life sciences p2voortrekkerafstandsleer.co.za/wp-content/uploads/2020/05/ls_june_… ·...

GRADE 12

LIFE SCIENCES P2

JUNE 2019

TOTAL: 150

TIME: 2½ HOURS

This question paper consists of 14 pages.

Life Sciences P2 2 FS/June 2019 Grade 12 Examination

Copyright reserved Please turn over

INSTRUCTIONS AND INFORMATION

Read the following instructions carefully before answering the questions.

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Answer ALL the questions. Write ALL the answers in the ANSWER BOOK. Start the answers to EACH question at the top of a NEW page. Number the answers correctly according to the numbering system used in this question paper. Present your answers according to the instructions of each question. Make ALL drawings in pencil and label them in blue or black ink. Draw diagrams, tables or flow charts only when asked to do so. The diagrams in this question paper are NOT necessarily drawn to scale. Do NOT use graph paper. You must use a non-programmable calculator, protractor and a compass, where necessary. Write neatly and legibly.



SECTION A

QUESTION 1

1.1 Various options are given as possible answers to the following questions. Choose the answer and write only the letter (A to D) next to the question number (1.1.1 to 1.1.10) in the ANSWER BOOK, for example 1.1.11 D.

1.1.1 If the strand of DNA reads GCC-ATG, then the complementary strand will read as follows.

A B C D

GCC-ATG CGG-TAC ATG-GCC TAA-CGT

1.1.2 If 16% of a DNA molecule is guanine, then …

A B C D

32% will be thymine. 16% will be cytosine. 68% will be adenine. 32% will be uracil.

1.1.3 Which ONE of the following could be the genotype of a normal

gamete?

A B C D

GRr GgRr Gr GgR

1.1.4 In the cross RrTt x rrtt what percentage of the F1 offspring will be tall

with red fruit? Use the following: R = red, r = white, T = tall, t = short

A B C D

100% 75% 50% 25%

1.1.5 When two plants are crossed and three quarters of the offspring

have purple flowers, the genotypes of the parents are most likely …

A

B C D

PP x ww. Pw x ww. Pw x Pw. PP x Pw.



1.1.6 The process in which a genetically identical replica of a molecule, a

cell or an entire organism is created.

A

B C D

Cloning Biotechnology Genetic modification Stem cells

1.1.7 The list below provides information relating to the replication of DNA.

(i) Complementary nucleotides bind to each of the two original

strands (ii) Hydrogen bonds form between the nucleotides (iii) The newly formed DNA molecules are identical to each other (iv) After unwinding, the DNA molecule forms two single strands Which is the correct order of the events as they occur in DNA replication is?

A

B C D

(i), (ii), (iii), (iv) (i), (ii), (iv), (iii) (iv), (i), (ii), (iii) (iv), (ii), (i), (iii)

1.1.8 In which ONE of the following cells will a mutation in the DNA be

passed from one generation to the next?

A

B C D

sperm cell brain cell liver cell muscle cell

1.1.9 If the frequency of the dominant allele in a particular characteristic

is 0,8 what is the frequency of the recessive allele?

A

B C D

0,8 0,2 0,4 0,64

1.1.10 The offspring of a homozygous white pigeon which had been

crossed with a homozygous black pigeon were all grey. What percentage of the F2 generation will be grey if two grey pigeons mate?

A

B C D

75% 100% 50% 25% (10 x 2)

(20)



1.2 Give the correct biological term for each of the following descriptions. Write

only the term next to the question number (1.2.1 to 1.2.10) in the ANSWER BOOK.

1.2.1

1.2.2 1.2.3 1.2.4 1.2.5 1.2.6 1.2.7 1.2.8 1.2.9 1.2.10

The specific position of a gene on the chromosome The building blocks of nucleic acids The structure that joins the chromatids of a chromosome together The three consecutive nitrogenous bases of mRNA A diagram that shows inheritance of characteristics over many generations The single set of chromosomes in a gamete The time period between two consecutive dividing phases during which cell growth and DNA replication occurs The area where the chromatids cross over and form breakage points The phase of meiosis during which the chromosome number halves

The type of cell division that produces identical daughter cells (10 x 1)

(10)

1.3 Indicate whether each of the descriptions in COLUMN I applies to A ONLY, B

ONLY, BOTH A and B or NONE of the items in COLUMN II. Write A only, B only, both A and B or none next to the question number (1.3.1 to 1.3.3) in the ANSWER BOOK.

COLUMN I COLUMN II

(6)

1.3.1 A plant with red flowers is crossed with a plant with white flowers and the offspring's flowers are red with white spots

A: B:

Incomplete dominance Co-dominance

1.3.2 The observable characteristics of an organism

A: B:

Phenotype Genotype

1.3.3 The "father" of genetics A: B:

Gregor Mendel James Watson

(3 x 2)



1.4 The diagram below represents a phase in meiosis.

1.4.1 How many of the following are there at the start of meiosis in the

diploid nucleus of the cell that resulted in the cells in the diagram?

(a)

(b)

Chromatids Chromosomes

(1) (1)

1.4.2 Write down the NUMBER of each of the following in one human

gamete which is formed during meiosis.

(a)

(b)

Nuclear membranes Centromeres

(1) (1)

1.4.3 Name the phase of meiosis in which each of the following events

occur.

(a)

(b)

Homologous chromosomes align at the equator Crossing over

(1) (1) (6)



1.5 The graph below shows the incidence of Down syndrome babies delivered by mothers at different ages.

1.5.1

1.5.2 1.5.3 1.5.4 1.5.5 1.5.6

Which process in meiosis is responsible for the development of Down syndrome? At which pair of chromosomes in the karyotype does the phenomenon mentioned in QUESTION 1.5.1 take place? At what maternal age, according to the graph, is there the highest risk for Down syndrome? How many individuals per 1000 births were there at age 30? How many more babies with Down syndrome were born from mothers 45 years old than mothers 35 years old? How many chromosomes does a Down syndrome sufferer have in each somatic cell?

(1) (1) (1) (1) (2) (2) (8)

TOTAL SECTION A: 50

0

2

4

6

8

10

12

14

16

18

20

20 25 30 35 40 45 50

Ind

ivid

ua

ls p

er

10

00

bir

ths

Maternal age

Incidence of Down syndrome babies from mothers at different ages



SECTION B QUESTION 2

2.1 The diagram below shows part of a nucleic acid.

2.1.1 (a)

(b) (c)

Identify the nucleic acid.

Give TWO visible reasons for your answer to QUESTION 2.1.1 (a) Name the parts X and Y.

(1) (2) (2)

2.1.2 Mention another nucleic acid found in humans. (1)

2.1.3 Give TWO types of the nucleic acid mentioned in QUESTION 2.1.2

and provide the location of each in the cell.

(4) (10)



2.2 The diagram below shows DNA profiles of different individuals.

2.2.1 Which TWO children are the biological offspring of Vuyi and

Koatsi?

(2) 2.2.2 Give an explanation for your answer to QUESTION 2.2.1 using

evidence from the DNA profiles.

(2) 2.2.3 Apart from paternity testing, state TWO more ways in which DNA

profiles is of use to humans.

(2) 2.2.4 Explain TWO reasons why some people are not supporting the use

of DNA profiles

(4) (10)



2.3 The diagram below shows a stage in protein synthesis.

2.3.1 Identify the stage of protein synthesis that is shown in the diagram. (1)

2.3.2 Identify X and Y. (2)

2.3.3 State the term for the group of three nitrogenous bases indicated

by V.

(1) 2.3.4 Give the nitrogenous bases on the DNA strand that codes for the

bases GUC as indicated by the diagram.

(2) 2.3.5 Use the table below to identify W. (2)

tRNA Amino acid

GUC Glutamine

UAA Isoleucine

AUA Tyrosine

CCC Glycine

GGG Proline

CAG Valine

2.3.6 Describe the stage of protein synthesis that takes place in the

nucleus.

(5) (13)

Stage in protein synthesis



2.4.1 2.4.2 2.4.3

Name the process taking place in the diagram. Where in the cell does this process take place? Explain the significance of the process mentioned in QUESTION 2.4.1

(1) (2) (4) (7)

TOTAL QUESTION 2: 40

2.4 The diagram shows a process taking place in the cell cycle.



QUESTION 3

3.1 A plant has a gene with the alleles Rr where (R) represents round seed and (r)

wrinkled seed.

3.1.1 Give the meaning of:

(a)

(b)

Alleles The notation Rr

(1) (2)

3.1.2 Provide the:

(a)

(b) (c) (d)

Dominant allele Seed shape represented by the recessive allele Phenotype of the plant under discussion Gene composition of the gametes

(1) (1) (1) (2) (8)

3.2 Genetic engineering uses biotechnology to satisfy human needs. An investigation

was done by Grade 12 learners to determine which pigs grow faster: pigs that are

selectively bred by genetic engineering for producing lean meat or pigs that are

selectively bred for fattier meat production.

The learners:

Used a sample of 30 two month old piglets

Knew that 15 piglets had been selectively bred for producing lean meat

and 15 had been selectively bred for fattier meat production

Kept all the pigs under the same environmental conditions.

Fed all the piglets with food consisting mostly of corn, vitamins and

mineral sources

Weighed the piglets regularly for a period of 45 days

The results of the investigation are shown in the table:

FEEDING PERIOD (DAYS)

MASS OF PIGLETS (g)

Selectively bred

for lean meat

Selectively bred

for fattier meat

1 250 200

8 500 400

20 1500 500

45 2500 600



3.2.1 Write the aim for this investigation. (2)

3.2.2 State:

(a)

(b) (c) (d)

The independent variable ONE advantage of repeating the investigation with 100 piglets THREE factors that the learners should keep constant in this investigation TWO benefits of the selective breeding of pigs, other than for increasing meat production

(1) (1) (3) (2)

3.2.3

3.2.4 3.2.5

Calculate the percentage mass increase of the pigs that were selectively bred for lean meat from day 8 to day 45. Show ALL working Write a suitable conclusion for the investigation based on the results in the graph. Explain ONE reason why selective breeding of pigs for fattier meat production may not be an advantage for the pigs if they were to live in the wild.

(3) (2) (2) (16)

3.3 Study the family tree below which shows inheritance of type of little finger

over four generations of a family.



3.3.1 How many members of the family have straight little fingers? (1)

3.3.2 Which type of little finger is controlled by a dominant gene? (1)

3.3.3 Explain your answer to QUESTION 3.3.2. (3)

3.3.4 In the fourth generation of the family, what proportion will be female

with a straight little finger?

(2) 3.3.5 Supply the genotype of parent B if (S) represents bent little fingers

and (s) represents straight little fingers.

(1) 3.3.6 State TWO reasons based on the phenotypes of individuals F and

G to support the conclusion that they are not identical twins.

(2) (10)

3.4 A mother with blood group A and a father with blood group B are both

heterozygous in terms of this characteristic. Use a genetic cross to show the possible genotypes of their children.

(6)

TOTAL QUESTION 3: 40

TOTAL SECTION B: 80

SECTION C

QUESTION 4

Explain how gene mutations occur and how it leads to altered characteristics in people with haemophilia and colour blindness respectively. Also describe THREE effects of gene mutations.

Content: Synthesis:

(17) (3) (20)

NOTE: NO marks will be awarded for answers in the form of tables, flow charts or

diagrams.

TOTAL SECTION C:

GRAND TOTAL: 20

150

life sciences p2voortrekkerafstandsleer.co.za/wp-content/uploads/2020/05/ls_june_… ·...

Documents