exam 1 sem 2

division of unicellular organisms

reproduces the entire organism

multicellular eukaryotes and cell division

needed for development from a fertilized egg, growth, and repair

cell cycle

the life of a cell from formation to its own division

most cell division results in

two daughter cells with identical genetic information, DNA

meiosis

a special type of division that can produce sperm and egg cells

prokaryotes and reproduction

reproduce by binary fission

first step of binary fission

chromosome replication began

second step of binary fission

one copy of the origin is now at each end of the cell

3rd step of binary fisison

replication finishes

4th step of binary fission

two daughter cells (clones) result

what happens with binary fission

the chromosome replicates, and the two daughter chromosomes actively move apart

plasma membrane and binary fission

pinches inward, dividing the cell into two

protein involved during binary fission

share resemblance with eukaryotic actin

in eukaryotes, cell division occurs by

mitosis and meiosis

cell cycle phase

G1 (first gap), S synthesis of DNA, G2 (second gap), M (mitosis and cytokinesis), G0 (substitues for G1 for cells postponing division or never dividing again)

external factors for decision to divide

environmental conditions, signaling molecules

internal factors to decide to divide

cell cycle control molecules and checkpoints

G1 phase

cell growth, signaling molecules can cause cell to accumulate molecular changes during G1 that promote progression through the cell cycle, if the cell passes the restriction point, the cell becomes committed to enter S phase

S phase

chromosomes replicate, two copies stay joined to each other called sister chromatids, G1 has 46 chromosomes, G2 has 92 chromatids (46 sister chromatids)

G2 phase

cell synthesizes proteins needed during cell division

three checkpoints of the cell cycle

G1 checkpoint (restriction point), G2 checkpoint, Metaphase checkpoint

checkpoint proteins

act as sensors to determine if the cell is in proper condition to divide

loss of checkpoints can lead to

mutations and cancer

what does restriction point check for

if conditions are favorable for cell division and if the DNA is damaged, G1 cyclin ismade in response to sufficient nutrients and growth factors

what does G2 checkpoint check for

DNA damage, determines if all the DNA is replicated, and monitors the levels of proteins needed

what does metaphase checkpoint check

if all chromosomes are attached to the spindle apparatus

original cell is called

mother cell

new cells are called

daughter cells, they are geneticall identical to the original

mitosis phases

prophase, prometaphase, metaphase, anaphase, telophase

sister chromatids

two identical copies with associated proteins, tightly associated at centromere, serves as attachment site for kinetochore

spindle formed from

microtubules which are made of tubulin

three types of microtubules

astral microtubules, polar microtubules, kinetochore microtubules

astral microtubules

position spindle in cell

polar microtubules

separate two poles

kinetochore microtubules

attached to kinetochore bound to centromeres

what does the mitotic spindle ensure

that each daughter cell will obtain the correct number and types of chromosomes

centrosomes

microtubule organizing centers, duplicate at the beginning of mitosis, define a pole

which cells have centrioles

only animal cells, not other eukaryotes

prophase

chromosomes are replicated, nuclear membrane dissociates, chromatids condense

prometaphase

nuclear envelope completely fragments, mitotic spindle is fully formed, centrosomes move apart, spindle fibers interact with sister chromatids, two kinetochores on each pair of sister chromatids are attached to kinetochore microtubules from opposite poles

metaphase

pairs of sister chromatids are aligned along a plane on the metaphase plate

anaphase

connections broken between sister chromatids, kinetochore microtubules shorten, overlapping polar microtubules lengthen

telophase

chromosomes have reached their poles and decondense, two seperate nuclei are formed

cytokinesis

two nuclei are segregated into seperate daughter cells

cytokinesis in animals

cleavage furrow constricts like a drawstring to separate the cells

cytokinesis in plants

cell plates forms a cell wall between the two daughter cells

variations in chromosome structure and number can cause

several human diseases, but it is important in evolution of new speciesi

structure of chromosome

short arm is p, long arm is q

different kinds of chromosomes

metacentric, submetacentric, acrocentric, telocentric

metacentric location of centromere

middle

submetacentric centromere location

off center

acrocentric location of centromere

near end

telocentric centromere location

at the end

banding pattern of chromosomes

Giemsa stain gives G banding

in diploid species, members of a pair of chromosomes are called

homologues

autosomes

each homologue is identical in size, we have 22 pairs of these

sex chromosomes

X and Y are very different from each other, we have either XX or XY

only haploid cells in the human body

gametes

life cycle

sequences of events that produces another generation of organisms

sexually reproducing organisms life cycle

alternation between haploid cells or organisms and diploid cells

diploid dominant species

most animal species

haploid dominant species

many fungi and protists, haploid cells form diploid zygote, which goes through meiosis to produce 4 haploid zygotes

sexual reproduction requires

a fertilization event in which two haploid gametes unite to create a diploid cell called a zygote

Meiosis

the process by which haploid cells are produce dfrom a cell that was originally diploid

bivalent

group of two homologous chromosomes

tetrad

the 4 sister chromatids

prophase 1

chromosomes condense, bivalents form from crossing over, nuclear membrane brakes down

prometaphase 1

spindle apparatus complete, chromatids attach to kinetochore microtubules, pairs of sister chromatids attached to one pole

synapsis

homologous pairs of sister chromatids associate with each other lying side by side to form a bivalent or tetrad

synaptonemal complex

a protein structure that connects homologous chromosomes, function is uncertain

crossing over

physical exchange between chromosome pieces of the crossing bivalent, increases genetic variation

chiasma

arms of the chromosomes tend to separate but remain adhered at a crossover site

metaphase 1

bivalents organized along metaphase plate as double row, mechanism to promote genetic diversity

anaphase 1

segregation of homologues, connections between bivalents break, but sister chromatids stay connected, both separated pairs move to either pole

telophase 1

sister chromatids have reached their respective poles and decondense and nuclear membranes reform

end of meiosis 1

two haploid cells, with no pairs of homologous chromosomes

in between meiosis 1 and meiosis 11

no s phase (duplication of DNA)

mitosis produces

two diploid daughter cells that are genetically identical

meiosis produces

four haploid daughter cells

heredity

the transmission of genetic information from parent to offspring

genetics

the science of heredity, studies both genetic similarities and genetic variation

gregor mendel

1822-1884, father of genetics, experiments with pea plants

mendel showed that

parents pass heritable factors to offsprings (genes)

advantages of using pea plants

different variable traits, observable characteristics, self fertilizing, easy to breed

monohybrid cross

one trait being tested for

what did mendel need to explain

why one trait disappeared in the F1 generation, and why it reappeared in F2

mendels law of segregation describes

inheritance of a single characteristic

mendels 1st hypothesis

genes are found in alternative versions called alleles, a genotype is the listing of alleles an individual carries

mendels second hypothesis

for each characteristic, an organism inherits two alleles, one from each parent

mendels third hypothesis

if the alleles differ, the dominant allele determines the phenotype

mendels fourth hypothesis

law of segregation, allele pairs separate from each other during the production of gametes so that a sperm or egg carries only one allele for each gene

for a pair of homologous chromosomes

alleles of a gene reside at the same locus

homozygous individuals have

same allele on both homologues

dihybrid cross

tracks two characteristics at once

dihybrid second generation ratio

9:3:3:1

law of independent assortment

each pair of alleles segregates indepndently of the other pairs of alleles during gamete formation

testcross

mating between an individual of unknown genotype and a homozygous recessive individual to show if the unknown genotype has a recessive allele

multiplication rule

the probability of two or more events happening together = the product of individual probabilities of the independent single events

addition rule

the probability of an event that can occur in two or more independent mutually exclusive ways, the sum of the individual probabilities

pedigree

shows the inheritance of a trait in a family through multiple generations, demonstrates dominant or recessive inheritance, to deduce genotypes of family members