gene product as XY or XO
Do flies perform X inactivation?
no
do flies use DAX or SRY system
Sxl transcriptional activator
X-linked gene in flies; forms protein homodimers
Homodimer
activates ovary formation in flies
sxl transcriptional inhibitor
autosome linked gene; forms heterodimer with activator
heterodimer
prevents ovary formation
amniocentesis
needle puncture of the amniotic sac to withdraw amniotic fluid for analysis
non-neonates
forms of genetic testing for juveniles and adults; very easy way to test (buccal swab, saliva sample, hair sample, blood test)
pedigrees
before genetic testing, how did genetic counselors determine the genes and diseases people might have?
proband
in genetics research, the individual displaying the trait or characteristic being studied
monogenic traits
Traits determined by a single gene.
pedigree male
square
pedigree female
Affected Female Pedigree
affected male
dead male/female
sex unspecified
diamond
consanguineous mating
mating between relatives
Carrier of x linked trait
abortion/stillbirth
non-identical twins
dizygotic twins
identical twins (monozygotic twins)
dominant traits
each affected indiv must have at least one affected parent; no carriers! unaffected indiv must be homozygous recessive
unaffected offspring
in a dominant trait, two two unaffected parents only produce
recessive traits
affected individual can arise from two unaffected parents (carriers); affected=homozygous recessive; must inherit two copies to show trait
recessive traits
often arise from consangineous mating
rescessive trait
generally occurs due to founder effect
founder effect
genetic drift that occurs after a small number of individuals colonize a new area (limited gene flow, consangineous mating); offspring more likely to inherit two copies of the recessive trait=>more people with the trait
X-linked inheritance
trait determined by gene located on X chromosome; males are only hemizygous
hemizygous
A gene present on the X chromosome that is expressed in males in both the recessive and dominant condition
mother
males only inherit an X-linked gene from
male
more likely to be affected by x-linked gene
Y-linked inheritance
only males!
affected
al male offspring of an affected father in y-linked genes are
recessive traits
tends to skip generations
dominant trait
does not skip generations
virus (infectious particles)
Non-living
Cause disease in BOTH eukaryotes and prokaryotes
Transmit genetic materially horizontally
Ex. Retroviruses: Hepatitis B and HIV;
DNA integrates into host genome, stays FOREVER!!
Drive organismal evolution!
bacteria
Prokaryotic organisms
Trade plasmid DNA
Allows rapid evolution within and between populations
Ex. Toxins shared between two different bacterial species
Development of antibiotic resistance (from plasmid genes!)
genome
total set of chromosomes in the organism; contains all genes necessary for organism survival
plasmid
A small ring of DNA that carries accessory genes separate from those of the bacterial chromosome; replicate independently
plasmid
contain genes that give organism extra capabilities (virulence factors, antibiotic resistance, ability to metabolize more diverse groups ,help organism survive in changing conditions)
no, but they are extremely helpful
are plasmids essential to survival of bacteria
origin of transfer
the location on an F factor or within the chromosome of an Hfr strain that is the initiation site for the transfer of DNA from one bacterium to another during conjugation
origin of replication
a particular sequence in a genome at which replication is initiated
vertical transmission
parent to offspring; mitosis and meiosis; coupled w/ cell division; prokaryotes and eukaryotes
horizontal transmission
transmission of genetic material (DNA or RNA) between two organisms; NOT limited to cell division process; not limited to same spp; not limited to genomic DNA; Can be within a generation, within or between species, types of organisms, intentional or unint
conjugation, transformation, transduction
three versions of horizontal transmission
conjugation
A temporary union of two organisms for the purpose of DNA transfer. involves sex pilus. between two live cells; can transfer antibiotic resistance
donor and recipient cells of same spp and sex pilus
conjugation requires
F+ cell
contains F factor as a plasmid
F- cell
does not have F plasmid anywhere
Hfr cell
a cell with the F factor integrated into the chromosome
F' cell
following unequal excision of F factor from chromosome, F' cells contain
extra genes from the donor cell's genome.
Have one full chromosome, F factor (as a plasmid), AND extra copies of
genomic DNA from donor cell
Creates partial diploid cells
transformation bacteria
artificially insert gene into competent bacteria; does not require live donor cell, only need live recipient cell
dna fragment
does not have an origin of replication,
so it must be integrated into chromosome (or existing plasmid);like in transformation; artificially done in test tube
Transduction in bacteria
DNA is transferred from a donor cell to a recipient via a bacteriophage
naked" donor DNA and competent recipient cell
what does transformation require
bacteriophage carrying bacterial DNA (but no viral DNA) from a previous infection and a recipient cell conducive to phage infection
what does transduction require