4.1- DNA, Genes & Chromosomes

Question 1

What are the three components of nucleotides?

Answer 1

A pentose sugar, a phosphate group, 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 (A, C, G, T). It is double-stranded, and hydrogen bonds between bases form a helix shape

Question 3

Describe the role of DNA

Answer 3

Carries genetic information, determines our inherited characteristics

Question 4

Describe structure of RNA

Answer 4

Made up of a ribose sugar, a phosphate group, and one of four organic bases (A, C, G, U). 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 in prokaryotic cells?

Answer 7

• Eukaryotic cells: found in nucleus, long and linear. Associated with histone proteins to form chromosomes. Mitochondria and chloroplasts contain prokaryotic-like DNA.
• Prokaryotic cells= short and circular. Not associated with proteins.

Question 8

What is the genetic code?

Answer 8

The order of bases on DNA. Consists of codons (triplets of bases that code for a particular amino acid)

Question 9

Identify features of the genetic code

Answer 9

• Non-overlapping: each triplet is only read once
• Degenerate: more than one triplet codes for the same amino acid (64 possible triplets for 20 amino acids)
• 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