2.7

Question 1

what happens when a cell divides

Answer 1

two daughter cells that are identical copies of the parental cells are formed

Question 2

what is replication

Answer 2

the formation of a new DNA molecule and occurs during the S phase of the cell cycle

Question 3

what happens to the chromosome number and genes during DNA replication

Answer 3

the chromosomes and genes stay the same, only the DNA molecules change as they double

Question 4

what are the steps of replication

Answer 4

1. unwind the coils to make the strand accessible to enzymes.
2. the enzyme helices then unwinds the double helix and separates the two DNA strands by breaking the hydrogen bonds between the bases
3. DNA polymerase can then stat making new strands of DNA using the two old parent strands as templates.

Question 5

what direction does replication alway take place in

Answer 5

5’ to 3’ prime

meaning as one is antiparallel, It moves in the reverse direction on the other strand

Question 6

what is DNA replication like

Answer 6

it is semi conservative because each daughter molecule formed contains one original strand from the old molecule and one newly synthesized strand

Question 7

Name the enzyme that separates the two strands of the DNA double helix during replication.

Answer 7

helicase

Question 8

what did Meselson and Stahl find

Answer 8

that DNA replicated semi conservatively

Question 9

what are the three possible ways DNA could be replicated

Answer 9

Dispersive - sections
conservative - two separate strands
Semi conservative - mix of each strand

Question 10

Steps of meselson ad stahl experiment

Answer 10

they cultured E.coli in the presence of a heavy isotope N15. DNA contains nitrogen in its nitrogenous bases so the radioactive would end up in the DNA of the bacteria. the result was that all bacteria had 15N in its bases

they then transferred the bacterial culture into a fish medium where the nitrogen was replaced by 14N a lighter isotope and the bacteria were allowed to grow for several generations.

DNA samples were then extracted from successive bacterial generations sand subjected so a cesium chloride equilibrium density gradient centrifugation .

this technique allowed the DNA to move to different positions in the centrifuge tube based on its density. DNA containing one or two strands with 15N was heavier and showed lower bands than those containing two strands with 14N.

Question 11

What did meselson and stahl find

Answer 11

after one generation one division of the bacteria, the resulting DNA strand consisted of a double helix where one strand was made up of 15 N, and the other contained 14N. the band obtained was in between those for DNA with both strands contains 15N or 14N only.

Question 12

what did the results of meselson and stahl demonstrate

Answer 12

DNA replication had to proceed in a semi conservative way and should involvecomplementary base pairing to ensure the fidelity fo the daughter molecules, results of the successive generations of bacteria further confirmed this theory

Question 13

Which method was used in Meselson and Stahl’s experiment to prove their theory about the semi-conservative nature of the DNA replication?

Answer 13

use of isotopes

Question 14

What takes place to the DNA in transcription

Answer 14

the coding information is copied/transcribed into a special molecule called messenger RNA (mRNA). the DNA functions as a template and the single stranded mRNA molecule that is made follows the complementary base paring rules of DNA,

Question 15

What is the corresponding base sequence of the DNA strand of GCU CCU GAG UUG

Answer 15

CGA GGA CTC AAC

Question 16

what is the role of RNA polymerase

Answer 16

responsible for separating the DNA strands of the double helix as well as for joining the ribonucloetides together by phosphodiester bonds to form an mRNA strand

Question 17

what is the DNA strand that is not transcribed called

Answer 17

sense strand

has the same sequence as the base of the mRNA except fo thymine

Question 18

what is the transcribed strand known as

Answer 18

the antisense strand

Question 19

Antisense strand - TGA CCG TTA

give sense and mNA strand

Answer 19

DNA sense sequence: ACT GGC AAT

mRNA strand: ACU GGC AAU

Question 20

what is the antisense strand also called

Answer 20

the template strand

Question 21

what enzyme is responsible for uncoiling and separating the DNA strands during transcription

Answer 21

RNA polymerase

Question 22

what step comes after transcription

Answer 22

translation

Question 23

what is translation

Answer 23

the synthesis of polypeptides on ribosomes according to the genetic code

Question 24

how does translation happen

Answer 24

with the involvement of either free ribosomes in the cytoplasm or ribosomes on rough endoplasmic reticulum

Question 25

what is a codon

Answer 25

also known as a replete, each set of three consecutive bases in RNA

Question 26

what is each codon translated into

Answer 26

one amino acid in a polypeptide chain

Question 27

what is the genetic code

Answer 27

degenerate, meaning some amino acids are encoded by more than one codon, it is also universal, means the genetic Information,ation is translated in the same was as other living organism

Question 28

what does it mean when something is degenerate

Answer 28

some amino acids are encoded by more than one codon

Question 29

how many codons are there that can be formed

Answer 29

64

Question 30

how many amino acids are there

Answer 30

20

Question 31

what are the specific codons that stop translation

Answer 31

UAG UGA UAA

Question 32

what codon starts translation

Answer 32

AUG

Question 33

what is AUG

Answer 33

methionine - start codon

Question 34

how many nucleotides are needed fro the stop codon

Answer 34

three nucleotides

Question 35

how would you calculate the amount of amino acids in 456 nucleotides

Answer 35

456 - 6 (3 start codons and 3 stop codons) 450 /3 ( each set of 3 nucleotides forms one codon) 150 codons = 150 + 1 amino acids, adding the amino acid methionine

Question 36

how many nucleotides are needed for the start codon

Answer 36

3

Question 37

where is the anticodon found on the tRNA

Answer 37

at the end of the molecule

Question 38

where is the amino acid four on the tRNA

Answer 38

on the 3' end attached to the beginning

Question 39

what bond does the amino acid form when attaching to the tRNA

Answer 39

an ester bond

Question 40

Brief outline of translation

Answer 40

1. complementary base pairing between codon and anticodon 2. Another amino acid is brought in attached to its tRNA 3. A condensation reaction forms a peptide bond 4. the ribosome moves along the mRNA by one triplet and a tRNA is released 5. another amino acid is brought in

Question 41

where does translation take place

Answer 41

in the cytoplasm of the cell

Question 42

what is the sequence of DNA

Answer 42

DNA - mRNA - protein

Question 43

two factors of the genetic code

Answer 43

universal and degenerate

Question 44

what is the role of tRNA in translation

Answer 44

it brings amino acids to the ribosomes

Question 45

what is PCR

Answer 45

Polymerase chain reaction is used to amplify small fragments of DNA

Question 46

what does PCR allow scientist to do

Answer 46

to clone genes, to work with minute amounts of DNA found at crime scene, identify the dead and sequence the DNA of extinct species

Question 47

what does PCR allow for

Answer 47

the rapid production of multiple copies of DNA using Taq DNA polymerase

Question 48

what does PCR technique use

Answer 48

uses cyclic heating and cooling of a DNA sample in the presence of primers, DNA nucleotides and Tax polymerase

Question 49

where does Taq polymerase come from

Answer 49

it is isolated from a bacterium in hot water springs at temperatures between 50 and 80 degrees, It is thermostable, can operate at high temperatures.

Question 50

how do transgenic organisms occur

Answer 50

when you place a gene from one organism into a different organism results

Question 51

how are transgenic organisms made

Answer 51

such as bacteria, are made by inserting a gene from another organism into the plasmid of their cells

Question 52

what can transgenic organisms be used for

Answer 52

bio factory for many of todays therapeutic drugs

Question 53

how can plasmids be used to produce different proteins

Answer 53

protein gene and plasmid are combined to make recombinant plasmid - made a transgenic bacteria - grow in a culture - human protein

Question 54

what insulin

Answer 54

a hormone produced by the beta cells of the pancreas

Question 55

what does insulin do

Answer 55

it regulates the glucose uptake and the conversion of glucose to glycogen in the liver

Question 56

how can we make human insulin

Answer 56

from bacteria due to the universality of the genetic code which allows for gene transfer between species

Question 57

what is a transgenic organism

Answer 57

a unicellular organism that carries a specific gene from another organism

Question 58

Which organelles are used in transferring genes from one organism to another?

Answer 58

plasmids