Download 2.5 Genetics - Science at St. Dominics

Leaving Cert Biology
Section 2.5 Genetics
Genetics
Leaving Cert Biology
Section 2.5 Genetics
Diversity of living things
Leaving Cert Biology
Section 2.5 Genetics
Species
A species is a group of similar organisms that are capable of
naturally interbreeding with each other to produce fertile
offspring.
Leaving Cert Biology
Section 2.5 Genetics
There can be individuality within species –
differences between members of a species which
does not affect their ability to interbreed.
Leaving Cert Biology
Section 2.5 Genetics
Heredity
• The passing on of traits from parents to
offspring by means of genes
Example eye colour!
Leaving Cert Biology
Section 2.5 Genetics
Are you able to…
• Define species?
• Explain what heredity is?
Leaving Cert Biology
Section 2.5 Genetics
Chromosomes
Nuclear membrane
Chromatin
Nuclear pore
Leaving Cert Biology
Section 2.5 Genetics
Chromosomes
• Chromosomes are long strands of DNA
coiled up with protein
Leaving Cert Biology
Section 2.5 Genetics
Gene
A gene is a section of DNA that causes the
production of a protein.
Strand of DNA
Leaving Cert Biology
Section 2.5 Genetics
Gene expression
• Gene expression is the way in which
genetic information in a gene is decoded
in the cell and used to make a protein
•Every protein made has an effect on
the organism
Leaving Cert Biology
Section 2.5 Genetics
Gene expression
Gene Expression produces characteristics
or traits that are inherited
Example: Gene for Tallness
Organism is small – Why?
Maybe due to poor nutrition
Characteristics =
heredity + environment
Leaving Cert Biology
Section 2.5 Genetics
Check your learning…
• State the location of chromosomes
• Tell about the structure of a chromosome
• Tell what genes are and where they are
found
• Give examples of some traits controlled by
genes
Leaving Cert Biology
Section 2.5 Genetics
2.5.4 DNA structure
Leaving Cert Biology
Section 2.5 Genetics
DNA structure
DNA =Deoxyribonucleic Acid
•DNA is a very long molecule
•It is made up of two parallel strands
•The strands are linked together by
paired bases.
The DNA Spiral Ladder
Leaving Cert Biology
Section 2.5 Genetics
DNA structure
• There are four different bases that
are found in DNA
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Leaving Cert Biology
Section 2.5 Genetics
The Base Pair Rule
• AT
– Adenine only joins to Thymine
• GC
– Guanine only joins to Cytosine
Leaving Cert Biology
Section 2.5 Genetics
Triplet base code
Coding DNA contains information to make proteins..
The sequence of the bases on a DNA strand directs what protein
our body will make.
DNA codes for each amino
acid by using a sequence of
three consequtive bases.
The amino acids are joined
together to make a protein
Leaving Cert Biology
Section 2.5 Genetics
Coding DNA
• Def Coding DNA is the DNA that contains
information to make proteins
Strand of DNA
Leaving Cert Biology
Section 2.5 Genetics
Non Coding DNA
Non coding DNA is the DNA that does not contain information
for the production of protein
Also called “Junk DNA”
Strand of DNA
Non coding DNA
Leaving Cert Biology
Section 2.5 Genetics
Can you..
• Describe the structure of a chromosome
• Tell what genes are and where they are
found
• Tell what DNA stands for
• Name the four bases found in DNA
• Know how base pairing happens in DNA
• Distinguish between coding and non
coding DNA
Leaving Cert Biology
Section 2.5 Genetics
Nucleic acid structure – HL
• Deoxyribonucleic Acid
(DNA) is a nucleic acid
• It is made up of nucleotide
units
• Its shape is called the
double helix
Leaving Cert Biology
Section 2.5 Genetics
•
Nucleotide structure
Each nucleotide unit has:
1. A phosphate
2. A deoxyribose sugar
3. one of four nitrogenous bases
adenine, ( a purine)
guanine ( a purine)
cytosine, ( a pyrimidine)
or thymine( a pyrimidine)
Leaving Cert Biology
Section 2.5 Genetics
Purine and pyrimidine couples!
Adenine (purine) bonds to thymine (pyrimidine)
Guanine (purine) bonds to cytosine (pyrimidine)
Bases pairs bond to each other by Hydrogen bonding
Leaving Cert Biology
Section 2.5 Genetics
Leaving Cert Biology
Section 2.5 Genetics
• HL 2011 q9A,
Try now..
Leaving Cert Biology
Section 2.5 Genetics
To isolate DNA from a plant
tissue
Leaving Cert Biology
Section 2.5 Genetics
Step 1
Add 10 ml washing-up liquid and 3 g salt to a
graduated cylinder. Make up to 100 ml and stir.
Leaving Cert Biology
Section 2.5 Genetics
Step 2
Add chopped onion to a beaker. Pour in the
salty washing-up liquid solution and stir.
Leaving Cert Biology
Section 2.5 Genetics
Step 3
Stand the beaker in a water bath
at 60°C for 15 minutes.
Leaving Cert Biology
Section 2.5 Genetics
Step 4
Cool the mixture by standing the
beaker in an ice bath for 5 minutes.
Leaving Cert Biology
Section 2.5 Genetics
Step 5
Blend the mixture for no more
than 3 seconds.
Leaving Cert Biology
Section 2.5 Genetics
Step 6
Filter the blended mixture
through coffee filter paper.
Leaving Cert Biology
Section 2.5 Genetics
Step 7
Add 2-3 drops of protease enzyme
to 10 ml of the onion extract.
Leaving Cert Biology
Section 2.5 Genetics
Step 8
Very carefully, pour 10 ml of ice cold ethanol
onto the surface of the onion extract.
Leaving Cert Biology
Section 2.5 Genetics
Step 9
DNA forms at the interface of the
ethanol and extract.
Leaving Cert Biology
Section 2.5 Genetics
Step 10
Draw the DNA out of the solution
by wrapping it around a glass rod.
Leaving Cert Biology
Section 2.5 Genetics
Leaving Cert Biology
Section 2.5 Genetics
Leaving Cert Biology
Section 2.5 Genetics
2.5.4 DNA Profiling
• DNA Profiling is the method of cutting up a persons
DNA into fragments that can be used to make a
pattern of bands that are unique to each person.
Leaving Cert Biology
Section 2.5 Genetics
2.5.4 DNA Profiling
1. Cells are broken down
to release DNA
2. DNA strands are
cut into fragments
using enzymes
4. The pattern of fragment
distribution is analysed.
3. Fragments are
separated on the
basis of size
Leaving Cert Biology
Section 2.5 Genetics
DNA Profiling applications
• Can be used to investigate crimes!
A DNA profile can be made form
blood , semen, hair, saliva
sample found at a crime scene.
The DNA profile can then be
compared to victims and
suspects DNA profiles in a crime
case
Leaving Cert Biology
Section 2.5 Genetics
DNA Profiling applications
• Can be used to resolve medical issues!
Paternity and maternity cases
resolved by comparing child's
DNA profile with parent DNA
profile.
Each band in a child's profile
must match a band form the
either the mother or the
father’s profile.
Leaving Cert Biology
Section 2.5 Genetics
Check your learning..
• What DNA Profiling is
• How DNA profiling is done (4 steps)
• Why DNA profiling is used – 2 examples
Leaving Cert Biology
Section 2.5 Genetics
Genetic screening
Def Genetic screening is doing diagnostic tests on an
organism to identify the presence or absence of changed
genes.
Foetal screening
or
Adult screening!
But could It cause the
potential for
discrimination??
Leaving Cert Biology
Section 2.5 Genetics
Cystic fibrosis
Leaving Cert Biology
Section 2.5 Genetics
Albinism
Leaving Cert Biology
Section 2.5 Genetics
DNA Replication
Leaving Cert Biology
Section 2.5 Genetics
Brainstorm
• Why do cells need to divide?
• What happens to a cell during its
interphase stage?
• What are the names of the 4 stages in
Mitosis?
Leaving Cert Biology
Section 2.5 Genetics
Mitosis
2.3.4 Mitosis
Interphase
• Def Mitosis is the division of the nucleus to produce two
daughter nuclei, containing identical sets of chromosomes.
Daughter nuclei with
chromosomes identical
to parent cell
Revision of Mitosis
Leaving Cert Biology
Section 2.5 Genetics
Mitosis: Stage 1
•The chromatin shortens, thickens and double stranded
chromosomes become visible in the nucleus.
•The Nuclear membrane breaks down
:
•Fibres are formed
Cell membrane
Double stranded
chromosomes
Fibres
Nucleus
Revision of Mitosis
Nuclear
membrane
Leaving Cert Biology
Section 2.5 Genetics
Mitosis: Stage 2
• Fibres attach to the chromosomes.
• The chromosomes line up along the centre of the cell.
Revision of Mitosis
Leaving Cert Biology
Section 2.5 Genetics
Mitosis: Stage 3
• Chromosomes are pulled apart to opposite ends of the cell
Chromosomes
pulled apart
Revision of Mitosis
Leaving Cert Biology
Section 2.5 Genetics
Mitosis: Stage 4
• A nuclear membrane forms around each set of new
chromosomes and the cell divides in two
Cell divides in two
Revision of Mitosis
Leaving Cert Biology
Section 2.5 Genetics
Leaving Cert Biology
Section 2.5 Genetics
Replication of DNA
• During the Interphase stage of the cell cycle each
chromosome in the nucleus makes a copy of itself.
Leaving Cert Biology
Section 2.5 Genetics
Replication of DNA – stage 1
(1) The double helix unwinds and the DNA strands separate.
Leaving Cert Biology
Section 2.5 Genetics
Replication of
DNA – stage 2
• Base pairing occurs between
the bases on the original
strands of DNA and new free
bases that enter the nucleus.
• New complementary strands
of DNA are formed alongside
original strands.
Leaving Cert Biology
Section 2.5 Genetics
Replication of DNA – Stage 3
• Two new double helixes of DNA
are made – each identical to the
original DNA double helix and
each other.
• Each new DNA double helix is
made up of:
½ old DNA and ½ new DNA!
Leaving Cert Biology
Section 2.5 Genetics
Check your learning..
• What happens during interphase in the cell cycle
• What forces hold DNA strands together usually?
• During which stage of DNA replication do the strands
separate?
• What does complementary mean?
• Where do the extra bases come from to make the new
strands?
• How do new DNA strands compare to the original strand
and to each other?