DLA 3: Cell Cycle Regulation

Question 1

Cyclins/CDK

G1

S

G2

M

Answer 1

-Regulate cellular processes and functions

G1:

• Cell growth
• Cyclin D, Cdk 4/6
• Retinblatoma protein (Rb)
• p53
• P21 if can be repaired

S:

• Genome replication (DNA synthesis)
• Cyclin E/A, Cdk 2

G2:

• Preparation for division
• Cyclin A, Cdk 1

M:

• Cell division occurs
• Cyclin B, Cdk 1

Question 2

Tumor Supressors

Answer 2

Functions:

• maintain normal cell growth
• Prevents unregulated cell cycle
• Loss of function of mutation

Retinoblastoma Protein (Rb):

• G1
• Gene: RB1
• Prevents G1 to S progression when active, cell cycle when inactive

P53:

• G1 (Arrests or activates G1-S checkpoint)
• Regulates cell cycle/repairs damaged DNA (sends repairable to P21)
• Gene: TP53
• Roles:
  1) Regulating cell cycle
  2) Initiation of apoptosis

Bracas- breast cancer, repair dbstranded DNA

ATM & ATR Kinases (regulators of DNA damage response)

Question 3

DNA Damage checkpoints

Answer 3

G0:
-These cells are unable to divide

G1:

• Stop cell cycle progression
• Starts at end of mitosis

S:

• Repairs double stranded DNA breaks
• DNA polymerase is active for proofreading

G2:

• Cdc25C Phosphatase- Happens when CDK 1 and cyclin B (Triggers G2 to M progression)
• When Cdc25C is inactivation by ATM/ATR doesn’t progress to mitosis

Question 4

Proto-oncogenes

Oncogenes

Answer 4

Proto-oncogenes:
-Genes that control cell growth and proliferation

Oncogenes:
-Mutated proto-oncogenes

Question 5

Nullisomy

Answer 5

Loss of two chromosomes

Question 6

Prometaphase

Answer 6

Breakdown of nuclear envelope

Spindle microtubules bind to kinetochores

Question 7

Leptolene

Zygotene

Pachytene

Diplotene

Diakinesis

Answer 7

Leptolene -condense and connect

Zygotene- Synapse/bind together

Pachytene- Crossing over

Diplotene-Begins to separate

Diakinesis- homog. chromosomes condense/nuclelous disappears

Question 8

Type of cells:

Labile

Stable

Permanent

Answer 8

Labile-Multiply throughout life (Lose a lot)

Stable- In G0 phase, if stimulated can divide (liver cells)

Permanent- In G0 phase 5ever, Can’t divide (Neurons, cardiac muscle cells)

Question 9

Mitotic Non-Disjunction

Meiosis I and II, males and females

Answer 9

-Chromosomes not separating properly

• Can lead to:
  1) Trisomy (2N+1) Chromosome 47, Downs syndrome
  2) Monosomy, X, (Y not compatible w life=will die), Chromosome 45

Meiosis-I Nonjunction: (males)

1) Turners, 45 Chromosome, X
2) Klinefelter, 47, XXY

Meiosis-II Nondisjunction: (males)

1) Turners, 45 Chromosome, X
2) Chromosome 47, XYY
3) Chromosome, 47, XXX

-45, Y = Die

Question 10

Maternal and Paternal Uniparental disomy

Imprinting

Answer 10

Maternal uniparental disomy:
-Both homologous chromosome obtained from mom

Paternal uniparental disomy:
-Both homologous chromosome obtained from mom

Imprinting:

• Maternal imprinting: Maternal gene is methylated =inactive
• Paternal imprinting: Paternal gene is methylated =inactive

Question 11

Germline Mosaic

Answer 11

• Somatic cells are one genotype
• Gametes have a different genotype

(Offspring more likely to have genetic disorder)

Question 12

Meiosis I and Meiosis II

Haploid/diploid?

Answer 12

Meiosis I = diploid

Meiosis II = haploid

Question 13

Important roles of meiosis I

Answer 13

• Crossing over/recombination in Prophase-I = increased diversity
• Primary oocytes arrest at prophase I of meiosis at birth