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AY is not teaching this course in 2022-
AY is not teaching this course in 2022-
NOT UPDATED FOR 2022
NOT UPDATED FOR 2022
Key Words and Definitions are super important in Biology. Quizlet is a good place to practice them, start with the small Genetic Keywords set then move on to the NCEA Level 1 set :)
CHAPTER ONE: Cells and DNA | DNA Replication | Mitosis | DNA to Proteins |
CHAPTER TWO: Sex determination | Genotype and Phenotype | Allele combinations | Punnett Squares | Pedigree Charts | Test Crosses |
CHAPTER THREE: Types of Variation | Sources of Variation | Asexual vs Sexual Reproduction | Meiosis | Mutations | Importance of Variation |
ONE: THE GENETIC CODE, Scipad:178-189
ONE: THE GENETIC CODE, Scipad:178-189
DNA Replication
DNA Replication
SciPAD Pages: 183
Key Steps to know:
DNA unwinds and an enzyme unzips the DNA
An enzyme adds free nucleotides to the exposed bases, using the Complimentary Base-Pairing Rule.
Another Enzyme makes sure the two new strands of DNA are fully attached together.
End up with two identical strands of DNA = Semi-conservative Replication (each is half new, half old).
MITOSIS
MITOSIS
SciPAD Page 184
Mitosis is the replicating of DNA and then the splitting of one cell into two. Mitosis is used for growth and repair of our bodies and occurs in every cell in your body (except your sex cells).
Basics steps of mitosis are:
DNA replicates and condenses
Nuclear membrane disappears
Chromosomes line-up on the cell equator
Chromosomes get pulled apart
Nuclear membranes form
Cell divides
End up with two identical daughter cells
DNA to PROTEINS
DNA to PROTEINS
SciPAD Page 185
All you need to know are the relationships:
Between Bases and Triplets
Between Triplets and Amino Acids
Between Amino Acids and Proteins
Between Proteins and Traits
By the end of the first chapter (pg178-186) you should be able to define the following terms:
Nucleus
Chromosome
Complimentary base pairing rule
Nucleotide
Mitosis
Amino Acid
Protein
Gene
Allele
If you're feeling confident with these terms then have a go at the end of chapter review questions (pg 190-192).
If you're feeling confident with these terms then have a go at the end of chapter review questions (pg 190-192).
End of Chapter Review will be on Friday 14th May.
End of Chapter Review will be on Friday 14th May.
TWO: PREDICTING INHERITANCE pg193-216
TWO: PREDICTING INHERITANCE pg193-216
SEX DETERMINATION
SEX DETERMINATION
SciPAD 194
The sex chromosomes are used to determine the sex of the offspring. In humans males have an X and a Y chromosome, and females have two X chromosomes. During reproduction there is a 50/50 chance of producing a XX or XY combination of sex chromosomes.
Genotype and Phenotype
Genotype and Phenotype
SciPAD 195
When predicting the inheritance of features we can look at Genotype or Phenotype.
- Genotype is the set of alleles it carries- often using pairs of letters to represent the two copies inherited (one from each parent) eg. Aa or XY or bb- Phenotype is what that set of alleles will look like, for example blue eyes.
Allele Combinations
Allele Combinations
SciPAD 195
Dominant: An allele that is ALWAYS expressed (Shown) - written as a capital letter e.g BRecessive: An allele that is only seen if there is two present - written as a lower case letter e.g bHomozygous: Both of the alleles for the gene are the SAME- eg BB or bbHeterozygous: The two alleles for the gene are DIFFERENT- eg. Bb
Example: Looking at the feature Blue Hair (B). A Homozygous Dominant individual will have two BB, a Homozygous Recessive individual would have two bb, a Heterozygous individual will have Bb.
PUNNETT SQUARES
PUNNETT SQUARES
Scipad 196-207
Using the alleles present in the parents, we can predict the possible allele combinations in the offspring.
A punnet square is a visual tool used to do this.
PEDIGREE CHARTS
PEDIGREE CHARTS
SciPAD 208-211
Like a family tree that is used to link genetic characteristics across generations.
TEST CROSS
TEST CROSS
SciPAD 212
A test cross is a way of determining is an individual is Pure-breed (two alleles the same) for a dominant feature.
We draw a punnet square crossing the unknown individual with a homozygous recessive individual.
If any offspring from the cross have the recessive feature we can determine that the unknown individual was Heterozygous.
If after many many offspring only the dominant feature is seen, we can determine it is more likely the unknown individual was Homozygous Dominant. But we can never know for sure.
THREE:Understanding Variation pg 220-237
THREE:Understanding Variation pg 220-237
TYPES OF VARIATION
TYPES OF VARIATION
SciPAD Pages 221-223
Variation is the differences between members of a species. These differences sit in two categories:
Continuous Variation- is a complete range of measurable differences. E.g. Height, Weight, Hand span
Discontinuous Variation- the possible options for the feature fit into set categories. E.g. Eye colour, Hair type, Blood type.
For measurable traits there is typically a Normal Distribution- the extremes of the feature are less common, the middle is most common.
SOURCES OF VARIATION
SOURCES OF VARIATION
SciPAD Pages 224
Variation of traits can be due to:
Sexual Reproduction- Crossing over + Independent Assortment
Fertilisation
Environment
Mutation
The first two mix up the genetics inherited from parents. This creates different combinations of existing features.
Only MUTATION creates new alleles for a gene.
ASEXUAL vs SEXUAL REPRODUCTION
ASEXUAL vs SEXUAL REPRODUCTION
SciPAD Page 225
Asexual Reproduction only involves 1 parent:
Uses Mitosis to make new cells
Creates offspring identical to parent
Quick
Less energy required
More likely to be impacted by change
SciPAD Page 228-229
Sexual Reproduction involves 2 parents:
Uses Meiosis to make new cells
Creates offspring different to parents
Time consuming- Find mate, Develop Baby
More energy required- Find mate, Develop Baby
Population copes better with changes
Meiosis is a type of cell division used to make Gametes (Sex Cells- sperm, egg). Unlike Mitosis, this cell division creates cells with a half the number (often referred to as haploid or (n)) of chromosomes. It is important for a sex cell to have half the chromosome number, so when fertilisation occurs the cell will have a full set of chromosomes (referred to as Diploid or (2n)).
SciPAD Pages 226-227
Key Steps:
Chromosomes replicate and condense
Homologous Pairs of chromosomes join up
CROSSING OVER occurs
Homologous pairs of chromosomes line up at Equator of cell
INDEPENDENT ASSORTMENT occurs
Homologous pairs are separated
Cell Divides
Chromosomes line up at Equator of cells
Chromotids separate
4 daughter cells made with (n), half chromosome numbers, each genetically different to each other
MUTATIONS
MUTATIONS
SciPAD pages 230-232
Mutations are the only way a NEW feature can appear in a population.
A mutation is a permanent change to the base sequence of DNA. Making the instructions code for different proteins than before.
Need to Know:
Gametic vs Somatic Mutations
Beneficial, Harmful, Neutral Mutations
IMPORTANCE OF VARIATION
IMPORTANCE OF VARIATION
SciPAD pages 232-236
-Natural Selection: Members of a species that are best suited to the environment survive and reproduce.
-Variation: differences in features, allowing a species to respond and survive in changing environments.
-Environmental factors: Each environment has different conditions. Members of a species with traits to match these different conditions will have a greater chance of survival.
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