4.1 DNA, Genes and Chromosomes

Question 1

What are the three components of nucleotides?

Answer 1

A pentose sugar, a phosphate group and an organic base

Question 2

Describe the structure of DNA

Answer 2

• Made up of a deoxyribose sugar, a phosphate group, and one of four organic bases
• Is double stranded, and hydrogen bonds between the bases form a helix shape

Question 3

Describe the role of DNA

Answer 3

Carries genetic information, determines our inherited characteristics

Question 4

Describe the structure of RNA

Answer 4

• Made up of a ribose sugar, a phosphate group, and one of four organic bases
• It is single stranded

Question 5

Describe the role of RNA

Answer 5

Transfers genetic information from DNA to ribosomes for protein synthesis

Question 6

Which bases are purine and which are pyrimidine?

Answer 6

• Purine (double ring) = adenine, guanine
• Pyrimidine (single ring) = cytosine, thymine, uracil

Question 7

How is DNA in eukaryotic cells different from prokaryotic cells?

Answer 7

• Eukaryotic cells = found in nucleus, long and linear, prokaryotic cells = short and circular
• Eukaryotic cells = associated with histone proteins to form chromosomes, prokaryotic cells = not associated with proteins
• Eukaryotic cells have mitochondria and chloroplasts that contain prokaryotic like DNA

Question 8

What is the genetic code?

Answer 8

• The order of bases on DNA
• Consists of codons - triplets that code for a particular amino acid

Question 9

Identify features of the genetic code

Answer 9

• Non-overlapping = each triplet only read once
• Degenerate = more than one triplet codes for the same amino acid
• Universal = same bases and sequences used by all species

Question 10

What is a gene?

Answer 10

• A sequence of bases on a DNA molecule that codes for a specific sequence of amino acids to make a polypeptide
• Can also code for functional RNA

Question 11

What is a locus?

Answer 11

The fixed position on a DNA molecule occupied by a gene

Question 12

What is an allele?

Answer 12

Different versions of the same gene, found at the same locus on a chromosome

Question 13

What are exons and introns?

Answer 13

• Exons = regions of DNA that code for amino acid sequences. Separated by one or more introns
• Introns = regions of DNA that do not code for anything

Question 14

Where are introns found?

Answer 14

• Between exons
• Within genes