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Biology > Molecular genetics > Flashcards

Molecular genetics Flashcards

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1
Q

Define DNA

A

DNA is the genetic material that organisms inherit from their parents, and carries genetic code (genes), used for synthesising specific polypeptides

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2
Q

Define a chromosome

A

A chromosome is a DNA molecule condensed during cell division

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2
Q

What does a nucleotide consist of

A
  • Phosphate group
  • Deoxyribose sugar
  • Nitrogenous base
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3
Q

How is the sugar phosphate backbone of a DNA molecule formed

A

Sugar phosphate backbone is formed when the phosphate group of one nucleotide joins with the deoxyribose sugar of the next nucleotide

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3
Q

What is the shape of the phosphate group

A

Circular

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3
Q

What is the shape of the deoxyribose sugar

A

Pentagon

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4
Q

What are the rules for complementary base pairing

A
  • Adenine forms double hydrogen bonds with thymine
  • Cytosine forms triple hydrogen bonds with guanine
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5
Q

Describe the process of DNA replication

A
  • DNA replicates following the process of semi-conservative replication
  • Each polynucleotide strand of original DNA acts as a template for the synthesis of a new complementary polynucleotide strand
  • Original double helix first separated by enzymes
  • Nucleotides are bound to separated polynucleotide strands following rules of complementary base pairing with the aid of enzymes
  • Results in the formation of 2 double-stranded DNA molecules
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5
Q

What are the nitrogenous bases

A
  • Adenine
  • Thymine
  • Guanine
  • Cytosine
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6
Q

Define a gene

A

A gene is a unit of inheritance with a specific sequence of nucleotides, as part of a DNA molecule that contains the information to make a polypeptide

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7
Q

How does genetic information flow

A

DNA > RNA > Protein

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8
Q

Define transcription

A

Transcription is when the message in the gene is copied into an mRNA in the nucleus

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9
Q

Describe how polypeptides are synthesised

A
  • In nucleus, message in gene is copied into an mRNA through process of transcription
  • mRNA travels to cytoplasm and attaches itself to a ribosome
  • Ribosome moves along the mRNA and synthesises a polypeptide through process of translation
  • Polypeptide is released when ribosome leaves the mRNA
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9
Q

Define translation

A

Translation is the synthesis of a polypeptide chain from mRNA

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10
Q

How many bases on the mRNA make up a codon

A

3

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11
Q

What happens when a change occurs to the nucleotide sequence

A
  • Type of amino acids on the chain changes
  • Structure of protein changes
  • Protein loses its function
11
Q

When is a polypeptide chain functional

A

When it folds into a specific 3D shape

11
Q

How many amino acids does a codon code for

A

1

11
Q

What determines the sequence of amino acids in a protein

A

Order of nucleotide bases

12
Q

What are the similarities between DNA and mRNA

A
  • Both have a sugar phosphate backbone
  • Both have 3 common nitrogenous bases
13
Q

What is the structure of DNA

A
  • 2 strands
  • Double helix structure
  • Deoxyribonucleotide monomer
  • Deoxyribose sugar as the pentose sugar
  • Contains thymine
  • Hydrogen bonds between bases
14
Q

What is the structure of mRNA

A
  • 1 strand
  • Straight chain structure (Mostly)
  • Ribonucleotide monomer
  • Ribose sugar as pentose sugar
  • Contains uracil
  • No hydrogen bonds if it is a straight chain structure
15
Q

Define down syndrome

A

Down syndrome is caused by the non-separation of chromosome 21 in meiosis during gamete formation, resulting in the zygote having an extra chromosome 21, so body cell ends up with 47 chromosomes instead of 46

15
Q

Define mutation

A

Mutation is a spontaneous or induced change in the DNA sequence of genes, or a change in the number or structure of chromosomes

16
Q

Define mutagens

A

Mutagens are physical or chemical agents that can cause alterations to DNA, resulting in changes in the sequence of DNA

17
Q

What is genetic engineering

A

Genetic engineering is used to transfer genes from one organism to another by using a vector

17
Q

Describe sickle cell anaemia

A
  • Sickle cell anaemia caused by a gene mutation, resulting in a substitution of a single amino acid in the haemoglobin protein
  • Sickle cell haemoglobin molecules aggregate into long rods that deform the cells into a sickle shape
18
Q

What is a vector

A

A vector carries the genes to the intended cells

19
Q

What are plasmids

A

Circular strands of DNA that replicate separately from bacterial DNA

19
Q

Why are bacteria used to produce insulin

A
  • Easy to transfer genes into bacteria
  • Bacteria contain plasmids, in which insulin genes can be inserted easily
  • Bacteria take a short time to replicate
20
Q

What is a restriction enzyme

A

A restriction enzyme is an enzyme that cuts the 2 ends of a gene to produce ‘sticky ends’

21
Q

Describe how a human insulin gene is inserted into bacterial DNA

A
  • Cut the human insulin gene with a restriction enzyme, producing ‘sticky ends’
  • Each ‘sticky end’ is a single strand sequence of DNA bases, which can pair with complimentary bases to form a double strand
  • Obtain a plasmid from a bacterium and cut the plasmid open with the same restriction enzyme, producing ‘sticky ends’ complementary to ends of insulin gene
  • Mix plasmid with DNA fragment containing insulin gene
  • DNA fragment with insulin gene will bind to plasmid by complementary base pairing of the ‘sticky ends’
  • Add DNA ligase to seal DNA fragment to plasmid, forming a recombinant plasmid
  • Mix plasmid with bacterium
  • Apply heat or electric shock to open cell membrane for plasmid to enter
  • Transgenic bacterium will synthesise insulin together with other proteins from plasmid
  • Insulin must be extracted and purified before use

Biology (20 decks)

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