B6-Inheritance, variation and evolution Flashcards
What are the 2 different types of reproduction?
Sexual and Asexual
What does sexual reproduction involve?
2 parents with seperate gametes-the fusion of male and female gametes
What does asexual reproduction involve?
Reproduction with 1 parent
What process occurs in sexual reproduction?
Meiosis to form the gametes
What process occurs in asexual reproduction?
Mitosis
What are the characteristics of asexual reproduction?
- It involves 1 parent only
- Gametes are not produced
- Offspring are genetically identical to the parent
- The cell division are only mitotic
- Fast reproduction
What are the characteristics of sexual reproduction?
- Involves 2 organisms
- Gametes are produced by the organisms
- Offspring show genetic variation
- Gametes are produced by meiotic divisions and zygote develops by mitotic division
- Comparatively the number produced is low
What is the process of meiosis?
The genetic material is copied and then the cell divides twice to form four gametes, each with a single, unique set of chromosomes
What are the characteristics of Mitosis?
- Copies of chromosomes are made
- Adult cells are made
- Cells produced are genetically identical
- Cells divide once
- Cells contain the same number of chromosomes as the original cell
- Used in Asexual reproduction
What are the characteristics of Meiosis?
- Copies of Chromosomes are made
- Sperm and egg cells are made
- Cells produced have variation
- Cells divide twice
- Cells contain half the number of chromosomes as the original cell
- Used in sexual reproduction
How do malaria parasites reproduce?
- Sexually in mosquitos and Asexually in their human host
How do fungi reproduce?
Mostly asexually by spores but can also reproduce sexually for variation
How do plants reproduce?
Mostly sexually with pollen and plant eggs however can also reproduce asexually e.g. by runners or bulb division
What is the structure of DNA?
A phosphate connected to a pentose sugar connected to an organic base (either A, T, C or G)
What is a base in DNA also called?
A nucleotide
What are the combimations of bases?
A&T or C&G
What is the code for a single amino acid?
A sequence of 3 bases
What do amino acids do?
Code for a particular protein
How is protein synthesis carried out?
1) A template strand of the DNA is made in the nucleus
2) The template strand leaves the nucleus and binds to a ribosome
3) The cytoplasm contains carrier molecules, each attached to a specific amino acid
4) The carrier molecules attach themselves to the template strand using complementary codes
5) The amino acids on the carrier molecules are joined together to form a specific protein
6) Carrier molecules keep bringing specific amino acids to add to the growing protein in the correct order until the template is complete
7) Once complete the protein detaches from the carrier molecules and folds to form a unique shape that will enable it to carry out its functions in the cell
What is it called when a gene codes for a protein that is synthesised in a cell?
The gene is expressed
How are mutations caused?
By the active site of proteins changing
What are different forms of the same gene called?
Alleles
What does Homozygous mean?
2 copies of the same alleles e.g. aa, AA
What does Heterozygous mean?
2 different alleles for the same characteristics e.g. Aa, aA
What does Genotype mean?
The alleles present or genetic makeup of an individual regarding a particular characteristic
What does Phenotype mean?
The physical appearance of an individual regarding a particular characteristic-genotype + environment
When is a dominant allele expressed?
When one or both alleles are dominant
When is a recessive allele expressed?
When both alleles are recessive
Is polydactyly dominant or recessive?
It’s dominant
Is cycstic fibrosive dominant or recessive?
Its recessive
What are the symptoms and treatments of polydactaly?
Symptoms: an extra finger or toe
Treatments: surgery to remove the extra digit
What are the symptoms and treatments of cyctic fibrosis?
Symptoms: persistent coughing, frequent lung infections, shortness of breath, mucus build up, poor growth, weight gain
Treatments: Antibiotics to prevent chest infections. physiotherapy
What are the 3 methods to screen embryos?
- Amniocentesis
- Chorionic villus sampling
- Pre implantive screening
How does amniocentisis work?
It involves taking some of the fluid from around the developing fetus at 15-16 weeks of pregnancy-containing fetal cells, which can then be used for genetic screening.
How does chrionic villus sampling work?
It involves sampling embryonic cells between 10-12 weeks of pregnancy by taking a small sample of tissue from the developing placenta.
How does pre implantive screening work?
It involves embryos produced by IVF to be tested before they are implanted in the mother-usually only done when the parents have a genetic disorder.
What are the advantages and disadvantages of amniocentisis?
Advantages: It can diognose certain birth defects, is highly accurate and can detect down’s synodrome.
Disadvantages: Increased chance of miscarriage, risk of infection, possibility of being past the date of abortion.
What are the advantages and disadvantages of chorionic villus sampling?
Advantages: It can get quick results as it is a fast procedure.
Disadvantages: Risk of infection, Can’t detect all issues, Increased chance of miscarriage
What are the advantages and disadvantages of pre implantive screening?
Advantages: Can reduce the chance of a miscarriage over the age of 36, Can help select known defects
Disadvantages: Not possible for normal contraception, very expensive-£10,000, no guarantees that it will work, ethical issues with ‘designer babies’
What is variation?
The differences in the characteristics of an individuals in a population
How does evolution by natural selection work? (5)
1) Mutation of DNA leading to variation within a population
2) Advatageous characteristic (phenotype)
3) Organism is more likely to survive and breed
4) Allele is passed on to its offspring
5) Frequency of the allelle/ characteristic in the population increases
How can evolution lead to new species?
If they can no longer interbreed to produce fertile offspring
What is selective breeding?
Breeding different plants and animals for desired characteristics
What are the issues with selective breeding?
There may be defects in some animals due to a lack of variation-this most often stems from inbreeding
What does Transgenic mean?
Genes from more than one place
What is the process of genetic engineering to create insulin? (6)
1) A Plasmid is taken out of a bacterium and a section of DNA is cut out using restriction enzymes-the DNA section is said to have ‘sticky ends’
2) The insulin gene is cut out of a human cell’s DNA using an enzyme-has ‘sticky ends’
3) The gene for insulin is inserted into the plasmid
4) Modified plasmids are put back into the bacterial cell-now transgenic
5) The bacteria multiply many times
6) The insulin is harvested and bottled
What are crops called that are genetically modified?
GM crops
What are clones?
Organisms that are genetically identical to one another
What are the 3 methods of cloning?
- Plant cuttings
- Embryo transplants
- Adult cell cloning
How do plant cuttings work?
Part of the plant is removed, a rooting hormone is added and the plant is added to soil.
How do embro transplants work?
- The egg is fertilised via IVF
- The egg grows into an embryo
- The embryo cells are seperated
- Each cell grows into a new embryo
- Each embyo is implanted into different surrogate mothers (given hormones to help them get ready for pregnancy)
- Identical cloned offspring are born
How does adult cell cloning work?
- A cell is taken from the animal (not a red blood cell)
- The nucleus is extracted from the cell and the cell is disposed of
- An unfertilised egg is taken and the nucleus is removed
- After the nucleus is inserted in the unfertilised egg cell electric shocks cause the egg to start dividing to form a ball of cells
- The embryo is placed into the womb of another animal to develop.
What are the advantages and disadvantages of plant cuttings?
Advantages:
* Cheap
* Fast
* Efficient
Disadvantages:
* Only works in plants
* Disease can spread
What are the advantages and disadvantages of embryo transplants?
Advantages:
* Can test the embryo for genetic disease
Disadvantages:
* Unethical
* Forcing females to be a surrogate
* Very expensive
What are the advantages and disadvantages of adult cell cloning?
Advantages: Provides an identical clone of any age
Disadvantages: Clones created will be a baby
What are the causes of extinction?
- Habitat destruction
- Introduced species
- Hinting and fishing
- Environmental change
- Extinction of a species from a food chain/web
Who came up with the theory of organisms changing in their lifetimes?
Jean-Baptiste
Why did people object to Darwin’s theory of evolution?
- It conflicted with the ideology that god made all life
- There was insufficient evidence
- There was no mechanism for explaining variation and inheritance-genetics weren’t understood until 50 years later
How do species come about?
- Isolation
- Natural selection
- Speciation
Who developed the theory of speciation?
Alfred Russel Wallace
How are fossils formed?
1)The reptile dies and falls to the ground
2)The flesh rots leaving the skeleton to be covered in sand or soil and clay before it is damaged
3)The skelaton becomes mineralised and turns to rock
4)Eventually the fossil emerges as the rocks move and erosion takes place
What is an example of a bacteria that has turned resistant?
Staphylococcus aureas-turned to MRSA (Methicillin Resistant Staphylococcus Aureus)
What is classification?
The organisation of living things into groups according to their similarities
Who is regarded as the ‘father of classsification’?
Carl Linnaeus
Who created the 3 domains system?
Carl Wouse
What are the rules for writing scientific names?
- The first name (genus) is written with a capital letted
- The second name (species) is written witb a lower case letter
- The 2 names are underlined if written, in italics if printed
What is the order of classification from largest to smallest?
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
What are archaea?
Primitive forms of bacteria that include the extremophiles
