DNA

Question 1

Define DNA

Answer 1

The chemical that determines inherited characteristics

Question 2

What is an individual nucleotide made up of?

Answer 2

• deoxyribose sugar
• phosphate group
• organic base, CGAT
  Joined by condensation reactions

Question 3

How is a polynucleotide formed?

Answer 3

The linking of multiple mononucleotides by condensation reactions to form a continuous chain

Question 4

What is the structure of DNA

Answer 4

A double helix

Question 5

Which 2 bases are purines (double ring)?

Answer 5

Adenine and guanine

Question 6

Which 2 bases are pyrimidines (single ring)?

Answer 6

Cytosine and thymine

Question 7

Which 2 bases are joined by 3 hydrogen bonds?

Answer 7

C + G

Question 8

What is the function of DNA?

Answer 8

• to pass on genetic information from cell to cell and generation to generation

Question 9

How is DNA adapted to carrying out its role?

Answer 9

• very large: can carry immense amounts of genetic info
• very stable: can pass to next generation without change
• hydrogen bonds between bases are easily hydrolysed for replication
• bases are protected by chemical and physical forces by sugar-phosphate backbone

Question 10

Define gene

Answer 10

A section of DNA that codes for 1 or more polypeptide

Question 11

Explain how DNA controls production of proteins.

Answer 11

DNA codes for amino acids. Chains of amino acids make polypeptides. Polypeptides are proteins.

Question 12

What is the evidence behind ‘The triplet code’?

Answer 12

• there are 20 amino acids, which each must have their own code
• there are 4 bases: pairs of bases would only make 16 combinations
• 4^3=64

Question 13

Give features of the triplet code

Answer 13

• degenerate: many a.a have more than 1 code
• universal: almost the same in every organism
• non-overlapping
• has start and stop codons which do not code for an a.a and mark the end of a chain

Question 14

Define chromosome

Answer 14

A structure made up of proteins and DNA by which hereditary info is passed to next generation

Question 15

How is DNA organised in prokaryotic cells?

Answer 15

• smaller
• form plasmids/loops
• not associated with proteins
• is circular

Question 16

How is DNA organised in eukaryotic cells?

Answer 16

• larger
• linear
• associate with proteins to form chromosomes

Question 17

Define homologous pair

Answer 17

A pair of chromosomes (1 from each parent) that contain genes for same characteristics

Question 18

Define haploid number

Answer 18

Number of chromosomes found in sex cells (half number found in somatic cells-diploid)

Question 19

Define allele

Answer 19

An alternate form of a gene

Question 20

What may happen if an individual inherits different alleles of a gene?

Answer 20

Each allele will code for a different polypeptide, hence a different protein. This protein may not function properly or at all, (e.g the active site of an enzyme may be altered, making it useless)