EXAM 1 - Population, DNA Replication, Mitosis Meiosis

Question 1

DNA Structure

Answer 1

Nitrogenous base
pentose
sugar
phosphate
double helix 5’-3’ antiparallel structure

Question 2

Nucleosome Structure

Answer 2

Two coils of DNA on Histone core
~ 200 base pairs of DNA
Octomere on each of H2A, H2B, H3, H4
H1 - space between nucleosome

Question 3

Chromatin Structure Hierarchies

Answer 3

• Primar struc. - 2 coils of DNA on nucleosomes core
• Secondary struc. - helical array of nucleosomes
• Tertiary - Packing of nucleosome arrays into chromatin

visible chromosomes are transcriptionally inert - so raveled up can’t unravel and make gene copies

Question 4

Types of Chromatin:

Answer 4

*Heterochromatin: densely packed, not transcribed (some nonsense, some repressed)
- Constitutive: repeated sequences, genes not
expressed
- Facultative: the form of an entire chromosome that
is expressed
- ex> — x chromosome barr body: color blind
(can’t see red or yellow well), hemophilia (unable
to clot blood)
*Euchromatin: active genes, transcribed as needed
- found on nucleosomes core and area between

Question 5

Cell Cycle - study on a white board

Question 6

Barr Body

Answer 6

small, densely staining structure in the cell nuclei of female mammals - condensed in X chromosome
ex. color blind, hemphilia

Question 7

Cyclin

Answer 7

Cyclins activate Mitotic cdks (cyclin dependent protein kinases)

Question 8

Role of Cyclins

Answer 8

Cyclins activate Mitotic cdks (cyclin dependent protein kinases)

Protein kinases phosphorylate proteins (enzymes) to catalyze cell reactions

When cyclins are added, cells move through cell cycle checkpoints

Question 9

Role of Cyclins

Answer 9

Cyclins activate Mitotic cdks (cyclin dependent protein kinases)

Protein kinases phosphorylate proteins (enzymes) to catalyze cell reactions

When cyclins are added, cells move through cell cycle checkpoints - found at 3 major checkpoints (G1, G2, M Phase)

Question 10

3 cell populations in the body:

Answer 10

Go (nondividing): muscle and nerves

Cells that barely divide but can when stimulated: Liver (G2)

Cells that rapidly divide:
- Skin, hair
- GI epithelium
- Bone marrow, blood
- Reproductive cells

Question 11

Role of p53

Answer 11

p = protein
53 = 53 kilodaltons
- Regulates cell division, wild type form halts cell divisions, arrests cells in G1
- mutant forms cause abnormal cell division
- half of all cancers involve mutation of this gene
- gene can trigger “apoptosis” – programmed cell death
- some carcinogens are found to alter p53

Question 12

Factors that stimulate cell cycle

Answer 12

• Oncogenic factors
• Bcl 1 and 2 genes (B cell lymphoma)
• BRCA 1 and 2: linked to 80% chance of breast, ovarian cancer
• Ras gene
• Cyclin proteins (may be triggered by bcl gene)

Question 13

Factors that inhibit cell cycle

Answer 13

• P53 gene
• bax genes
• ICE (interleukin converting enzyme)
• Ubiquitin
• these same factors can also trigger apotosis

Question 14

Factors that inhibit cell cycle

Answer 14

• P53 gene
• bax genes
• ICE (interleukin converting enzyme)
• Ubiquitin
• these same factors can also trigger apoptosis

Question 15

Initiation of DNA replication

Answer 15

Initiator Proteins: unwind DNA double helix
Helicase: continues winding
Topoisomerase: swivel prevents tangling of DNA supercoils

Question 16

DNA replication

Answer 16

DNA polymerase directs DNA replication
DNA replicates in a 5’ to 3’ direction
Begins w/ attachment of RNA primer
followed by DNA polymerase
Where possible, RNA primer replaced via exonuclease/ ligase

Question 17

DNA Replication Enzymes

Answer 17

Initiator Protein
Helicase
Topoisomerase
Exonucleases
Endonucleases
RNA Primer
DNA Ligases
DNA Polymerase
Leading Strand
Lagging Strand

Question 18

Initiation Protein

Answer 18

Unwind DNA - binds to origin of replication an initiate unwinding of DNA double helix - both cell types

Question 19

Helicase

Answer 19

Unwinds dsDNA - both cells (eukary and prokary)

Question 20

Topoisomerase

Answer 20

Sins the ends of the DNA so the stands won’t get knotted up

Question 21

Exonucleases

Answer 21

an enzyme which removes successive nucleotides from the end of a polynucleotide molecule

Question 22

Endonucleases

Answer 22

an enzyme which cleaves a polynucleotide chain by separating nucleotides other than the two end ones

Question 23

DNA Polymerase

Answer 23

DNA synthesis
1. Leading Strand: s looking greek symb. - eu -
2. Lagging Strand - alpha - eu -

Question 24

DNA Ligases

Answer 24

(both cell types) – makes covalent bonds to join together adjacent DNA strands, including the Okazaki fragments in lagging-strand DNA synthesis and the new and old DNA segments in excision repair of DNA

Question 25

Factors that stimulate the cell cycle:

Answer 25

Ras gene - gets triggered by viruses

Question 26

Factors that inhibit cell cycle

Answer 26

Ubiquitin - causes the destruction of dividends

Question 27

Constitutive:

Answer 27

repeated sequences, genes not
expressed

Question 28

Facultative:

Answer 28

the form of an entire chromosome that
is expressed
- ex> — x chromosome barr body: color blind
(can’t see red or yellow well), hemophilia (unable
to clot blood)