LIFE SCIENCE STUDY GUIDE:
x
- GENETICS
- Specific to IEB SAGGs Document (2023)
230
- GENETIC ENGINEERING
- All notes have been sourced from different
documents however it is still recommended
to use these as a guide in your own research.
0
, DEFINITIONS:
COMMON TERMS:
A unit of inheritance containing a small section of DNA that controls heredity passed from
GENE
parent to child.
GENOME The complete set of genes of an organism.
LOCUS The position/location of genes/alleles on a specific chromosome.
CHROMOSOMES Thread like structures, made up of DNA, found in the chromatin network (nucleus) of each cell.
An alternative form/variation of a gene, responsible for controlling different versions of a trait.
ALLELES Capital Letter ® Dominant Gene
Lowercase Letter ® Recessive Gene
The set of all genes (genetic information) in a population of sexually reproducing organisms.
GENE POOL Large Gene Pool ® High genetic diversity ® Increased chance of survival.
Small Gene Pool ® Low genetic diversity ® Increased possibility of extinction.
The physical appearance of an organism (Height / Eye Colour / Hair Colour / etc…)
PHENOTYPE
® Determined by genotype.
The genetic make-up of an organism (Cannot be seen by looking at an organism)
GENOTYPE
® Represented by 2 letters ® Each letter represents 1 allele in the gene pair (TT/Tt/tt).
DOMINANT ALLELE The allele of a gene that will produce a certain phenotype (even if other alleles are present).
The trait is only expressed when an organism has two recessive alleles for that gene.
RECESSIVE ALLELE
( \ Homozygous Recessive)
2 identical alleles for a specific trait.
HOMOZYGOUS Homozygous Dominant ® TT
Homozygous Recessive ® tt
HETEROZYGOUS 2 different alleles for a specific trait ® Tt
PURE BREEDING Identical individuals (homozygous) that produce offspring carrying the same phenotype to them.
Known as Hybridization.
CROSS BREEDING Mixing different species or varieties of animals or plants and thus to produce hybrids.
Animal breeding ® crosses within a single species
MONOHYBRID The inheritance of characteristics controlled by a single gene. It is used to study a pair of
INHERITANCE contrasting characteristics at a time (Tall vs Short).
COMPLETE The characteristic that is fully expressed in the phenotype of a heterozygous organism
DOMINANCE (Dominant Allele) ® Only expressed when allele is homozygous.
HYBRID Organism / Offspring that results from two different species of parent organisms.
Animal Breeding ® crosses breed between different species.
FILIAL Any generation resulting from a genetically controlled mating (following parental mating).
GENERATIONS F1 ® Filial Generation 1 (the first generation that results from the crossing of two parental
lines).
ANTHER Male reproductive part of a flower.
STIGMA Female reproductive part of a flower.
SELF POLLINATION Transfer of pollen from anther to stigma of the same flower
CROSS Transfer of pollen from anther of one flower to stigma of the same species of flower on a
POLLINATION different plant
2
, Mutations caused by insertions or deletions of a number of nucleotides in a DNA sequence
FRAMESHIFT
(and not divisible by three). The effect of this mutation ripples along the gene from the place
MUTATION
where the mutation occurred.
POINT MUTATION Mutation will show it’s effect only at the point where the mutation occurs.
GENETIC
Any direct manipulation of an organisms genes.
ENGINEERING
Form of DNA that does not exist naturally, it is produced by combining DNA sequences that
RECOMBINANT would not normally occur together.
DNA TECHNOLOGY Technology ® is a form of biotechnology, used to introduce beneficial genes into an organism
to create GMO’s.
A living organism molecule (often plasmid or virus) that is used as a vehicle to carry a particular
VECTOR
DNA segment into a host cell
TRANSGENIC An organism containing foreign DNA from another species, inserted into its genome.
ORGANISM
GENETICALLY
MODIFIED An organism containing introduced foreign DNA that results in new and useful traits.
ORGANISMS
Using various biological processes with living organisms to create useful products, benefiting
BIOTECHNOLOGY
humans.
GENE THERAPY Replacing mutated or missing genes that cause disorders or diseases.
RESTRICTION Cuts the DNA strand at specific sites to isolate the gene.
ENZYME
DNA LIGASE ® Joins together the ends of 2 single strands of DNA
ENZYME ® Forms Recombinant DNA.
3
, GREGORY MENDEL:
CONTEXT: WHY PEA PLANTS?
- Gregor Mendel ® The father of - SIMPLE STRUCTURE:
genetics [Contained both male and female reproductive parts \ easy for Mendel
to control the pollination]
- Aim: To determine how characteristics
- QUICK REPRODUCTIVE CYCLE:
were inherited. [\ He could collect results quickly and conduct many repeat
- 1860: No pre-existing knowledge of the experiments]
concept of Genes/DNA/Chromosomes. - CONTRASTING CHARACTERISTICS:
It was thought inheritance was via [Clear, observable traits \ easy to record and distinguish]
blood.
- Began a series of experiments with pea CONTRASTING CHARACTERISTICS:
plants which he observed and recorded. - SEED SHAPE:
- His work (which is still used today) was [Round vs Wrinkled]
only published after his death.
- SEED COLOUR:
[Yellow vs Green]
WHY HIS EXPERIMENTS WERE SCIENTIFIC:
- FLOWER COLOUR:
- CAREFULLY SELECTED:
[Purple vs White]
[Initially only selected plants that were true breeding/pure breeding]
- PLANT HEIGHT:
- STUDIED 1 CHARACTERISTIC AT A TIME:
[Tall vs Short]
[\ Results were recorded independently]
- FLOWER POSITIONS:
- CONTRASTING CHARACTERISTICS:
[Terminal vs Axial]
[\ results were easy to distinguish / easily observable]
- PLANTS GREW QUICKLY:
[Results were seen in 1 year]
- CONTROLLED POLLINATION:
[\ self-pollination was prevented]
- RECORDED & OBSERVED RESULTS:
[Counted all offspring that grew ® recorded observable information in a journal]
- LARGE SAMPLE SIZES:
[\ He could collect results over many generations]
HOW HE STARTED HIS EXPERIMENTS:
1. ONLY CROSSED PURE BREEDING PLANTS:
E.g: Yellow Seeded Pea Plant crossed with Yellow Seeded Pea Plant ® offspring
was Yellow Seeded.
® Collected yellow seeds ® Planted them ® Plant would grow and flower.
2. TRANSFERRED POLLEN BETWEEN PLANTS:
® Cross Pollination: Transferred pollen from a flower of one plant, to the
flower of another.
® After seeds had formed, he would collect only the yellow seeds (seeds
homogenous to parents).
3. REPLANTED THE SEEDS:
® Planted the yellow seeds he collected and allowed them to flower.
® He then cross pollinated the flowers again 4
, MENDEL’S FIRST EXPERIMENTS: (MONOHYBRID CROSSES] .
® Cross between two individuals, concentrating on one characteristic only.
Mendel studied seed colour first.
1. COLLECTED POLLEN:
® Extracted pollen from a flower which grew from the seed of a pure breeding purple flowered pea plant.
2. TRANSFERRED POLLEN:
® Transferred the purple pollen to a flower which grew from the seed of a pure breeding white flowered pea plant.
® Also took pollen from the white flowered plant and transferred it to a purple flowered plant.
3. REPEATED PROCESS:
® He did this for thousands of plants and waited for seeds to form.
® Once the seeds formed, he planted them again and waited for the flowers that grew from them.
HE FOUND THAT THE FLOWERS THAT GREW FROM THIS GENERATION (F1) WERE ALL PURPLE.
® He cross pollinated flowers from F1 with one another and collected the seeds that were produced.
® F2 Results: ¾ of the flowers were purple / ¼ of the flowers were white. [See Punnet Square]
MENDEL’S CONCLUSIONS: MENDEL’S LAW OF DOMINANCE:
® If two alleles are different, only
- Characteristic of an organism is determined by two factors called genes.
the dominant allele will be
- Gene One: From the Mother. expressed.
Gene Two: From the Father.
MENDEL’S LAW OF SEGREGATION:
- Hence, a gene pair is formed on homologous chromosome pairs
(chromosomes that carry genes for the same traits in the same location). ® During Meiosis, homologous
chromosomes separate, resulting in
- Each particular gene may be expressed in two different forms each gamete carrying only one allele
® the same characteristic is affected in different ways for each gene.
® Alleles (Alternative forms of the same gene)
MENDEL’S LAW OF INDEPENDENT
- One allele of a gene pair can mask the other allele ® The Dominant Allele. ASSORTMENT:
- The allele that is masked / not visibly expressed ® The Recessive Allele. ® The allele a gamete receives for one
gene does not influence the allele
NOTE: Mendel did not use the words ‘gene’ or ‘allele’ ® He used the term ‘Factor’. received for another gene
PUNNET SQUARES:
® Represents a genetic cross.
® Determines the probability of the likelihood of the outcome of a genetic cross
Example: Mr. and Mrs. Adams need your help. They both have a history of cystic fibrosis in their families, but they do not
physically have the disease themselves. After testing, you have found them to be heterozygous/carriers of cystic fibrosis.
Determine the % chance that one of their children will have cystic fibrosis. Ensure to make use of a punnet square.
KEY:
STEPS: P1 Phenotype:
A ® Unaffected
1. Make a key for parents Unaffected / Unaffected
a ® Affected
A a genotype ® Place the genotype
of each parent on the outside of
P1 Genotype:
Aa / Aa
1 2
the punnet square. Gametes:
A AA Aa 2. Fill in the punnet square.
A a A a
(Ignore numbers) F1 Genotype(s):
3 4 1 ® Homozygous Dominant 1x Phenotype(s)
F1 Homozygous Dominant (AA)
2 ® Heterozygous 2x Heterozygous Dominant (Aa)
Aa aa 3 ® Heterozygous
a 4 ® Homozygous Recessive
1x Genotype(s)
F1 Homozygous Recessive (aa)
F1 Phenotype(s):
3. Write conclusion and calculate 1x Affected 5
probability. 3x Unaffected
x
- GENETICS
- Specific to IEB SAGGs Document (2023)
230
- GENETIC ENGINEERING
- All notes have been sourced from different
documents however it is still recommended
to use these as a guide in your own research.
0
, DEFINITIONS:
COMMON TERMS:
A unit of inheritance containing a small section of DNA that controls heredity passed from
GENE
parent to child.
GENOME The complete set of genes of an organism.
LOCUS The position/location of genes/alleles on a specific chromosome.
CHROMOSOMES Thread like structures, made up of DNA, found in the chromatin network (nucleus) of each cell.
An alternative form/variation of a gene, responsible for controlling different versions of a trait.
ALLELES Capital Letter ® Dominant Gene
Lowercase Letter ® Recessive Gene
The set of all genes (genetic information) in a population of sexually reproducing organisms.
GENE POOL Large Gene Pool ® High genetic diversity ® Increased chance of survival.
Small Gene Pool ® Low genetic diversity ® Increased possibility of extinction.
The physical appearance of an organism (Height / Eye Colour / Hair Colour / etc…)
PHENOTYPE
® Determined by genotype.
The genetic make-up of an organism (Cannot be seen by looking at an organism)
GENOTYPE
® Represented by 2 letters ® Each letter represents 1 allele in the gene pair (TT/Tt/tt).
DOMINANT ALLELE The allele of a gene that will produce a certain phenotype (even if other alleles are present).
The trait is only expressed when an organism has two recessive alleles for that gene.
RECESSIVE ALLELE
( \ Homozygous Recessive)
2 identical alleles for a specific trait.
HOMOZYGOUS Homozygous Dominant ® TT
Homozygous Recessive ® tt
HETEROZYGOUS 2 different alleles for a specific trait ® Tt
PURE BREEDING Identical individuals (homozygous) that produce offspring carrying the same phenotype to them.
Known as Hybridization.
CROSS BREEDING Mixing different species or varieties of animals or plants and thus to produce hybrids.
Animal breeding ® crosses within a single species
MONOHYBRID The inheritance of characteristics controlled by a single gene. It is used to study a pair of
INHERITANCE contrasting characteristics at a time (Tall vs Short).
COMPLETE The characteristic that is fully expressed in the phenotype of a heterozygous organism
DOMINANCE (Dominant Allele) ® Only expressed when allele is homozygous.
HYBRID Organism / Offspring that results from two different species of parent organisms.
Animal Breeding ® crosses breed between different species.
FILIAL Any generation resulting from a genetically controlled mating (following parental mating).
GENERATIONS F1 ® Filial Generation 1 (the first generation that results from the crossing of two parental
lines).
ANTHER Male reproductive part of a flower.
STIGMA Female reproductive part of a flower.
SELF POLLINATION Transfer of pollen from anther to stigma of the same flower
CROSS Transfer of pollen from anther of one flower to stigma of the same species of flower on a
POLLINATION different plant
2
, Mutations caused by insertions or deletions of a number of nucleotides in a DNA sequence
FRAMESHIFT
(and not divisible by three). The effect of this mutation ripples along the gene from the place
MUTATION
where the mutation occurred.
POINT MUTATION Mutation will show it’s effect only at the point where the mutation occurs.
GENETIC
Any direct manipulation of an organisms genes.
ENGINEERING
Form of DNA that does not exist naturally, it is produced by combining DNA sequences that
RECOMBINANT would not normally occur together.
DNA TECHNOLOGY Technology ® is a form of biotechnology, used to introduce beneficial genes into an organism
to create GMO’s.
A living organism molecule (often plasmid or virus) that is used as a vehicle to carry a particular
VECTOR
DNA segment into a host cell
TRANSGENIC An organism containing foreign DNA from another species, inserted into its genome.
ORGANISM
GENETICALLY
MODIFIED An organism containing introduced foreign DNA that results in new and useful traits.
ORGANISMS
Using various biological processes with living organisms to create useful products, benefiting
BIOTECHNOLOGY
humans.
GENE THERAPY Replacing mutated or missing genes that cause disorders or diseases.
RESTRICTION Cuts the DNA strand at specific sites to isolate the gene.
ENZYME
DNA LIGASE ® Joins together the ends of 2 single strands of DNA
ENZYME ® Forms Recombinant DNA.
3
, GREGORY MENDEL:
CONTEXT: WHY PEA PLANTS?
- Gregor Mendel ® The father of - SIMPLE STRUCTURE:
genetics [Contained both male and female reproductive parts \ easy for Mendel
to control the pollination]
- Aim: To determine how characteristics
- QUICK REPRODUCTIVE CYCLE:
were inherited. [\ He could collect results quickly and conduct many repeat
- 1860: No pre-existing knowledge of the experiments]
concept of Genes/DNA/Chromosomes. - CONTRASTING CHARACTERISTICS:
It was thought inheritance was via [Clear, observable traits \ easy to record and distinguish]
blood.
- Began a series of experiments with pea CONTRASTING CHARACTERISTICS:
plants which he observed and recorded. - SEED SHAPE:
- His work (which is still used today) was [Round vs Wrinkled]
only published after his death.
- SEED COLOUR:
[Yellow vs Green]
WHY HIS EXPERIMENTS WERE SCIENTIFIC:
- FLOWER COLOUR:
- CAREFULLY SELECTED:
[Purple vs White]
[Initially only selected plants that were true breeding/pure breeding]
- PLANT HEIGHT:
- STUDIED 1 CHARACTERISTIC AT A TIME:
[Tall vs Short]
[\ Results were recorded independently]
- FLOWER POSITIONS:
- CONTRASTING CHARACTERISTICS:
[Terminal vs Axial]
[\ results were easy to distinguish / easily observable]
- PLANTS GREW QUICKLY:
[Results were seen in 1 year]
- CONTROLLED POLLINATION:
[\ self-pollination was prevented]
- RECORDED & OBSERVED RESULTS:
[Counted all offspring that grew ® recorded observable information in a journal]
- LARGE SAMPLE SIZES:
[\ He could collect results over many generations]
HOW HE STARTED HIS EXPERIMENTS:
1. ONLY CROSSED PURE BREEDING PLANTS:
E.g: Yellow Seeded Pea Plant crossed with Yellow Seeded Pea Plant ® offspring
was Yellow Seeded.
® Collected yellow seeds ® Planted them ® Plant would grow and flower.
2. TRANSFERRED POLLEN BETWEEN PLANTS:
® Cross Pollination: Transferred pollen from a flower of one plant, to the
flower of another.
® After seeds had formed, he would collect only the yellow seeds (seeds
homogenous to parents).
3. REPLANTED THE SEEDS:
® Planted the yellow seeds he collected and allowed them to flower.
® He then cross pollinated the flowers again 4
, MENDEL’S FIRST EXPERIMENTS: (MONOHYBRID CROSSES] .
® Cross between two individuals, concentrating on one characteristic only.
Mendel studied seed colour first.
1. COLLECTED POLLEN:
® Extracted pollen from a flower which grew from the seed of a pure breeding purple flowered pea plant.
2. TRANSFERRED POLLEN:
® Transferred the purple pollen to a flower which grew from the seed of a pure breeding white flowered pea plant.
® Also took pollen from the white flowered plant and transferred it to a purple flowered plant.
3. REPEATED PROCESS:
® He did this for thousands of plants and waited for seeds to form.
® Once the seeds formed, he planted them again and waited for the flowers that grew from them.
HE FOUND THAT THE FLOWERS THAT GREW FROM THIS GENERATION (F1) WERE ALL PURPLE.
® He cross pollinated flowers from F1 with one another and collected the seeds that were produced.
® F2 Results: ¾ of the flowers were purple / ¼ of the flowers were white. [See Punnet Square]
MENDEL’S CONCLUSIONS: MENDEL’S LAW OF DOMINANCE:
® If two alleles are different, only
- Characteristic of an organism is determined by two factors called genes.
the dominant allele will be
- Gene One: From the Mother. expressed.
Gene Two: From the Father.
MENDEL’S LAW OF SEGREGATION:
- Hence, a gene pair is formed on homologous chromosome pairs
(chromosomes that carry genes for the same traits in the same location). ® During Meiosis, homologous
chromosomes separate, resulting in
- Each particular gene may be expressed in two different forms each gamete carrying only one allele
® the same characteristic is affected in different ways for each gene.
® Alleles (Alternative forms of the same gene)
MENDEL’S LAW OF INDEPENDENT
- One allele of a gene pair can mask the other allele ® The Dominant Allele. ASSORTMENT:
- The allele that is masked / not visibly expressed ® The Recessive Allele. ® The allele a gamete receives for one
gene does not influence the allele
NOTE: Mendel did not use the words ‘gene’ or ‘allele’ ® He used the term ‘Factor’. received for another gene
PUNNET SQUARES:
® Represents a genetic cross.
® Determines the probability of the likelihood of the outcome of a genetic cross
Example: Mr. and Mrs. Adams need your help. They both have a history of cystic fibrosis in their families, but they do not
physically have the disease themselves. After testing, you have found them to be heterozygous/carriers of cystic fibrosis.
Determine the % chance that one of their children will have cystic fibrosis. Ensure to make use of a punnet square.
KEY:
STEPS: P1 Phenotype:
A ® Unaffected
1. Make a key for parents Unaffected / Unaffected
a ® Affected
A a genotype ® Place the genotype
of each parent on the outside of
P1 Genotype:
Aa / Aa
1 2
the punnet square. Gametes:
A AA Aa 2. Fill in the punnet square.
A a A a
(Ignore numbers) F1 Genotype(s):
3 4 1 ® Homozygous Dominant 1x Phenotype(s)
F1 Homozygous Dominant (AA)
2 ® Heterozygous 2x Heterozygous Dominant (Aa)
Aa aa 3 ® Heterozygous
a 4 ® Homozygous Recessive
1x Genotype(s)
F1 Homozygous Recessive (aa)
F1 Phenotype(s):
3. Write conclusion and calculate 1x Affected 5
probability. 3x Unaffected
