AS paper 1 mistakes

Question 1

Are the 2 male sperm nuclei in plant fertilisation genetically identical?

Answer 1

Yes

Question 2

Why do cells carry out mitosis?

Answer 2

For growth or repair
which needs genetically identical cells to be formed

Question 3

What happens to the DNA content and number of chromosomes in DNA replication?

Answer 3

DNA content doubles
New chromatids formed
Number of chromosomes stay the same

Question 4

If an enzyme inhibits transcription in a pollen tube, why can the pollen tube still grow?

Answer 4

There was some mRNA in pollen grain
So some protein synthesis can take place

Question 5

Describe the process of translation

Answer 5

mRNA attaches to ribosome
tRNA is attached to specific amino acid
tRNA anticodon binds to mRNA codon
Peptide bonds form between amino acids
Process involves stop/ start codons

Question 6

Describe how monomers are bonded to a polypeptide chain.

Answer 6

Formation of peptide bonds
Between amino group and carboxyl group
By a condensation reaction

Question 7

What is meant by ‘allele’?

Answer 7

A different version of a gene

Question 8

Describe the process of crossing over that occurs during meiosis?

Answer 8

Homologous chromosomes line up
Chiasmata form
Break in chromosome occurs
Genetic information exchanged between chromatids

Question 9

What are obligate anaerobes?

Answer 9

Bacteria that are destroyed by normal concentrations of oxygen.

Question 10

What are obligate aerobes?

Answer 10

Bacteria that need oxygen to survive.

Question 11

What are facultative anaerobes?

Answer 11

Bacteria that can live in the presence of oxygen but don’t require it.

Question 12

What does a nucleosome consist of?

Answer 12

8 histone proteins (octamer) with DNA looped twice around

Question 13

Name a stain that can be used to show the stages of mitosis

Answer 13

Toluidine blue

Question 14

Explain how to make a temporary preparation to show the stages of mitosis, after adding a stain to the slide.

Answer 14

Squash the tissue to separate the cells
Heat to intensify the stain

Question 15

State one structural difference between a spermatid and a mature spermatazoom

Answer 15

Spermatids have no tail

Question 16

Differences between a fibrous protein and a globular protein

Answer 16

Fibrous proteins have little to no tertiary structure
Fibrous proteins are insoluble in water whereas globular proteins can be semi soluble/soluble in water

Question 17

Explain why some microtubules decrease in length after a certain amount of time.

Answer 17

they shorten in the same way as they do
during cell division
some of the microtubules may break / were
shortened by the centriole