B5 – Inheritance
Variation: Difference within a species.
Phenotype: Observation characteristic of an organism.
There two categories of variation are:
1. Genetic variation is caused by the genes you inherit from your parents. E.g. Eye
colour, blood group.
2. Environmental Variation is caused by the environment in which you live. E.g.
Accent, Scars.
Some characteristics can be caused by both like Intelligence and height.
Continuous: Discontinuous:
-Can take any value within a range. -Can take result in discrete values.
-Caused by genetic variation.
-Caused by genetic and environmental variation.
-Controlled by multiple genes. -Controlled by one (or a few) genes.
-Displayed on a histogram. -Displayed on a bar chart.
-E.g. length of fur; skin colour; height -E.g. gender; eye colour
Clone: Organism that is genetically identical to its parent.
Bacteria reproduce asexually. The offspring are genetically identical to the parent
cell. Bacteria reproduced by mitosis.
Plants that use asexual reproduction:
-Strawberry
-Potatoes
Animals that use asexual reproduction:
-Star Fish
-Sea anemones
Sexual Reproduction:
-Requires two parents.
-Leads to genetic variation due to DNA coming from both parents
-Used by most animals.
Sexual Reproduction:
A gamete is a sex cell.
In humans, these are the sperm and the egg.
The gamete are haploid. This means they have 1/2 the number of chromosomes in
a body cell.
Plants also use sexual reproduction. Pollen (male) will fuse with an egg cell in the
ovule to produce a seed. The seed then grows into the new plant.
Advantages of sexual Advantages of asexual
reproduction reproduction
Produces variation in offspring: Only one parent is needed.
- This means that if the
environment changes it is likely
that an organism in the species will
have a characteristic that allows
them to survive (called a survival
, advantage).
- Although some individuals may
die, variation decreases the chance
of the whole species become
extinct.
It allows us to use selective Uses less energy and is faster as
breeding. organisms do not need to find a
mate.
Speeds up natural selection In favourable conditions lots of
identical offspring can be
produced.
Haploid and Diploid:
Normal human body cells have 46 chromosomes, they are diploid. This means they
contain 2 sets of each chromosome
The sex cells have 23 chromosomes. They are haploid. This means they contain 1
set of each chromosome. Your sex is determined by the X and Y chromosomes.
Male: XY
Fertilisation: Female: XX
During fertilisation, two haploid gametes join to form a diploid cell called zygote
This zygote will divide many In
times
this by mitosis
Punnet to produce
square, aa
there is new
50% organism. Every
chance that
organism produced by sexual reproduction
babies would behas a unique
either a boygenome
or girl. (all genetic
material of an organism) expect identical twins.
Meiosis
Gametes are produced by Meiosis.
Meiosis produced 4 haploid cells from one diploid parent cell.
In humans this takes place in the ovaries or testes.
Stage 1: Chromosomes are copied ( DNA replication)
Stage 2: Chromosomes line up along the equator in pairs (one from the mother, one
from the father)
Stage 3: Chromosomes are pulled to opposite poles
Stage4: Cell divides into two (cytokinesis)
Stage 5: Chromosomes line up along the equator
Stage 6: Chromosomes are pulled in half so copy of each chromosome moves to the
poles.
Stage 7: Each cell divides into two.
Variation
Variation is caused by:
-Random assortment of the chromosomes at the equator.
-Crossing over the chromosomes.
-Random fertilisation of an egg with a sperm.
You have two copies of every gene – one from the mother and from the father.
These genes may be the same or they could be different.
Alleles: Different forms of a gene. E.g. blue eyes and brown eyes.
Most phenotypes are causes by the influence of multiple genes rather than a single
When a mutation happens in a gene,
the DNA bases may:
-be changed
Variation: Difference within a species.
Phenotype: Observation characteristic of an organism.
There two categories of variation are:
1. Genetic variation is caused by the genes you inherit from your parents. E.g. Eye
colour, blood group.
2. Environmental Variation is caused by the environment in which you live. E.g.
Accent, Scars.
Some characteristics can be caused by both like Intelligence and height.
Continuous: Discontinuous:
-Can take any value within a range. -Can take result in discrete values.
-Caused by genetic variation.
-Caused by genetic and environmental variation.
-Controlled by multiple genes. -Controlled by one (or a few) genes.
-Displayed on a histogram. -Displayed on a bar chart.
-E.g. length of fur; skin colour; height -E.g. gender; eye colour
Clone: Organism that is genetically identical to its parent.
Bacteria reproduce asexually. The offspring are genetically identical to the parent
cell. Bacteria reproduced by mitosis.
Plants that use asexual reproduction:
-Strawberry
-Potatoes
Animals that use asexual reproduction:
-Star Fish
-Sea anemones
Sexual Reproduction:
-Requires two parents.
-Leads to genetic variation due to DNA coming from both parents
-Used by most animals.
Sexual Reproduction:
A gamete is a sex cell.
In humans, these are the sperm and the egg.
The gamete are haploid. This means they have 1/2 the number of chromosomes in
a body cell.
Plants also use sexual reproduction. Pollen (male) will fuse with an egg cell in the
ovule to produce a seed. The seed then grows into the new plant.
Advantages of sexual Advantages of asexual
reproduction reproduction
Produces variation in offspring: Only one parent is needed.
- This means that if the
environment changes it is likely
that an organism in the species will
have a characteristic that allows
them to survive (called a survival
, advantage).
- Although some individuals may
die, variation decreases the chance
of the whole species become
extinct.
It allows us to use selective Uses less energy and is faster as
breeding. organisms do not need to find a
mate.
Speeds up natural selection In favourable conditions lots of
identical offspring can be
produced.
Haploid and Diploid:
Normal human body cells have 46 chromosomes, they are diploid. This means they
contain 2 sets of each chromosome
The sex cells have 23 chromosomes. They are haploid. This means they contain 1
set of each chromosome. Your sex is determined by the X and Y chromosomes.
Male: XY
Fertilisation: Female: XX
During fertilisation, two haploid gametes join to form a diploid cell called zygote
This zygote will divide many In
times
this by mitosis
Punnet to produce
square, aa
there is new
50% organism. Every
chance that
organism produced by sexual reproduction
babies would behas a unique
either a boygenome
or girl. (all genetic
material of an organism) expect identical twins.
Meiosis
Gametes are produced by Meiosis.
Meiosis produced 4 haploid cells from one diploid parent cell.
In humans this takes place in the ovaries or testes.
Stage 1: Chromosomes are copied ( DNA replication)
Stage 2: Chromosomes line up along the equator in pairs (one from the mother, one
from the father)
Stage 3: Chromosomes are pulled to opposite poles
Stage4: Cell divides into two (cytokinesis)
Stage 5: Chromosomes line up along the equator
Stage 6: Chromosomes are pulled in half so copy of each chromosome moves to the
poles.
Stage 7: Each cell divides into two.
Variation
Variation is caused by:
-Random assortment of the chromosomes at the equator.
-Crossing over the chromosomes.
-Random fertilisation of an egg with a sperm.
You have two copies of every gene – one from the mother and from the father.
These genes may be the same or they could be different.
Alleles: Different forms of a gene. E.g. blue eyes and brown eyes.
Most phenotypes are causes by the influence of multiple genes rather than a single
When a mutation happens in a gene,
the DNA bases may:
-be changed
