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117 Cards in this Set

  • Front
  • Back

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


dna molecule

visible before division

somatic cells

46 chromsomes or two sets of 23


sperm and egg cell

have half as many chromosomes ad somatic cells


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



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


splitting of cytoplasm

two separate cells


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


chromosomes line up in the midplane of cell

chromosomes are highly condensed

2 types of microtubules(kinetichore and polar)

mitosis checkpoint


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


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


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


similar shape size and centromere position

genetic info. for same traits


number of sets of chromosomes in a cell


one set

gametes: egg and sperm


chromosome other than sex


union of gametes to form zygote

diploid number is restored in fertilized egg


3n or more

rare in animals; mostly fatal in human

common in plasnts

mitosis vs meiosis


-single nulcear division

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


-diploid cell undergoes 2 nuclear divisions

-genetic rearrangement

-resulting in 4 genetically different haploid daughter cells


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.




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


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...


formation of gametes(meiosis)


male gametogenesis

4 haploid sperm cells per cell


female gametogenesis

one egg cell per cell

polar bodies

trisomy 21

down syndrome


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


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



heritable factors: now genes

transfer of characteristics (traits) from parent to offspring


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


physical appearance of an organism with respect to a specific trait


expression of an organisms genes


genetic makeup of an organism

combination of alleles


segment of DNA that serves as a unit of heredity

locus (loci)

location of a particular gene on a chromosome


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


having a pair of unlike alleles


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


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


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


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



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


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


corresponding chromosomes from the opposite-sex parent

independent assortment

alleles of unlinked loci are randomly distributed to gametes


chromosomal composition of an individual


one set of chromosomes per nucleus


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.


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

found in mice experiment


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



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.


-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.