2018 P1

Question 1

Give two pieces of evidence from Figure 1 that this cell was undergoing mitosis. (2)

Answer 1

The CHROMOSOMES are visible because they have CONDENSED

Chromosome is made up of two chromatids because DNA has REPLICATED

Question 2

Tick one box that gives the name of the stage of mitosis shown in Figure 1. (1)

Answer 2

3. Prophase

Question 3

Suggest how this procedure moved the chromosomes apart. (2)

Answer 3

Water moves into the cells by OSMOSIS so cell gets BIGGER

Question 4

Suggest one way the structure of the chromosome could differ along its length to result in the stain binding more in some areas. (1)

Answer 4

Differences in base sequences

Question 5

What is a homologous pair of chromosomes? (1)

Answer 5

Two chromosomes that carry the same GENES

Question 6

Give two ways in which the arrangement of prokaryotic DNA is different from the arrangement of human DNA in Figure 1. (2)

Answer 6

CIRCULAR not linear

Not associated with HISTONES

Question 7

Describe the method the student would have used to obtain the results of Figure 3. Start after all potato cubes have been cut. (3)

Answer 7

Ensure all cut surfaces of the 8 cubes are FULLY SUBMERGED in sucrose solution

Control the TEMPERATURE

DRY cubes with filter paper to remove excess liquid BEFORE MEASURING

Question 8

Is rate of osmosis per mm2 per min different between A and B during this time? (3)

Answer 8

A = 1.6 x 10^-5
B = 1.5 x 10^-5

Question 9

Structure of amino acid (1)

Answer 9

R
H2N - C - COOH
H

Question 10

What is meant by degenerate genetic code? (2)

Answer 10

MORE THAN ONE CODON codes for a single amino acid

eg. UCU UCA UCC UCG all code for Ser

Question 11

What is the minimum number of bases in the gene coding for this polypeptide? (1)

Answer 11

465 x 3 = 1395

Question 12

Use info in Table 1 to tick one box that shows a single base substitution mutation in DNA that would result in a change from Val to Ala at 203. (1)
MC

Answer 12

1. CAA –> CGA

Question 13

Use all the info and your knowledge of protein structure to suggest reasons for the differences between the effects of the two changes. (3)

Answer 13

Both NEGATIVELY CHARGED TO POSITIVELY CHARGED change in amino acid
Change at AA 300 doesn’t change shape of ACTIVE SITE
AA 279 may have been involved in a bond AND so shape of active site change

Question 14

Complete Figure 7 to show the chromosomes content of cells that result from a normal meiotic division. (2)

Answer 14

1. One big one small pair

2. One big one small single

Question 15

Complete Table 3 to show expected number of plants… (2)

Answer 15

52 and 4

Question 16

What does this result suggest about the difference between the observed and expected result and what can the scientists conclude (2)

Answer 16

There is a LESS than 0.05 probability that the difference BETWEEN observed and expected occurred by CHANCE

Calculated value is greater than critical value so the null hypothesis can be REJECTED

Question 17

Use your knowledge of directional selection to explain the results shown in Table 3. (3)

Answer 17

The scientists selected breeding plants that produced 2n gametes
so these plants passed on their ALLELES to the next generation
so the FREQUENCY OF ALLELES for production of 2n gametes increased

Question 18

The scientists concluded that this heat treatment damaged the phloem. Explain (2)

Answer 18

.Radioactively labelled carbon is CONVERTED INTO SUGAR during photosynthesis

.Mass flow in phloem throughout the plant is only in UNTREATED plants

Question 19

The scientists also concluded that this heat treatment did not affect the xylem. Explain (2)

Answer 19

.The water content of the leaves was not different because the STANDARD DEVIATIONS OVERLAP

.Water is therefore still being transported in the xylem

Question 20

What can you conclude about the movement of Fe3+ in barley plants? (4)

Answer 20

.Heat treatment has a greater effect on YOUNG leaves than old

.Heat treatment DAMAGES the phloem

.HIGHER RATIO OF FE3+ in old leaves than young

.But NO STATS TEST to show if the difference is significant

Question 21

Describe gross structure of human gas exchange system and how we breathe in and out. (6)

Answer 21

1+2. Air moves into body via mouth –> trachea –> bronchi –> bronchioles –> alveoli

3. BREATHING IN - diaphragm contracts and EXternal intercostal muscles contract
4. causes volume increase and pressure decrease in thoracic cavity, which results in air moving in
5. BREATHING OUT - diaphragm relaxes and INternal intercostal muscles contract
6. causes volume decrease and pressure increase in the thoracic cavity, resulting in air moving out

Question 22

Compare and contrast the structure and properties of triglycerides and phospholipids (5)

Answer 22

BOTH:
contain ester bonds
contain glycerol
insoluble in water

CONTRAST:
triglyceride has 3 fatty acids AND phospholipids have 2 fatty acids plus a phosphate group
triglycerides are hydrophobic AND phospholipids have a hydrophobic and hydrophilic region

Question 23

Describe how lactose is formed and where in the cell it would be attached to a polypeptide to form a glycoprotein (4)

Answer 23

GLUCOSE + GALACTOSE join in a CONDENSATION reaction with a GLYCOSIDIC BOND.
It would be attached to a polypeptide in GOLGI