Download Year 10 Science Revision Booklet WHANAUMAITANGA

Year 10 Science Revision Booklet
WHANAUMAITANGA- GENETICS REVISION AND
QUESTIONS 2015
Key words:
Nucleus
Sperm
Zygote
Phenotype
Homozygous
Cytoplasm
Egg
Gene
Cells
Heterozygous
Cell Membrane
Meiosis
DNA
Selective Breeding
Chromosomes
Mitosis
Allele
Punnett Square
Gamete
Fertilisation
Genotype
Clones
Key definitions to learn:
Chromosome
Gene
DNA
Allele
Homozygous
Heterozygous
Genotype
Phenotype
Thread-like structures which carry the genetic information
Sections of the chromosome. Each gene codes for a specific
characteristic (trait)
The molecule that contains genes.
Different versions of a gene ( dominant version and recessive
version)
Both of an individual’s alleles are the same eg BB or bb
Both alleles are different for the particular trait eg Bb
The pair of alleles inherited by an individual i.e. Hh
The physical expression of the genotype eg Blonde hair
Key Learning Points:
A cell is made of a nucleus
embedded in cytoplasm
surrounded by a cell
membrane. Inside the
nucleus are chromosomes.
Chromosomes are made of
DNA.
Human cells contain 46 chromosomes in the nucleus of each cell except for
sex cells (sperm and egg cell) and red blood cells. Sperm and egg cells have
23 chromosomes.
The parents make their sex cells (sperm / egg cell) by a process called
meiosis. Each cell has half the number of chromosomes as the original
parent cell.
The diagram below shows the key steps in human reproduction
Year 10 Science Revision Booklet
When a sperm and an egg cell join together at fertilisation their
chromosomes mix to make 46 chromosomes in the new cell which is called a
zygote.
When this new cell forms it must copy itself to make many new ones. Each
cell makes 2 new ones in a process called mitosis. All the cells made are
identical.
The table below that outlines some of the features of this process
Name of
Process
Meiosis
Fertilisation
Mitosis
Effect on
Chromosomes
Halves the
number in new
sex cell
Joins the two half
sets of
chromosomes
Keep the same
number in new
cell
Product of
this step
Daughter
cells are the
sperm and
egg
zygote
Purpose of this step
Divide the chromosome pairs and
make sex cells with half the
genetic info.
identical
daughter
cells
To copy the chromosomes exactly
and to make new cells for growth
and repair
Join chromosome pairs from
different parents
Boy or girl
A male baby’s sex chromosome is XY and a female baby’s sex chromosome is XX
All eggs contain only an X chromosome, but Sperms contain either an X or a Y
chromosome.
A boy baby forms when the egg cell is fertilised by a sperm containing a Y sex
chromosome. A girl baby forms when an egg cell is fertilised by an X sperm.
Punnet Squares
This Punnet Square shows the male parent (XY) and female parent (XY).
XY
X
Y
X
XX
XY
X
XX
XY
XX
Every time a child is born there is a
50% chance that the child is female.
Website URL for revision:
http://www.bbc.co.uk/schools/gcsebitesize/science/21c/genetics/
Year 10 Science Revision Booklet
Method
Selective
breeding
Description
Advantages
Disadvantages
Breeding an
organism that
has a
desirable trait
with another
so that the
desirable trait
is passed to
the next
generation
 Producing an organism with  Continuous in-breeding and
the right characteristics and
selective breeding of particular
genes runs the risk of losing
 It is less costly to small scale
some of the other genes from
farmers.
the gene pool altogether, which
is irreversible
(This reduces the genetic pool
and variation of this organism,
which increases the chance of
all the organisms being
drastically reduced by one
disease or responding to
environmental change)
 You can only cross two related
species
In
biotechnology,
obtaining a
group of
genetically
identical cells
from a single
cell; making
identical
copies of a
gene
 An advantage is that many
organisms could be efficiently
produced in a short time
(although not true with
animals yet). This is
especially true for plants
which take a long time to
grow and produce seeds.
 The possibility of producing
not a complete body but just
an organ to save the life of a
human being who requires
the transplant of that organ.
 A critically endangered
species could benefit from
cloning.
 A disadvantage is that they
are genetically identical and
drastic changes in the
environment or diseases may
wipe them out since they may
all be susceptible to these.
 Very expensive and resource
heavy to clone animals.
 Side effects may be harmful
to the organism.
 Unethical.
Genetic
engineering
Taking a
specific
section of
DNA and
inserting it into
the DNA of
another
organism
 We can create SPECIFIC
new products
 Much faster than selective
breeding, you can express a
trait in one generation
 You can cross two completely
unrelated species
 The products produced can
be lifesaving, eg insulin,
golden rice
 It is more expensive than
artificial selection
 Ethical implications of ‘playing
god’
 What happens if a new
product escapes into the
ecosystem?
 Unintentional consequences
Assisted
reproductive
Technology
that helps
 Gives equal opportunity for all
couples to have offspring
 Unequal availability to these
technologies (due to wealth)
Cloning
Year 10 Science Revision Booklet
technologies infertile
eg IVF
couples to
reproduce
 With these new technologies
we have the ability to remove
undesirable traits and
diseases
 Ethical problems, how much
should be ‘choose’ our traits
 Which diseases do we
consider ‘too bad to be born’
Revision Questions:
1. Draw a generalised animal cell and label the following parts: Cell
membrane, nucleus, chromosomes, cytoplasm.
2. Fill in the blanks:
Our bodies are made up of trillions of c_________. Each cell has a
n____________. In the nucleus there are 46 or 23 pairs of
c__________________. Sections of c________________ are called
g______________. Different versions of the same gene are called
a______________.
3. Discuss the relationship between chromosomes, DNA, genes and
alleles.
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4. Compare and contrast Selective Breeding and Cloning. What are the
similarities and differences, and what are the advantages and
disadvantages of each?
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Year 10 Science Revision Booklet
Draw a mind map for this unit:
Add to it, as you develop your learning.
Relationship from Cells to
Alleles:
Selective Breeding vs Genetic
engineering
Similarities:
Differences:
Genetics
From Gametes to Zygote.
Cell Division: Mitosis
Well done you have completed another revision unit.
Now reflect on how you can improve further:
Which aspects of the unit do I need to revise more carefully?
Which aspects of the unit do I need help with?
How will I seek this help?