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117 Cards in this Set

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binary fission

chromosome replication begins


one copy of the region moves to other end


replication finishes, plasma membrane grows inward and new cell wall is deposited


2 daughter cells result

chromatin

dna molecule


visible before division

somatic cells

46 chromsomes or two sets of 23

gametes

sperm and egg cell


have half as many chromosomes ad somatic cells

genome

complete dna sequence for an organism; contains complete set of instructions for organism

chromosome when cell is not dividing

in form of long, thin chromatin fiber

chromosome after duplication

chromosomes condense; each chromatin fiber becomes coiled and folded, making them shorter and thicker.

eukaryotic cell cycle

interphase+mitosis+cytokinesis

interphase

G1 phase


S phase


G2 phase

where does most of the cellular growth occure in the eukaryotic cell cycle?

G1 phase

what happens in G2

cells are preparing to enter cell division

what is mitosis

cell division

cytokinesis

splitting of cytoplasm


two separate cells

prophase

chromatin condense forming chromosomes


sister chomatids are joined at centromere


microtubules bind to kinetochore



outcome of prophase

nuclear membrane dissapears


nucleoli have disinegrated


sister chromatids are attached by kinetochores to microtubules from opposite poles

mitotic spindle

fibers of microtubules and proteins


assembly starts at centrosome



metaphase

chromosomes line up in the midplane of cell


chromosomes are highly condensed


2 types of microtubules(kinetichore and polar)


mitosis checkpoint



anaphase

sister chromatids seperate and are moved toward opposite poles


protein tethers at centromere bw the chromatids are broken


each sister chromatid can now be called a chromsome

what does anaphase assure?

that each daughter cell recieves one of the duplicate sets of chromosomes

prometaphase

some spindle microtubules attach to the kinetochores


motor proteins move the chromosomes towards the poles


kinetochore microtubules shorten behind moving chromomes


polar micro. lengthen


motor proteins on polar micro. push chrom. apart

telophase

essentially the reverse of prophase


mitotic spindle disinigrates; chromosomes decondense; nuclear membranes reform.


nucleoli reappear.

cytokinesis in animal cells

cleavage furrow.


begins in telophase


2 daughter cells form.

cytokinesis in plant cells

cell plate.

cell plate

developed from vesicles originated from the golgi


grow until reaches plasma membrane and then cells separate

cell cycle

events leading to replication of cells

cell cycle control system

cell-cycle checkpoints


genes encode molecules involved

cell cycle checkpoints

ensure all events of a particular stage have been completed before next stage begins

key checkpoints in cell cycle

G1-S checkpoint


G2-M checkpoint


metaphase-anaphase checkpoint(spindle checkpoint)

meiosis (sexual reproduction)

2 parents


genetic variation


adaptation to changing enviroments

homologou chromosomes

paired


similar shape size and centromere position


genetic info. for same traits

ploidy

number of sets of chromosomes in a cell

haploid

one set


gametes: egg and sperm

autosome

chromosome other than sex

fetilization

union of gametes to form zygote


diploid number is restored in fertilized egg

polyploidy

3n or more


rare in animals; mostly fatal in human


common in plasnts

mitosis vs meiosis

mitosis


-single nulcear division


-2 diploid daughter cells which are genetically identical to each other and original cell


meiosis


-diploid cell undergoes 2 nuclear divisions


-genetic rearrangement


-resulting in 4 genetically different haploid daughter cells

meiosis

reduces chromsome number (2n to n)


dna replicates once (interphase)


undergoes 2 divisions


four haploid nuceli

prophase 1

homologous chromosomes exchange segments by crossing over; nuclear envelope breaks down

metaphase 1

tetrad(new chromosome formed) line up in middle


tetrads held together at chiasmata (site of crossing over)



anaphase 1

homo. chromosomes seperate and move to opposite poles.


sister chromatids stay attached at their centromeres

telophase 1

one of each pair of homo. chromosomes is at each pole.


cytokinesis occurs

prophase 2

chromosomes condense again following brief period of interkinesis.


dna does not replicate again

metaphase 2

chromosomes line up along the cells midplane

anaphase 2

sister chromatids seperateand chromosomes move to opposite poles

telophase 2

nuclei form at opposite poles of each cell.


cytokinesis occurs


four haploid cells form.


animals-gametes


plants-spores

synapsis

during prophase 1


homologous chromosomes line up and become connected by a zipper like protein called synaptonemal complex

crossing over

occurs in prophase 1


enzymes break down and rejoin DNA molecules allowing paired homo chromosomes to exchange genetic material.


produces new combinations of genes(genetic recombination)


major source of genetic variation

meitotic tetrad with 2 chiasmata

metaphase 1


the 2 chiasmata are the result of seperate crossing over events

chiasma

location where two homologous chromatids previously crossed over

genetic variations

independent assortment


crossing over

independent assortment

maternal and paternal chromosomes of homo pairs seperate independently at anaphase 1

crossing over

exchange of DNA segments between maternal and paternal homo chromo. during prophase 1

animal life cycles

gametes-fertilization-zygote-multicellular diploid organism-meisis-gametes...

gameteogenesis

formation of gametes(meiosis)

spermatogenesis

male gametogenesis


4 haploid sperm cells per cell

oogenesis

female gametogenesis


one egg cell per cell


polar bodies

trisomy 21

down syndrome

histones

positively charged proteins in cell nucleus that connect to the negatively charger DNA

nucleosomes

repeating units of chromatin structure; each consisting of a length of DNA wrapped around a complex of 8 histone molecules.


adjacent nucleosomes are connected by a DNA linker region associated with another histone protein.

Mendle's principle of inheritance


1860s


heredity

heritable factors: now genes


transfer of characteristics (traits) from parent to offspring

genetics

the science of heredity and variation in living organisms

gregor mendel

father of modern genetics


used pea plants to study inheritance of traits

P generation(P1)

parental generation

F1 generation

first generation

F2 generation

second generation

phenotype

physical appearance of an organism with respect to a specific trait


or


expression of an organisms genes

genotype

genetic makeup of an organism


combination of alleles

gene

segment of DNA that serves as a unit of heredity

locus (loci)

location of a particular gene on a chromosome

alleles

alternative versions of a gene

dominant allele

dominates over others

recessive allele

no phenotypic expression in the presence of a dominant allele

homozygous alleles

pair of identical alleles

heterozygous

having a pair of unlike alleles

hybrid

result of pure lines crossed

monohybrid cross

cross between individuals that are both heterozygous for the gene that you are following

mendel's hypothesis or model

1. alleles account for variation in inherited characteristics


2. for each trait, an organism inherits 2 alleles; one from each parent


3. alleles: dominant is expressed over recessive


4. law of segregation

law of segregation

during segregation of chromosomes in anaphase (meiosis) gametes only carry one allele for each inherited trait

monohybrid cross results

3:1 phenotype(color) ratio


1:2:1 genotype(allele) ratio

test cross

reveals the genotype of the dominant parent, or at least give some idea of the probable genotype

mendel's law of independent assortment

dihybrid cross


meiosis 1

dihybrid cross

individuals are both heterozygous for 2 different traits phenotype ratios of 9:3:3:1

varitaions on mendel's laws

1. incomplete dominance


2. codominance


3. multiple alleles


4. pleiotrophy


5. gene interactions


6. polygenic inheritance

incomplete dominance

heterozygote with intermediate phenotype between the 2 homozygous parents


dominance has no true meaning here

codominance

the heterozygote expresses characteristics of both alleles


each allele is distinctly expressed


example: ABO human blood type


three alleles of a single gene type


mutliple alleles

pleiotrophy

single gene locus


many variations


affects many aspects of the phenotype: multiple characteristics(traits)


seen with many diseases(sickle cell disease)

gene interactions

two or more genes interact to produce a novel (new) phenotype

epistasis

type of gene interaction


one gene influences the phenotype that is controlled by the second gene


preventing or masking any effects of alleles at the second gene


no novel phenotype is produced here


one gene is dependent on the presence of one or more modifier genes

albinism

epistatic


dominant allele expresses pigment of skin colr; homozygous recessive, masks the expression of pigment, regardless how many other alleles are present(even dominant)

polygenic inheritence

two or more genes have additive effects on a single characteristic


they usually are measured traits(quantitative)


--height, skin color, body form

sex chromosomes

all individuals require an X


X-female


Y- determines male


X and Y are not true homologous

in male, X from mother contains what?

active genes


male is neither homo or heterozygous


said to be hemizygous

pure breeding plants make up the

P1 generation

when mendel crossed true breeding tall plants with true breeding short, the offspring were the...

F1 generation

homologous

corresponding chromosomes from the opposite-sex parent

independent assortment

alleles of unlinked loci are randomly distributed to gametes

karyotype

chromosomal composition of an individual

haploid

one set of chromosomes per nucleus

diploid

two sets of chromosomes per nucleus

fredrick griffith

discovered genetic role of DNA in 1928


mice experiment


called it transformation

mice experiment

2 strands of bacteria: S-caused disease(pathogenic), R-not cause disease(non-patho.)


mice injected with S die, injected with R survive.


kills pathogenic bacteria with heat and mix its parts with living nonpathogenic bacteria and then injects it back into mice.


some of mice die


finds living S cell in the blood.

transformation

change in genotype and phenotype due to the assimilation of external DNA by the cell.


found in mice experiment

bacteriophage

virus that infects and kills bacteria; made of essentially DNA and protein.

james watson and francis crick 1953

molecular model for DNA

DNA replication

making copies of itself


happens in interphase, specifically S phase

mechanism of DNA replication

1.helical DNA must first untwist


2.copies its new strands


3.semiconservative



semiconservative

each strand works as a template for making a complementary strand


results in 2 new DNA molecules:


each one has old strand from parent molecules and a newly synthesized strand

where does it begin on the double helix?

origin of replication: forking point


both directions

why can new strand only grow in the 5' to 3' direction?

the daughter strand can be synthesized in one continuous piece by a DNA polymerase working from the 3 prime end

anzymes add_________to a growing strand.

nucleotides


-DNA polymerase

how is the other strand made?

new daughter strand is synthesized in short pieces as the fork opens up.


another enzyme called DNa ligases links the pieces together into a single DNA strand.

lagging strand

3' to 5' forms discontinuously



Okazaki fragments

short seperated DNA fragments (100-2000 nucleotides)

leading strand

grows continuously 5'-3' end of the old strand

DNA ligase

joins leading and lagging strands of DNA

DNA polymerase

fixes most mistakes


removes incorrect nucleotide and replaces it with the correct one


DNA repair

mismatch repair system

mistakes not removed by DNA poly. but by special enzymes that recognize the mistake and remove it; DNA poly. then fills in the correct nucleotide.