4.1 - DNA, genes and chromosomes

What are the three components of

nucleotides?

A pentose sugar, a phosphate group, an

organic base

Describe the role of DNA.

Carries genetic information, determines

our inherited characteristics.

Describe the structure of DNA.

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 the bases form a helix shape.

Describe the structure of RNA

Made up of a ribose sugar, a phosphate

group, and one of four organic bases

(A,C,G,U). It is single stranded.

Describe the role of RNA.

Transfers genetic information from DNA

to ribosomes for protein synthesis.

Which bases are purine and which are

pyrimidine?

Purine (double ring) = adenine, guanine.

Pyrimidine (single ring) = cytosine,

thymine, uracil.

How is DNA in eukaryotic cells different

from in prokaryotic cells?

● 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.

What is the genetic code?

The order of bases on DNA. Consists of

codons (triplets of bases that code for a

particular amino acid).

Identify features of the genetic code.

● 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.

What is a gene?

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.

What is a locus?

The fixed position on a DNA molecule

occupied by a gene.

What is an allele?

Different versions of the same gene,

found at the same locus on a

chromosome

What are exons and introns?

Exons= regions of DNA that code for

amino acid sequences. Separated by

one or more introns.

Where are introns found?

between exons

within genes