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A-level Biology AQA > 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
Describe stage 2 of semi-conservative replication
Each original single strand acts as template for new strand: Free nucleotides are attached to their complementary base on the backbone (orginal strand)
26
Describe stage 3 of semi-conservative replication
* Condensation reactions join nucleotides - catalysed by enzyme DNA polymerase * H bonds form between bases (on original and new strands)
27
Describe stage 4 of semi-conservative replication
Each new DNA molecule contains one strand from original DNA molecule and one new strand (Double strand twists again)
28
\_\_\_\_\_\_ Eukaryotic DNA is _____ & ______ with \_\_\_\_\_\_
**Nuclear** Eukaryotic DNA is **Linear** & **Associated** with **Proteins**
29
What is a DNA molecule in eukaryotic cells wound around?
(Proteins called) histones
30
What do histone proteins do?
Help support the DNA
31
DNA molecules and histone are coiled up very tightly to make _____ \_\_\_\_\_\_\_\_
compact chromosomes
32
\_\_\_\_\_\_\_\_\_\_\_\_ and ___________ in eukaryotes have their own DNA
Mitochondria and chloroplast
33
What is the DNA in mitochondria and chloroplast (in eukaryotes) like?
Similar to prokaryotic DNA ∵ its circular and shorter than DNA in nucleus & it's not associated with histone proteins
34
What is DNA like in prokaryotic cells?
DNA molecules are shorter and circular & isn't wound around histones
35
How does prokaryotic DNA fit into cells?
Condenses to fit in cell by supercoiling
36
What is a gene?
Sequence of DNA bases that codes for either a polypeptide or functional RNA
37
What do different polypeptides have?
They have different no. and order of amino acids
38
What determines the order of amino acids in a polypeptide?
The order of bases in a gene
39
What is each amino acid coded by?
A sequence of 3 bases in gene = called triplet
40
What is functional RNA?
RNA molecules other than mRNA (e.g. tRNA & rRNA)
41
What is meant by a cell's genome?
The complete set of genes in the cell
42
What is meant by a cell's proteome?
Full range of proteins that the cell is able to produce
43
Most DNA in eukaryotic cells _____ code for polypeptides
DON'T
44
In eukaryotic DNA, genes that code for _______ contain sections that...
In eukaryotic DNA, genes that code for _polypeptides_ contain sections that **don't code for amino acids**
45
What are introns?
Sections of DNA that don't code for amino acids
46
Can there be several introns within a gene?
Yes
47
What are exons?
Bits of gene that do code for amino acids
48
When are introns are removed?
During protein synthesis
49
Prokaryotic DNA doesn't have \_\_\_\_
introns
50
Eukaryotic DNA contains regions of _____ \_\_\_\_\_ ____ of genes
Eukaryotic DNA contains regions of _multiple_ _repeats_ _outside_ of genes
51
What are multiple repeats?
DNA sequences that repeated over and over again e.g. CCTTCCTTCCTT
52
Multiple repeats ____ code for amino acids & are called ______ \_\_\_\_
Multiple repeats _don't_ code for amino acids & are called _non-coding_ _repeats_
53
What is order of bases like in alleles and what does this lead to?
Order of bases in each alleles is slightly different ∴ they code for slightly different versions of the same polypeptide
54
What is homologous pair?
Pair of matching chromosomes: both chromosomes are same size & have same genes (BUT could have different alleles)
55
Where are alleles coding for the same characteristic found on chromsomes in a homologous pair?
Found at same fixed position (locus) on each chromosome in a homologous pair
56
Explain why DNA helicase is important in DNA replication (2)
* Breaks H-bonds * (So) nucleotides can attach/strands can act as templates
57
Draw 2 nucleotides joining together

A-level Biology AQA (43 decks)

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