2.4 Unlocking DNA code.

Question 1

What makes organisms unique?

Answer 1

The order that the bases appear in.

Question 2

What does DNA do?

Answer 2

It provides the instructions for proteins to be created.

Question 3

What is a polymer?

Answer 3

Polymers are molecules made of repeating subunits of monomers joined together in long chains.

Question 4

What are the links between DNA and proteins?

Answer 4

DNA is made up of nucleotides which contain Phosphate, Sugar and a nitrogenous base.

The Base sequence of nucleotides is called a triplet and codes for amino acid.

Question 5

What is a triplet?

Answer 5

A sequence of 3 nucleotides.

Question 6

How is DNA code read?

Answer 6

It is read 3 nitrogenous bases at a time. (ATT, ATC)

Question 7

How is RNA different to DNA?

Answer 7

RNA:

contains the sugar ribose (instead of deoxyribose)

contains the nitrogenous base uracil (instead of thymine)

is shorter and single-stranded, so it can fit through a nuclear pore.

Question 8

What are the 3 main forms of RNA.

Answer 8

Messenger RNA (mRNA)
Transfer RNA (tRNA) and Ribosomal RNA (rRNA).

Question 9

What is mRNA?

Answer 9

single-stranded RNA transcribed from a DNA template that then carries the genetic to a ribosome to be translated into a protein

Question 10

What is tRNA?

Answer 10

Transfer RNA
molecules located in the cytosol that transport specific amino acids to complementary mRNA codons in the ribosome

Question 11

What is rRNA?

Answer 11

a special type of RNA that forms the structure of ribosomes

Question 12

What is the relationship between DNA and RNA?

Answer 12

DNA makes mRNA through the process of transcription. The RNA then moves to a ribosome in the cytoplasm where the genetic message is translated into a protein in a process known as translation.

Question 13

What are the steps of Transcription?

Answer 13

DNA is unzipped (the two strands are separated).

One strand is used as a template strand.

RNA nucleotides that are complementary to the DNA template are added to form a mRNA strand using a special enzyme known as RNA polymerase. (The complementary mRNA codon for the start triplet TAC in DNA, for example, would be AUG.)

The newly synthesised mRNA is released from the template. For example, a DNA template with the sequence TACGACG would be transcribed into mRNA as UACGACG. Remember, there is no T in RNA — it is instead replaced with a U.

Question 14

What are introns in DNA?

Answer 14

They are non-coding sequences.

Question 15

What are exons in DNA?

Answer 15

Sections that provide instructions to form a protein in translation.

Question 16

What is a Codon?

Answer 16

It is a group of 3 nitrogenous bases in RNA.

Question 17

What is the process of translation?

Answer 17

mRNA enters the ribosome and is read one codon at a time (always starting with AUG).

A tRNA molecule brings the matching amino acid for the codon to the ribosome. The amino acid is determined by the codon chart, as seen in figure 2.38.

The appropriate amino acid is added to form a protein (or polypeptide).

The next codon is read, and another amino acid is added.

Amino acids continue to be added, joining together as a protein.

When a STOP codon is reached, and the new protein is released.

Question 18

Why are proteins important?

Answer 18

Proteins form parts of cells, regulate many cell activities and even help defend against disease.