Lecture 5 Flashcards
meiosis creates
gametes or spores, sex cells
Living organisms have genetic material…
- composed of nucleic acid DNA
- organized into chromosomes
- does not include viruses
mitosis leads to
production of 2 cells
- each with same number of chromosomes uncoil into a diffuse network within the nucleus: chromatin
When are chromosomes uncoiled into a diffuse network within the nucleus?
- uncoiled chromosomes is chromatin
- during nondivisional phases
what are the two main types of cells
- prokaryotic (bacteria and archaea)
- eukaryotic (protists, plants, fungi, animals)
what is the common features in all cells
- plasma membrane
- DNA
- ribosomes
Plasma membrane
- surrounds all cells
- delimits cell from external environment
plasma membrane of plants
- have a cell wall which is composed mainly of cellulose (polysaccharide)
plasma membrane of bacterial cells
have peptidogylcan in their cell walls
Glycocalyx
- is a cell coat
- covering on plasma membrane of animal cells
- made of glycoproteins and polysaccharides
Function of glycocalyx
biochemical identity at cell surface
Receptor molecules
found on the surface of cells
- recognition sites that transfer specific chemical signals across the cell membrane into the cell
Cell nucleus
- found in eukaryotes
- membrane bound
- houses genetic material, DNA
- nucleolus: where ribosomal RNA (rRNA) is synthesized
- nucleolus organizer region (NOR): DNA that encodes rRNA
Nucleoid
- found in prokaryotes
- not membrane bound
Cytoplasm includes:
- extra nuclear cellular organelles
- cytosol: colloidal material surround organelles
- cytoskeleton made of extensive system of tubules and filaments
Microtubules
- in cytoskeleton
- made up of the protein tubulin
Microfilaments
- in cytoskeleton
- derived from the protein actin
Endoplasmic reticulum
- compartmentalizes cytoplasm
- increases surface area for biochemical synthesis
Smooth endoplasmic reticulum
site of fatty acid and phospholipid synthesis
Rough endoplasmic reticulum
studded with ribosomes and the site of protein synthesis
mitochondria
- in animals and plant cells
- site of oxidative phases of cell respiration which generate ATP
chloroplasts
plants, algae, and protozoans
- site of photosynthesis
centrioles
- found in centrosome of animal and plant cells
- organize spindle fibers for movement of chromosomes during meiosis and mitosis
- made up of microtubules
Homologous chromosomes
- chromosomes exist in homologous pairs in diploid organisms
- are similar but not identical
- carry genes for the same inherited characteristics
- may carry different versions of the same gene called alleles
- contain identical gene sites along their lengths and each site is called a locus
Centromeres
- constricted regions on chromosomes
- location of centromere establishes appearance of chromosome: metacentric, submetacentric, acrocentric, telocetric
what is the q arm
long arm
what is the short arm
p arm
metacentric
middle
submetacentric
between middle and end, p and q arms
acrocentric
close to the end
telocentric
at end
somatic cells
have homologous pairs
exceptions: many bacteria and viruses have one chromosome
karyotype
- illustrates the physical appearance of the different pairs of homologous chromosomes
- the human mitotic chromosomes have been photographed, cut out of the print, and matched up
genome
-genetic information in haploid set
-23 chromosomes, 46 chromatids
biparental inheritance
inheritance from 2 parents
- diploid organisms contain to copies of each gene
alleles
alternative forms of the same gene can exist
Sex-determining chromosomes
- not homologous
- behave as homologs in meiosis
X and Y in humans
Zygote
- single-celled fertilized egg of multicellular organisms
- diploid
Karyokinesis
genetic material partitioned to daughter cells during nuclear division
Cytokinesis
cytoplasmic division follows mitosis
cell cycle is composed of
interphase and mitosis
interphase includes:
- S phase: DNA is synthesized
- 2 gap phases G1 and G2
G0: point in G1 phase where cells are non-dividing, but a metabolically active state (neuron)
During the 2nd part of G1 phase
- DNA: ORI is established, strands are primed and ready for replication
interphase
characterized by the absences of visible chromosomes
- chromosomes are extended and uncoiled, forming chromatin
Prophase
- centrioles divide, move, and establish poles
- nuclear envelope breaks down
- chromosomes condense and become visible
sister chromatids
2 parts of each chromosome that are connected at the centromere
- held together by multi-subunit protein complex called cohesion
Prometaphase
- period of chromosome movement to equatorial plane of cell
- equatorial plane referred to as metaphase plate
- centrioles reach poles
- spindle fibers form
- chromosomes are clearly double structures
Metaphase
- chromosome configuration following migration
- centromeres align on metaphase plate
Kinetochore
- proteins associated with centromere
- spindle fibers bind to kinetochore; chromosomes migrate
Kinetochore microtubules
have one end near the centrosome region and the other end anchored to the kinetochore
cohesion
protein complex that holds sister chromatids together
separase
enzyme that degrades cohesion
Shungoshin
protein that protects cohesion from being degraded by separase
Anaphase
Disjunction
- sister chromatids separate now called daughter chromosomes
- migrate to opposite poles by shortening of spindle fibers
- motor proteins or molecular motors use ATP
telophase
- cytokinesis
- uncoiling of the chromosomes
- re-formation of the nuclear envelop
- spindle fibers disappear
- nuclear envelope reforms
cytokinesis
2 new cells are produced
telophase of plant cells
a cell plate is synthesized and laid down across the metaphase plate which becomes the middle lamella
telophase of animal cells
a constriction of the cytoplasm or cell furrow
From DNA synthesis to anaphase
there are 92 chromosomes in the cell
cell division cycle mutations
enzymes called kinases:
- can add phosphate to other proteins to regulated the cell cycle
- are master control molecules functioning in conjunction with cyclin proteins
purpose of cell cycle checkpoints
monitor mitosis for errors
