Unit 3.4

Question 1

Give one process which occurs in the nucleus of a cell during interphase which is necessary before cell division can take place.

Answer 1

Cell replication. ✔️

Question 2

Explain one advantage of cells lining the human gut dividing very frequently.

Answer 2

To replace old cells with new cells. ✔️

Question 3

Explain how a mutation leads to the formation of a non-functioning enzyme.

Answer 3

• changed tertiary structure
• therefore disulphide bridges and hydrogen bonds form in different places on the chain.
• therefore no enzyme substrate complexes forms ✔️

Question 4

Explain how a spread in mutation may occur.

Answer 4

Breeding between populations ✔️

Question 5

What’s the order of taxons (starting with domain)?

Answer 5

Domain, kingdom, phylum, class, order, family, genus, species.

King philip comes occasionally for grape squash ✔️

Question 6

DNA of past recent ancestors was found and analysed. Suggest one source of this DNA.

Answer 6

Bones/skin remains ✔️

Question 7

Suggest two reasons why populations might show low levels of genetic diversity.

Answer 7

1. Inbreeding

2. Small population ✔️

Question 8

During an experiment with bacteria, a student passes forceps through a Bunsen burner flame between each experiment. Why do they do this?

Answer 8

• kills microorganisms that could’ve been on the forceps

* so no unwanted bacteria will grow ✔️

Question 9

Give three ways in which courtship behaviour increases the probability of successful mating.

Answer 9

1. Only attracts animals of the same species
2. Attracts the opposite gender
3. Stimulates hormones ✔️

Question 10

What’s the biological importance of reducing the chromosome number when the cells divides by meiosis?

Answer 10

The cells will later fuse/fertilise restoring the diploid number. ✔️

Question 11

What are 4 differences between mitosis and meiosis?

Answer 11

1. Meiosis reduces the chromosome number, mitosis has the same as the parent cell.
2. Cytokinesis happens once for mitosis, twice for meiosis.
3. Homologous pairs in meiosis, no pairs in mitosis.
4. Crossing over occurs in meiosis, dosent occur in mitosis. ✔️✔️

Question 12

What is a species?

Answer 12

Organism is yay can produce fertile offspring. ✔️

Question 13

What’s the equation for the index is diversity?

Answer 13

N(N-1)
d = ———— ✔️✔️
Σ n(n-1)

Question 14

A forest was cleared to make more land for agriculture. After the forest was cleared the species diversity of insects in the arse decreased. Explain why.

Answer 14

• fewer plant species
• fewer types of food
• fewer types of habitats ✔️

Question 15

Explain how copping bases more than once may give rise to a difference in a protein.

Answer 15

• it will cause a frame shift

* therefore different base sequence means different amino acids therefore different protein. ✔️

Question 16

What stage of the cell cycle would errors in copying DNA bases occur?

Answer 16

Interphase ✔️

Question 17

Starting with mRNA in the nucleus of a cell, describe how a molecule of protein is synthesised.

Answer 17

• mRNA reptates out is the nucleus via nuclear pores
• in the cytoplasm, ribosome attaches to mRNA and moves down the mRNA
• tRNA brings amino acids using an anticodon that fits to the mRNA.
• tRNA has a amino acid on the end
• specific tRNAs being specific amino acids (due to anticodon)
• peptidyl transferase forms peptide bonds form between the 2 amino acids in the ribosome to form proteins. ✔️✔️