Download Blood group

LIFE SCIENCES
GRADE 12
PAPER 1
TEACHER RESOURCE
2
REVISION ANSWERS
DNA and GENETICS
1.1.1 DNA
1.1.2 1 – Hydrogen bond
5 – Cytosine
1.1.3 Nucleotide
1.1.4 - DNA produces two exact copies of itself. 
- During interphase/before cell division
- Two chromatids that are identical are formed
- The two chromatids are identical to that of the parent
1.1.5

DNA
1. Double-stranded molecule/paired
bases
2. Contains deoxyribose sugar
3. Contains the nitrogenous base
thymine
4. A is proportional to T and G is
proportional to C
5. Longer
6. Helix shape
RNA
Single stranded molecule/unpaired
bases
Contains ribose sugar
Contains the nitrogenous base
uracil
Different relative numbers of A, U, G
and C
Shorter
No helix
1.2.1 Test tube 2

1.2.2 Percentage of A does not equal T and percentage of C does not equal
G in test tube 2 therefore no base pairing

OR
The percentages of A is equal to T and C is equal to G in test tube 1
therefore base pairing

Therefore test tube 2 contains the single stranded virus
DNA molecule
3
1.3.1 No
1.3.2 There was more than 1 person involved in the murder
1.3.3 Suspect 1
1.3.4 The DNA fingerprint of the skin found under the victim’s fingernail
matches the DNA fingerprint of suspect 1
1.3.5 No
1.3.6 - The hair/skin tissue could have been plantedat the crime scene
O
R
- The DNA from the skin tissue could have been under the
victim’s fingernails- before the murder
O
R
- The suspect may have an identical twin who has the same DNA
fingerprint
O
R
- The samples taken may be mixedwith othersin the laboratory (2)
1.3.7 Tracing criminals would be made easier
O
R
It infringes on the rights of people who might not want their
fingerprint done
O
R
It would cost the country too much money which could be used for
basic needs like food/housing
4
3
ATG
It determines the codes for the sequence of amino acids
which determines the type of protein
1.4.1
1.4.2
1.4.3

1.4.4
(a)
AUG
(b)
- tRNA picks up specific amino acids
- its anticodon matches up with the codon of mRNA
- therefore the amino acids are arranged in a particular
sequence
- to form particular polypeptides/proteins
1.4.5
1.5.1
1.5.2
Errors/mistakes/changes may occur during DNA
replication
Extra nucleotide pair may be added to the sequence
A nucleotide pair may be left out or replaced by a
different base
change the order/sequence of the bases
would result in a different protein with different
functions from the original protein
CAA
UAC
ACC (in sequence)
Phenylalanine Valine Methionine (in sequence)
1.6.1 Translation
1.6.2 Ribosome
1.6.3 (a)
(b)
(c)
(d)
Isoleucine
CAG /cytosine,adenine,guanine
Codon
Have arginine instead of alanine/have different amino
acids
1.6.4 GTA
1.7.1
A - Chromosome
B - Centromere
C - Chromatid
D - Chiasma
1.7.2 Crossing over
1.7.3 Mixing of genetic material/variation and gametes are different from
each other
5
1.7.4


Mark allocation:
Chromosome drawn
Chromosome has shaded and unshaded part in the correct proportion
1.8.1 A - daughter chromosome/chromatid
B - Spindle thread/spindle fibre
1.8.2
2
1.8.3
2
1.8.4 Reduction/halving of chromosome number/keep chromosome
number constant from generation to generation/prevents
doubling of chromosome number at fertilisation
Promotes/contributes to genetic variation
Formation of gametes/cells containing one allele of a gene pair
6
1.8.5
Mitosis
Occurs in body cells
Cell nucleus divides once
Two daughter cells are formed
Daughter cells are identical to one
another and to the parent cell
Chromosome number remains
constant
Chromosomes are in a single layer on
the equator
Crossing over does not occur
Centromere divides
Daughter chromosomes move to
opposite poles
1.9.1
1.9.2

Meiosis
Occurs in sex organs
Cell nucleus divides twice
Four daughter cells are formed
Daughter cells are not identical to
each other and to the parent cell
Chromosome number is halved
During meiosis 2 the chromosomes
are in homologous pairs with one of
each pair on either side of the equator
Crossing over occurs
In meiosis 1 the centromere does not
divide
One chromosome of each
homologous pair moves to opposite
poles in meiosis 1
Polyploidy animals do not survive
Plants are harder, larger and faster growing with larger flowers and fruit.
7
1.10.1
P1
phenotype
genotype
Red x white
RR x rr
Meiosis
Fertilization
F1 
1.11.1
gametes
r
r
R x r
G
genotype
phenotype
R
Rr
Rr
R
Rr
Rr
OR
Rr
red
1 mark for correct
gametes
1 mark for correct
genotypes
8
1.11.2 25%
1.11.3 Ff
1.11.4 Individual B would have one dominant gene since he/she has free earlobes
and the other gene must be recessive since they were able to produce offspring
with attached earlobes/the recessive characteristic
1.11.5 Two separate
1.11.6 One is male and the other is female
Identical twins are identical in every respect /from the same sex
1.11.7 No
1.11.8 Since C and D have attached earlobes they have only recessive genes and can
therefore have no dominant gene for free earlobes to pass to their offspring.
8
1.12.1 1 - Gg
3 - Gg
1.12.2
gg
1.12.3 Yes
1.12.4
gg
Gg
Gg
OR
 (correct clear shape)
gg
 (correct shaded shape)
1.12.5 - Understand that there will be a 50% chance of having a normal child
and 50% having a child with cystic fibrosis
- Go for genetic counselling
- Accept responsibility for their decision/make an informed decision
1.13.1 female
1.13.2 The sex chromosomes/23rd pair have the same size and
shape/identical in appearance
OR
XX chromosomes present/two X chromosomes present
OR
No Y chromosome/no XY chromosomes
1.13.3 47/46 +1 /23 pairs +1 - Down's syndrome/Trisomy 21
9
1.14.1
(a) 13
(b) 26
1.14.2 Has a full set of chromosomes /Diploid number of chromosomes/
complete set of chromosomes/26
1.14.3 They have same/identical chromosomes/genetic material/DNA from the
nucleus of the somatic/body cell collected from the same frog/X
1.14.4 Cloning
1.14.5(a)
In favour:
- Producing individuals with desired traits
- Better yield
- Resistant to diseases
- Organisms produced in a shorter time
- Saving endangered species
- Producing body parts
- Produce offspring for organisms that cannot have offspring
(b)Against:
- Objection to interfering with God’s/Supreme Being’s
creation/nature
- Reducing the gene pool by reducing variation/ Reduces
genetic diversity
- Cloned organisms may have developmental/morphological problems
- Costly process
- May generate more experimental waste
- May lead to killing of clones to obtain spare body parts
- Cruelty to animals
1.15.1 AB
1.15.2 Represent separate/discrete/different entities /blood groups/units
OR
Discontinuous variable
OR
No intermediate groups
10
1.15.3 Frequency of blood groups in a small human population
Blood group
AB
A
B
O
Percentage
5
40
10
45
Caption
Column headings
Row headings
3 or 4 correct percentages
1 or 2 correct percentages
Draw table
1.16.1 Mouse 2 - XY
Mouse 3 - XX
1.16.2 50%
1.16.3 Mouse 2
1.16.4 A cross between mouse 3 and mouse 4 produced offspring with
white/recessive coat colour and white colour will only show up if
both parents have at least one recessive gene
1.17.1 Albert
Beatrice
Carol
Eckhart
Fiona
Xh Y √
X H Xh √
Xh Xh √
Xh Y √
XH Xh √
1.17.2 25% √
1.17.3 P1
Genotype – (Fiona)
Phenotype-
XH Xh
x
(Fred) Xh Y √
(carrier)
(haemophilic)
Gametes
XH
Xh
Xh
XH Xh
Xh Xh
H
Y
X Y
Xh Y
1 mark for correct gametes
1 mark for correct genotypes
F1 Xh Xh √
XhY
haemophilic haemophilic
girl
boy
1 mark for the correct genotype of Helen
* Chance would be 1 in 4 or 25% √
XH Xh
carrier
girl
XH Y
normal boy
11
1.18.1 The gene for curly hair is dominant√ and the dominant
shows up√ in either the homozygous or heterozygous condition
condition
1.18.2
P1 Phenotype
Genotype
Meiosis
Gametes/G
Man
Curly hair X
Hh
X
H, h
Woman
Curly hair√
Hh√
X
H, h√

Fertilisation
OR
F1
Genotype
HH Hh Hh
hh√


Gametes
H
h
H
HH
Hh
h
Hh
hh
1mark for correct gametes
1 mark for correct genotypes
Phenotype
Curly hair Straight hair
1 mark for stating P1 and F1
1 mark for stating meiosis and fertilization
If another letter is used, candidates will lose marks for P1
F1 genotypes
1.19.1 May have fewer side effects
May not be cont
No problem from a religious perspective
Can be mass produced/produced faster
Avoids killing animals
1.19.2 Against:
risk to human health
risk to the environment
risk to the health and well-being of other organisms
interference with nature/God’s creation
cultural sensitivitye.g. objection to the use of pigs and cows
1.20.1
- Determine the sample size/ number of boys and girls per grade
- Design a table to record the results
- Organise the ink pad and paper to take the fingerprint type
of each learner/organise a way to obtain fingerprints
- Time and place to be arranged
1.21.1
24:8 or 3:1
1.21.2
To increase the reliability of their results OR reduces chances of
errors 
12
1.21.3
Results of the number of different colour/phenotypes
of offspring per breeding pair
9
8
Number of offspring
7
6
5
Black
Brown
4
3
2
1
0
1
2
3
4
Breeding pairs
NOTE:
If the wrong type of graph is drawn:
- Marks are forfeited for ‘correct type of graph’ ; ‘drawing of graph’
If graphs are not drawn on the same system of axes:
- Mark the first graph only using the given criteria –
Candidates will lose 2 marks for the incorrect drawing of the pair of bars
13
Mark allocation for graph
Correct type of graph
Caption of graph
Correct label for X-axis
Graphs labeled/keyprovided for 2
graphs
Correct label for Y-axis
Appropriate scale for Y-axis
Drawing of bars
1.22
1
1
1
1
1
1
1 mark if 1 pair of bars plotted
correctly
2 marks if 2 to 3 pairs of bars plotted
correctly
3 marks if all 4 pairs of bars are
plotted correctly
Male
XY
P1 genotype
x
x
Female
XX
Meiosis
Gametes
X or Y
X or X
Fertilisation
F1 genotype:
Phenotype:
Gametes X
Y
X
XX
XY
X
XX
XY
XX,
XY,
XX,
XY
Female, male, Female, male
They have a 50% chance of having a daughter.
14
1.23.1 1:2:1
1.23.2
The proportions of different genotypes for coat colour of cattle
WW
RR
RW
Rubric for the mark allocation of the pie chart
Correct type of graph
Caption
Correct proportions of slices
Label / key for each slice
1.23.3
1
1
1: 1 correct slice
2: 2 to 3 correct slices
1 mark for each label
Both alleles for fur colour are equally dominant and therefore
both are expressed in the phenotype
OR
Neither of the alleles for red or white colour are dominant over each other
and
therefore no one colour alone is expressed/
masked in the phenotype
***************************************
15
REVISION ANSWERS
EVOLUTION
1.1.1 (a) Darwin
- As a result of genetic variationin the giraffe population
- some giraffes have longer necks than others
- Environmental change/competition for resources occurred
- causing those with shorter necks to die
- and those with longer necks to survive
- This is natural selection/survival of the fittest
- The genes/genotype for longer necks
- were passed on to subsequent generationsmost of which now
have long necks
1.1.1 (b) Lamarck
All giraffes had short necks originally
Giraffes frequently stretched/used their necks to reach
for leaves of tall trees
necks become longer
The long necks acquired in this way
could be passed on to the next generation /were inherited
1.1.2 Acquired characteristicsare not inherited/do not cause any
change to the DNA of an organism's gametes (sperms or ova)
OR
Organisms did not evolve because they want to evolve/
Lamarck’s theory is deterministic
1.2.1 When a geographical barrier e.g. mountain, river, sea, etc.
separates a subpopulation of breeding individuals from the parent
population
1.2.2
(Less) seeds available on the island/competition for seeds
available/availability of different sources of food
16
1.2.3
1.3.1
1.3.2
There is a great deal of variation amongst the
finches√ such as different shapes of beaks
On each island the finches lived under different
environmental conditions√ / had different sources of
food
The finches underwent natural selection√
Only those finches that were better suited√
to obtain the type of food available survived√
Continued natural selection on each island
over many generations √
resulted in each island having species that were very different
(genotypically and phenotypically) from each other√
These differences prevented them from interbreeding√
leading to the formation of new species
This is termed allopatric speciation/adaptive radiation√
Speciation (1)
-
-
In diagram 1 the rabbits were able to
interbreed√/genes
can flow freely in the population
In diagram 2 the two populations were separated by the
river√/geographic barrier
The two populations cannot interbreed√/no gene flow
Within each of the two separated populations there was
variation√
Each group underwent natural selection√independently√
as a result of varying environmental conditions√
Each group becomes genotypically√ and
phenotypically√different
In diagram 3 the geographic separation no longer exist√
but the two populations do not interbreed√/no gene flow
even though they can mix
because of the presence of reproductive isolating
mechanism√
They are now 2 different species√
17
1.4
1.4.1 Long roots
1.4.2 Natural selection/survival of the fittest
1.4.3 - There is variation in the length of roots among the cacti plants
- The cacti with the long roots have the desirable characteristic/are
better adapted/ long roots absorb water from deep underground
- for surviving under dry/unfavourable conditions
- more of the cacti with long roots survive
- most of the cacti with the short roots die
- most of the offspring produced have long roots 
1.5
1.5.1 - During prophase 1
- crossing over takes place
- and genetic material is exchanged/recombination occurs
between chromatids of homologous chromosomes
- which ensures that the gametes formed are different from each
other
- During metaphase 1
- Homologous chromosomes arrange themselves randomly/
independent assortment along the equator
- which ensures that the gametes formed are different from
each other
1.5.2 - Sudden random changes
- occur in the genetic code/gene/DNA
1.5.3 -
1.6
-
-
Large number of gametes produced
Gametes are different because they are produced by meiosis
random fusion of gametes
therefore the offspring produced
will be genetically different
The population will split up into two groups
and each group adapts to the new environmental factors/
develops separately/each group undergoes natural selection
independently
each group may become genotypically
and phenotypically different
which might prevent them from interbreeding/become
reproductively isolated leading to the formation of a new
species
18
1.7.1 


-
A large number of offspring is produced
There is a large amount of variation within a species
Of the large number of offspring only a small number survive
Characteristics are inheritable from parent to offspring 
Animal breeders can selectively breed for certain
characteristics

1.7.2

Lamarck
Darwin
1. Law of use and disuse
1. Law of natural selection
2. The acquiredcharacteristics are 2. Inherent genetic characteristics
passed on to the next generation
can be inherited from parents
3. Organisms have an internal drive 3. Organisms
do
not
to change/deterministic
have an internal drive to
change/nature selects the best
survive change
4. Individuals change
4. to
Populations
5. Infers that no extinction because 5. Extinction occurs since
organisms get better and better
organisms may have features that
and therefore survive
do not favour survival 
1.8.1
-
1.8.2(a)


1.8.2(b)
There was variationwith regard to the feet within the ancestral
duck populations
Some ancestral ducks had skin attached between the toes
As food became scarce/environment changed
Competition for food increased
Those ducks which had skin attached between their toes/
desired characteristic could swim better
To secure food and survived
Those ducks that did not have skin attached between their toes
were unable to swim well
Did not secure food and died
Through natural selection entire populations of ducks with
webbed feet evolved
If you use organs/structures repeatedly it
develops/
and organs and structures that are not used,
disappear
Acquired characteristics are inherited
Acquired characteristics are not inherited/only
characteristics that
are controlled by the genes are inherited
19
1.9.1
1.9.2
1.9.3
1.9.4
Sympatric speciation
Occurs when a new species forms in populations that are not physically
or geographically separated from one another but can be
reproductively isolated.
Species – specific courtship behaviour/ behavioral isolation
The female fishes display mate preferences for males with new colour
patterns. They therefore mate more with these males than with males
displaying other colour patterns.
1.10.1
Speciation
1.10.2
The population of species A has split up into two
The sea forms a physical barrier
and each group adapts to the new environmental factors
Each group undergoes natural selection independently
and develops separately
Each group may become genotypically
and phenotypically different
Might prevent them from interbreedingwhen they come
into contact again/become reproductively isolated leading to the
formation of a new species
……………………………………………..
20
ANSWERS OF ADDITIONAL QUESTIONS
GENETICS
1.1.1
Incomplete dominance
1.1.2
(a) RR
(b) RW 
(c ) WW
1.2.1
P1/parent
phenotype
genotype
Father
Normal x
XHY
x
Mother
Normal
XHXh 
Meiosis
G/gametes
XH , Y
Fertilisation
F1/offspring
x
XH ,
Xh
OR
XH XH , XH Xh , XH Y , Xh Y 
Gametes
XH
H
H
X
X XH
Y
XHY
Xh
Xh
Xh Y
XH
1 mark for correct gametes
1 mark for correct genotypes
2 normal daughters, 1 normal son, 1 son with
haemophilia
P1 and F1/Parents and offspring
Meiosis and fertilisation
1.2.2
25% chance /1 out of 4
1.2.3
The male has only one X chromosome  Y chromosome does not
have the allele for this trait /can only be affected or unaffected/if
he had ‘h’ he would be a sufferer, therefore he must have had ‘H’.
21
1.3.1
Disadvantages of genetic engineering





Expensive /research money could be used for other needs
May be hard for poor people to access/compete
Interfere with nature /immoral/ we cannot play God
Domination of the world food products by only a few companies 
Loss of flora and fauna biodiversity by inbreeding /entire species to be wiped
out if exposed to disease against it has no resistance /such as allergens
 Potential health impacts
 Violation of natural organism’s intrinsic value /right to independent existence by
changing the genetic make up of an organism
 Unsure of long term effects
 Genes from transgenic organisms could escapeand be transferred to wild
organisms
(Mark first THREE only)
Any 3
Advantages of genetic engineering
1.3.2










Production of medication/resources cheaply
Control pests with specific genes inserted into the crop
Selecting the best genes to produce better resistant crops
Using specific genes to increase crop yields / food security
Selecting genes to increase shelf life of plant products
Selecting genes that delay ripening of fruits to meet the demand
Using specific genes to improve nutritional valueof food for better health
Using specific genes to introduce new traits in crops to suit specific needs of a
population (e.g. to increase vitamin A in food)
DNA and proteins of transgenic organisms unlikely to cause problems since it
is digested in human gut.
Transgenic organisms do not survive easily in wild 
(Mark first THREE only)
Any 3
22
Height distribution of Grade 12 girls
35
Number of girls
30
25
20
15
10
5
0
150-151
1
152-153
2
154-155
3
156-157
4
158-159
5
Height (cm)
1.4.1 Rubric for the mark allocation of the graph
Correct type of graph
Title of graph
Correct label and units for X-axis
Correct label for Y-axis
Appropriate width and interval of bars
Appropriate scale for Y-axis
Drawing of the bars
1:
2:
3:
1
1
1
1
1
1
1 to 3 bars plotted correctly
4 to 5 bars plotted correctly
All 6 bars plotted correctly
NOTE: If the wrong type of graph is drawn: marks will be lost for



'correct type of graph'
‘appropriate width and interval of bars’ and
‘drawing of bars’
1.4.2
Polygenic inheritance/polygeny
1.4.3
Polygenic: Genes at different/multiple loci
One gene: Gene at one locus 
OR
Polygenic: Has a range of intermediate phenotypes for the trait/
continuous variation
One gene: Has distinct  phenotypic traits/discrete variation
1.4.4
-Environmental factors /Nutrition
-Sex /Gender
-Age
Any 2
160+
6
23
1.5.1
1.5.2
1.6.1
1.6.2
1.6.3
Process by which the DNA of a person/organism is mapped/
DNA sequence of an individual is determined.
- The DNA evidence was planted at the
scene of crime/ he was framed
- Human error during DNA profiling process
- He had an identical twin brother who had the same DNA
profile as him
- DNA codes for a particular protein but cannot leave nucleus
- One strand is used as a template
- To form mRNA
GCC AUA
GGA (in sequence)
Glycine Proline Serine (in sequence)
24
1.7 Possible answer
Genetic variation
Meiosis introduces genetic variation through:
Crossing-over and random arrangement of chromosomes at the equator
Max
Crossing – over
- Homologous chromosomes/bivalents pair up
- Each chromosome has 2 chromatids
- Chromatids overlap/cross over
- Points at which crossing-over takes place are referred to as chiasmata
- Genetic material is exchanged between non-sister chromatids
- After the process of crossing-over chromosomes have genes from its
homologous partner 
-This means that each gamete formed will have a mix of genes from maternal
and paternal parents
- Brings about variation in the gametes formed and also the offspring
Max
Random arrangement of chromosomes at the equator
- Each pair of homologous chromosomes may line up either way on the
equator of the spindle 
- Independently of what the other pairs are doing
-This means that gametes will have differing number/mix of maternal and
paternal chromosomes 
Max
Down’s syndrome
- During gamete formation/ Anaphase I/ meiosis I/meiosis II
the chromosome pair 21 does not separate 
- Referred to as non-disjunction
- One gamete will have an extra 21 chromosome/ two 21 chromosome
- If this gamete fuses with a normal gamete /with 23 chromosome
- The resulting zygote will have Chromosome ‘pair’ 21 having 3 chromosomes
instead of 2
- This is known as trisomy/ Down’s syndrome
Max
Polyploid organisms
- During gamete formation/ Anaphase I/ meiosis I
- There is a lack of separation of ALL homologous chromosomes/nondisjunction
- One gamete will inherit the diploid set of chromosomes
- When a diploid gamete is fertilized by a normal haploid gamete
- The zygote/offspring will have 3 sets of chromosomes/triploid
- In the similar way, tetraploid and other polyploid offspring could be formed
Max
Advantages of polyploidy in agriculture
- Forms seedless varieties of fruit such as watermelons/bananas/some apples
- Polyploidy cells are bigger therefore produce larger flowers/fruits/storage
organs
- Infertile plants become fertile e.g. wheat
Max
25
EVOLUTION
1.8.1
More/fewer dark peppered moths/ pale peppered moths survive
in the polluted /unpolluted environment than in the unpolluted /
polluted environment
OR
No difference in the number of dark/ pale peppered moths that
survive in both environments
1.8.2
- Was not a closed system so moths could fly in and out of the
environment
- The number of predators might have been different in both
polluted and unpolluted environment
- Both environments could have been different with regard to
vegetation found in them
- Both environments could have been different with regard to
climatic conditions 
1.8.3
-
1.9
Variation in the moth population produces dark and pale
forms
The dark moths were camouflaged by black tree trunks/not
easily detected by birds/predators
More dark moths survived/fewer eaten by birds
Pale moths were NOT camouflaged by the black tree trunks/
easily detected by birds
Fewer pale moths survived/more eaten by birds
- There is variation in a population
- *Populations separate into groups in the same area /
Occupying different niches
- Due to differences in behavioural patterns/ feeding habits/ due
to polyploidy
- Each group undergoes natural selection independently
and develops differently
- Genotypically and phenotypically
- Gene flow/reproduction between the different populations does
not occur
- The differences that develop between the different populations
- prevent them from inter-breedingeven if they were to mix
- Such that each group becomes a new species
Max 5+1*(compulsory mark)
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