Unit 3 (3.4.1) DNA, genes and chromosomes

Question 1

Together a DNA molecule and its associated proteins form a ____________?

Answer 1

chromosome

Question 2

What is the structure of DNA molecules found in prokaryotic cells?

Answer 2

Short, circular and not associated with histones

Prokaryotic DNA is typically plasmid-like and lacks histones.

Question 3

How do the DNA molecules in eukaryotic cells differ from those in prokaryotic cells?

Answer 3

Eukaryotic longer
Eukaryotic linear vs prokaryotic circular and
Eukaryotic associate with histones vs Prokaryotic no histones.

Eukaryotic DNA is organized into chromosomes within the nucleus.

Question 4

What type of DNA do mitochondria and chloroplasts contain?

Answer 4

Short, circular and not associated with histones

This DNA is similar to prokaryotic DNA.

Question 5

Define a gene.

Answer 5

A base sequence of DNA that codes for the amino acid sequence of a polypeptide or a functional RNA.

Functional RNAs include ribosomal RNA and tRNAs.

Question 6

What is the fixed position of a gene on a DNA molecule called?

Answer 6

Locus

Each gene occupies a specific locus on a chromosome.

Question 7

What does a sequence of three DNA bases, known as a triplet, code for?

Answer 7

A specific amino acid

Triplets are the basic units of the genetic code.

Question 8

What are the three key characteristics of the genetic code?

Answer 8

Universal, non-overlapping, and degenerate

The genetic code is the same across all known forms of life.

Question 9

What are exons?

Answer 9

Sequences within a gene that code for amino acid sequences

Exons are expressed sequences, while introns are non-coding.

Question 10

What is a none coding sequence called?

Answer 10

An intron

Introns are removed during RNA splicing.