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AQA A Level Biology > 3.1.7 DNA, Genes & Chromosomes > Flashcards

3.1.7 DNA, Genes & Chromosomes Flashcards

1
Q

What is the basic function of DNA?

A

Used to store genetic information

(all instructions organism needs to grow and develop from fertilised egg to adult)

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2
Q

What is the main function of RNA?

A

Transfer genetic information from DNA to ribosomes

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3
Q

What do ribosomes (AKA body’s ‘protein factories’) do?

A

Read RNA to make polypeptides in process called translation

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4
Q

What are ribosomes made from?

A

RNA and proteins

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5
Q

What 3 things does a nucleotide consist of?

A
  • Nitrogen-containing organic base
  • Pentose sugar
  • Phosphate group
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6
Q

What are monomers that make up DNA & RNA?

A

Nucleotides

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7
Q

How are polynucleotides formed?

A
  • Nucleotides join via condensation reaction between phosphate group of one nucleotide and sugar of another
  • This forms a phosphodiester bond
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8
Q

What is a chain of sugar and phosphates called?

A

Sugar-phosphate backbone

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9
Q

What is the pentose sugar in a DNA nucleotide?

A

Deoxyribose

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10
Q

Each DNA nucleotide has same sugar & phosphate group but a different ___

A

base

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11
Q

Name the 4 possible bases in a DNA nucleotide

A
  • Adenine (A)
  • Thymine (T)
  • Cytosine (C)
  • Guanine (G)
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12
Q

What is the pentose sugar in a RNA nucleotide?

A

Ribose

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13
Q

Name the 4 possible bases in a RNA nucleotide

A
  • Adenine (A)
  • Uracil (U)
  • Cytosine (C)
  • Guanine (G)
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14
Q

Describe how the structure of DNA is formed

A
  1. 2 DNA polynucleotide strands join together by hydrogen bonding between complementary base pairs
  2. 2 hydrogen bonds form between A & T, and 3 hydrogen bonds form between C & G
  3. 2 antiparallel polynucleotide strands twist to form DNA double-helix
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15
Q

What does adenine pair with?

A

Thymine (A - T)

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16
Q

What does cytosine pair with?

A

guanine (C - G)

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17
Q

There is always _____ amounts of A & T in DNA molecule and C & G

A

EQUAL

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18
Q

Ratio of A & T to G & C varies from…

A

species to species

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19
Q

Describe the structure of RNA

A

Made from single polynucleotide chain = much shorter than most DNA polynucleotides

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20
Q

Name the 3 Types of RNA in every cell

A
  • tRNA
  • rRNA
  • mRNA
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21
Q

What does rRNA do?

A

Type of RNA that makes up ribosomes

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22
Q

Explain how the structure of DNA is related to its functions (6)

A
  1. Double helix protects bases from corruption
  2. Large molecule so can store lots of genetic information
  3. Helix/coiled so compact
  4. Double stranded so replication can occur semi-conservatively
  5. (Weak) H-bonds for replication
  6. Many H-bonds so stable
  7. Complementary base pairing so accurate identical copies can be made
  8. Base sequence allows information to be stored
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23
Q

Explain why the replication of DNA is described as semi-conservative (2)

A
  • Each strand copied / acts as a template
  • DNA has one new strand & one orginial
24
Q

Describe stage 1 of semi-conservative replication

A

DNA helicase breaks H bonds between bases = backbone is unzipped = helix unwinds

25
Q

Describe stage 2 of semi-conservative replication

A

Each original single strand acts as template for new strand:

Free nucleotides are attached to their complementary base on the backbone (orginal strand)

26
Q

Describe stage 3 of semi-conservative replication

A
  • Condensation reactions join nucleotides - catalysed by enzyme DNA polymerase
  • H bonds form between bases (on original and new strands)
27
Q

Describe stage 4 of semi-conservative replication

A

Each new DNA molecule contains one strand from original DNA molecule and one new strand

(Double strand twists again)

28
Q

______ Eukaryotic DNA is _____ & ______ with ______

A

Nuclear Eukaryotic DNA is Linear & Associated with Proteins

29
Q

What is a DNA molecule in eukaryotic cells wound around?

A

(Proteins called) histones

30
Q

What do histone proteins do?

A

Help support the DNA

31
Q

DNA molecules and histone are coiled up very tightly to make _____ ________

A

compact chromosomes

32
Q

____________ and ___________ in eukaryotes have their own DNA

A

Mitochondria and chloroplast

33
Q

What is the DNA in mitochondria and chloroplast (in eukaryotes) like?

A

Similar to prokaryotic DNA ∵ its circular and shorter than DNA in nucleus & it’s not associated with histone proteins

34
Q

What is DNA like in prokaryotic cells?

A

DNA molecules are shorter and circular & isn’t wound around histones

35
Q

How does prokaryotic DNA fit into cells?

A

Condenses to fit in cell by supercoiling

36
Q

What is a gene?

A

Sequence of DNA bases that codes for either a polypeptide or functional RNA

37
Q

What do different polypeptides have?

A

They have different no. and order of amino acids

38
Q

What determines the order of amino acids in a polypeptide?

A

The order of bases in a gene

39
Q

What is each amino acid coded by?

A

A sequence of 3 bases in gene = called triplet

40
Q

What is functional RNA?

A

RNA molecules other than mRNA (e.g. tRNA & rRNA)

41
Q

What is meant by a cell’s genome?

A

The complete set of genes in the cell

42
Q

What is meant by a cell’s proteome?

A

Full range of proteins that the cell is able to produce

43
Q

Most DNA in eukaryotic cells _____ code for polypeptides

A

DON’T

44
Q

In eukaryotic DNA, genes that code for _______ contain sections that…

A

In eukaryotic DNA, genes that code for polypeptides contain sections that don’t code for amino acids

45
Q

What are introns?

A

Sections of DNA that don’t code for amino acids

46
Q

Can there be several introns within a gene?

A

Yes

47
Q

What are exons?

A

Bits of gene that do code for amino acids

48
Q

When are introns are removed?

A

During protein synthesis

49
Q

Prokaryotic DNA doesn’t have ____

A

introns

50
Q

Eukaryotic DNA contains regions of _____ _____ ____ of genes

A

Eukaryotic DNA contains regions of multiple repeats outside of genes

51
Q

What are multiple repeats?

A

DNA sequences that repeated over and over again

e.g. CCTTCCTTCCTT

52
Q

Multiple repeats ____ code for amino acids & are called ______ ____

A

Multiple repeats don’t code for amino acids & are called non-coding repeats

53
Q

What is order of bases like in alleles and what does this lead to?

A

Order of bases in each alleles is slightly different ∴ they code for slightly different versions of the same polypeptide

54
Q

What is homologous pair?

A

Pair of matching chromosomes: both chromosomes are same size & have same genes (BUT could have different alleles)

55
Q

Where are alleles coding for the same characteristic found on chromsomes in a homologous pair?

A

Found at same fixed position (locus) on each chromosome in a homologous pair

56
Q

Explain why DNA helicase is important in DNA replication (2)

A
  • Breaks H-bonds
  • (So) nucleotides can attach/strands can act as templates
57
Q

Draw 2 nucleotides joining together

A

AQA A Level Biology (41 decks)

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