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Flashcards in test 1 Deck (114):
1

asexual cell division

makes identical cells

2

sexual cell division

makes non-identical cells

3

diploid cells

have homologous pairs

4

haploid cells

don't have homologous pairs

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chromosomes

composed primarily of DNA and protein
# of chromosomes varies greatly from organism to organism

6

DNA

one long linear molecule

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protein

eukaryotic cells have more protein than DNA (by MW)

8

histones

basic proteins that are the most abundant protein bound to eukaryotic chromosomes

9

cell cycle

G1 (gap 1), S (synthesis), G2 (gap 2), M (mitosis)

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what 2 things occur during mitosis

karyokinesis (division of cell nucleus) and cytokinesis (division of cell insides to give 2 cells)

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what happens in G2 before mitosis

pair of centrioles replicates creating 2 pairs of centrioles

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cell cycle checkpoints

G1/S checkpoint
G2/M checkpoint
M checkpoint

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G1/S checkpoint

cell checks to make sure cell is of sufficient size and there is no DNA damage

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G2/M checkpoint

DNA replication must be complete and DNA must be undamaged in order for cell to proceed beyond this checkpoint

15

M checkpoint

cell checks to insure that spindle apparatus has properly formed

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G1 (gap 1) stage

stage for DNA replication preparation

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S (synthesis) stage

stage during which DNA replication (chromosome replication) occurs

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G2 (gap 2) stage

stage for mitosis preparation

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M (mitosis) stage

stage during which visible events of cell division occur and the replicated chromosomes segregate to separate daughter cells.

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what does mitosis do

makes multicellular organisms from fertilized eggs, replaces old cells, regenerates organs, and is a means of asexual reproduction for many organisms

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4 stages of mitosis

prophase
metaphase
anaphase
telophase

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prophase

chromosomes condense
nuclear membrane disappears
nucleolus disappears
spindle apparatus forms--spindle fibers attach to kinetochore of centromere
each chromosome made up of 2 sister chromatids held together at the centromere

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metaphase

chromosomes line up along equatorial plane (chromosomes most easily observed)
protein cohesin holds sister chromatids together

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chromosomes classified according to

size and position of their centromere (expressed as chromatid arm ratio)
short arm=p
long arm=q
classified by q/p ratio

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metacentric

have their centromeres more or less in the middle
q/p=1-1.7

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submetacentric

centromere located nearer to one end
q/p=1.7-3

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acrocentric

centromere located very near one end
q/p=3-7

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telocentric

centromere located almost at the end
q/p greater than/equal to 7

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anaphase

sister chromatids (now chromosomes) disjoin and move to opposite poles
movement occurs due to molecular motors and the microtubules of spindle

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telophase

events of prophase reversed and cytokinesis occurs
in plants: plate (middle lamella) forms between 2 poles
in animals: cleavage furrow pinch cell in 2

31

sexual cell division

meiosis
produces 4 haploid cells from 1 diploid cell through 2 divisions (meiosis I and meiosis II)
in higher organisms: meiosis occurs in sex organs producing haploid sperm and egg
produces cells that are genetically distinct from each other and from mother cell

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other name for meiosis I

reductional division

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other name for meiosis II

equational division

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meiosis I

preceded by and S phase (chromosomes replicate) and is subdivided into 4 stages
prophase I
metaphase I
anaphase I
telophase I

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prophase I

chromosomes condense, nuclear membrane disappears
nucleolus disappears, spindle apparatus forms--spindle fibers attach to kinetochore of centromere (same as prophase of mitosis) PLUS synapsis and crossing over
each chromosome made up of 2 sister chromatids held together at the centromere
further subdivided into 5 stages

36

subdivisions of prophase I

leptonema
zygonema
pachynema
diplonema
diakinesis

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leptonema

stage when chromosome condensation begins
chromomeres may be present

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zygonema

-synapsis (pairing) occurs with appearance of proteinaceous synaptonemal complex made up of 2 lateral elements and 1 central element
-synapsis may start in the end of the chromosomes (at telomeres) which may be bound to nuclear membrane
proceeds as chromosomes "zip up" toward centromere
-condensation continues

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pachynema

tighter pairing and crossing over occur at this stage
recombination nodules may appear on synaptonemal complex and are thought to be the sites of crossing over

40

crossing over

usually occurs between a pair of chromosomes with most showing double, triple, quadruple (or more) crossover
where crossover occurs along chromosome varies with each meiosis
double crossover may be 2, 3, or 4 strand

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diplonema

synaptonemal complex disappears and pairing is relaxed
chromosomes still held together at site of crossover (chiasmata)
relaxins

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diakinesis

homologous pairs continue to pull apart and terminalization of chiasmata seen (chiasmata slip toward telomeres)

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metaphase I

homologous pairs (still synapsed) line up on metaphase plate

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anaphase I

homologous pairs (not sister chromatids) separate

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nondisjunction

when sister chromatids don't separate in anaphase I

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telophase I

cytokinesis divides cell into 2 cells

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meiosis II

events are exactly the same as meiosis I except the cells have half the number of chromosomes

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prophase II

stage is often skipped
chromosomes do not elongate and then recondense--instead when telophase I is complete 2 daughter cells proceed directly to metaphase II

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metaphase II

chromosomes align along metaphase plate

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anaphase II

sister chromatids separate

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telophase II

cytokinesis produces 4 cells

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tetrad/bivalent

paired chromosomes at prophase I

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monad

chromosome consisting of just 1 chromatid

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dyad

chromosome consisting of 2 chromatids

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male cell cycle

2n spermatogonia--> primary spermatocytes (cells in middle of meiosis I)--> secondary spermatocytes (cells in middle of meiosis II)--> 1n spermatids
lose most of their cytoplasm and grow a flagellum and become sperm

56

female cell cycle

2n oogonia-->oocytes (stops here in embryo)
cytokinesis at telophase I and II are unequal producing a primary and secondary polar body that doesn't survive
prophase I arrest
meiosis II not completed until after fertilization

57

pre-mendelian concepts of heredity

spontaneous generation
preformation
inheritance of acquired characteristics
blood as the hereditary material

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spontaneous generation

said that new life continually arises from non-living material
denial of concept of heredity
disproved by redi and pasteur

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preformation

tiny preformed human (homonculus) is present in one of the gametes
if so, heredity would come from 1 parent only

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inheritance of acquired characteristics

idea that traits acquired during organisms lifetime can be passed along to the offspring
lamarck's theory (lamarkism)

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blood as the hereditary material

genetic material is in the blood (or sap) and crossing mixes the blood of 2 organisms

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mendel

augustinian monk
"father of genetics"
experimented with the garden pea (available in many varieties, produced many offspring, and could be self-crossed and crossed)

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monohybrid cross

crossing things differing in only 1 trait (round seeds x wrinkled cotyledons)

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conclusions of monohybrid cross

pairs of factors
dominance
segregation

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pairs of factors

each individual has a pair of factors for each trait

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dominance

if an individual has 2 different factors, 1 will be expressed (dominant one) and 1 will no (recessive one)

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segregation

when the individual produces gametes, the pair separates with 1 going to each gamete (law of segregation)

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gene

factors mendel described

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allele

pair of factors

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genotype

genetic make up
usually expressed by designating symbols for the genes (DD, Dd, dd)

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phenotype

expression of the genotype (what you see)
yellow seeded vs. green seeded

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homozygous

individual with 2 identical alleles

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heterozygous

individual with 2 different alleles

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reciprocal cross

cross in which sex of the 2 parents is reversed
tall F x dwarf M vs. dwarf F x dwarf M

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test cross

cross to a homozygous individual
usually done to determine genotype of an unknown individual

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back cross

cross to an individual with the same genotype as one of the parents

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dihybrid cross

cross between plants differing by 2 traits
yellow round seed x green wrinkled seed

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conclusions of dihybrid cross

independent assortment

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independent assortment

segregation of 1 pair of alleles is independent of the segregation of another pair of alleles (law of independent assortment)

80

correns, devries, and tschermak

in 1900, these 3 discovered mendel's article and made his work known to the scientific world

81

n-hybrid crosses

mendel's idea can be applied to crosses involving multiple genes
to predict outcome of cross, first determine gametes produced

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number of gametes F1 produces in n-hybrid cross

2^n

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number of genotypes F2 produces in n-hybrid cross

3^n

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number of phenotypes F2 produces in n-hybrid cross

2^n
assuming simple dominance

85

basic genetic notation systems

plant system
drosophila system

86

plant system

gene abbreviations begin with upper case (dominant allele) or lower case (recessive allele)

87

drosophila system

gene abbreviations represented by letters with (wild-type allele) or without (mutant allele) a + sign
mutant allele begins with capital letter if mutant is dominant to wild type and with lower letter if the mutant is recessive to the wild type allele
w+ dominant to w
B dominant to B+

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exceptions to mendel's idea of dominance

incomplete dominance
incomplete dominance with variable expressivity
co-dominance
incomplete penetrance

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incomplete dominance/partial dominance/lack of dominance

one allele is not completely dominant to the other and the phenotype is an intermediate
ex. flower color of snapdragons

90

co-dominance

one allele is not completely dominant to the other and the phenotype shows the expression of both alleles
ex. ABO blood type

91

incomplete penetrance

occurs when dominant allele sometimes behaves as if it were recessive
in the heterozygote one allele is expressed most of the time but not always
ex. huntington's disease with 95% penetrance (5% of heterozygotes never develop the disease)

92

variable expressivity

closely related to incomplete penetrance but is seen with quantitative traits
degree of expression (color/height) varies among individuals with the same genotype

93

overdominance

in some cases the most extreme phenotype is seen in the heterozygote (not homozygous dominant)
ex. sickle cell anemia (in malaria environment)

94

exceptions to mendel's idea of traits/genes/alleles relationaship

multiple alleles
multiple genes/polygenes/quantitative traits/multiple factor traits
gene interactions
pleiotropy
lethal genes

95

multiple alleles

all genes have more than just 2 alleles but each individual only has 2
ex. ABO blood type (I^A, I^B, i)

96

multiple genes

some traits are determined by more than 1 gene
many human traits are multifactorial traits and also have an environmental component

97

gene interactions

sometimes multiple genes produce unusual phenotypes
when there are gene interactions use genotypic ratio: 1 AABB: 2 AABb: 1 AAbb: 2 AaBB: 4 AaBb: 2Aabb: 1 aaBB: 2aaBb: 1 aabb

98

epistasis

gene interaction that occurs when 1 gene masks the effect of another
the gene that is doing the masking is the epistatic gene and the 1 that is being masked is the hypostatic gene
ex. albinism

99

tyrosinase

catalyzes an initial step in the synthesis of melanin
mutated tyrosinase=albinism

100

gene suppression

special type of epistasis where second mutation reverses the effect of the first mutation

101

complementation test

performed to to determine if mutations are alleles (same gene) or not alleles (different genes)
cross homozygotes for 2 mutations
wild type=not alleles (same gene)
mutant=alleles (different genes)

102

pleiotropy

1 gene can effect more than 1 trait

103

lethal genes

genes that kill
both recessive and dominant lethal genes but dominant lethals don't usually stay around long
huntington's=exception (dominant lethal but shows up after reproductive age so individual has already passed gene on to offspring by the time it shows up)

104

conditional mutations/temperature sensitive mutations

expression of some phenotypes is dependent upon environmental conditions
ex. siamese cat color=white when hot and black when cold (bc of temperature sensitive mutation in tyrosinase gene in homozygotes so it only produces color when cold temperature)

105

position effect

expression of a gene can be altered by moving it to a new chromosomal location
effects may be related to heterochromatinization or other effects

106

maternal effect

phenotype may be influenced by the genotype of the mother
ex. direction of coiling in shells (right coiled if mother is L_ and left coiled if mother is ll)
DOES NOT MATTER WHAT GENOTYPE OFFSPRING IS

107

probability

the number of "favorable" outcomes divided by the number of possible outcomes (assuming all outcomes are equally likely)

108

probability of independent events

2 events are independent if the outcome of 1 event does not influence the outcome of the other event (and)
probability=probability of event 1 x probability of event 2

109

probability of mutually exclusive events

2 events are mutually exclusive if only 1 of the 2 events can occur (or)
probability=probability of event 1 + probability of event 2

110

binomial expansion

this can be used to calculate the probability of a combination of 2 independent events occurring
(p+q)^2=p^2 + 2pq + q^2

111

chi squared

can be used to determine how close a set of numbers is to and "expected" ratio
test takes a set of numbers and asks how good it fits an expected ratio (like 9:3:3:1)
it calculates the probability of getting as bad or worse a fit to your expected ratio (P)

112

chi squared formula

E((O-E)^2)/expected

113

degrees of freedom (df)

n-1
n=number of classes

114

pascals triangle

used to find the coefficients of each factor in a binomial equation as well as the numerator in multi-factor quantitative cross