1.3 Biological Molecules 2

Question 1

What are the three named enzymes involved in DNA replication?

Answer 1

DNA Helicase
DNA Ligase
DNA Polymerase

Question 2

Describe the roles of three named enzymes involved in DNA replication.

Answer 2

DNA Helicase = breaks hydrogen bonds
DNA Ligase = joins sections of DNA together by forming phosphodiester bonds between phosphate and deoxyribose
DNA Polymerase = joins the sugar phosphate backbone between nucleotides

Question 3

What is a genome?

Answer 3

The entire genetic material of an organism

Question 4

Describe the properties of the genetic code.

Answer 4

1. Triplet code = sequence of three bases
2. Non-overlapping = adjacent codons do not overlap and the same letter is not used for 2 different codons
3. Degenerate = multiple codons or sets of 3 nucleotides can code for the same amino acid during protein synthesis

Question 5

What is mRNA?

Answer 5

Messenger RNA = RNA formed in the nucleus that carries the genetic code out into the cytoplasm

Question 6

What is the antisense strand?

Answer 6

DNA strand that codes for proteins or sometimes called the template strand

Question 7

What is the tRNA?

Answer 7

Transfer RNA = molecules are small units of RNA that pick up particular amino acids from the cytoplasm and transport them to the surface of the ribosome to align with the mRNA codon

Question 8

What is the anticodon?

Answer 8

Sequence of 3 bases on tRNA that are complementary to the bases in the mRNA codon

Question 9

What is the rRNA?

Answer 9

Ribosomal RNA = RNA that makes up about 50% of the structure of the ribosomes

Question 10

Describe how the process of DNA replication produces 2 identical DNA molecules.

Answer 10

Hydrogen bonds between nucleotides are broken by DNA Helicase
Complementary nucleotides bind
As hydrogen bonds will only form between cytosine and guanine and adenine and thymine
Phosphodiester bonds are also formed by DNA polymerase

Question 11

Describe the structure of a DNA molecule.

Answer 11

Composed of adenine, thymine, guanine and cytosine
Held together by phosphodiester bonds
The complementary base pairs are held together by hydrogen bonds

Question 12

Describe the process of translation.

Answer 12

mRNA is attached to the ribosome
The tRNA is attached to a specific amino acid
The tRNA anticodon binds to mRNA codons
Peptide bond forms between amino acids

Question 13

Describe the process of transcription.

Answer 13

DNA strands separate
Antisense strand is used as a template for mRNA
RNA polymerase then synthesises mRNA

Question 14

Describe the structure of a ribosome.

Answer 14

Composed of protein and RNA
Arranged in 2 subunits - one large and one small subunit

Question 15

Describe the role of ribosomes in protein synthesis.

Answer 15

Used during translation
To hold the tRNA on the mRNA
Whilst peptide bonds form to join adjacent amino acids together

Question 16

What are gene mutations?

Answer 16

A.K.A point mutation = a change in one small or a small number of nucleotides affecting a single gene

Question 17

What is a substitution mutation?

Answer 17

Type of point mutation in which one base in a gene is substituted for another

Question 18

What is a deletion mutation?

Answer 18

Type of point mutation in which a base is completely lost

Question 19

What is an insertion mutation?

Answer 19

Type of point mutation in which an extra base is added into a gene, which may be a repeat or a different base

Question 20

What are chromosomal mutations?

Answer 20

Changes in the position of the entire genes within a chromosome

Question 21

What are whole-chromosome mutations?

Answer 21

The loss or duplication of a whole chromosome

Question 22

What is sickle cell disease?

Answer 22

Human genetic disease affecting the protein chains making up the Haemoglobin in the red blood cells and therefore changing the shape of the cell