4. DNA in Euk and Prok cells

Question 1

Question 2

What is a Chromosome

Answer 2

Chromosomes structures made of the polynucleoide DNA (Deoxyribonucleic acid) which has a double helix structure

Question 3

What is a gene

Answer 3

Genes are small sections of DNA that code for a particular combination of amino acids which are built into polypeptide chains that make up proteins

Question 4

Eukaryotic DNA

Answer 4

Eukaryotic cells include Animal, Plant & Fungal cells.
DNA is found within a distinct nucleus, surrounded by the nuclear envelope.
The DNA double helix is wrapped around Histone proteins to form Nucleosomes.
Nucleosomes are then coiled up to form chromatin which is organised into chromosomes.
The DNA is compact so large amounts can be stored in a small space and organised.

Question 5

What does Eukaryotic DNA contain?

Answer 5

The DNA contains:
Genes – base sequences of DNA that code for the amino acid sequence of a polypeptide OR a functional RNA (rRNA & tRNA)

WITHIN the gene are many non-coding base sequences or Introns

BETWEEN the genes are non-coding base sequences that repeat multiple times, these are called multiple repeats.

Question 6

Match

Answer 6

Question 7

Chromosomes are made of DNA and it’s associated proteins

Answer 7

Chromosomes in Eukaryotic cells are found in pairs – called Homologous pairs.
One of the chromosome pair has been inherited from the mother (maternal) and one has been inherited from the father (paternal).
The chromosomes are the same size and carry the same gene found in the same fixed position or (locus).

Question 8

Prokaryotic DNA

Answer 8

Prokaryotes include the Bacteria and Archaea. These organisms have no true nucleus.

The DNA is shorter, circular and is not wrapped around histone proteins. It is condensed by supercoiling

The DNA is found in a main chromosome (the nucleoid) and smaller structures called plasmids.

Question 9

Chloroplast and Mitochondrial DNA
1. What are mitochondria & chloroplasts and where are they found?
2. What is the role of each?
3. What would the DNA in each organelle code for?

Answer 9

A: Organelles found in Eukaryotic cells – (chloroplasts only in plant and some protocists).
A: Chloroplasts are the site of photosynthesis reactions and in mitochondria the reactions of aerobic respiration take place
A: Enzymes that catalyse the reactions of photosynthesis and aerobic respiration; membrane proteins to transport substance in/out of the organelles and functional RNA (tRNA & rRNA)

Question 10

Fill in the boxes

Answer 10

Question 11

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

Answer 11

Comparisons

1. Nucleotide structure is identical;
2. Nucleotides joined by phosphodiester bond,

OR

Deoxyribose joined to phosphate (in sugar, phosphate backbone);

3. DNA in mitochondria / chloroplasts same / similar (structure) to DNA in prokaryotes: Accept shorter than nuclear DNA/is circular not linear/is not associated with protein/histones unlike nuclear DNA;

Contrasts

4. Eukaryotic DNA is longer
5. Eukaryotic DNA contain introns, prokaryotic DNA does not,
6. Eukaryotic DNA is linear, prokaryotic DNA is circular,
7. Eukaryotic DNA is associated with / bound to protein / histones, prokaryotic DNA is not

Question 12

Q2.

(a) Draw the general structure of an amino acid.

Answer 12