DNA, Genes and Chromosomes QP

Question 1

Describe how a gene is a code for the production of a polypeptide. Do not
include information about transcription or translation in your answer.

Answer 1

Base/nucleotide sequence
in triplet
determines the specific order of amino acids /primary structure

Question 2

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

Answer 2

condensation reaction between deoxyribose and phosphate group
catalysed by DNA polymerase

Question 3

The two DNA strands of a particular gene contain 168 guanine bases
between them. The relationship between the numbers of guanine bases
(G), adenine bases (A), thymine bases (T) and cytosine bases (C) in these
two strands of DNA is shown in the following equation.
G = 4(A + T) – C
Use this information and your understanding of DNA structure to calculate
the maximum number of amino acids coded by this gene.
Show your working

Answer 3

70
420 TOTAL BASES IN GENE

Question 4

Name the protein associated with DNA in a chromosome

Answer 4

Histone

Question 5

Complete Table 1 to show three differences between DNA in the nucleus
of a plant cell and DNA in a prokaryotic cell.

Answer 5

Prokaryote
Circular
Has Plasmids
Shorter
not associated with histones

Question 6

Scientists investigated the genetic diversity between several species of
sweet potato. They studied non-coding multiple repeats of base sequences.
Define ‘non-coding base sequences’ and describe where the non-coding
multiple repeats are positioned in the genome.

Answer 6

DNA that does not code for protein/amino acid sequence
positioned by genes

Question 7

The nucleus and a chloroplast of a plant cell both contain DNA.
Give three ways in which the DNA in a chloroplast is different from DNA in
the nucleus.

Answer 7

Choroplast
Circular in chloroplast linear in DNA nucleus
Shorter but longer in DNA
Fewer genes but more in DNA
Not associated to histone DNA is

Question 8

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

Answer 8

Triplets code for same amino acid
Occurs in introns /non-coding sequence

Question 9

Compare and contrast the DNA in eukaryotic cells with the DNA in
prokaryotic cells.

Answer 9

PROKARYOTIC CONTRAST
CIRCULAR NOT LINEAR
HAS PLASMIDS
IS SHORTER
NOT ASSOCIATED TO HISTONE/PROTEIN EUKARYOTIC ARE
COMPARISION
joined by phosphodiester bonds
mitochrondria similar structure
Nucleotide structure is identical

Question 10

The dark stain used on the chromosomes binds more to some areas of the
chromosomes than others, giving the chromosomes a striped appearance.
Suggest one way the structure of the chromosome could differ along its
length to result in the stain binding more in some areas.

Answer 10

Differences in base sequences

Question 11

In Figure 2 the chromosomes are arranged in homologous pairs.
What is a homologous pair of chromosomes?

Answer 11

Two chromosomes that) carry the same genes