Bio Final `Exam (before the final)

cell division in multicellular organisms

growth, maintenence, repair of cell tissues

cell division of single celled organisms

reproduction

The genome is made up by

the cell’s DNA

DNA in prokaryotes

one double-stranded, circular DNA molecule, resides in the nucleoid

Where are plasmids sometimes present

the genome

exchange of plasmids with other cells allows for?

gene transfer in prokaryotes

somatic cells typically have2 matched sets of what

chromosomes, makes them diploid (2n)

gametes (egg and sperm cells) have? and are?

half the number of chromosomes, haploid (1n)

Eukaryotic genome

several double-stranded DNA molecules in the form of chromosomes

DNA molecules in eukaryotic organisms also called

chromosomes

T/F: the number of DNA molecules (chromosomes) differs among species

true

Is chromosome number consistent within a species?

yes, it may vary with developmental stage or cell type though

nucleosome

8 histone proteins + 146/7 nucleotide base pairs of DNA

levels of DNA packaging

DNA double helix, nucleosomes (packaged) w/histone, radial loop domains, hetero-chromatin, metaphase chromosome

what is produced by the arrangement of chromosomes by size

a karyotype, full profile of a person’s set of chromosomes

homolog

chromosome

homologs that pair in reproduction of diploid cells

homologous

example of genomes that have pairs and don’t match

X and Y chromosomes in humans

name for genomes that have pairs that don’t match

heterologous pairs

histone proteins

short stretches of DNA wrap around a core of 8 histone proteins (like a string of beads)

nucleosome

histone-DNA complex (the bead)

connecting DNA string in packaging

linker DNA

the structure created in packaging (DNA wrapped around histone) forms this

a chromatin fiber

what happens after a chromatin fiber is formed

fibrous proteins further pack each chromosome

cell cycle

an ordered series of events in cell life

formed through mitosis

2 daughter cells

2 major phases of cell cycle

interphase and mitotic phase

interphase in mitosis

normal growth and preparation for cell division

mitotic phase

replicated DNA and cytoplasm are split and cell divides

G1 Phase (first gap)

change is not evident (“gap”) but the cell is biochemically active

What occurs in the S phase

DNA synthesis

In this phase of interphase, identical copies of DNA molecules (sister chromatids are joined at the centromere)

S phase

In this phase, centrosomes produce the mitotic spindles to move chromosomes

S of mitosis

In animal cells, centrosomes are associated with centrioles to organize cell division in this phase of mitosis

S phase of interphase

In this phase, energy is replenished, organelles reproduce, and the cytoskeleton breaks down

G2

produces mitotic spindles to move chromosomes

centrosomes

another word for mitosis

karyokinesis

first step of mitotic phase

mitosis =. nuclear division

second portion of mitotic phase

cytokinesis = cytoplasm divided into two daughter cells

Parts of the cell in G2 - mitosis

centrosomes w/centriole pairs, chromosomes (replicated, decondensed), plasma membrane, nucleolus, and the nuclear envelope

prophase components - mitosis

early mitotic spindle, centromere, 2 sis chromatids of one chromosome, fragments of nuclear envelope

prometaphase components- mitosis

microtubules overlap, kinetochore, kinetochore microtubules

metaphase in mitosis- components

spindle, centrosome at one spindle pole, metaphase plate

anaphase

daughter chromosomes separate

telophase and cytokinesis

nucleolus forms, cleage furrow, nuclear envelope forms

envelope breaks down in this phase

prophase

membranous organelles disperse toward edges of cell in this phase

mitosis

nucleolus disappears in this phase

prophase

centrosomes begin migration to poles in this phase

prophase

microtubules of spindle form in this phase

prophase

sister chromatids coil together in this phase

prophase

aids sister chromatids to coil tightly

condensin proteins

sister chromatids develop kinetochore in the centromere in this phase

prometaphase

the kinetochore protein does this

attaches the chromatids in the spindle microtubules (see photo)

cell division is completed via the physical separation of the cytoplasmic components into two daughter cells

cytokinesis in mitosis

when to chromosomes line up along this plate?

metaphase

sister chromatids remain attached by cohesion proteins in this phase

metaphase

cohesion proteins degenerate in this phase, allowing chromatids to separate

anaphase

in this phase separated sister chromatids move in opposite directions toward centrosomes to which their microtubules are attached

anaphase

In this phase, chromosomes reach opposite poles and begin to decondense (unravel)

telophase

In this phase, spindles depolymerize into tubulin monomers that form cytoskeletal components for daughter cells

telophase

nuclear envelopes form around chromosomes and nucleosomes appear in nuclear area in this phase

telophase

difference of cytokinesis in plants and animals in separation of daughter cells

cleavage furrow in animals and phragmoplast in plant cells (cell plate)

3 places of regulation at internal check points

1. near the end of G1

2. at the G2 to mitosis transition

3. In the metaphase of mitosis

external triggers which can initiate or inhibit the cell cycle

death of nearby cells, release of growth hormones, and cell crowding

factors which can regulate progress in cell cycle

internal factors

G1 checkpoint goal

determines whether all conditions are favorable for cell division

checkpoint assessing external influences, adequate cell reserves, and size

G1

check for genomic DNA damage

G1

2 options if conditions are not met in G1

stop cycle and fix problem or enter G0 and wait for better conditions

G2 checkpoint

prevents entry into mitotic phase if certain conditions are not met

most important role of G2 checkpoint

ensure all chromosomes have been replicated and replicated DNA is not damaged

What happens when problems are detected in G2

cell cycle stops while the cell attempts to complete DNA replication or repair damaged DNA

when does M checkpoint occur

near the end of metaphase

M checkpoint goal

determine whether all sister chromatids are correctly attached to spindle microtubules

another name for M checkpoint

“spindle checkpoint”

when does cycle procede in M checkpoint

kinetochores of each pair of sister chromatids are firmly anchored to at least 2 spindle fibers

what happens if kinetochores of each pair of sis chormatids are not firmly anchored to at least two spindle fibers

potential non-disjunction of chromatids

positive regulators in cell cycle

promote movement to next step of the cell cycle

negative regulators in cell cycle

stop advancement of the cell cycle

Cdks

cyclins and cyclin-dependent kinases: levels of these proteins fluctuate predictably throughout the cell cycle

internal and external signals can trigger increases in these protein levels

Cdks

binary fission

the way prokaryotes (such as bacteria) propogate, the only way new individuals are produced

start of binary fission

prokaryotes have a single, circular chromosome

what happens when the cell elongates in binary fission?

the FtsZ proteins migrate toward the midpoint of the cell

when duplicated chromosomes separate and move away from each other in binary fission, what does the FtsZ protein do?

forms a ring around the periphery of the midpoint between the chromosomes

what forms septum in binary fission

FtsZ protein (mlasma membrane and cell wall materials accumulate at this point)

what happens when septum is complete in binary fission

the cell pinches in two, forming two daughter cells, Ftsz is dispersed in cytoplasm of new cells

How is genetic diversity increased in meiosis

the mixing of chromosomes from two individuals with the combination of gametes from two parents in fertilization

why is reduction of chromosomes necessary

to avoid doubling in every generation

reproductive structures that produce gametes or spores have cells with what set of chromosomes?

single set, haploid, 1n

meiosis reduces number of chromosomes to ? to produce ? cells

1/2 , haploid (1N) cells

Meiosis I is preceded by?

normal interphase: G1, S, G2

what does chromosome replication in the S phase make (meiosis I)

identical sister chromatids

in Meiosis I, where are sister chromatids attached

the centromere

what does the synaptonemal complex do?

holds homologous chromosomes in synapsis

When does crossing over happen in Meiosis

Prophase I

crossing over

segments of chromosomes are exchanged

chiasmata

visible structures at cross over points

Tetrad

4 chromatids held together by chiasmata