Chapter 14: Molecular Genetics Flashcards
What are the 3 main components of a nucleotide?
- Deoxyribose sugar (/pentose sugar) molecule
- Phosphate group
- Nitrogenous base
What are the 4 different types of nitrogenous bases?
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)
Rule complementary of base pairing?
Nitrogenous Bases w/ complementary shapes bond w/ each other in a 1:1 ratio:
Adenine+Thymine
Guanine+Cytosine
Describe the formation of DNA double helix.
- Complementary base pairing occurs betw. nucleotides of opp. strands (A+T,G+C)
- Two polynucleotide stands are held tgt by hydrogen bonds betw. nitrogenous bases of opp. polynucleotide strands.
- DNA molecule is made up of 2 anti-parallel polynucleotide stands, running in opp. directions.
- DNA then twists to resemble a spiral structure/double helix
PHRASING: Two anti-parallel strands of the DNA molecule coil to form a double helix structure.
How is DNA organised inside cells?
NUCLEOTIDE->
POLYNUCLEOTIDE CHAIN/DNA STRAND->
DNA MOLECULE->
DNA molecule wrapped around protein=CHROMATIN THREADS->
chromatin threads condense= CHROMOSOMES (in cell nucleus)
What is a gene?
-Basic units of inheritance
-A sequence of DNA nucleotides (bases)/ segment of DNA molecule that codes for the formation of one specific polypeptide
Name the steps of protein synthesis and briefly describe each process
- Transcription:
The DNA template strand codes for a mRNA - Translation:
The mRNA codes for a single polypeptide
Describe the process of Transcription.
- Double-stranded DNA molecule unwinds and unzips
- One of the 2 strands a template strand, which contains a DNA nucleotide sequence that determines the structure of a polypeptide
- Template strand codes for a single-stranded molecule called mRNA
- mRNA id transcribed & synthesised via rules of complementary base pairing
- mRNA strand exits nucleus thru nuclear pore into cytoplasm
Describe the process of Translation.
- mRNA travels to cytoplasm and attaches to a ribosome
- As ribosome moves along mRNA, it synthesises a polypeptide
- The bases of mRNA are read in threes/codons (3 bases-> 1codon, 1 codon-> 1 amino acid)
- The amino acids join up (held by peptide bonds) to form a polypeptide
- When ribosome leaves mRNA, the polypeptide is released
Differences between DNA and RNA?
DNA-Double-stranded molecule
RNA-Single-stranded molecule
DNA-Deoxyribose sugar in nucleotide
RNA-Ribose sugar in nucleotide
DNA-Contains A, T, G, C
RNA-Contains A, U(uracil), G, C
DNA-Longer
RNA-Shorter
DNA-Found in nucleus
RNA-Found in cytoplasm
Similarities between DNA and RNA?
-Both contain genetic material (/genes/genetic sequences/3 nucleotides in 1 codon)
-Both are polynucleotides (/nucleotides as basic units/ consists of pentose sugar, phosphate group and nitrogenous base)
[Application]
How does mutation affect the specific characteristic or trait controlled by the gene?
- Mutation changes nitrogenous base/nucleotide/codon, which results in a different amino acid in the protein
- Sequence of amino acids in polypeptide changes, a **different polypeptide will form **
- Change of characteristic/ trait expressed by gene
How is a recombinant DNA made?
- DNA strands from 2 diff. organisms are cut at their RESTRICITION SITE by the same RESTRICTION ENZYME to produce COMPLEMENTARY STICKY ENDS.
- DNA fragments from 2 diff. sources are mixed tgt with DNA ligase (an enzyme)
- The 2 diff. DNA fragments will bind tgt by complementary base pairing
- They are then sealed tgt by DNA ligase to form recombinant DNA
Describe the process of transferring the human insulin gene into bacteria.
- Identify & isolate the human insulin gene and cut it out using a restriction enzyme
- Cut the bacterial plasmid with the same restriction enzyme
- This produces complementary sticky ends on both sides.
- Mix the plasmid with the DNA fragment containing the insulin gene. (DNA ligase binds the sticky ends together through complementary base pairing and forms a recombinant plasmid)
- Reinsert the recombinant plasmid into the bacterium by applying heat or electricity in the presence of calcium ions to create pores in the membrane of the bacteria for entry of the plasmid.
TRANSGENIC BACTERIA IS FORMED!
Advantages of genetic engineering?
- Low cost of production of medicines-> drugs become more affordable
- Production of crops that can grow in extreme conditions
- Pesticide-resistant crops-> Use of costly pesticides that may damage the the env. is reduced
- Foods designed to meet specific nutritional goals