Genetic information, variation and relationships between organisms

Question 1

explain DNA in prokaryotes

Answer 1

DNA molecules are short, circular and not associated with proteins.

Question 2

explain DNA is eukaryotes

Answer 2

In the nucleus of eukaryotic cells, DNA molecules are very long, linear and associated with proteins, called histones. Together a DNA molecule and its associated proteins form a chromosome.

Question 3

explain DNA is mitochondria and chloroplasts

Answer 3

mitochondria and chloroplasts of eukaryotic cells also contain DNA which, like the DNA of prokaryotes, is short, circular and not associated with protein.

Question 4

what does DNA code for

Answer 4

the amino acid sequence of a polypeptide and a functional RNA

Question 5

where on a DNA molecule is a gene

Answer 5

a fixed position called the locus

Question 6

what is a triplet

Answer 6

sequence of three DNA bases

Question 7

what does a triplet code for

Answer 7

for a specific amino acid

Question 8

what are the main features of triplet code

Answer 8

The genetic code is universal, non-overlapping and degenerate.

Question 9

explain triplet code being degenerate

Answer 9

different codons to code for the same amino acid

Question 10

explain triplet code being universal

Answer 10

the same codon will code for the same amino acid in every organism

Question 11

explain triplet code being non overlapping

Answer 11

each codon is read separately to the next

Question 12

what is an exon

Answer 12

an amino acid coding codon

Question 13

what are introns

Answer 13

non amino acid coding sequence

Question 14

what is transcription

Answer 14

the production of mRNA from DNA

Question 15

explain the process of transcription

Answer 15

in the nucleus part of a dna molecule unwinds catalysed by helicase, This exposes the gene to be transcribed, A complementary copy of the code from the gene is made by mRNA, free RNA nucleotides pair up with hydrogen bonds, the deoxyribose phosphate backbone is bonded together by RNA polymerase, once the gene is transcribes the strand is spliced and the mRNA leaves via nuclear pores

Question 16

what is the difference in transcription in eukaryotes and prokaryotes

Answer 16

In prokaryotes, transcription results directly in the production of mRNA from DNA.
In eukaryotes, transcription results in the production of pre-mRNA; this is then spliced to form mRNA.

Question 17

what is translation

Answer 17

the production of polypeptides from the sequence of codons carried by mRNA.

Question 18

explain the process of translation

Answer 18

occurs in the cytoplasm, After leaving the nucleus, the mRNA molecule attaches to a ribosome, tRNA molecule in the cytoplasm bond an amino acid on one end and has a specific anticodon on the other which binds the the complementary mRNA codon on the ribosome, two tRNA molecules attach to the ribosome at the same time and the two amino acids they carry form a peptide bond, energy in the form of ATP from mitochondria is required for this bond, this continues until a ‘stop’ codon is reached in an mRNA molecule. Finally a polypeptide chain is formed