B5 - Genes, Inheritance and selection Flashcards
Definitions of: Genome Chromosomes Gene Alleles
Genome: all the genetic material of an organism
Chromosomes: Long coiled up molecule of DNA which humans have 23 pairs (46 in total) and contains many genes
Gene: a short section of DNA that codes for a protein
Alleles: Different variations of the same gene
Genotype vs phenotype:
Genotype: All the genes and alleles an organism has
Phenotype: the gene that the organism displays -> the characteristic expressed
Mutations in coding DNA vs non coding DNA?
Mutations in coding DNA:
- affects the protein coded for by the gene
Mutations in Non-coding DNA:
- affects how genes are expressed - whether or not the gene is ‘switched on’
Difference between mitosis and meiosis?
MITOSIS:
- Occurs all over the body for growth and repair - replacing cells that need replacing and makes new cells
- 1 division event
- Produces genetically identical cells (produces diploids)
- fertilised egg (zygote) undergoes mitosis into an embryo
46 chromosome original cell -> splits into two cells with 46 chromosomes (diploid)
MEIOSIS:
- Only for gamete (sex cell - sperm and egg) production
- 2 division event
- Produces cells which are not genetically identical (produces haploids)
46 chromosome original cell -> splits into two cells with 46 chromosomes (diploid) -> the two diploid cells split again into cells with 23 chromosomes (haploid cells)
Steps to meiosis:
1) Before cell divides, it duplicates its DNA
2) In the first division, the chromosomes line up in pairs in the centre of the cell and are pulled apart
3) Mixing; chromosomes from the father and mother mix creating variation
4) Chromosomes pull to opposite ends of the cell and cell divides
5) Genetically different gamete cells with 23 chromosomes formed
Advantages and disadvantages of asexual reproduction and sexual reproduction?
ASEXUAL REPRODUCTION:
Advantages:
- Can produce offspring very quickly
- One parent is needed - reproduce when conditions favor them
Disadvantages:
- No genetic variation, if the environmental conditions change, the whole population will be affected
SEXUAL REPRODUCTION:
Advantages:
- Creates genetic variation between offspring, so if the environmental conditions change, it is more likely that some individuals can survive, leads to evolution and better adapted species
Disadvantage:
- Takes more time and energy so organisms produce less offspring in their lifetime
- Two parents are need for reproduction
Definitions of Dominant allele Recessive allele Homozygous Heterozygous
Dominant allele: Only one allele is needed for characteristic to be expressed
Recessive allele: Two alleles are needed for characteristic to be expressed
Homozygous: If you have two alleles the same for that particular gene eg. (BB)
Heterozygous: If you have two different alleles for that particular gene eg. (Bb)
Plummet squares
- Predict the probability of the offspring obtaining a characteristic
How to draw it?
1) Draw 4 squares
2) Outside the squares label the parents genotype
3) Pair up the parents genes and fill in the 4 square
DRAW IT
What is artificial classification?
A classification system only reliant on observable features to place organism into groups - such as whether they lay eggs or fly
What is natural classification?
Is a method of classification based on evolutionary relationships
What is the 5 kingdoms?
Plants Animals Fungi Protists Prokaryotes
What is the Hierarchical classification system?
Kids Prefer Candy Over Fancy Green Salads
Kingdom Phylum Class Order Family Genus Species
How to form a binomial name?
Binomial name = Genus + species
Genus = capital Species = lower case
E.G: Genus = lemur
Species = catta
Binomial name = Lemur catta
Species definition?
A group of organism that can breed with each other to produce fertile offspring
What is phylogenetics?
- a diagram which shows evolutionary relationships
- the branches on a phylogeny show a common ancestor
- species which are closer together are more closely related
Definition of:
Adaptation
Evolution
Adaptation: characteristics which enable survival and makes an organism suited to its habitat
Evolution: The gradual change in inherited characteristics of a population over time through the process of natural selection
3 ways a genetic variation is created in a population?
1) Mutation: spontaneous and natural change in sequence of bases in DNA.
2) Sexual reproduction: Two organism are required to produce an offspring. This produces new variations of genes
3) Meiosis: Produces genetically different gametes. All gametes are different to each other creating new variation of genes
Evolutionary sequence?
1) A population of organisms show variations. Not all organism are the same
2) Environmental changes
3) Some of the organism die and those with the best adaptations survive
4) The survivors are more likely to reproduce and pass on their genes
5) Their offspring inherit their characteristics which help them better survive
What scientist discovered the natural selection theory?
Darwin discovered the theory - he proposed that organisms adapt over generations
Lamarck - believed that characteristics can be adapted in a lifetime
Why might extinction occur?
- New disease
- New predators
- More successful competitors
- Changes to the environment over geological time - like climate change
- A single catastrophic event - like an asteroid
Extinction occurs when there is a change in the environment which is too large or rapid for species to adapt
What is the evidence for evolution?
Fossils
- The deeper the rock containing a fossil, the older the fossil
- We can use this to chronological order fossil and changes in characteristics over time
how does bacteria become antimicrobial?
1) Bacteria has variation - some bacteria has an antimicrobial gene and some don’t
2) You take the antimicrobial drug
3) Bacteria without the antimicrobial gene are killed while the bacteria with the antimicrobial gene survive
4) The resistant bacteria are now more common and reproduce more - this passes on the gene to the offspring
5) You take the drug again and it won’t work as all the bacteria are more resistant
How has evolution helped modern biology?
Classification - more accurate as it is based more on evolutionary relationships
Antibiotic resistance - know the important of finishing a course to prevent resistant bacteria spreading
Conservation - understand the importance of genetic variation to help populations adapt to the changing environment
How are seed banks protecting biodiversity?
- seed bank stores lots of seeds - therefore genetic material.
- If a plant becomes extinct in the wild the stored seeds can be used to cultivate new seeds and protect biodiversity
How do we know if a person is male or female by looking at chromosomes?
-We look at the last pair of chromosomes (the gender chromosomes)
Females at birth have XX chromosomes (they look the same)
Males at birth have XY chromosomes (they look different)
Ethics of embryo screening?
- There is risk on the child which haven’t been consented to
- If baby has genetic illness it could promote abortion which some may disagree with
Genetic, environmental or both characteristics:
GENETIC: Natural eye colour, Natural hair colour, Blood group
ENVIRONMENTAL: scars, tattoos, Hair length
BOTH: Weight, Height
Why don’t we have a complete fossil record?
- Most early organisms were soft bodies (don’t fossilise)
- Fossils may have been destroyed
- Traces (eg footprint) can be destroyed
- conditions for fossilisation are rare
