Chapter 14: Molecular Genetics

Question 1

What are the 3 main components of a nucleotide?

Answer 1

1. Deoxyribose sugar (/pentose sugar) molecule
2. Phosphate group
3. Nitrogenous base

Question 2

What are the 4 different types of nitrogenous bases?

Answer 2

Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)

Question 3

Rule complementary of base pairing?

Answer 3

Nitrogenous Bases w/ complementary shapes bond w/ each other in a 1:1 ratio:

Adenine+Thymine

Guanine+Cytosine

Question 4

Describe the formation of DNA double helix.

Answer 4

1. Complementary base pairing occurs betw. nucleotides of opp. strands (A+T,G+C)
2. Two polynucleotide stands are held tgt by hydrogen bonds betw. nitrogenous bases of opp. polynucleotide strands.
3. DNA molecule is made up of 2 anti-parallel polynucleotide stands, running in opp. directions.
4. 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.

Question 5

How is DNA organised inside cells?

Answer 5

NUCLEOTIDE->
POLYNUCLEOTIDE CHAIN/DNA STRAND->
DNA MOLECULE->
DNA molecule wrapped around protein=CHROMATIN THREADS->
chromatin threads condense= CHROMOSOMES (in cell nucleus)

Question 6

What is a gene?

Answer 6

-Basic units of inheritance
-A sequence of DNA nucleotides (bases)/ segment of DNA molecule that codes for the formation of one specific polypeptide

Question 7

Name the steps of protein synthesis and briefly describe each process

Answer 7

1. Transcription:
   The DNA template strand codes for a mRNA
2. Translation:
   The mRNA codes for a single polypeptide

Question 8

Describe the process of Transcription.

Answer 8

1. Double-stranded DNA molecule unwinds and unzips
2. One of the 2 strands a template strand, which contains a DNA nucleotide sequence that determines the structure of a polypeptide
3. Template strand codes for a single-stranded molecule called mRNA
4. mRNA id transcribed & synthesised via rules of complementary base pairing
5. mRNA strand exits nucleus thru nuclear pore into cytoplasm

Question 9

Describe the process of Translation.

Answer 9

1. mRNA travels to cytoplasm and attaches to a ribosome
2. As ribosome moves along mRNA, it synthesises a polypeptide
3. The bases of mRNA are read in threes/codons (3 bases-> 1codon, 1 codon-> 1 amino acid)
4. The amino acids join up (held by peptide bonds) to form a polypeptide
5. When ribosome leaves mRNA, the polypeptide is released

Question 10

Differences between DNA and RNA?

Answer 10

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

Question 11

Similarities between DNA and RNA?

Answer 11

-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)

Question 12

[Application]
How does mutation affect the specific characteristic or trait controlled by the gene?

Answer 12

1. Mutation changes nitrogenous base/nucleotide/codon, which results in a different amino acid in the protein
2. Sequence of amino acids in polypeptide changes, a **different polypeptide will form **
3. Change of characteristic/ trait expressed by gene

Question 13

How is a recombinant DNA made?

Answer 13

1. DNA strands from 2 diff. organisms are cut at their RESTRICITION SITE by the same RESTRICTION ENZYME to produce COMPLEMENTARY STICKY ENDS.
2. DNA fragments from 2 diff. sources are mixed tgt with DNA ligase (an enzyme)
3. The 2 diff. DNA fragments will bind tgt by complementary base pairing
4. They are then sealed tgt by DNA ligase to form recombinant DNA

Question 14

Describe the process of transferring the human insulin gene into bacteria.

Answer 14

1. Identify & isolate the human insulin gene and cut it out using a restriction enzyme
2. Cut the bacterial plasmid with the same restriction enzyme
3. This produces complementary sticky ends on both sides.
4. 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)
5. 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!

Question 15

Advantages of genetic engineering?

Answer 15

1. Low cost of production of medicines-> drugs become more affordable
2. Production of crops that can grow in extreme conditions
3. Pesticide-resistant crops-> Use of costly pesticides that may damage the the env. is reduced
4. Foods designed to meet specific nutritional goals

Question 16

Potential disadvantages of genetic engineering?

Answer 16

1. Economic hazards-> Poorer farmers may not benefit from GM crops if prices are not regulated
2. Environmental hazards-> GM crops that produce insect toxins may result in loss of insect biodiversity
3. Health hazards-> Genes that code for antibiotic resistance may accidentally be incorporated into bacteria that cause human diseases
4. Social & ethical hazards-> Class distinctions and religious disputes (?)

Question 17

What are the bonds between nucleotides of the same strand?

Answer 17

Phosphodiester bonds