Zusammenfassung der Ressource
B2.5 Simple Inheritance in Animals and Plants
- Cell Division and Growth
- Cells
- New cells are needed to
replace old ones, repair
damaged tissue, grow,
etc, but they much have the
same genetic material
- They have a nucleus containing
genes (some DNA). Different forms
of genes are alleles. Genes are
grouped in chromosomes.
- 46 chromosomes in a nucleus. 23
pairs. One from a pair is inherited
from father and one from mother.
Gametes have only one of each pair
- Mitosis
- two identical
cells
- Same chromosomes
- asexual
- no genetic variation
- Produces copies
of chromosomes
then cell divides
- eg, skin
- Differentiation
- In embryos cells
are unspecialised
(stem cells)
- Some genes are
switched on to
specialise certain cells
and differentiate them
- In adult animal cells
differentiation has already
occured so mitosis is
common yet plants can still
differentiate making them
easy to clone
- Cell Division in Sexual Reproduction
- Meiosis
- ova made in
ovaries. Sperm
in testes
- Chromosomes are copied, cell
divides twice leaving 4 sex cells
with half the chromosomes
- Introduces variety
- random
chromosome
areas
- Fertilisation
- more variety as
they each have
23
chromosomes
which pair
- Meiosis then Mitosis
- Variation
- Asexual = no variation
- sexual = variation
- Stem Cells
- The Function
- egg and sperm fuse to form a zygote (a
single cell). This divides to form a ball of
cells (embryo). The inner cells of this ball
are stem cells which will differentiate
- bone marrow
is a stem cell
- They are needed for diseased or injured tissue
- Using Stem Cells
- Spinal injuries cause paralysis
- Embryonic stem
cells can be cultured
and differentiated into
the right cells
- We may be able to grow whole organs
- Problems with Stem Cells
- Some embryonic stem
cells come from abortions,
some from fertility treatment
which may cause ethical
issues
- Human rights
- Slow, difficult,
expensive and
hard to control
- May cause cancer
- The Future
- There are stem cells in the umbilical
cord blood solving ethical issues
- new ways of growing
adult stem cells, and
have even grown
tracheas.
- Theraputic cloning uses
adult cells to clone an
embryo of themselves,
- From Mendel to DNA
- Mendel's discoveries
- Born 1822 worked
in a monestry
- cross bred peas
- Found a pattern in the characteristic of offspring
- considered
dominant
genes
- DNA
- Chromosomes
are made up of
long chain of
DNA and are
found in nuclei
- Double
helix
structure
- Genes are a small
section of DNA
- Carries
instructions to
make the
proteins that form
cell structures
- include enzymes to
control cell chemistry
- The Genetic code
- DNA is made of
4 different
chemicals
- grouped into 3s. Each 3 is an amino acid
- A gene is
made of
hundreds of
thousands of
these bases
- The order of
bases controls
the order of
amino acids to
make protein.
- A mutation in a base
will change the whole
protein structure
- DNA fingerprinting
- DNA is
unique to
you
- UNLESS
YOU HAVE
AN
IDENTICAL
TWIN
- Both developed
from one cell
- Your DNA
can be used
to identify
you.
- Your DNA pattern
is more similar to
relatives. You can
get your pattern
from bodily fluids
- Can be used for
crimes and DNA
tests in parenting
- Inheritance in action
- How inheritance
works
- Sex Chromosomes
- XX is female, XY is male
- Genes have different alleles
which result in a different protein
- Most characteristics
are controlled by a
number of genes but
some are only 1.
- You get dominant and
recessive alleles
- Genetic terms
- Homozygous - two
identical alleles (DD,dd)
- Heterozygous
- an individual
with different
alleles (Dd)
- Genotype -
the genetic
makeup of an
individual
- Phenotype -
physical
appearance
(dimples)
- Family Trees
- Can be used for
tracing genetic
changes
- Can track diseases
- Inherited conditions in humans
- Polydactyly
- When a baby
has excess
fingers or toes
- Caused by a
dominant allele
- If 1 parent has it,
you have a 50%
chance as half
the gametes have
the fault. If they
are homozygous,
you have no
chance
- Cyctic Fibrosis
- Organs get
clogged by mucus
- Treatment =
physiotherapy
and antibiotics
- Caused by a
recessive allele
- must be
inherited by
both parents
- Carriers have
both alleles but
no symptoms
because the
dominant is
healthy
- The Genetic Lottery
- When an egg
and sperm
combine it is up
to luck which
alleles combine
- Use a
punnet
square
- Curing Genetic Disease
- Scientists hope genetic
engineering will be the
answer as they can cut out
faulty alleles and replace
them with healthy ones
- Genetic tests show people
what faulty alleles they have
and the probability of children
having them
- They can then decide whether they
want a family. It raises ethical issues
- Stem Cells and Embryos
- RELIGION AND SHIZZLE