B5 DNA

Question 1

what is DNA

Answer 1

a molecule that carries genetic information.

Question 2

why is DNA important

Answer 2

• forms the entire genome of an organism
• important for all cellular functions
• found in the nucleus of almost all cells – chromatin strands and chromosomes
are made up of DNA and proteins

Question 3

what is the structure of DNA

Answer 3

Each DNA molecule consists of two strands twisted around each other to form a double helix.

Question 4

what is a nucleotide

Answer 4

the basic unit of DNA

Question 5

what is each nucleotide made up of

Answer 5

1. sugar molecule (deoxyribose)
2. phosphate group
3. nitrogenous base: adenine(A)/ cytosine(C)/ guanine(G)/ thymine(T)

Question 6

how do we form polynucleotides

Answer 6

Nucleotides are joined to form long chains called polynucleotides.

Question 7

what is a DNA molecule made up of

Answer 7

The DNA molecule is made up of two anti-parallel polynucleotide chains.

Question 8

what are the complementary base pairs

Answer 8

Complementary base pairs:

adenine (A) and thymine (T)
cytosine (C) and guanine (G)

Question 9

how are complementary base pairs joined

Answer 9

Complementary bases are joined by hydrogen bonds.

Question 10

what is a gene

Answer 10

A gene is a sequence of DNA nucleotides (bases) that controls the formation of a single polypeptide, which can be used to make proteins.

Question 11

what does each gene consist of

Answer 11

Each gene consists of two polynucleotide chains. The template chain is the one that determines the type of protein made.

Question 12

how is an amino acid coded and how is this read

Answer 12

• Three bases (= a codon) code for one amino acid. The genetic code is ‘read’ as triplets.

Question 13

what is transcription

Answer 13

Transcription: the process by which the DNA template is used to make a single-stranded messenger RNA (mRNA).

Question 14

how does mRNA get formed and how does this leave the nucleus

Answer 14

o mRNA has a base sequence complementary to that of template DNA
o mRNA carries genetic code out of nucleus to the cytoplasm

Question 15

what is translation

Answer 15

Translation: the process by which the sequence of mRNA codons is used to make a polypeptide

Question 16

how does mRNA get turned into a protein

Answer 16

o the message in mRNA is translated into a sequence of amino acids
which are joined by peptide bonds to form a polypeptide, which will eventually fold to form a protein

Question 17

what is a genetic mutation

Answer 17

a change in the DNA (nucleotide) sequence of a gene

Question 18

what can a genetic mutation alter and how does this affect a trait

Answer 18

• A mutation may or may not lead to a change in the protein product.
• A change in the protein product may or may not lead to an observable
phenotype.

Question 19

what are some phenotypic changes caused by genetic mutation

Answer 19

• Examples: albinism, sickle-cell anaemia

Question 20

what is each gene made up of

Answer 20

Each gene is made up of a specific sequence of bases (or nucleotides), which forms the genetic code.

Question 21

where does transcription occur

Answer 21

o occurs in the nucleus

Question 22

where does translation occur

Answer 22

o occurs at the ribosomes (in cytoplasm)