4.1 DNA, gene and chromosomes

Question 1

What are three components of nucleotides?

Answer 1

A pentose sugar, a phosphate group, an nitrogenous organic base

Question 2

Describe the components of DNA

Answer 2

DNA is made up of a deoxyribose sugar, a phosphate group, and one of four organic bases (A, C, G, T)

Question 3

Describe the structure of DNA

Answer 3

DNA is double-stranded, and hydrogen bonds between the bases form a helix shape

Question 4

Describe the role of DNA

Answer 4

DNA carries genetic information and determines our inherited characteristics

Question 5

Describe the components of RNA

Answer 5

RNA is made up of ribose sugar, a phosphate group, and one of four organic bases (A, C, G, U)

Question 6

Describe the structure of RNA

Answer 6

RNA is relatively short, single-stranded polynucleotide chain

Question 7

Describe the role of RNA

Answer 7

RNA transfers genetic information from DNA to ribosomes for protein synthesis

Question 8

How are nucleotides joined together?

Answer 8

Nucleotides join together by phosphodiester bonds formed in condensation reactions

Question 9

Which bases are purine and which are pyrimidine?

Answer 9

Purine = adenine, guanine
Pyrimidine = cytosine, thymine, uracil

Question 10

How is DNA in eukaryotic cells different from in prokaryotic cells?

Answer 10

• 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 11

What is the genetic code?

Answer 11

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

Question 12

How are the amino acids joined together?

Answer 12

The amino acids are joined together by peptide bonds and form a polypeptide chain

Question 13

Identify features of the genetic code

Answer 13

• 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 14

What is a gene?

Answer 14

A sequence of bases on a DNA molecule that codes for a specific sequence of amino acids to make a polypeptide (it can also code for a functional RNA)

Question 15

What is a locus?

Answer 15

The fixed position on a DNA molecule occupied by a gene

Question 16

What is an allele?

Answer 16

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

Question 17

What are exons?

Answer 17

Exons are regions of DNA that code for amino acid sequences. Separated by one or more introns

Question 18

What are introns?

Answer 18

Introns are regions of DNA that do not code for anything

Question 19

Where are introns found?

Answer 19

Between exons within genes