Genetics and Cell Division

Question 1

G0 Cell

Answer 1

A cell that will never divide within its lifetime, such as a muscle cell, a nerve cell, or a red blood cell

Question 2

G1 Phase

Answer 2

• Cell is metabolically active
• Organelles duplicate
• Centrosome replication begins
• Approx. 8-10 hours

Question 3

S Phase

Answer 3

• DNA replicates
• Approx. 8 hours

Question 4

G2 Phase

Answer 4

• Cell growth continues
• Enzymes and protein are synthesized

Question 5

Somatic Cell

Answer 5

• Diploid
• While in G1, the cell has one copy of each gene from both parents, making two total copies. Each copy is unwound but has only one chromatid worth of genetic material
• When S phase occurs, each chromatid doubles into a chromosome, therefore each chromosome has two copies of the genetic material it contains
• Homologous pairs contain two chromosomes that each code for the same gene (4 copies of genetic material), one from the mother and one from the father
• Reproduce during mitosis

Question 6

Mitotic Prophase

Answer 6

• Chromatin condenses into chromosomes
• Nuclear wall degenerates
• Centrosomes begin to move apart

Question 7

Mitotic Prometaphase

Answer 7

• Nuclear membrane fully disappears
• microtubules connect centromeres to centrosomes
• Kinetochore proteins appear, which link the centromere to the spindle fiber microtubule

Question 8

Mitotic Metaphase

Answer 8

• Centromeres of chromosomes gather at the metaphase plate
• Microtubules begin to form into spindle fibers

Question 9

Mitotic Anaphase

Answer 9

• Centromeres of chromosomes split
• Sister chromatids move toward opposite sides of the cell
• Non-kinetochore microtubules overlap and push on each other to elongate the cell

Question 10

Mitotic Telophase

Answer 10

• Spindle fibers dissolve
• Chromosomes become chromatin
• New nuclear membrane forms
• Cleavage furrow develops

Question 11

Cytokinesis

Answer 11

• Occurs with telophase
• Cytoplasm divides
• Actin and Myosin behave like a drawstring and pinch the cell into two individual cells
• The new cells not enter interphase

Question 12

G1 Checkpoints

Answer 12

• Nutrients are sufficient
• Cell size big enough
• DNA undamaged

Question 13

G2 Checkpoints

Answer 13

-Cyclin and cyclin dependent kinase
- These combine to form maturation promoting factor
- MPF triggers mitosis

Question 14

External Development Checkpoints

Answer 14

• Growth hormone
• Density dependent inhibition: if an area becomes too densely packed with cells, they stop dividing
• Anchorage dependence: cells must be attached to substratum in order to divide

Question 15

Cancer Cells

Answer 15

• No density dependent inhibition
• No anchorage dependence

Question 16

Gamete Cells

Answer 16

• Haploid
• Contains chromatids from the parent cell that have undergone crossing over
• Used for reproduction
• Produced through meiosis

Question 17

Meiosis I vs Meiosis II

Answer 17

• Meiosis I reduces the chromosomes from diploid to haploid
• Meiosis II Produces four genetically unique daughter cells

Question 18

Crossing Over

Answer 18

• Occurs when a tetrad forms what is known as a chiasma and transfers genetic material from one chromosome to the next
• Increases genetic variability by forming a completely unique new chromosome

Question 19

Meiosis I

Answer 19

• Prophase chromatin condenses into tetrads and crossing over occurs
• Metaphase tetrads line up at the metaphase plate
• Anaphase homologous chromosomes move to opposite ends of the cell
  -Telophase chromosomes become chromatin, nuclear membrane reforms, cytokinesis occurs
• The cell is now haploid

Question 20

Meiosis II

Answer 20

• Exactly like mitosis except the chromosomes are genetically unique

Question 21

Independent Assortment

Answer 21

Each chromosome pair is broken apart and sorted into its new cell independently of the others, so there are many possible combinations

Question 22

Meiosis I VS Meiosis II malfunctions

Answer 22

• If a cell malfunctions during meiosis I, all daughter cells will have the wrong number of chromatids
• Il a cell malfunctions during meiosis II, only half the cells will be messed up

Question 23

Codominance

Answer 23

• Two distinct alleles each affect the phenotype
• Both phenotypes will appear at the same time

Question 24

Incomplete Dominance

Answer 24

• A mix of two alleles creates its own distinct phenotype

Question 25

Pleiotropy

Answer 25

• One allele affects multiple different phenotypes

Question 26

Polygeny

Answer 26

• When a phenotype is determined by two or more phenotypes