Ch 2 Chromosomes and Cellular Reproduction Flashcards
Describe the differences between a eukaryote and prokaryote.
Prokaryote:
- absent nucleus
- small cell diameter
- usually consists of one circular DNA molecule
- no membrane-bound organelles
Eukaryote:
- nucleus
- large cell diameter
- multiple linear DNA molecules with large amounts of DNA
- histones associate with DNA to form tightly packed chromosomes
- membrane-bound organelles
unicellular organism with relatively simple cell structure; bacteria and archaea
prokaryote
unicellular or multicellular organisms that have a compartmentalized cell structure
eukaryote
what are the purpose of histones?
histones associate with DNA to form tightly packed chromosomes; help regulate DNA accessibility to enzymes and proteins
complex of DNA and histone proteins
chromatin
describe the differences between bacteria and archaea?
both are prokaryotes, however some genetic processes in archaea are more similar to those in eukaryotes
simple structures composed of an outer protein coat surrounding a nucleic acid
viruses
are viruses prokaryotic or eukaryotic?
viruses are neither
where can viruses reproduce?
viruses can only reproduce within host cells
what is binary fission, and describe it
binary fission is prokaryotic cell division
1) replication begins at a single origin of replication
2) after replication, the two origins move away from each other to the opposite ends of the cell
3) a new cell wall forms between the two chromosomes and divides them, producing two cells
how is eukaryotic genetic information organized in a cell?
- ## chromosomes are located in the nucleus
what is a homologous pair
one set of a chromosomes has a corresponding chromosome in the other set
what does the ploidy of a cell indicate?
how many sets of genetic info it has
two sets of genetic information
diploid
one set of genetic information
haploid
more than two sets of genetic information
polyploid
what are the three elements of a chromosome
- centromere
- telomeres
- origins of replication
attachment point on a chromosome for spindle microtubules
centromere
how do spindle microtubules attach to centromeres of chromosomes?
a kinetochore assembles on the centromere, allowing the spindle microtubules to attach to the kinetochore
how are chromosomes classified?
they are classified based on location of the centromere
what are the four types of chromosomes
- submetacentric
- metacentric
- telocentric
- acrocentric
regions of specific DNA sequences and proteins at the ends of chromosomes that protect and stabilize chromosome ends
telomeres
what are sister chromatids and when are they present?
two identical copies of a chromosome, held together at the centromere; they are present only after replication occurs
series of steps where one cell passes from one division to the next
cell cycle
key points throughout the cell cycle that allow or prohibit a cell from continuing to the next stage
checkpoints
what are the two major phases of the cell cycle
interphase
mitotic phase
phase where cell grows, develops, and functions
interphase
phase of active cell division
mitotic phase
process of nuclear division
mitosis
cytoplasmic division
cytokinesis
stage where the cell grows and synthesizes necessary proteins for cell division
G1 stage
describe the G1/S checkpoint
holds the cell in G1 until all necessary cell components for replication are made
what is G0 phase?
a stable state during which cells are nondividing
stage where DNA replication/synthesis occurs
S phase
what stage would sister chromatids appear?
sister chromatids appear in S phase, after DNA is replicated
stage where additional biochemistry events occur to prepare the cell for division
G2 phase
describe the G2/M checkpoint
ensures DNA is replicated and undamaged, and if there is some damage or missing DNA, it will prevent the cell from proceeding further
what state are the chromosomes in throughout interphase?
the chromosomes are relaxed and uncoiled
describe prophase
- chromosomes condense
- mitotic spindle forms
group of proteins that bind to DNA and help condensation of chromosomes
condensins
describe prometaphase
- nuclear envelop disintegrates
- spindle microtubules enter nuclear regions and attach to sister chromatids
describe metaphase
- chromosomes line up on the metaphase plate
describe the importance of the spindle-assembly checkpoint
it verifies chromosomes are aligned and attached during metaphase
describe anaphase
- sister chromatids separate and move toward opposite poles
describe telophase
- chromosomes arrive at spindle poles
- sister chromatids now considered separate chromosomes
- nuclear membrane reforms around each set of chromosomes
- chromosomes decondense and relax
what are the five steps of mitosis?
prophase
prometaphase
metaphase
anaphase
telophase
describe cytokinesis
- cytoplasm divides
- in plants, a cell wall forms
what are the products of mitosis?
genetically identical daughter cells
what are the two processes of sexual reproduction?
meiosis and fertilization
what are the two parts of meiosis
meiosis I
meiosis II
describe prophase I
- chromosomes condense
- homologous chromosomes pair up
- crossing over occurs
- nuclear membrane breaks down
- spindle forms
describe metaphase I
- homologous pairs align along metaphase plate
- microtubules attach to each chromosome of homolog pair
describe anaphase I
- homologous chromosomes separate
- sister chromatids stay attached
describe telophase I
- chromosomes arrive at spindle poles and cytoplasm divides
process in which homologous chromosomes exchange genetic information
crossing over
location where two chromosomes cross
chiasma
period between meiosis I and meiosis II
interkinesis
describe what occurs in interkinesis
- nuclear membranes reform around chromosomes
- spindle breaks down
- chromosomes relax
describe prophase II
- chromosomes recondense
- spindle reforms
- nuclear membrane breaks down
describe metaphase II
- replicated chromosomes line up on metaphase plate and sister chromatids face opposite poles
describe anaphase II
- sister chromatids separate
- chromatids pulled to opposite poles and now considered distinct chromosomes
describe telophase II
- chromosomes arrive at opposite poles
- nuclear membrane reforms
- chromosomes decondense
- cytoplasm divides
what kind of division is the result of meiosis I?
reductional division
what kind of division is the result of meiosis II?
equational division
how many and what kind of cells are produced from meiosis?
four genetically different daughter cells
what two processes allow for genetic variation in meiosis?
- crossing over
- random separation of homologous chromosomes
creation of new combinations of alleles on a chromatid
recombination
when does crossing over occur?
prophase I
describe how random separation of homologous chromosomes leads to genetic variation?
homologous chromosomes randomly align in metaphase I, where the orientation may cause different variations in whether a cell gets a maternal or paternal chromosome. this produces different combinations of chromosomes in the resulting cells
how do you determine the number of possible combinations of cells?
2^n, where n = # of homologous pairs
protein that holds chromatids together
cohesin
what allows sister chromatids to separate in mitosis?
cohesin along the length of chromosomes is broken down by separase
what allows homologs to separate in anaphase I, but not sister chromatids?
cohesin breaks along the chromosome arms, so the homologs can separate, but shogushin prevents the sister chromatids from separating
protein that protects cohesin at centromere to prevent sister chromatids from separating
shugoshin
