chapter 2 - chromosomes and cellular reproduction

characteristics of a euakaryotic cell

relatively large, nucleus, large genome, linear chromosomes, membrane-bound organelles

characteristics of a prokaryotic cell

small, no nucleus, small genome, circular chromosomes and not complexed by histones

what is a genome

all the genetic material of an organism, consists of double stranded DNA in all cellular life

what is most of a cells genome comprised of

chromosomes

besides chromosomes, what else does a genome consist of

mitochondrial DNA and chloroplast DNA (in plants), and plasmids in prokaryotes

t/f: a genome includes the coding regions and noncoding DNA

true

t/f: some viruses have RNA genomes

true

t/f: viruses are cells

false

how can viruses be characterized

as replicating particles

characteristics of viruses

obligatory intracellular parasites, replicating particles of nucleic acid and protein (sometimes lipids), infect specific species, or types of cells

t/f; viruses are living

false

what is a chromosome

an individual DNA molecule in a cell

t/f: a replicated chromosome is still one chromosome

true

centromere

the region of the chromosome that leads chromosome movement during mitosis

kinetochore

complex protein structure that attaches centromere to spindle microtubules

sister chromatids

the replicated copies of the chromosome prior to their separation in M phase

what is the ploidy difference between prokaryotes and eukaryotes

pro - haploid; euk- diploid

what is ploidy

the number of sets of chromosomes in a cell

haploid

having a single set of chromosomes; typical of prokaryotes, some eukaryotes and gametes

diploid

having two sets of chromosomes, typically one from ah parent

triploid

having three sets of chromosomes

tetraploid

having four sets of chromosomes

polyploid

many sets of chromosomes

aneuploid

having an abnormal number of chromosomes; the opposite of euploid

characteristics of a haploid

smaller, faster-growing, and spread advantageous alleles much more rapidly

why is diploidy advantageous

protection against consequences of somatic mutation in multicellular organism (aids in preventing cancer), allows more genetic/phenotypic diversity in individuals (due to heterozygosity), maintains alleles (bad and good) in populations for longer than haploids, can tolerate a higher mutation rate and greater protection against DNA damage

how many chromosomes does the human genome have and what types

23; 22 autosomes and 1 sex chromosome

how many copies/ alleles do diploids have and what characteristics do the alleles have

two; can be identical or may differ

what is a chromatin

eukaryotic DNA bound to nucleosomes and other proteins

how do bacterial cells divide

through binary fission

describe the process of binary fission

the chromosome replicates as the cell grows, replicated chromosomes separate gradually from one another prior to cell division, chromosome condensation not obvious

how do eukaryotic cells typically divide

through mitosis

what products does mitosis produce

genetically identical daughter cells

what are the phases of mitosis

prophase, metaphase, anaphase, telophase

phases of the eukaryotic cell cycle

S phase, G2 phase, M phase, G1 phase

what occurs during the S phase

DNA synthesis

what phase does mitosis occur in

M phase

t/f: mitosis changes ploidy

false

how does ploidy stay the same during mitosis

each chromosome present is replicated and one copy is segregated to each daughter cell

what happens to DNA content compared to ploidy during the mitotic cell cycle

DNA content doubles while ploidy remains constant

when do eukaryotic chromosomes condense

after DNA replication but prior to mitosis

why is chromosome condensation needed

for efficient segregation of daughter chromosomes to daughter cells; DNA cells are too big for the proper replication process to occur

what occurs during prophase

the nuclear envelope (NE) dissolves and microtubules attach to centromeres

what occurs during the metaphase

chromosomes align at middle of cell

what occurs during anaphase

sister chromatids separate and are pulled to opposite poles

what occurs during the telophase

microtubules disappear and the NE reforms

what is cytokinesis

when daughter cells separate

what are the genetic consequences of the cell cycle

produces 2 identical cells (also identical to parent cells), new cells contain a full complement of chromosomes, each cells contains ~ half the cytoplasm, and organelle content of the original parent cell, though, some daughter cells have unequal cell content

when can the cell cycle arrest

at different checkpoints if certain crucial conditions have not been met

entering what phase is an irreversible decision

S phase

what are the different checkpoints in which the cell cycle can arrest at

G2, metaphase, and G1

what does the metaphase checkpoint do

prevents chromosome separation at anaphase until all kinetochores are under physical tension

what do kinetochores also serve as

a censor of tension

what enzyme is used break down the proteins holding chromatids together

separase

what are two deleterious consequences of spindle/kinetochore attachment problems

chromosome non-disjunction and lagging chromosome at anaphase

what occurs during chromosome non-disjunction

both sister chromatids get pulled to the same pole

what is the result of chromosome non-disjunction

one cell with an extra chromosome and the other cell with a missing chromosome

laging chromosome at anaphase

can occur if the kinetochore of one chromatid is attached to microtubules pulling toward opposite poles.

what can lagging chromosome at anaphase cause

to chromosome damage and/or non-disjunction