4.1 - DNA, Genes and Chromosomes

Question 1

Describe the structure of dna in eukaryotes prokaryotes and mitochondria/chloroplast

Answer 1

-Only eukaryotic DNA is linear -the rest are short and circular.
- only eukaryotic DNA is associated with histones
- only eukaryotic DNA can form chromosomes.

Question 2

What is a gene?

Answer 2

Prokaryote DNA also lacks introns

A gene is a base sequence of DNA that codes for:
* the amino acid sequence of a polypeptide 

* a functional RNA (including ribosomal RNA and tRNAs).

Question 3

3. What is a ‘locus’?

Answer 3

The position of a gene on a chromosome

Question 4

4. What do these words mean when referring to the genetic code?

Answer 4

a. Universal: The same three bases code for the same amino acid in all organisms
b. Non-overlapping: Each base is only part of one ‘triplet’ (it is only ‘read’ once)
c. Degenerate: Some amino acids are coded for by more than one set of three bases

Question 5

5. What is an exon?

Answer 5

A base sequence within a gene which codes for a sequence of amino acids

Question 6

6. What is an intron?

Answer 6

A base sequence within a gene which is non-coding

Question 7

7. What is meant by a ‘non-coding’ base sequence?

Answer 7

Does not code for amino acid/tRNA/rRNA;

Question 8

8. What is a “non-coding multiple repeat base sequence”

Answer 8

A short sequence of bases which repeats a number of times, e.g. CAGCAGCAGCAG, or ATATATAT
These can be found between genes and do not function as sequences that code for amino acids