DNA, Genes, Chromosomes

Question 1

What is a “gene?”

Answer 1

• A base sequence (ie. section of DNA) that will code for the amino acid sequence of a polypeptide and code for a functional RNA.

Question 2

Give two examples of functional RNA.

Answer 2

• tRNA
• Ribososomal RNA.

Question 3

What is meant by term “locus?”

Answer 3

• FIXED position of particular gene on DNA molecule (known as locus.)

Question 4

True or False

The hair colour gene will have a different locus for each human.

Answer 4

• False.
• Hair colour gene will always have the same locus (ie. same location on DNA molecule) in all humans.
• BUT… the versions of the gene may be different (ie. different alleles.)

Question 5

What is an “allele?”

Answer 5

• An allele is one of a number of alternative forms of a gene (ie. two genes that code for SAME TYPE OF CHARACTERISTIC -e.g., hair colour - but different alleles = brown/ black.)

() - extra info for claririfcation.

Question 6

What is a chrosome? Where are they found in eukayrotic cells? How many pairs of chromosomes do humans have in somatic cells?

Answer 6

• Compact DNA associated with histones forms a chromosome.
• Found in nucleus (in eukaryotic cells.)
• Pairs of chromosomes: 23 pairs (46 in total.)

Question 7

What is a “homologous pair” of chromosomes?

Answer 7

• Homologous pair of chromosomes are exactly the same size, have exactly the same genes but may have different alleles.

Question 8

How many homologous pairs of chromosomes does a human have?

Answer 8

• 23 homologous pairs of chromosomes.

Question 9

What is DNA like in euakryotic cells?

Answer 9

• DNA is linear in shape.
• DNA is tightly-coiled to fit in nucleus (as chromosomes), tightly-wound around proteins; called histones –> forming chromosomes.
• DNA = very long
• Found in nucleus.

Question 10

What is DNA like in prokaryotic cells?

Answer 10

• DNA is short
• DNA is circular
• DNA is not associated with proteins.
• DNA found free-floating in the cytoplasm.

Question 11

True or False

The DNA of mitochondria/ chlorplasts are like the DNA of eukaryotic cells - as these structures are found in eukaryotic cells.

Answer 11

• FALSE!!
• DNA contained in mitochondria/ chloroplasts = short, circular, not associated with histones/ proteins (DNA like that in prokaryotic cells.)

Question 12

What is the name of the protein that DNA winds around in eukaryotic cells to form chromosomes?

Answer 12

• Histones

Question 13

True or False

The locus of a particular gene can change.

Answer 13

• False.
• Locus is FIXED position of the gene.