Chapter 10 Flashcards
Prokaryotic cell division occurs as ______
binary fission
What is the genetic information in a prokaryote called?
Nucleoid
Where does copying begin in prokaryotes?
Replication origin
What direction does copying proceed in for prokaryotes?
Bi-directionally
Describe the process of binary fission
- Bacterial cell has an origin of replication
- Replication begins at origin and proceeds in opposite directions
- Replicated origins move to two ples of the cell as replication continues
- Plasma membrane grows inward, new cell wall is synthesized
- Cell cuts in two
How many chromosomes are in humans?
46 (23 nearly identical pairs)
How many chromosomes do eukaryotes tend to have?
10-50
What are the three parts of a cell’s life cycle?
Cell growth, including DNA replication
Nuclear division/mitosis
Division of the cytoplasm in cytokinesis
What is mitosis?
DNA is equally and precisely divided, generating daughter cells that are genetic copies of the parent cells. This occurs with almost perfect fidelity and is facilitated by the mitotic cytoskeleton.
What is meiosis?
Daughter nuclei with half the number of chromosomes are produced; the arrangement of genes on chromosomes are different from parent cells
What are chromosomes?
Linear DNA molecules combined with proteins.
The complex of DNA and all its proteins is called ____
Chromatin
What proteins pack DNA into a shorter length?
Histone proteins
What is the structure of a nucleosome?
An 8-protein nucelosome core particle forms when DNA winds around 2 molecules each of H2A, H2B, H3, and H4
What segment connects nucleosomes?
A linker segment
What is the 10-nm chromatin fiber?
Compacts DNA by a factor about 7
30-nm chromatin fiber
Forms when Histone H1 attaches, which causes the structure to coil
Complex of DNA and all associated proteins is called
Chromatin
What is the solenoid model?
It predicts that the nucleosomes spiral helically with about six nucleosomes per turn
Euchromatin vs heterochromatin
Euchromatin is more loosely packed and more highly expressed in comparison to heterochromatin regions
What are sister chromatids?
Replicated chromosomes connected to eachother at the centromere- held together via sister chromatid adhesion (cohesion) until mitosis separates them
What holds sister chromatids together?
Cohesin
The equal distribution of chromosomes into each of two daughter nuclei is called
Chromosome segregation
What is the difference between sister chromatids and homologous chromosomes?
Sister chromatids are identical, homologous chromosomes code for same genes but have different alleles
What is ploidy?
The number of chromosome sets in a cell or species
If an organism has only one copy of each chromosome type, it is a ____
haploid
Most eukaryotes have two copies of each type of chromosome, making them
Diploids
What is polyploidy?
When species have 3 or more of each type od chromosome
The two chromosomes of each pair in a diploid cell are called homologous chromosomes because
One is from the mother, one is from the father, and they have the same genes in the same order
What does a karyotype show?
An individual’s array of chromosomes
How are cells prepared for a karyotype?
Sample is added to a culture medium that has a stimulator for growth and division of cells incubated at 37 C
Cell is stained so chromosomes are visible
Chromosomes are photographed
What are the steps of interphase?
G1 (primary growth, longest phase)
S (DNA replication)
G2 (organelles replicate, microtubules organize)
Eukaryotic cell cycle
Interphase (G1,S,G2), Mitosis, Cytokinesis
T or F: G1 varies in length
True
What is special about the G1 phase?
Here, many cells stop dividing and are instead put in a G0 phase, where some never resume the cell cycle
What happens in G1?
G1 is a period of growth where RNA, proteins, and molecules needed for S phase are created
S phase
DNA is replicated and copies are held together
G2 phase
No DNA synthesis, but protein and RNA synthesis continues to prepare for mitosis
How many hours spent in each stage?
G1- 10 hrs
S- 9 hrs
G2- 4 hrs
Mitosis- 1 hr
What are the checkpoints in the cell cycle?
G1/S
G2/M
Mitotic spindle checkpoint
Mitosis divided into 5 phases
Prophase
Prometaphase
Metaphase
Anaphase
Telophase/cytokinesis
Mitosis requires the formation of
a spindle
Centrosome
The main microtubule organizing center of animal cells and protists
What happens to the centrosome in mitosis
Centrosome has centrioles that are duplicated and divided
Microtubles extending from the centrosomes produce
Arrays/asters at the tips that form the poles of the spindle
What is the spindle
Separated centrosomes and the mass of microtubules in between them
G1
Chromosomes are unreplicated and extend through nucleus
S
DNA replication
G2
DNA condensation using cohesins which align the sister chromatids tightly- centriole has also doubled
Prophase
Individual condensed chromosomes first become visible
Condensation continues
Spindle apparatus assembles and centrosomes move to opposite poles, generating the spindle as they separate
Nuclear envelope starts to disintegrate and nucleolus disappears
Prometaphase
Transition occurs after disassembly of nuclear envelope
Spindle microtubules grow from centrosomes at opposite spindle poles towards the center of the cell
A kinetochore forms on each sister chromatid at the centromere
Kinetochore microtubules bind to kinetochores
Nonkinetochore microtubules from opposite sides overlap at the spindle point
Chromosomes begin to move to center of cell in a process called congression (facilitated by motor proteins at kinetochores and assembly/disassembly of microtubules)
Metaphase
Spindle microtubules move chromosomes into alignment at the spindle midpoint/metaphase plate
Condensation gives each chromosome a characteristic shape
Karyotypes formed here according to size and shape