Inheritance, Variation and Evolution - 6 Flashcards
What is the simple idea behind evoluion? (E IVE Bi)
through the process of natural selection, all species of living things have evolved from simple life forms over a period of time.
Main points of evolution: (E IVE Bi)
- Individuals show variation, because of differences in genes.
- ‘survival of the fittest’ - individuals with characteristics most suited to the enviroment are more likely to survive + reproduce. passed onto offspring so characteristics become more comman.
- poorly adapted are unlikely to survive and pass on genes
- over a period of time a species will gradually eveolve
- genes and enviroment can cause variation, only genetic information can be passed on through offspring.
- if two populations of the same species become increasingly different in phenotype (physical characteristics) that they can no longer bread to form fertile offspring, this can produce two new species.
e.g peacocks.
Who proposed the theory of evolution by natural selection? (E IVE Bi)
Alfred Russel Wallace
What year did Darwin and Wallace produce scientific journals together? (E IVE Bi)
1858
Who worked out the structure of DNA and when? (DNA IVE Bi)
James Watson and Francis Crick in 1953
What structure is DNA in?
A dounle helix
What is the DNA structure made out of? (DNA IVE Bi)
DNA is a polymer which is made from four different nucleotides, each of these bases are attached to one sugar and each sugar is attached to a phosphate.
How are the four nucleotides in DNA arranged in? (DNA IVE Bi)
Arranged in a repeating fashion.
What are the four different bases in DNA? (DNA IVE Bi)
- THymine T
- Adenine A
- Guanine G
- Cytosine C
What is complementory base pairing? (DNA IVE Bi)
There are chemical cross links between the two strands of DNA, formed by pairs of bases. They always pair up in a particular way.
What are the two pairs of bases? (DNA IVE Bi)
Thymine and adenine (T-A)
Guanine and Cytosine (G-C)
What forms a code for a particular amino acid? (DNA IVE Bi)
A sequence of three bases. know as a triplet or the triplet code.
What is a mutation and can it be inherited? (M V Bi)
Mutation is a change in a gene or chromosome (base). It is a rare, random change in the genetic material and it can be inherited.
Mutations can be sponatanious but can also happen because of: (M V BI)
- ionising radiation
- chemical mutagens (tar from cigarette smoke)
What are the ionising radiation, and what does the dose mean for the chances of cell mutaion? (M V Bi)
- gamma rays
- X-rays
- ultraviolet rays
the greater the dose of raditation a cell gets, the greater the chance of mutation
What can mutations do to some genes and an example? (M V Bi)
- cause different genes to be switched on or off
- this could create a different or faulty gene to be synthesised
- if a protein is an important enzyme _ the specific substrate might not fit into the substrate binding site
- if it a structural protein like collagen _ it may lose its strength
What does a change from the normal order of bases lead to? (M V Bi)
different types of gene mutation. as the bases are read in the triplet code, it may result in a different amino acid being synthesised, and a different protein.
What does the shape of a protein do? (M V Bi)
Determines its function
Why is it that some mutations don’t change the amino acid sequence? (M V Bi)
Different base triplets can encode for the same amino acid (most of mutations are like this) so it doesn’t change its function.
What does a mutation do in a non-coding part of the DNA and a dangerous example? (M V Bi)
Can affect how genes are switched on and off
Example : a cell could produce a protein that it is not meant to have at that time. This could cause uncontrolled mitosis leading to cancer.
What does a mutation do in a non-coding part of the DNA and a dangerous example? (M V Bi)
Can affect how genes are switched on and off
Example : a cell could produce a protein that it is not meant to have at that time. This could cause uncontrolled mitosis leading to cancer.
What is Cystic Fibrosis? (ID V Bi)
an inherited disorder of cell membranes that mainly affects the lungs and digestive system. The membranes can become clogged with lots of thick, sticky mucus as too much is produced.
After years, the kungs become increasingly damaged and may stop working properly.
Average life expectancy is reduced despite a number of available treatments.
What causes Cystic Fibrosis? (ID V Bi)
a faulty recessive allele on chromosome 7.
What does a recessive allele mean for the chances of inheriting the disorder? (ID V Bi)
- a child born has to have inherited two of the faulty genes. 25%.
- Parents are likley not to have the disorder.
What type of allele allows a child to develop cystic fibrosis? (ID V Bi)
only homozygous people with the recessive allele
What makes a person a carrier of cystic fibrosis? (ID V Bi)
heterozygous people. They carry the recessive allele but will not develop it nor have any symptoms
What is Polydactyly and what type of allele is it caused by? (ID V Bi)
inherited condition when someone has extra fingers or toes. It is caused by a dominant allele of a gene.
What type of people with develop Polydactyly? (ID V Bi)
both homozygous and heterozygous people will develop it. DD Dd. not dd. offspring only need one dominant allele to inherit the condition. so its 75%
What is a genetic test? (ID V Bi)
analysis of a person’s DNA to see if they carry alleles that cause genetic disorders. They can be done in any stage in a person’s life.
What are the three types of genetic test? (ID V Bi)
- ANTENATAL
- NEONATAL
- PRE-IMPLANTATION GENETIC DIAGNOSIS
What is Antenatal testing? (ID V Bi)
- testing is used to analyse an individual’s DNA or chromosomes before they are born.
- offered to couples who may have an increased risk of producing a baby with an inherited disorder
- it can’t detect all the risks of inherited disorders.
What is Neonatal testing? (ID V Bi)
- testing known as the new born blood spot test.
- involves analysing a sample of blood that is taken from pricking a babies heel. It detects an inherited disorder in order to treet it early
What is Pre- Implantation genetic diagnosis? (ID V Bi)
- used on embryos before implantation.
- fertility drugs stimulate the release of several eggs
- the eggs are fertilised in a Petri dish. This is known as in vitro fertilisation (IVF).
- Once the embryos have reached the eight cell stage, one cell is removed.
- The cells are tested for the disorder causing alleles.
- Embryos that don’t contain the disorder allele are implanted into the uterus.
What does a Pedigree Analysis Chart show? (FT V Bi)
how genetic disorders are inherited in a family. It can be used to work out the probability that someone in a family will inherit a condition.
When is Pedigree Analysis usually undertaken? (FT V Bi)
If families are reffered to a genetic counsellor following the birth of an affected child.
What is the simple process of genetic engineering? (GE VE Bi)
- genes from one organism are cut out and transferred to cells of a different organism e.g bacteria
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> the genome of the bacteria is modified and now includes a human gene.
What is the example of genetic engineering? (GE VE Bi)
Insulin
What is the method for insulin genetic engineering? (GE VE Bi)
- Insulin is a hormone ivolved in glucose regulation in humans
– people with type 1 diabetes cannot make their own insulin so they need to inject themselves with it regularly - Bacteria are then genetically modified and contain the human insulin gene.
– They now produce human insulin which can then be purified and used for type one diabetes.
What is the simple meaning of GM Crops? (GE VE Bi)
we transfer genes into plants to produce genetically modified Crops and generally, these crops produce a greater yield than normal crops.
What can genetically modified crops do? (GE VE Bi)
- crops that are resistant to disease or insect attack
- produce bigger / better crops
- some are resistant to herbicides which means that farmers can spray their fields with weed killers without causing harm to the crop.
Are genetically modified crops safe? (GE VE Bi)
they can be hramful to insects or wildflowers
What can genetic modification/gene therapy may be able to do? (GE VE Bi)
What are the long-term affects?
treat inherited disorders in humans.
Long term affects are unknown e.d don’t know the effects on other genes
What are the main steps of Genetic Modification / Gene Therapy? (GE VE Bi)
-
IDENTIFICATION
Identify the gene that we want to transfer (human, animal, plant) -
ISOLATION
use enzymes to isolate the gene -
TRANSFERING
transfer this gene into a small circle of DNA called a plasmid, or into a virus. THEN the desired gene is transfered into the cells of the target organism. We do this stage at the early stage of the orgaisms development.
What are plasmids? (GE VE Bi)
These originally came from bacteria and are very useful for transfering DNA from one organism to another.
Why are plasimds and viruses called vectors? (GE VE Bi)
They transfer DNA from one organism to another.
Why do we always transfer the gene at an early stage of the organisms development in Gene Therapy / Genetic Modification? (GE VE Bi)
To make sure that all the cells contain this transferred gene. That way the organism develops with the characteristics that we want.
