Chapter 6: Reproduction at the Cellular Level Flashcards
define genome
complete set of genes or genetic material in a cell
define histones
- proteins
- DNA folds around them to create chromatin
- helps package DNA and control gene expression
define nucleosomes
- structural unit consisting of a length of DNA wrapped around a histone
- cube of 8 histones with DNA wrapped around
define chromatin
- complex made of DNA and proteins to form chromosomes
- condenses during cell division
define chromatid
an entire DNA molecule
define sister chromatids
- two identical copies of a chromosomes
- formed after DNA replication
define chromosome
- each protein bound DNA molecule
- chromatin condenses into chromosomes
define centromere
where two sister chromatids are connected
define centrosome
- organelle found near the nucleus
- made of centrioles and a dense protein
- microtubule organizing center
define centriole
- pair of cylindrical-shaped structure of microtubules
- made of tubulin protein
- located in the centrosome
- organize microtubules to form the cytoskeleton
define kinetochore
- proteins
- at centromere
- what microtubules attach to on the sister chromatids to pull them apart during division
define spindle apparatus
- collection of all spindle fibers during cell division
- includes astral microtubules, kinetochore microtubules, and polar microtubules
define astral microtubules
- extend from centrioles to plasma membrane
- anchor to cell membrane
- keep mitotic spindle in place
define kinetochore microtubules
- extend from centrioles to kinetochores on sister chromatids
- bind to chromosomes and pull them apart during cell division
define polar micortubules
- extend from centrioles to middle of the cell
- push single poles apart during division
define somatic cells
- body cells
- soma means body
- diploid (2n)
define gametes
- sex cells (egg and sperm)
- haploid (1n)
define karyotype
- number and visual appearance of chromosomes in a cell
- picture of all the chromosomes paired up
what is the purpose of cell division in single celled organisms
reproduction
what is the purpose of cell division in multicellular organisms
- reproduction
- growth and development
- tissue repair
- tissue maintenance
is cell division the only part of the cell cycle
- no
- is integral part but not only part
what two major things happen during cell division
- duplication of genetic material
- cell physically divides
what does mitosis cell division result in
- genetically identical daughter cells
- ensures each daughter cell receives an exact copy of DNA
what are the similarities between prokaryote and eukaryote DNA
- double stranded; form double helix
- same nucleotides
- same genetic code; combinations of nucleotides code for amino acids
differences between prokaryote and eukaryote DNA
- prokaryote: in nucleoid region; 1 circular chromosome; have plasmids (small circular pieces of DNA)
- eukaryote: in nucleus; several linear chromosomes; have histones (protein DNA folds around to make chromatin)
what is the only part of eukaryotic cells that has circular DNA
mitochondria
how many chromosomes are in a cells nucleus
- varies among species
- chromosome number is consistent within a species
which human cells don’t contain DNA
- red blood cells
- allows for more room to carry oxygen
are chromosomes always x-shaped
- no
- only after condensing during cell division
why are centrioles important in cell division
- migrate to opposite sides of the nucleus before cell divides
- form mitotic spindle which attaches to chromosomes to pull them apart
- form microtubules for cilia and flagella
define diploid
2 matching sets of chromosomes
define haploid
1 set of chromosomes
how many chromosomes are in human somatic cells
- 46 total
- 2 pairs: 1 from mom and 1 from dad
how many chromosomes are in human gamete cells
23
define homologous chromosomes
chromosomes that pair in reproduction of diploid cells
define heterologous chromosomes
- pairs of chromosomes that don’t match
- example: X and Y chromosomes in humans
define interphase
- consists of G1, S, and G2 phase
- time for growth and preparation for cell division
- takes up most of the cell cycle
define mitotic phase
- includes mitosis and cytokinesis
- replicated DNA and cytoplasm are split and the cell divides
define mitosis/karyokinesis
- nuclear division
- 5 steps: prophase, prometaphase, metaphase, anaphase, telophase
define cytokinesis
- cytoplasmic division
- cell physically separates
define G1 phase
- first phase of interphase
- change is not obvious
- cell is very biochemically active
define S phase
- second phase of interphase
- DNA synthesis
- chromosomes are replicated
- centrosomes produce mitotic spindles to move chromosomes
define G2 phase
- third phase of interphase
- energy replenished
- organelles reproduce
- cytoskeleton breaks down
- visible cell growth
define G0 phase
- cellular state outside of replicative cell cycle
- when cells are not actively dividing
- can be reversible or irreversible
define quiescent
- reversible G0 phase
- where cells reside before entering the cell cycle
define senescent
- irreversible G0 phase
- in response of DNA damage or degradation
- cells don’t replicate but still perform normal functions
- alternative to apoptosis
define differentiated
- irreversible G0 phase
- stem cells that have terminally differentiated
- perform main functions indefinitely
- example: neurons
define prophase; what happens
- chromosomes condense and become visible
- nuclear envelope breaks down
- nucleolus disappears
- centrosomes migrate to opposite poles
- microtubules of the spindle begin to form
- organelles move towards the edge of the cell
define prometaphase; what happens
- chromosomes continue to condense
- kinetochores appear at the centromere
- mitotic spindle microtubules attach to kinetochores
- centrosomes move towards opposite poles
define metaphase; what happens
- chromosomes line up at metaphase plate by movement of microtubules attached to their kinetochores
- sister chromatids remain attached by cohesion proteins
define anaphase; what happens
- cohesion proteins degenerate to allow sister chromatids to separate
- separated sister chromatids (now called chromosomes) move to opposite poles; pulled by microtubules to centrosomes
- cell elongates
define telophase; what happens
- chromosomes reach opposite ends of the cell and start to decondense
- spindles depolymerize to tubulin monomers that will make cytoskeleton
- nuclear envelope forms around chromosomes
- nucleosomes appear within nuclear areas
define condensin proteins
aids chromosomes condensing during prophase
define cohesion proteins
- keep sister chromatids attached before they divide
- disintegrate during anaphase
define cleavage
- process by which animal cells undergo cytokinesis
- cleavage furrow forms and cell divides
what are the two major phases of the cell cycle (mitosis)
- interphase
- mitotic phase
what are the two major phases of the mitotic phase
- mitosis: division of the nucleus
- cytokinesis: division of the cytoplasm
how does cytokinesis occur in animal cells
- process known as cleavage
- cleavage furrow forms
- plasma membrane drawn in by ring of actin fibers
- furrow deepens until cell is pinched in two
how does cytokinesis occur in plant cells
- vesicles were formed in interphase from golgi apparatus with enzymes and glucose
- vesicles combine to form cell plate in old metaphase plate
- cell plate strengthens and becomes cell wall
how do cells control the cell cycle
- through checkpoints
- external and internal signals
what external signals initiate or inhibit the cell cycle
- death of nearby cells
- release of growth hormones
- cell crowding
what internal factors regulate the cell cycle
- G1 checkpoint
- G2 checkpoint
- M checkpoint
why are internal checkpoints (the molecular control system) important
- ensure new cell is an exact duplicate of the original
- doesn’t let any mistakes throughout the cycle continue into daughter cells
when does the G1 checkpoint take place
end of G1 phase
when does the G2 checkpoint take place
at G2 and mitosis transition
when does the M checkpoint take place
during metaphase in mitosis
what checkpoint is the primary decision point for the cell
G1 checkpoint
what does the G1 checkpoint check for
- cell size
- enough nutrients
- growth factors
- no DNA damage
what options does a cell that didn’t pass the G1 checkpoint have
- stop the cycle and try to fix the issue
- enter G0 and wait for signs that conditions are better
what does the G2 checkpoint check for
- DNA replication complete
- DNA damage in replicated DNA
what options does a cell that didn’t pass the G2 checkpoint have
- attempt to complete DNA replication
- attempt to repair damaged DNA
what does the M checkpoint check for
- chromosomes lined up in metaphase plate correctly
- spindle fibers are attached to both sister chromatid kinetochores
what happens if a cell doesn’t pass the M checkpoint
- cell cycle will halt until kinetochores of each sister chromatid are anchored
- failure to correct it could lead to non-disjunction of chromatids; genetic abnormalities
define cancer
- many disorders characterized by uncontrolled cell growth
- caused by problems with genes regulating checkpoints; usually after multiple divisions mutations build up
define protooncogenes
- normal genes that code for positive cell regulators (tell cell when to go)
- becomes oncogene when mutated
- example: Cdk
define oncogenes
- mutated versions of protooncogenes
- leads to accelerated cell division
- genes telling cells when to go override everything to cell division accelerates
define tumor suppressor genes
- normal genes that code for negative cell regulators (tell cell when to stop)
- prevent cell from dividing if there is a problem
- can’t stop the cell when mutated causing uncontrolled cell division
- example: P53
define binary fission
- how prokaryotes reproduce/divide
- only way they can reproduce
do prokaryotes go through mitosis
no
explain the process of binary fission
- bacterial chromosomes replicate
- 2 daughter chromosomes move apart
- septum forms and divides the cell
