Genetics: Cell division and chromosome Heredity

Question 1

Mitosis

Answer 1

Ongoing process that with each division creates two identical daughter cells that are exact genetic replicas of the parental cells they are derived from
2n gives two 2n

Question 2

Meoisis

Answer 2

produces games that have half cell number of chromosomes as the original cell
Gametes are not genetically identical to one another

Question 3

Diploid number vs haploid number

Answer 3

2n vs n
46 pair of chromosomes found in the nuclei of animals’cell
Haploid=> One of each chromosome pair ,23 chromosomes

Question 4

Cell cycle

Answer 4

life cycle cells must pass through in order to replicate their DNA and divide.

Question 5

The eukaryotic cell cycle is divided into two steps

Answer 5

The Interphase-> longer period between one M phase and the next.
The M phase-> a short segment of cell cycle during which cells divide

Question 6

What are stages of interphase? Give details of each stage

Answer 6

G0-> cells express their genetic information and carry out nonfunctional functions but do not progress through cell cycle. Terminal differentiation and arrest of cell division.
G1-> Although the genes transcription occurs continuously throughout the cell cycle, cells rates transcription and translation are particularly high during G1. During this stage gene expression aNd cell activity are activated and prepared for DNA synthesis
S phase-> DNA replication and chromosome duplication. It is the synthesis phase
G2-> phase of the cell cycle, during which cells prepare for division.
Interphase ends when the cell enter M phase

Question 7

important tip about meoisis

Answer 7

They need to reduce the DNA content from 2n to n
Paternal and maternal chromosomes are assorted randomly before they are packed into the gamete - creates diversity
Sister chromosomes exchange genetic information in a process called recombination- creates diversit

Question 8

M phase has five stages

Answer 8

Prophase: Chromatin in the nucleus begins to condense and becomes visible in the light microscope as chromosomes. The nucleolus disappears. Centrioles begin moving to opposite ends of the cell and fibers extend from the centromeres. Some fibers cross the cell to form the mitotic spindle.
Prometaphase: The nuclear membrane dissolves, marking the beginning of prometaphase. Proteins attach to the centromeres creating the kinetochores. Microtubules attach at the kinetochores and the chromosomes begin moving.
Metaphase: Spindle fibers align the chromosomes along the middle of the cell nucleus. This line is referred to as the metaphase plate. This organization helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive one copy of each chromosome.
Anaphase: The paired chromosomes separate at the kinetochores and move to opposite sides of the cell. Motion results from a combination of kinetochore movement along the spindle microtubules and through the physical interaction of polar microtubules.
Teleophase: Chromatids arrive at opposite poles of cell, and new membranes form around the daughter nuclei. The chromosomes disperse and are no longer visible under the light microscope. The spindle fibers disperse, and cytokinesis or the partitioning of the cell may also begin during this stage
and cytokinesis : In animal cells, cytokinesis results when a fiber ring composed of a protein called actin around the center of the cell contracts pinching the cell into two daughter cells, each with one nucleus. In plant cells, the rigid wall requires that a cell plate be synthesized between the two daughter cells.

Question 9

Sister chromatids

Answer 9

The two copies that were duplicated in S phase

Question 10

Kinetochore

Answer 10

A specialized protein complex that facilitates chromosome division later in M phase

Question 11

Kinetochore microtubules

Answer 11

Are embedded in the protein complex called kinetochore that assembles at the centromere of each chromatid. Kinetochore microtubules are responsible for chromosome movement during cell division

Question 12

Polar microtubules or nonkinetochore microtubules

Answer 12

Extend toward the opposite of their centrosome and overlap with polar microtubules from that pole. These microtubules contribute to the elongation of the cell and to cell stability during division

Question 13

Astral microtubules

Answer 13

grow toward the membrane of the cell, where they attach and contribute to cell stability

Question 14

Sister chromatid cohesion

Answer 14

Tension produced by protein cohesion that localizes between sister chromatids and holds them together to resist the pull of kinetochore

Question 15

Cell cycle checkpoints

Answer 15

Times during the cell cycle when cells are monitored by protein interactions that asses the status of the cell and its readiness to progress to the next stage.

Question 16

Give an example of a mechanism that is involved in cell cycle checkpoints. Give details of how it works by using some key words.

Answer 16

Protein complexes that join a protein kinase with a second protein known as a cyclin protein.
Protein kinases are usually present continuously in cells at relatively steady concentration and catalyze protein phosphorylation. Phosphorylation changes the conformation of a target protein. Cyclins proteins have concentrations that are cyclic and linked to cell cycle stage

Question 17

Give an example of a mechanism that is involved in cell cycle checkpoints. Give details of how it works by using some key words.

Answer 17

Protein complexes that join a protein kinase with a second protein known as a cyclin protein.
Protein kinases are usually present continuously in cells at relatively steady concentration and catalyze protein phosphorylation. Phosphorylation changes the conformation of a target proteins and ca either activate or inactivate the target protein. Cyclins proteins have concentrations that are cyclic and linked to cell cycle stage. Cyclin production is stimulated by growth factor proteins that are produced by other cells. The protein kinase components of these complesxes are activated only when tehy associate with a cyclin; thus, the protein knases are called cyclin-dependent kinases,cdk.
Cdk phospphorylate numerous target proteins ad regulate cell cycle progression at various checkpoints.

Question 18

Nondisjunction

Answer 18

Failed chromosome separation