2021
Life Science Examination
Notes
Grade 12
by Abigail de Klerk
,Table of Contents
Chapter 1: DNA and protein synthesis ________ 0
Alternation of generations ______________ 15
Revision of cellular structure _____________ 0
Mitosis vs meiosis _____________________ 15
The nucleus _______________________ 0
Similarities _______________________ 15
The structure of nucleic acids _____________ 0 Differences _______________________ 15
Nucleic acids ______________________ 0 Meiosis 1 vs meiosis 2 ______________ 15
Basic structure of a nucleotide ________ 0
Abnormal meiosis _____________________ 16
Chromosomes _____________________ 1
Down syndrome (mongolism) ________ 16
DNA (deoxyribonucleic acid) _____________ 2 Other examples of aneuploidy ________ 17
DNA _____________________________ 2
Chromosomes _____________________ 2 Chapter 3: Diversity of reproductive strategies 18
A brief history of DNA _______________ 2
External vs internal fertilisation __________ 18
The structure of DNA ________________ 3
External fertilisation ________________ 18
The role of DNA ____________________ 3
Internal fertilisation ________________ 18
RNA (ribonucleic acid) __________________ 4
Reproductive strategies ________________ 19
RNA _____________________________ 4
Ovipary __________________________ 19
The location of RNA _________________ 4
Ovovivipary_______________________ 19
The structure of RNA ________________ 4
Vivipary __________________________ 19
Comparison between DNA and RNA _______ 4
Amniotic egg _________________________ 19
Similarities ________________________ 4
Four membranes __________________ 20
Differences ________________________ 4
Development of the embryo _____________ 20
DNA Replication _______________________ 5
Precocial development______________ 20
Steps _____________________________ 5
Altricial development _______________ 20
Errors that occur during DNA replication ____ 6
Parental care_________________________ 20
DNA profiling _________________________ 6
What DNA profiles are used for________ 6 Chapter 4: Human reproduction ____________ 21
Problems with DNA profiling __________ 6
Introduction _________________________ 21
Protein synthesis_______________________ 6 Key terminology ___________________ 21
Proteins and amino acids _____________ 7
The male reproductive system ___________ 21
Protein synthesis occurs in two stages __ 7
Diagram _________________________ 21
The effect of mutation on protein
Structures and functions ____________ 22
structure___ Error! Bookmark not defined.
The female reproductive system__________ 24
Practical: Extracting DNA from wheat germ _ 9
Diagram _________________________ 24
Structures and functions ____________ 24
Chapter 2: Meiosis _______________________ 10
Puberty _____________________________ 25
Meiosis vs Mitosis_____________________ 10
Secondary sexual characteristics ______ 25
Importance of meiosis ______________ 10
Haploid vs diploid cells______________ 11 Gametogenesis _______________________ 26
Gonosomes ______________________ 11 Spermatogenesis __________________ 26
Autosomes _______________________ 11 Oogenesis ________________________ 27
Oogenesis vs spermatogenesis _______ 27
Mitosis revision_______________________ 11
What happens during mitosis? _______ 11 The menstrual cycle ___________________ 28
Key terminology ___________________ 28
Meiosis _____________________________ 12
Ovarian cycle _____________________ 29
What happens during meiosis? _______ 12
Uterine cycle______________________ 30
Where does meiosis take place? ______ 12
Meiosis 1 ________________________ 12 Hormonal control of the menstrual cycle ___ 31
Meiosis 2 ________________________ 13 Negative and positive feedback
mechanisms ______________________ 32
Production of gametes in animals ________ 14
1
, Fertilisation and development of zygote to Structures and functions ____________ 46
blastocyst ___________________________ 32 The spinal cord ____________________ 47
Implantation of the blastocyst and
Peripheral nervous system ______________ 47
gestation ________________________ 33
Somatic nervous system ____________ 48
Autonomic nervous system __________ 48
Chapter 5: Genetics and inheritance _________ 35
Neurons _____________________________ 48
Introduction _________________________ 35
Diagrams_________________________ 48
Concepts in inheritance ________________ 35 Structures and functions ____________ 49
Classification of neurons ____________ 50
Gregor Mendel as the father of genetics ___ 36
Mendel’s laws of inheritance_________ 36 Reflex action and reflex arc _____________ 51
How a reflex action takes place _______ 51
Genetic diagrams _____________________ 37
Genetic crosses ___________________ 37 Disorders of the nervous system__________ 52
Alzheimer’s disease ________________ 52
Monohybrid crossing __________________ 37
Multiple sclerosis __________________ 52
Complete dominance_______________ 37
Incomplete dominance _____________ 38 Sense organs _________________________ 52
Co-dominance ____________________ 38 The human eye ____________________ 52
Sex determination _________________ 38 Diagram _________________________ 53
Sex-linked disorders ________________ 39 Structures and functions ____________ 53
Multiple alleles – blood grouping _____ 40 Accommodation ___________________ 56
Polygenic inheritance_______________ 40 Pupillary mechanism _______________ 56
Visual defects _____________________ 57
Dihybrid crossing _____________________ 41
The human ear _______________________ 59
Genetic pedigree diagrams _____________ 42
Key terminology ___________________ 59
The full ear _______________________ 59
Chapter 6: Human responses to the environment
The outer ear _____________________ 59
______________________________________ 43
Structure and functions _____________ 60
Introduction _________________________ 43 The middle ear ____________________ 60
Key terminology ___________________ 43 Structure and functions _____________ 60
The inner ear _____________________ 61
Human responses to the environment _____ 43
Structure and functions _____________ 62
The human nervous system _____________ 43 Summary ________________________ 63
Key terminology ___________________ 44 Functioning of the ear ______________ 64
Central NS and Peripheral NS ________ 44 Adaptations of the ear for its function _ 65
Hearing defects ___________________ 66
Central nervous system ________________ 45
The brain ________________________ 45
Diagram _________________________ 45
1
, Chapter 1: DNA and protein synthesis
Revision of cellular structure
ð Cytoplasm is the watery substance that
holds all the cell organelles and allows for
metabolic reactions.
ð Ribosomes are attached to the ER
(Endoplasmic reticulum) or floating freely in
the cell, which are the basis for protein
synthesis and consist of RNA and protein.
The nucleus
ð Controls all the cell activities.
ð Double nuclear membrane encloses the
nucleus and contains small pores to allow
substances in and out of it.
ð Nucleoplasm is a jelly-like fluid inside the
nucleus.
ð Nucleolus is a dark body suspended in the
nucleoplasm which contains free
nucleotide bases and produces ribosomes.
ð Chromatin network found in the
nucleoplasm contains the DNA which
forms chromosomes containing the
genetic code of an organism.
The structure of nucleic acids
ð Nucleic acid is an organic compound.
ð Monomer is a building block.
ð Nucleotide is the monomer that forms DNA and RNA.
Nucleic acids
ð DNA: Deoxyribonucleic acid.
ð RNA: Ribonucleic acid.
Basic structure of a nucleotide
ð P: Phosphate group.
ð S: Sugar molecule (either deoxyribose or
ribose).
ð NB: Nitrogenous base (adenine, guanine,
cytosine and thymine (uracil for RNA).
0
Life Science Examination
Notes
Grade 12
by Abigail de Klerk
,Table of Contents
Chapter 1: DNA and protein synthesis ________ 0
Alternation of generations ______________ 15
Revision of cellular structure _____________ 0
Mitosis vs meiosis _____________________ 15
The nucleus _______________________ 0
Similarities _______________________ 15
The structure of nucleic acids _____________ 0 Differences _______________________ 15
Nucleic acids ______________________ 0 Meiosis 1 vs meiosis 2 ______________ 15
Basic structure of a nucleotide ________ 0
Abnormal meiosis _____________________ 16
Chromosomes _____________________ 1
Down syndrome (mongolism) ________ 16
DNA (deoxyribonucleic acid) _____________ 2 Other examples of aneuploidy ________ 17
DNA _____________________________ 2
Chromosomes _____________________ 2 Chapter 3: Diversity of reproductive strategies 18
A brief history of DNA _______________ 2
External vs internal fertilisation __________ 18
The structure of DNA ________________ 3
External fertilisation ________________ 18
The role of DNA ____________________ 3
Internal fertilisation ________________ 18
RNA (ribonucleic acid) __________________ 4
Reproductive strategies ________________ 19
RNA _____________________________ 4
Ovipary __________________________ 19
The location of RNA _________________ 4
Ovovivipary_______________________ 19
The structure of RNA ________________ 4
Vivipary __________________________ 19
Comparison between DNA and RNA _______ 4
Amniotic egg _________________________ 19
Similarities ________________________ 4
Four membranes __________________ 20
Differences ________________________ 4
Development of the embryo _____________ 20
DNA Replication _______________________ 5
Precocial development______________ 20
Steps _____________________________ 5
Altricial development _______________ 20
Errors that occur during DNA replication ____ 6
Parental care_________________________ 20
DNA profiling _________________________ 6
What DNA profiles are used for________ 6 Chapter 4: Human reproduction ____________ 21
Problems with DNA profiling __________ 6
Introduction _________________________ 21
Protein synthesis_______________________ 6 Key terminology ___________________ 21
Proteins and amino acids _____________ 7
The male reproductive system ___________ 21
Protein synthesis occurs in two stages __ 7
Diagram _________________________ 21
The effect of mutation on protein
Structures and functions ____________ 22
structure___ Error! Bookmark not defined.
The female reproductive system__________ 24
Practical: Extracting DNA from wheat germ _ 9
Diagram _________________________ 24
Structures and functions ____________ 24
Chapter 2: Meiosis _______________________ 10
Puberty _____________________________ 25
Meiosis vs Mitosis_____________________ 10
Secondary sexual characteristics ______ 25
Importance of meiosis ______________ 10
Haploid vs diploid cells______________ 11 Gametogenesis _______________________ 26
Gonosomes ______________________ 11 Spermatogenesis __________________ 26
Autosomes _______________________ 11 Oogenesis ________________________ 27
Oogenesis vs spermatogenesis _______ 27
Mitosis revision_______________________ 11
What happens during mitosis? _______ 11 The menstrual cycle ___________________ 28
Key terminology ___________________ 28
Meiosis _____________________________ 12
Ovarian cycle _____________________ 29
What happens during meiosis? _______ 12
Uterine cycle______________________ 30
Where does meiosis take place? ______ 12
Meiosis 1 ________________________ 12 Hormonal control of the menstrual cycle ___ 31
Meiosis 2 ________________________ 13 Negative and positive feedback
mechanisms ______________________ 32
Production of gametes in animals ________ 14
1
, Fertilisation and development of zygote to Structures and functions ____________ 46
blastocyst ___________________________ 32 The spinal cord ____________________ 47
Implantation of the blastocyst and
Peripheral nervous system ______________ 47
gestation ________________________ 33
Somatic nervous system ____________ 48
Autonomic nervous system __________ 48
Chapter 5: Genetics and inheritance _________ 35
Neurons _____________________________ 48
Introduction _________________________ 35
Diagrams_________________________ 48
Concepts in inheritance ________________ 35 Structures and functions ____________ 49
Classification of neurons ____________ 50
Gregor Mendel as the father of genetics ___ 36
Mendel’s laws of inheritance_________ 36 Reflex action and reflex arc _____________ 51
How a reflex action takes place _______ 51
Genetic diagrams _____________________ 37
Genetic crosses ___________________ 37 Disorders of the nervous system__________ 52
Alzheimer’s disease ________________ 52
Monohybrid crossing __________________ 37
Multiple sclerosis __________________ 52
Complete dominance_______________ 37
Incomplete dominance _____________ 38 Sense organs _________________________ 52
Co-dominance ____________________ 38 The human eye ____________________ 52
Sex determination _________________ 38 Diagram _________________________ 53
Sex-linked disorders ________________ 39 Structures and functions ____________ 53
Multiple alleles – blood grouping _____ 40 Accommodation ___________________ 56
Polygenic inheritance_______________ 40 Pupillary mechanism _______________ 56
Visual defects _____________________ 57
Dihybrid crossing _____________________ 41
The human ear _______________________ 59
Genetic pedigree diagrams _____________ 42
Key terminology ___________________ 59
The full ear _______________________ 59
Chapter 6: Human responses to the environment
The outer ear _____________________ 59
______________________________________ 43
Structure and functions _____________ 60
Introduction _________________________ 43 The middle ear ____________________ 60
Key terminology ___________________ 43 Structure and functions _____________ 60
The inner ear _____________________ 61
Human responses to the environment _____ 43
Structure and functions _____________ 62
The human nervous system _____________ 43 Summary ________________________ 63
Key terminology ___________________ 44 Functioning of the ear ______________ 64
Central NS and Peripheral NS ________ 44 Adaptations of the ear for its function _ 65
Hearing defects ___________________ 66
Central nervous system ________________ 45
The brain ________________________ 45
Diagram _________________________ 45
1
, Chapter 1: DNA and protein synthesis
Revision of cellular structure
ð Cytoplasm is the watery substance that
holds all the cell organelles and allows for
metabolic reactions.
ð Ribosomes are attached to the ER
(Endoplasmic reticulum) or floating freely in
the cell, which are the basis for protein
synthesis and consist of RNA and protein.
The nucleus
ð Controls all the cell activities.
ð Double nuclear membrane encloses the
nucleus and contains small pores to allow
substances in and out of it.
ð Nucleoplasm is a jelly-like fluid inside the
nucleus.
ð Nucleolus is a dark body suspended in the
nucleoplasm which contains free
nucleotide bases and produces ribosomes.
ð Chromatin network found in the
nucleoplasm contains the DNA which
forms chromosomes containing the
genetic code of an organism.
The structure of nucleic acids
ð Nucleic acid is an organic compound.
ð Monomer is a building block.
ð Nucleotide is the monomer that forms DNA and RNA.
Nucleic acids
ð DNA: Deoxyribonucleic acid.
ð RNA: Ribonucleic acid.
Basic structure of a nucleotide
ð P: Phosphate group.
ð S: Sugar molecule (either deoxyribose or
ribose).
ð NB: Nitrogenous base (adenine, guanine,
cytosine and thymine (uracil for RNA).
0
