DNA, genes, protein synthesis

Question 1

what are the differences between prokaryotic and eukaryotic DNA?

Answer 1

1. Eukaryotes have linear DNA whereas prokayotes have circular DNA
2. Eurkaryotes have their DNA in the form on chromosomes in the nucleus whereas prokayotes have their DNA free in the cytoplasm.
3. Eukaryotes have their DNA wrapped around proteins called histones which also helps to support the DNA whereas prokayotes have no histones.
4. Eukaryotes DNA is longer than prokayotes DNA which is shorter.
5. Eukaryoitc DNA and the histone coils up tightly whereas prokaryotic DNA fits into the cell via super-coiling.

Question 2

what is unique about Mitochondria and Chloroplasts ?

Answer 2

they have their own circular DNA so they bale to produce many proteins and enzymes required for their function.

Question 3

what is a gene?

Answer 3

a section of DNA

Question 4

what does a gene code for?

Answer 4

it codes for a polypeptide or for functional RNA (such as tRNA or mRNA)

Question 5

what is the sequence of amino acids called?

Answer 5

the primary structure

Question 6

what does a triplet codon code for?

Answer 6

amino acid

Question 7

what is a genome?

Answer 7

the complete set of genes

Question 8

what is a proteome?

Answer 8

the complete set of proteins

Question 9

what is an intron?

Answer 9

sections of DNA that dont code for amino acids

Question 10

what are exons?

Answer 10

sections of DNA that do code for amino acids

Question 11

introns get removed during protein synthesis in what way?

Answer 11

splicing

Question 12

what is an allele?

Answer 12

a different version of the same gene

Question 13

how many pairs of homologous chromosomes do humans have?

Answer 13

23

Question 14

what is protein synthesis?

Answer 14

the production of polypeptides (proteins

Question 15

briefly outline transcription

Answer 15

DNA is copied into mRNA

Question 16

briefly outline translation

Answer 16

mRNA joins with the ribosome and the code it carries is used to synthesis proteins.

Question 17

where is mRNA made and what does it carry?

Answer 17

it is made during transcription and it carries the genetic code from the DNA to the ribosome

Question 18

what us tRNA involved in and what does it carry?

Answer 18

it is involved in translation and it carries the amino acid used to make proteins to the ribosome

Question 19

Explain the process of Transcription

Answer 19

• DNA helicase breaks the hydrogen bonds separating the DNA strands
• Free complementary RNA nucleotides bind to the exposed bases on the template strand (complementary base pairing)
• RNA polymerase catalyses the condensation reaction that joins the nucelotides together
• H-bonds reform
• This makes pre-mRNA (contains introns)
• Splicing occurs to remove the introns and then the exons join

Question 20

Explain the process of translation

Answer 20

• mRNA leaves the nucleus via the nuclear pores
• mRNA attaches to the ribosome at the start codon
• Complementary tRNA carrying specific specific amino acids bind to the codon if they have the complementary anti-codon
• amino acids are joined via peptide bonds.

Question 21

what is the genetic code?

Answer 21

the sequence of base triplets in mRNA which codes for specific amino acids

Question 22

the genetic code is non-overlapping. What does this mean?

Answer 22

This means that successive triplets are read in order. Each nucleotide is part of only one triplet codon.

Question 23

what is meant by degenerate?

Answer 23

the same amino acid can be coded for by multiple codons

Question 24

How many amino acids are there and how many possible combinations are there?

Answer 24

20 amino acids

64 possible combinations

Question 25

what are some differences between mRNA and tRNA?

Answer 25

• mRNA had codons whereas tRNA has anti-codons
• tRNA is clover shape held by H-bonds whereas mRNA is linear shaped.
  tRNA has an amino acid binding site whereas mRNA doesn’t.