Genetics and Cell Cycle: Lecture 8

Question 1

transcription

Answer 1

process of making mRNA copy of DNA (transcript); exit nucleus through nuclear pore into cytoplasm to ribosomes

Question 2

RNA polymerase

Answer 2

enzyme builds transcript; binds to gene; brings in complementary nucleotides, linking them together to form mRNA

Question 3

general stages of transcription and translation

Answer 3

1. initiation
2. elongation
3. termination

Question 4

initiation (transcription)

Answer 4

beginning; protein transcription factors bind to promoter region near gene on template strand of DNA; RNA polymerase also binds to promoter; DNA unwinds with aid of enzyme helicase

Question 5

helicase

Answer 5

enzyme that unwinds DNA

Question 6

elongation (transcription)

Answer 6

RNA polymerase covalently bonds complementary (to DNA template) nucleotides to growing mRNA molecule

Question 7

termination (transcription)

Answer 7

when last triplet of gene is reached, and the newly formed pre-mRNA molecule is ready for modification

Question 8

modification (transcription)

Answer 8

RNA processing- introns in pre-mRNA must be removed and exons spliced together
-when complete, mRNA exits nucleus through nuclear pore, enters cytosol, ready for translation into protein

Question 9

introns/exons

Answer 9

introns: noncoding sections of gene do not specify amino acid sequence
exons: sections that do specify amino acid sequence

Question 10

translation

Answer 10

occurs at ribosome
-nucleotide sequence of mRNA is translated into amino acid sequence with tRNA
-tRNA is made in nucleus, picks up specific amino acids and transfers to ribosome

Question 11

anticodons

Answer 11

-sequences of three nucleotides found on tRNA molecules
-pairs with the complementary codon on the mRNA

Question 12

binding sites for tRNA

Answer 12

A site, P site, E site

Question 13

A site (aminoacyl)

Answer 13

binds to incoming tRNA carrying amino acid

Question 14

P site (peptidyl)

Answer 14

amino acid is removed from its tRNA; added to growing peptide chain

Question 15

E site (exit)

Answer 15

empty tRNA then exits ribosome from site; free to pick up another amino acid

Question 16

initiation (translation)

Answer 16

initiator tRNA binds to mRNA start codon in ribosome’s P site

Question 17

elongation (translation)

Answer 17

next tRNA binds to open A site; allows two amino acids to be linked by peptide bond; first tRNA exits from E site; second tRNA moves into P site; A site is open for next tRNA to bind

Question 18

termination (translation)

Answer 18

end of translation when ribosome reaches stop codon on mRNA and new peptide is released

Question 19

posttranslational modification

Answer 19

polypeptides folded properly; sometimes combined with other polypeptides to become fully functional

Question 20

cell cycle main phases

Answer 20

interphase: G1, S, G2
M phase

Question 21

interphase

Answer 21

period of growth and preparation for cell division
subphases: G1, S, G2

Question 22

G1

Answer 22

cell performs normal daily metabolic activities (production of new organelles, cytoskeleton, and other proteins), prepares cell for next phase

Question 23

S phase

Answer 23

synthesis; DNA synthesis (replication); vital for cell to proceed to next phase

Question 24

G2

Answer 24

cellular growth; proteins required for cell division are rapidly produced and centrioles are duplicated

Question 25

DNA synthesis or replication

Answer 25

S phase: chromatin unwinds each base pair is duplicated using existing DNA strand as template; helicase unwinds

Question 26

primase

Answer 26

enzyme builds RNA primer on exposed DNA strands

Question 27

DNA polymerase

Answer 27

adds nucleotides to RNA primer; can only add to existing chain of nucleotides; proceeds in opposite directions along each strand as helicase separates; -RNA primer eventually removed and replaced with DNA nucleotides

Question 28

semiconservative replication

Answer 28

one old strand and one new strand

Question 29

M phase

Answer 29

overlapping processes of mitosis and cytokinesis

Question 30

mitosis

Answer 30

newly replicated genetic material is divided between two daughter cells

Question 31

cytokinesis

Answer 31

cell's proteins, organelles, and cytosol are divided between two daughter cells

Question 32

stages of mitosis

Answer 32

prophase prometaphase metaphase anaphase telophase

Question 33

prophase

Answer 33

-chromatin becomes compact; each individual chromosome has two sister chromatids joined at centromere -nucleolus disintegrates, mitotic spindle forms, pairs of centrioles (from newly duplicated centrosomes) migrate to opposite sides of cell; organize spindle fibers

Question 34

prometaphase

Answer 34

-spindle fibers from each centriole attach to each sister chromatid at centromere -nuclear envelope begins to break apart

Question 35

metaphase

Answer 35

-second and longest -spindle fibers from opposite poles of cell pull sister chromatids into line along middle (equator) of cell

Question 36

anaphase

Answer 36

-sister chromatids pulled toward opposite poles; individual chromosomes then called daughter chromosomes -each new daughter cell will have 46 chromosomes (23 pairs) -cytokinesis may begin at end of this stage

Question 37

telophase

Answer 37

-fourth and final stage -as daughter cells separate the nuclear envelope is reassembled, nucleoli reappear, and chromosomes uncoil becoming chromatin

Question 38

cytokinesis

Answer 38

divides cytosol and organelles equally between two new daughter cells -cells split apart as actin and myosin proteins tighten around equator creating cleavage furrow -eventually separates into genetically identical cells

Question 39

cleavage furrow

Answer 39

equator between cells splitting apart

Question 40

G0 phase

Answer 40

cells remain in G1 phase and never proceed through rest of cycle; non-dividing state

Question 41

checkpoints for cell cycle

Answer 41

stop/go signals for cell; most important G1 checkpoint occurs about 3/4 of way through G1 -responds to variety of extracellular signals and may not proceed if conditions are not favorable

Question 42

extracellular signals for cell division

Answer 42

-enough nutrients in ECF -growth factors (proteins) must be secreted by other cells to stimulate cell division -density of cells -anchored to neighboring cells and surrounding environment

Question 43

apoptosis

Answer 43

programmed cell death when cell cannot pass through checkpoints and cannot be repaired

Question 44

tumor

Answer 44

cells may form growth or mass because of loss of cell cycle control and uncontrolled cell division

Question 45

benign tumor

Answer 45

confined to original location; does not invade surrounding tissues; less likely to cause death

Question 46

malignant tumor

Answer 46

made up of cancer cells; not inhibited by high cellular density or loss of anchorage to other cells; with enough nutrients, grow and divide indefinitely

Question 47

metastasis

Answer 47

cells spread into other tissues; can cause widespread tissue destruction; may cause death