Biology Topic 4

Question 1

Name the fixed position occupied by a gene on a DNA molecule?

Answer 1

Locus/loci

Question 2

Describe how a gene is a code for the production of a polypeptide?

Answer 2

1) The base / nucleotide sequence in triplets determines the amino acid sequence and so the primary structure int he polypeptide

Question 3

Define the term exon?

Answer 3

Base / nucleotide sequence coding for polypeptide or sequence of amino acids and so the primary structure

Question 4

When given a nucleotide triplet sequence and asked to find another sequence using it. How do I do it?

Answer 4

Find the complementary nucleotide triplets and put into a sequence.
If mRNA then U instead T.

Question 5

Describe how a phosphodiester bond is formed between two nucleotides
within a DNA molecule?

Answer 5

There is a condensation reaction between phosphate and deoxyribose using DNA polymerase

Question 6

Name the protein associated with DNA in a chromosome?

Answer 6

Histone

Question 7

Show 5 differences between DNA in a plant cell’s nucleus and DNA in a prokaryotic cell?

Answer 7

1) There are histones wrapped around DNA vs No histones in DNA
2) Linear vs Circular
3) Introns vs no introns
4) Longer vs Shorter
5) No plasmids vs plasmids

Question 8

Define ‘non-coding base sequences’ and describe where the non-coding
multiple repeats are positioned in the genome?

Answer 8

Non coding base sequences = DNA that don’t code for polypeptides
Positioned between genes

Question 9

Give 5 ways in which the DNA in a chloroplast is different from DNA in
the nucleus?

Answer 9

1) DNA shorter in chloroplass not longer like in nucleus
2) Fewer Genes in chloroplasts not many in mucleus
3) DNA is circular in chloroplasts not linear in Nucleus
4) There are no histones in DNA in chloroplasts but there are histones in Nuclear DNA
5) No introns in chloroplasts but there are introns present in Nuclear DNA

Question 10

Give one other difference (than U replaces T )between the structure of a DNA nucleotide and
the structure of an RNA nucleotide?

Answer 10

There is Deoxyribose sugar in DNA and ribose sugar in RNA

Question 11

2 key places on a diagram of a tRNA molecule?

Answer 11

The anticodon and the amino acids

Question 12

Not all mutations in the nucleotide sequence of a gene cause a change in
the structure of a polypeptide.
Give two reasons why.

Answer 12

1) More than one triplet codes for the same amino acid so it is degenerate
2) This happens in the introns which are non-coding sequences

Question 13

Compare and contrast the eukaryotic cells DNA with
prokaryotic cells DNA?
6 points
2 similar
4 differences

Answer 13

1) Nucleotide structure is identical same in both
2) Nucleotides joined by phosphodiester bond same in both
3) Eukaryotic DNA is longer and Prokaryotic DNA is shorter
4) Eukaryotic DNA contain introns and Prokaryoic dna doesn’t
5) Eukaryotic DNA is Linear and Prokaryotic is Circular
6) Eukaryotic DNA has hisones but Prokaryotic doesn’t have histones.

Question 14

Suggest one way the structure of the chromosome could differ along its length to result in the stain binding more in some areas?

Answer 14

Adjustments to length such as differences in base sequences, histone or condensation

Question 15

What can differences in condensation reaction of chromosomes lead to?

Answer 15

Super coilling of the chromosome.

Question 16

What is a homologous pair of chromosomes?

Answer 16

Two chromosomes that carry the same genes and have the same loci or the same genes for the same characteristics.

Question 17

What is the bond between complementary base pairs and between adjacent nucleotides in a DNA strand?

Answer 17

1) Base pairs = Hydrogen bonds
2) Nucleotides in a base pair = Phosphodiester Bonds

Question 18

Two differences between the structure of a tRNA molecule and
the structure of an mRNA molecule?