inheritance of sameness

Question 1

Purine and pyrimidine base-pairing in DNA/RNA

Answer 1

guanine=cytosine

adenine=thymine(or uracil)

Question 2

Direction of movement of DNA polymerase on template strands

Answer 2

DNA polymerase moves from 5’ to 3’ on the template strand.

Question 3

Meaning of semi-conservative, leading strand and lagging strand

Answer 3

DNA replication is semiconservative; each stand in double helix acts as a template strand for synthesis of a new complimentary, antiparallel strand.

during DNA replication, leading strand is made as a continuous piece - other one, lagging strand is made in small pieces (due to 5’to3’ polarity).

Question 4

General action of proteins

Answer 4

helicase: unwinds double helix.
topoisomerase: avoids twisting of DNA ahead of replication fork.
primase: synthesizes RNA primer in the 5’to3’ direction to initiate new DNA strand.
DNA polymerase III: extends RNA primer by adding DNA nucleotides to it.
DNA polymerase I:uses 5’to3’ exonucleus activity to remove/replace RNA
DNA ligase: seals nick left b/w fragmentd after RNA primer replaced with DNA.

Question 5

3’ vs 5’ polarity of nucleic acid chains involved in DNA replication

Answer 5

phosphate group bound to 5’ carbon of deoxyribose sugar and hydroxyl group is bound to 3’ carbon of deoxyribose sugar

Question 6

Direction of elongation

Answer 6

3’ to 5’. the 5’ end cant extend

Question 7

STUDY THIS !! Structure of a replication bubble

Answer 7

USE SIMUTEXT!!!

Question 8

Main features of chromosome anatomy

Answer 8

centromere at middle, telomere at ends.

Question 9

Meaning of “n” and “C”

Answer 9

n is the number of unique chromosomes. its coefficient(ploidy) tells #of unique sets present in organism. e.g. homologous pair is 2n

c is the amount of DNA in one set of organism’s nuclear chromosome (genome size). its coefficient tells how many times entire genome is present in a cell. e.g. homologous pair is 4c

Question 10

Changes in the coefficient of n and C throughout the cell cycle (i.e n vs 2n, 2C vs 4C etc.)

Answer 10

c duplicates during s phase and reverts near end of mitosis.

n remains constant!!

Question 11

What does n imply about C, or vice versa?

Answer 11

nothing!!

Question 12

The C-value paradox

Answer 12

value varies among diff species. DNA size doesn’t determine complexity of organism.

Question 13

STUDY THIS!! How to solve problems when given a karyotype (can you determine ploidy, n-value, how many copies of genome…?)

Answer 13

Q!!

Question 14

The structure of DNA

Answer 14

phosphate group attached to 5-carbon sugar attached to nitrogenous base.
3’to5’ end on each strand confers polarity on DNA backbone in opposite direction

Question 15

Mechanisms that ensure inheritance of sameness

Answer 15

daughter cells inherit same DNA.

DNA polymerase only adds to free 3’OH - maintains sameness thru complementary base pairing. replisomes replicate one strand continuously, the other discontinuously.

DNA synthesizes 5’to3’ direction using 3’to5’ template.

when converting DNA to RNA, will change thymine to uracil which is still complementary to adenine.

Question 16

STUDY THIS!! Structure of replication bubble (leading strand, lagging strand, placement of primers…)

Answer 16

Q

Question 17

Cell senescence (/hayflick limit) and why cells reach this stage. what happens if it doesnt reach cell senescence?

Answer 17

the hayflick limit is #of times a cell can divide before cell division stops (60-70times) due to telomere running out. this leads to cell senescence (irreversible cell cycle arrest).

if cells fails to cell senescence it will undergo apoptosis or has the risk of become cancer cell.

Question 18

telomere repetitive sequence

Answer 18

TTAGGG

Question 19

Why chromosomes shorten at each replication

Answer 19

bc of incomplete replication of DNA molecule by DNA polymerase - ends can’t be copied.

Question 20

Mechanism of telomerase action

Answer 20

extends template allowing new primers to be put on & so that DNA polymerase can extend it. (telomerase is not present in all cells - e.g. it is in stem, cancer, male germline, and embryonic stem cells)

Question 21

telomere’s function

Answer 21

ends of chromosome that protects critical information

Question 22

which mechanism can lead to mutation and why?

Answer 22

non-homologous end joining and excision repair bc they make changes in both strands

Question 23

does transposition leave a copy of its transposon at original site?

Answer 23

not always - there are two methods, one in which they do so

Question 24

how does distance of alleles affect recombination/crossing over?

Answer 24

alleles more likely to recombine if they’re further from one another

Question 25

what is translocation?

Answer 25

a type of mutation. where segment of allele moved to a non-homologous chromosome