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HSC BIOLOGY > BP S4 > Flashcards

BP S4 Flashcards

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1
Q

What are the first step of DNA replication?

A

Step 1: Enzyme helicase breaks the hydrogen bonds between the base pairs and unzips the strand to make two new strands

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2
Q

What are the 2nd step of DNA replication?

A

Step 2: DNA strands transcribed on mRNA & complimentary nucleotide bases made on ribosome and return to DNA

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3
Q

What are the third step of DNA replication?

A

Step 3: DNA Polymerase slots complementary nucleotide bases into the leading and lagging strands

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4
Q

What are the fourth step of DNA replication?

A

Step 4: Two double stranded molecules are now present – RECOILS BACK UP

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5
Q

Why is DNA replication important?

A
  • Essential for meiosis and mitosis which support growth, repair and reproduction
  • If meiotic cell division did not involve DNA replication, there could be no crossing over or variation when gametes are formed
  • Genes can be transferred between generations
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6
Q

Whats the process by which DNA controls the production of Polypeptides?

A

• DNA:
o Genetic material in cells
o Each gene contains coded information required to make polypeptides for the cell
• Polypeptide synthesis: involves RNA (ribonucleic acid)
• RNA: - single strand of nucleotide bases
- ribose sugar
- uracil replaces thymine
• Transcription  information on DNA copied onto an mRNA molecule by RNA Polymerase
• Translation
o Information on mRNA used to make a new polypeptide chain
o mRNA leaves nucleus and takes copied code to ribosomes
• have 3 active binding sites (1 holds mRNA and 2 hold tRNA
o tRNA carries amino acids in cytoplasm
o matches up to mRNA on ribosomes
o amino acids join together to create a polypeptide chain
o Codon: three nucleotide bases together form one amino acid
o ‘stop’ – polypeptide released into cytoplasm
o polypeptide chain: make up a protein
Polypeptide chains combine to make proteins e.g. enzyme, hormone, haemoglobin etc

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7
Q

Explain the relationship between proteins and polypeptides

A

o Proteins: building materials and enzymes of an organism
o Made up of amino acids bonded together by peptide bonds
o Made up of at least one polypeptide chain
• Polypeptide: chain of amino acids
Folded and twisted to give them structure that characterises certain proteins, and linked to what the protein

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8
Q

Give an example that explains the relationship between proteins and polypeptides

A

o Insulin  small protein  made up of a chain of 51 amino acids
o Haemoglobin  large protein  four polypeptide chains

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9
Q

Explain how mutations in DNA may lead to the generation of new alleles

A
  • Mutation = change in DNA, results in changes to polypeptides that are produced = source of new alleles
  • To produce change in allele = mutation must occur in sex cells to be passed onto next generation
  • Mutation needs to occur at right time for evolutionary change to occur
  • New gene must be beneficial
  • Only become beneficial when the organisms need it to adapt to their changing environment.
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10
Q

Give an example of how mutations in DNA may lead to the generation of new alleles.

A

an animal develops a mutation that resists virus’ = gets passed onto offspring = uses it when virus comes = ones who don’t develop resistance will die
(natural selection)

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11
Q

Discuss evidence for the mutagenic nature of radiation

A

Types of radiation that cause mutations:
• Cancer: indirect evidence for mutagenic nature of radiation
o X-ray
• 1895 = danger of atomic radiation became apparent
o X-ray technician developed skin cancer and died
o Atomic radiation
• 1900’s = most first generation radiation therapists died of cancer
o Ultraviolet light
• 1905 = physicians notice the rise of skin cancer on the necks of grape pickers who were exposed to sun for long time

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12
Q

Discuss more evidence or lack of for the mutagenic nature of radiation

A

– Not so easy to collect evidence
– Much evidence is not concluded
– Evidence not clear because sometimes the damaged chromosomes are repaired by the cell
• Dubrova 2004  radiation caused mutations in next two generation of mice who were exposed to X-rays
• Radio-therapy cancer patients  no change in genetic inheritance to offspring
• Survivors of atomic bombs WWII  No evidence of increased genetic defects of offspring, but children had lower IQ’s and higher rates of mental retardation
=> This proves that obvious mutations are passed through gametes

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13
Q

Explain how an understanding of the source of variation in organisms has provided support for Darwin’s theory of evolution by natural selection

A
  • Evolution by natural selection = the world has limited resources = organisms produce more offspring than can survive
  • Darwin observed variations = occur because of recombination of genes in sexual reproduction, crossing over and mutations.
  • Some organisms have DNA-controlled features that help them to survive and better able to use resources
  • These organisms live longer = produce more offspring = pass on survival characteristics
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14
Q

Describe the concept of punctuated equilibrium in evolution and how it differs from the gradual process proposed by Darwin

A

• Darwin: evolutionary change occurred over a long period of time
= periods of rapid development and slow development
• Punctuated equilibrium (1970’s): most species continue to change until they reach a stable stage
= sudden process
= may last millions of years but can be interrupted by rapid evolutionary change
= Evidence: Fossil record incomplete
– Record of mass extinctions followed by appearance of new species
– If evolution happens in short time, forms are not around long enough to be apparent in fossil record

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15
Q

Simply what is DNA replication?

A
  • The production of 2 identical double stranded molecules of DNA from one original double helix molecule
  • 2 strands of the original DNA molecule separate and each gives a rise to a new complementary strand
  • This ensures that genetic material is copied exactly
  • It occurs just before cell division
  • It ensures that each cell receives one full and exact copy of the coded instructions
  • Process of replication occurs in three steps.
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16
Q

Name the first step in DNA replication.

A

The DNA double helix unwinds, and an enzyme called helicase causes the DNA to progressively unwind.

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17
Q

Name the second step in DNA replication.

A

The DNA unzips, weak hydrogen bonds break exposing the nucleotide bases.

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18
Q

Name the third step in DNA replication.

A

Nucleotides are added to each single strand, as each strand acts as a template for the production of a new strand of DNA, free nucleotides are picked up from a pool by DNA polymers and matched up to their opposite base partner.
The base pairing is then checked by another DNA polymerase enzyme which checks for any incorrect additions.
The replicated DNA molecules rewind into double helix

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19
Q

An incorrect base pairing during DNA replication means?

A

The base sequence will change = mutation.

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20
Q

DNA replication is essential for the completion of the steps that occur in both…

A

Meiosis and mitosis.

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21
Q

Meiosis and mitosis support what within the cell?

A

Growth repair and reproduction

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22
Q

Why is DNA replication significant to the process of mitosis?

A

The importance of the replication is so that identical healthy offspring cells can be produced during mitosis.

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23
Q

Why is DNA replication significant to the process of meiosis?

A

If meiotic cell division, which must occur to produce sex cells did not involve the replication of DNA and so also the formation of chromatids, there would be no crossing over or the high level of variation in gametes formed.

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24
Q

Outline the process by which DNA controls the production of polypeptides.

A

Polypeptide synthesis involves a type of nucleic acid call RNA.
There are two types of RNA that are involved in polypeptide synthesis, messenger RNA (mRNA) and transfer RNA (tRNA)
IN the nucleus the double stranded DNA molecules unzip and the DNA code is transcribed in the single stranded mRNA molecule. The mRNA moves out of the nucleus into the cytoplasm and attaches itself to a ribsome. In the cytoplasm, the mRNA is translated into amino acids.
At the ribosome the mRNA lines up forming a template, a group of three bases called a codon, codes for a specific amino acid. There are codes that start and stop the chain formation. AUG is the starting point for translation
tRNA has an anticodon (non amino acid forming codon) on one end and an amino acid on the other. A polypeptide is formed as each amino acid is added from tRNA to a chain following the sequence on the mRNA.

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25
Q

Whats RNA?

A

Ribonucleic acid. RNA is the intermediary between DNA and polypeptide synthesis. It is a single strand of nucleic bases. It has ribose sugar and the nitrogen base, thymine which is replaced by uracil which bonds with adenine.

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26
Q

Explain the relationship between proteins and polypeptides.

A

A protein I made up of one or more polypeptides and a polypeptide is made up of a chain of many amino acids.

27
Q

Give a simple model for polypeptide synthesis.

A

DNA => mRNA => tRNA => Polypeptide.

28
Q

What was James Watson, and Francis Cricks role in the determination of DNA structure?

A

They suggested the double helix structure of DNA, they also suggested the pairing of bases. They suggested that this pairing gave DNA the mechanism for copying its genetic material (a way for DNA replication)

29
Q

What did Rosalind Franklin do in relation to the determining of DNA structure?

A

She provided the crucial evidence of which Watson and crick based their double helix model upon.
Franklin used the technique of xray diffraction and initially use it to detail the structure of carbon
The sexism in the scientific world slowed the progress, if crick had worked with franklin sooner there would have been more process.

30
Q

What did Maurice Wilkins do in relation to the determination of the DNA structure?

A

Was a physicist that made it possible for the use of x ray diffraction patterns that made it possible for Watson and crick to detail the DNA model. (it is said that franklin made some of these and wilkins passed it on without her permission)

31
Q

IN 1962 who won the Nobel prize?

A

Watson, Crick and Wilkins for physiology or medicine. Franklin didn’t get any attention since she had died four years prior.

32
Q

Why was Beadles and Tatum’s Hypothesis “One gene one protein” altered to “one gene one polypeptide”?

A

Because one gene one protein only holds true for some enzymes but not all
It has been altered to the other because one gene is the portion of the DNA strand specifying a single polypeptide chain.

33
Q

Who were Beadle and Tatum?

A

American geneticists who in the early 1940s developed techniques to screen and detect nutritional mutants in pink bread mould.

34
Q

What’s the step transcription in DNA production  for polypeptides.

A

It occurs in the nucleus as one strand of DNA acts as a template for the production of a single stranded mRNA which then moves from the nucleus out to a ribosome.

35
Q

What step happens after transcription?

A

Translation.

36
Q

What does the step translation involve?

A

mRNA moves to the ribosome, and then the ribosome moves along the mRNA, ribosome enzymes connect the amino acids to form a polypeptide chain. Amino acids are carried into position be tRNA (transfer RNA molecules)

37
Q

New alleles in organisms come about by

A

A result of mutations

38
Q

A mutation is a change in DNA usually involving?

A

A change in bases.

39
Q

In nature, mutations arise by chance and many are…

A

Harmful

40
Q

Mutations in body cells may cause changes in the organisms body such as cancer; these changes cannot be passed onto offspring but?

A

Mutations in sex cells can be passed on to offspring.

41
Q

Any accidental change to genetic material is a?

A

Mutation.

42
Q

There are certain factors that can increase the likelihood of mutations what are these factors?

A

Mutagens, and this can include high temperatures (mutation rates are higher in hotter climates)
Certain chemicals (eg some pesticides)
And radiation is also a factor. (UV from the sun)

43
Q

Effects of mutation on meiosis?

A

Mutation during meiosis affects the gamete involved in fertilisation. The offspring might get a new inheritable gene. The new trait might be:
Detrimental, less chance to survive
In improvement helps survival
Neither good nor bad just different
The mutation becomes a new variation to be inherited by future generations.

44
Q

Effects of mutation on mitosis?

A

Mutation might have no effect on cell
Cell might not be able to function properly, cell dies and no effect on multicellular organism
Mutation might cause malfunction in cell, which becomes cancerous, and he organism can be severely affected though future generations are not.

45
Q

Dr Dubrova, professor of genetics in 2004 and for reported?

A

That radiation caused genetic mutation in the next two generation of mice exposed to fission neutrons or x rays.

46
Q

What did Dr Dubrova find in Belarus and Ukraine in relation to the disaster of Chernobyl?

A

They studied families from heavily contaminated rural areas of Ukraine and Belarus. They found a 1.6fold increase in mutation rates in the germ line of exposed fathers while the maternal germ line mutation rate was not changed.

47
Q

Name an example of mutagenic effect of radiation?

A

Laboratory experiments have shown that mice exposed to high alpha radiation from plutonium-238, even in small doses had a high frequency of chromosome damage.

48
Q

Why is evidence of the effect of radiation on mutation not always clear?

A

Because chromosomes are repaired by the cell.

49
Q

Mutations occur at random in the…

A

DNA molecules and chromosomes

50
Q

Usually new mutant genes are…

A

Recessive alleles.

51
Q

Because mutations are recessive what does it take for a mutation to be seen in the phenotype?

A

Only when two heterozygous individuals mate and bring together a pair of recessive genes does the new phenotype actually appear.

52
Q

New phenotypes of mutations may include?

A
  • Slightly bigger ears
  • Slightly shorter toes
  • New colour pigment in the fur
  • A slightly longer intestine
    It is these small differences that give the variation to a population for natural selection to work on
53
Q

Complete Darwin and Wallace’s theory of evolution.

A
  1. All organisms produce more offspring that can survive
  2. In every species there is variation, and the new traits originate from genetic mutation. Traits are mixed in new combinations by meiosis and sexual reproduction, producing greater variation
  3. Natural selection chooses the survivors
  4. The “fittest” individuals reproduce and pass on their characteristics as genes (DNA) inherited by the processes of genetics
  5. Over generations a species evolves
54
Q

Insecticide resistance in insect pests is an example of?

A

Natural Selection

55
Q

Species that lay a large number of eggs and reproduce several times in mating season are more likely to have offspring with?

A

Genetic Variation.

56
Q

Offspring with genetic mutation result in?

A

Better adaption for survival

57
Q

How does punctuated equilibrium differ from Darwin’s views?

A

Darwin always imagined that evolution was a very slow process, taking at least 100,000 generations perhaps over millions of years. Though sometimes significant change could be seen in one rock layer in Darwin’s opinion it was just “patchiness” of the fossil record.

58
Q

What is punctuated equilibrium?

A

Suggests that evolution does not occur in slow and steady ways, but in short, sharp bursts of rapid change in between long periods of little or no change at all.

It suggests that species might change significantly within just a few thousand years rather than millions.

59
Q

Analyse information from secondary sources to outline the evidence that led to Beadle and Tatum’s one gene – one protein’ hypothesis and to explain why this was altered to the ‘one gene – one polypeptide’ hypothesis

A

• ‘one gene – one protein’ hypothesis
o 1940’s: created nutritional mutated strains with X-rays in bread to create pink bread mould (Neurospora crassa)
o each strain unable to produce specific amino acid
o mould unable to grow unless amino acid was added
o contribution: genes controlled biochemical processes
o significance: showed how genes could control protein synthesis
• changed to… ‘one gene – one polypeptide’
o because the ‘protein’ hypothesis isn’t true for all enzymes
o One gene is the portion of the DNA strand specifying a single polypeptide chain
o Several genes required to specify enzymes involved in biochemical processes

60
Q

When you made a flow chart that shows the changes in DNA sequences and how it can result in changes in cell activity… (go do that) explain the flow chart and why changes impact the end result.

A

• One base pair lost = frame shift mutation = different polypeptides produced = protein becomes truncated and is premature = dysfunctional enzyme

61
Q

Process and analyse information from secondary sources to explain a modern example of ‘natural’ selection

A
  • Modern day example: Insecticide resistance in insect pests
  • Insects reproduce frequently and in large numbers  more likely to have genetic mutation in offspring
  • Population has variety of characteristics
  • Some insects more resistant to insecticide than others
  • When first sprayed, most population will die
  • Few insects with most resistant gene will survive  they reproduce and pass characteristics to offspring
  • Some offspring will inherit, some won’t.
  • Resistance grows stronger after each generation
62
Q

James Watson and Francis Crick in determining the structure of DNA?

A
  • Suggested the double helix structure
  • Suggested pairing of bases (A-T, G-C)
  • Pairing of bases would allow DNA to replicate itself
63
Q

Rosalind Franklin in determining the structure of DNA?

A
  • Learned techniques of X-ray diffraction (initially used it to describe structure of carbon)
  • Applied the technique to DNA fibres obtained by Wilkins
  • Watson abused her work, claiming Franklin to be a ‘mad feminist scientist’
64
Q

Maurice Wilkins in determining the structure of DNA?

A
  • Physicist
  • Supplied X-ray diffraction techniques used by Watson & Crick to build DNA model
  • Some references note that Franklin actually produced the X-ray technique but Wilkins passed on without permission
  • 1962  Watson, Crick and Wilkins won Nobel Prize for physiology and medicine (Franklin died four years before so didn’t get prize)

HSC BIOLOGY (21 decks)

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