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Biology 2: 6/13, 1/13, 6/12, 1/12, 6/11, 1/11, 6/10. 1/10 > DNA > Flashcards

DNA Flashcards

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1
Q

DNA helicase is important in DNA replication. Explain why.

A
  1. Separates/unwinds/unzips strands/helix / breaks H-bonds2. (So) nucleotides can attach/are attracted / strands can act as templates
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2
Q

Cytarabine is a drug used to treat certain cancers. It prevents DNA replication. Cytarabine has a greater effect on cancer cells than on healthy cells. Explain why.

A

(Cancer cells/DNA) divide/replicate fast(er)/ uncontrollably

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3
Q

Describe how DNA is replicated (6)

A
  1. Strands separate / H-bonds break2. DNA helicase (involved)3. Both strands/each strand act(s) as (a) template(s)4. (Free) nucleotides attach5. Complementary/specific base pairing / AT and GC6. DNA polymerase joins nucleotides (on new strand)7. H-bonds reform8. Semi-conservative replication / new DNA molecules contain one old strand and one new strand
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4
Q

A polypeptide has 51 amino acids in its primary structure. What is the minimum number of DNA bases required to code for the amino acids in this polypeptide?

A

153

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5
Q

The gene for this polypeptide contains more than this number of bases. Explain why

A

Some regions of the gene are non-coding/ introns / start/stop code/triplet / thereare two DNA strands

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6
Q

A sample of epithelial tissue from the small intestine of an animal was analysed. Some of the cells had 8.4 units of DNA, others had only 4.2 units.Use your knowledge of the cell cycle to explain why some cells had 8.4 units of DNA and others had only 4.2 units.

A
  1. 8.4/cells with twice DNA content = replicated DNA / late interphase / prophase / metaphase / anaphase2. 4.2 = DNA not replicated / (early) interphase / telophase / cell just divided / finished mitosis;
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7
Q

The diagram shows a short sequence of DNA bases.TTTGTATACTAGTCTACTTCGTTAATAWhat is the maximum number of amino acids for which this sequence of DNA bases could code?The number of amino acids coded for could be fewer than your answer. Give one reason why.

A

9Introns / non-coding DNA / junk DNAStart/stop code/triplet

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8
Q

Explain how a change in the DNA base sequence for a protein may result in a change in the structure of the protein.

A

Change in amino acid/s /primary structureChange in hydrogen/ionic/ disulfide bondsAlters tertiary structure

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9
Q

A gene codes for the α-polypeptide chain. There are 423 bases in this gene that code for amino acids. How many amino acids are there in the α-polypeptide chain?

A

141

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10
Q

The total number of bases in the DNA of the α-polypeptide gene is more than 423. Give 4 reasons why there are more than 423 bases.

A
  1. Stop/start sequences2. Non coding DNA (in the gene)/introns/multiplerepeats/junk DNA3. Two chains/a non-coding strand/complementary basepairs4. Addition of base by mutation
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11
Q

What is the difference between horizontal and vertical gene transmission?

A

Vertical gene transmission = Bacteria reproduce asexually, so each daughter cell is an exact copy of the parent. This means that each daughterr cell has an exact copy of the parents cells genes, including any that give it antibiotic resistance. Genes for antibiotic resistance can be found in the bacterial chromosome or in plasmids. The chromosome and any plasmids are passed on to the daughter cells during reproduction.Horizontal gene transmission = Genes for resistance can also be passed on horizontally, two bacteria join together in a process called conguation and a copy of a plasmid is passed from one cell to the other. Plasmids on to a member of the same species or a totally different species.

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12
Q

What is an intron?

A

Sections of DNA which don’t code for amino acids.Introns are removed during protein synthesis.

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13
Q

What is a homologous pair of chromosomes?

A

Pairs of matching chromosomesIn a homologous pair, both chromosomes are the same size and have the same genes although they could have different alleles.

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14
Q

How are Nucleotides joined together?

A

1) DNA nucleotides join together to form polynucleotide strands2) The nucleotides join up between the phosphate group of one nucleotide and the sugar of another creating a sugar-phosphate backbone3) Two DNA polynucleotide strands join together by hydrogen bonds between the bases4) Each base can only join with one particular partner - this is called specific base pairing5) Adenine always pairs with thymine and guanine always pairs with cytoside6) The two strands wind up to form the DNA double-helix

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15
Q

What are the three main components of nucleotides?

A

1) A deoxyribose sugar (stays the same)2) a phosphate group (stays the same)3) nitrogenous base (varies)

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16
Q

Describe how DNA is different in Eukaryotic cells and prokaryotic cells

A

Prokaryotic cells = DNA molecules are shorter and circular, it isn’t wound around proteins Eukaryotic cells = The DNA is linear, really long and wound around proteins.

17
Q

What name is used for the non-coding sections of a gene?

A

Introns

18
Q

Gene mutations occur spontaneously.During which part of the cell cycle are gene mutations most likely to occur?Why?

A

Interphase/ S/synthesis (phase)DNA/gene replication/synthesis occurs / longest stage

19
Q

What is an allele?

A

a different basesequence of a gene

20
Q

Ribonuclease is an enzyme. It is 127 amino acids long.What is the minimum number of DNA bases needed to code for ribonuclease?

A

381 / 384 / 387

21
Q

Explain how a change in a sequence of DNA bases could result in a non-functional enzyme.

A

Change in (sequence of) amino acids/primary structureChange in hydrogen/ionic/disulfide bondsAlters tertiary structure/active site (of enzyme)Substrate cannot bind / no enzyme-substrate complexes form

22
Q

what 3 things does each nucleotide consist of:

A
  • A sugar called deoxyribose.- A phosphate group.- An organic base belonging to one of two groups: (a) Single-ring: cytosine and thymine. (b) Double-ring: adenine and guanine.
23
Q

The deoxyribose sugar, phosphate group and organic bases are a result of condensation reactions to give a _________.Two nucleotides combine to form a __________.The continuous linking of monucleotides forms a long chain known as a ____________.

A

mononucleotidedinucleotide.polynucleotide.

24
Q

Adenine always pairs with_________ by ________

A

thymine by two hydrogen bonds

25
Q

Guanine always pairs with_________ by ________

A

cytosine by three hydrogen bonds

26
Q

DNA is adapted to carry out its functions in 4 ways

A
  • It is very stable and can pass to generations without change.- Its two separate strands are joined only with hydrogen bonds which allow them to separate during replication.- It is a large molecule and carries an immense amount of information.- By having the base pairs in the helical cylinder the information is protected from being corrupted
27
Q

Chromosome structure-only visible as distinct structure when a cell is dividing. The rest of the time they are widely dispersed throughout the nucleus.When visible they appear as two threads joined at a single point.Each thread is called a __________

A

ChromatidThe DNA in chromosomes is held in position by proteins.The length of DNA is highly coiled and folded. The DNA is coiled and the looped and further coiled before being packed into the chromosome.

28
Q

What is an allele?

A

Each gene exists of two, or occasionally more different forms. Each of these forms is called an allele. Each individual inherits one from each parent. Any differences in the base sequence of an allele may result in a different sequence of amino acids being coded for.

29
Q

why may there be a difference between the separation temps between the same species

A


(Same species) have different alleles/different base sequences/ (different) mutations/introns/ non-coding DNA/multiple repeats;

30
Q

explain how the structure of DNA relates to its function

A
  1. Sugar-phosphate (backbone)/double stranded/helix so provides strength/stability /protects bases/protects hydrogen bonds;
  2. Long/large molecule so can store lots of information;
  3. Helix/coiled so compact;
  4. Base sequence allows information to be stored/ base sequence codes for amino acids/protein;
  5. Double stranded so replication can occur semi-conservatively/ strands can act as templates;
  6. Complementary base pairing / A-T and G-C so accurate replication/identical copies can be made;
  7. (Weak) hydrogen bonds for replication/ unzipping/strand separation;
  8. Many hydrogen bonds so stable/strong;
31
Q

some people have suggested that vaccines to help smokers stop smoking should not be given free

A

yes- people choose to smoke and it may be more beneficial to spend the money on preventing people from smoking
no- unethical not to treatLess money needed to treat the effects of smoking/cancer / smokers pay taxes so are entitled to treatment;

Biology 2: 6/13, 1/13, 6/12, 1/12, 6/11, 1/11, 6/10. 1/10 (13 decks)

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