2.7 Flashcards

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1
Q

what happens when a cell divides

A

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

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2
Q

what is replication

A

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

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3
Q

what happens to the chromosome number and genes during DNA replication

A

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

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4
Q

what are the steps of replication

A
  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.
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5
Q

what direction does replication alway take place in

A

5’ to 3’ prime

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

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6
Q

what is DNA replication like

A

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

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7
Q

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

A

helicase

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8
Q

what did Meselson and Stahl find

A

that DNA replicated semi conservatively

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9
Q

what are the three possible ways DNA could be replicated

A

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

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10
Q

Steps of meselson ad stahl experiment

A

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.

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11
Q

What did meselson and stahl find

A

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.

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12
Q

what did the results of meselson and stahl demonstrate

A

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

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13
Q

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

A

use of isotopes

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14
Q

What takes place to the DNA in transcription

A

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,

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15
Q

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

A

CGA GGA CTC AAC

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16
Q

what is the role of RNA polymerase

A

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

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17
Q

what is the DNA strand that is not transcribed called

A

sense strand

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

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18
Q

what is the transcribed strand known as

A

the antisense strand

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19
Q

Antisense strand - TGA CCG TTA

give sense and mNA strand

A

DNA sense sequence: ACT GGC AAT

mRNA strand: ACU GGC AAU

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20
Q

what is the antisense strand also called

A

the template strand

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21
Q

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

A

RNA polymerase

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22
Q

what step comes after transcription

A

translation

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23
Q

what is translation

A

the synthesis of polypeptides on ribosomes according to the genetic code

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24
Q

how does translation happen

A

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

25
Q

what is a codon

A

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

26
Q

what is each codon translated into

A

one amino acid in a polypeptide chain

27
Q

what is the genetic code

A

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

28
Q

what does it mean when something is degenerate

A

some amino acids are encoded by more than one codon

29
Q

how many codons are there that can be formed

A

64

30
Q

how many amino acids are there

A

20

31
Q

what are the specific codons that stop translation

A

UAG

UGA
UAA

32
Q

what codon starts translation

A

AUG

33
Q

what is AUG

A

methionine - start codon

34
Q

how many nucleotides are needed fro the stop codon

A

three nucleotides

35
Q

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

A

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

36
Q

how many nucleotides are needed for the start codon

A

3

37
Q

where is the anticodon found on the tRNA

A

at the end of the molecule

38
Q

where is the amino acid four on the tRNA

A

on the 3’ end attached to the beginning

39
Q

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

A

an ester bond

40
Q

Brief outline of translation

A
  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
41
Q

where does translation take place

A

in the cytoplasm of the cell

42
Q

what is the sequence of DNA

A

DNA - mRNA - protein

43
Q

two factors of the genetic code

A

universal and degenerate

44
Q

what is the role of tRNA in translation

A

it brings amino acids to the ribosomes

45
Q

what is PCR

A

Polymerase chain reaction is used to amplify small fragments of DNA

46
Q

what does PCR allow scientist to do

A

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

47
Q

what does PCR allow for

A

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

48
Q

what does PCR technique use

A

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

49
Q

where does Taq polymerase come from

A

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.

50
Q

how do transgenic organisms occur

A

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

51
Q

how are transgenic organisms made

A

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

52
Q

what can transgenic organisms be used for

A

bio factory for many of todays therapeutic drugs

53
Q

how can plasmids be used to produce different proteins

A

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

54
Q

what insulin

A

a hormone produced by the beta cells of the pancreas

55
Q

what does insulin do

A

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

56
Q

how can we make human insulin

A

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

57
Q

what is a transgenic organism

A

a unicellular organism that carries a specific gene from another organism

58
Q

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

A

plasmids