4-1 DNA, genes, chromosomes

Question 1

Describe the structure of DNA?

Answer 1

• Deoxyribose sugar
• Phosphate group
• One of the organic bases, adenine, cytosine, guanine, or thymine.
• Adenine and guanine both have double ring structures and are classified as purine bases.

Question 2

Describe the structure of RNA?

Answer 2

• Ribose sugar
• Phosphate group
• One of the organic bases, adenine, cytosine, guanine, or uracil.
• Thymine, uracil and cytosine all have single ring structure and are classified as pyrimidines.

Question 3

How do nucleotides join?

Answer 3

• Phosphodiester bond formed in a condensation reaction.

Question 4

What is the genetic code?

Answer 4

• The order of bases on DNA.

Question 5

What does it consist of?

Answer 5

• Triplets of bases, with each triplet of bases coding for a particular amino acid known as a codon.

Question 6

How do amino acids join?

Answer 6

• Peptide bond formed in a condensation reaction forming a polypeptide chain.

Question 7

What is a gene?

Answer 7

• A sequence of bases on a DNA molecule coding for a sequence of amino acids in a polypeptide chain.

Question 8

What is a locus?

Answer 8

• The location of a gene.

Question 9

What are introns?

Answer 9

• Non-coding sections of DNA.

Question 10

What are exons?

Answer 10

• Coding sections of DNA.

Question 11

What are the features of the genetic code?

Answer 11

• The genetic code is non-overlapping meaning that each triplet is only read once, and triplets don’t share any bases.
• Genes are separated by non-coding repeats of bases.
• Genetic code is degenerate meaning that more than one triplet codes for the same amino acid.
• The genetic codes contain start and stop codons.

Question 12

Describe the structure of DNA in eukaryotic cells?

Answer 12

• DNA found in nucleus and long and linear.
• Associated with proteins called histones to form structures called chromosomes.
• Mitochondria and chloroplasts contain DNA.

Question 13

Describe the structure of DNA in prokaryotic cells?

Answer 13

• DNA is short and circular.
• Not associated with proteins.

Question 14

How many chromosomes do humans have?

Answer 14

• 46, 23 homologous pairs that consist of two chromosomes carrying the same genes.
• 23 chromosome decides sex of the individual with female being XX and male being XY.

Question 15

What is an allele?

Answer 15

• An allele is described as an alternative form of the same gene, with every gene existing in two or more possible forms.
• Every individual inherits two allele of every gene from their parents.