4.1 DNA, GENES & CHROMOSOMES

Question 1

What are genes?

Answer 1

A specific sequence of DNA that codes polypeptides & RNA.

They occupy a specific location on DNA called the locus. The same genes are always at the same loci on DNA.

Question 2

What is the genetic code?

Answer 2

Non-overlapping
Universal
Degenerate
Exclusive
Stop-codon capability

Question 3

What does a degenerate genetic code mean?

Answer 3

Most amino acids are coded for by more than one codon.

Question 4

What does a universal genetic code mean?

Answer 4

Always the same codons for the same amino acids.

Question 5

What does an exclusive genetic code mean?

Answer 5

Some amino acids are only coded for by 1 codon.

Question 6

What is an exon?

Answer 6

Parts of DNA that are expressed.

Question 7

What is an intron?

Answer 7

Parts of DNA that are NOT expressed.

Question 8

What is a chromosome?

Answer 8

A structure of DNA that carries genetic information in the form of genes.

Question 9

How are chromosomes formed?

Answer 9

• DNA is coiled tightly with histones to form nucleosomes.
• Nucleosomes coil tightly to make chromatin loops.
• Chromatin loops are wrapped around each other to form chromosomes.
• Each chromosome has a telomere at the end for protection.

Question 10

What are some features of prokaryotic DNA?

Answer 10

• Shorter DNA molecule
• Circular DNA
• DNA is NOT associated with histones
• Doesn’t form chromosomes, so DNA is loose

Question 11

What are some features of eukaryotic DNA?

Answer 11

• Longer DNA
• Linear DNA
• DNA is associated with histone proteins
• Does form chromosomes.

Question 12

What are amino acids made up of?

Answer 12

A unique three-base sequence called a codon.

Question 13

What are homologous chromosomes?

Answer 13

A chromosome that carries the same genes, but different alleles. (usually maternal & paternal chromosomes).