DNA genes and chromosomes

Question 1

What does the cell nucleus contain?

Answer 1

Genetic material in the form of chromosomes

Question 2

What are chromosomes?

Answer 2

Long lenths of DNA coiled up

Question 3

What is a gene?

Answer 3

A short section of DNA

Question 4

How many chromosomes does a human nucleus contain?

Answer 4

46 chromosomes in total, 23 pairs

Question 5

What shape is a DNA moecule?

Answer 5

Double helix

Question 6

How many different bases are there and what are they called?

Answer 6

4 - adenine (A), cytosine (C), guanine (G), thymine (T)

Question 7

How are the bases paired?

Answer 7

Complementary base pairing - A-T and G-C

Question 8

What does DNA control in the cell?

Answer 8

The production of proteins

Question 9

What are proteins made up of?

Answer 9

Amino acids

Question 10

How many bases code for an amino acid?

Answer 10

3

Question 11

How many amino acids are there?

Answer 11

20

Question 12

What does the nucleus contain?

Answer 12

Genetic material in the form of chromosomes

Question 13

What are the two stages of protein synthesis?

Answer 13

Transcription and translation

Question 14

Where are proteins made?

Answer 14

Cytoplasm

Question 15

What subcellular structures make protein?

Answer 15

Ribosomes

Question 16

What molecule carries genetic information from the DNA to the ribosome.

Answer 16

mRNA (messenger RNA)

Question 17

Three differences between DNA and mRNA?

Answer 17

• mRNA is shorter
• mRNA is a single strand
• in mRNA, uracil (U) is used instead of thymine (T) as a base

Question 18

What enzyme is involved in making mRNA?

Answer 18

RNA polymerase

Question 19

Describe the steps of transcription.

Answer 19

1) RNA polymerase binds to a region of non-coding DNA in front of a gene.
2) The two DNA strands unzip and the RNA polymerase moves along one of the strands of DNA.
3) It uses the coding DNA in the gene as a template to make the mRNA. Base pairing between the DNA and RNA ensures that the mRNA is complementary to the gene.
4) Once made, the mRNA molecule moves out of the nucleus and joins the ribosome in the cytoplasm.

Question 20

Describe the steps of translation.

Answer 20

1) Amino acids are brought to the ribosome by another RNA molecule called transfer RNA (tRNA).
2) The order in which the amino acids are brought to the ribosome matches the order of the codons on mRNA.
3) Part of the tRNA’s structure is called an anticodon - it is complementary to the codon for the amino acid. The pairing of the codon and anticodon makes sure that the amino acids are brought to the ribosome in the correct order.
4) The amino acids are joined together by the ribosome. This makes a protein.