Study-Term 2 Flashcards
Genetics
Studies heredity
Heredity is the passing of traits from parents to offspring this involves 2 nucleic acids, DNA and RNA
The big picture
A living organisms is made up of cells which contain in the nucleus chromosomes with contain genes which are made up of DNA
Genes
Genes are a region of DNA made of nucleotides which contain the information to produce a protein or functional RNA molecule
DNA
a nucleic acid located in the nucleus of the cell, double stranded, it’s role is to store coded instructions about how to make proteins, directs cell division, growth and function, the main part of chromosomes
RNA
nucleic acid, located in the nucleus of the cell, single stranded, it’s role is to copy the DNA and create proteins from the DNA’s instructions
DNA structure
Nucleotides are the building blocks of DNA and RNA
nucleotides consist of a five carbon sugar a phosphate group, and a nitrogen containing base, double stranded helix
Components of DNA
DNA and RNA are made up of three parts:
- Sugar- makes up part of the backbone
- Phosphate groups- forms the other part of the backbone
- Nitrogenous bases- bond nucleic acids together (Adenine, guanine, thymine/uracil and cytosine)
Nucleotide
A sugar, phosphate and base
DNA is made up of a series of nucleotides
Nitrogenous bases
there are four bases in a strand of DNA Adenine Thymine Guanine Cytosine
How do the nitrogenous bases pair up
Adenine + thymine
Guanine + cytosine
What is held together by hydrogen bonds
The 2 sides of the ladder
DNA structure (just like a ladder)
The rails of the ladder are represented by the alternating deoxyribose and phosphate
The pairs of bases ( cytosine-guanine or thymine-adenine) form the steps
The process of replication
DNA has the unique ability to make an exact copy of itself
Why does DNA need to replicate before cells divide?
So that the 2 daughter cells have identical copies of DNA
Helicase
Breaks Hydrogen bonds (unwinds and unzips the 2 strands)
DNA polymerase
Adds complementary nitrogenous bases
RNA primase
Adds a primer to each nitrogenous bases
Ligase
Fills gaps in lagging strands and glues the strands together
Lagging
Built in fragments called Okazaki fragments 3’ to 5’
Leading
Built continuously in 5’ to 3’
Karyotype
a ‘map’ of what chromosomes are contained in the nucleus of a particular organisms cells
Body cells
46 chromosomes
Types of chromosomes
The sex chromosomes determine whether you are a boy (xy) or a girl (xx)
The other chromosomes are called autosomes
6 stages of mitosis
Interphase Prophase Metaphase Anaphase Telophase
Interphase
The normal state of the cell (the resting state)
The cell is coping it’s DNA preparing for division
Prophase
Pro=before
The cell is preparing to divide
Chromosomes become visible and pair up
Spindle divers emerge from centrosomes
Metaphase
M=middle
Centrosomes move to opposite poles of the cell
Mitotic spindle is fully developed
Chromosomes have lined up
Spindle divers are attached to each sister chromatid
Anaphase
A=away
Chromatids seperate and are pulled toward opposite poles
Spindle finer lengthen making the cell longer
Telophase
T=two
Chromosomes arrive at opposite poles
Nuclear envelope forms around each set of chromosomes
Mitotic spindle breaks down
Genome
An organisms complete set of DNA including all of its genes. Each genome contains all of the information needed to build and maintain that organism. Protein synthesis is the process in which cells make proteins. It occurs in two stages: transcription and translation
Transcription
Transcribes the DNA into a message (MRNA), occurs in the nucleus, initiated by RNA polymerase, Delivers MRNA out of the nucleus into the cytoplasm to find a ribosome(protein factory) to begin translation. RNA uses the base ‘uracil’ instead of thymine
Translation
The process of creating proteins from an MRNA template. The sequence of nucleotides on the RNA is translated into the amino acid sequence of proteins and this reaction is carried out by ribosomes
Translation
MRNA bases—>3 bases=codon—>amino acid—>protein
Codon
Made up of a series of three bases each bases carry a code for a particular amino acid when a chain of amino acids are put together this creates a protein
In transcription
a DNA sequence is rewritten or transcribed into a strand of MRNA it is intimated by RNA polymerase and occurs within the nucleus of a cell to be delivered out into the cytoplasm to a ribosome
In translation
The sequence of the MRNA is decided in the rRNA by the tRNA to create the. Amino acid sequence of a polypeptide (protein chain)
In an MRNA
The instructions for building a protein are in the form of RNA nucleotides (As,Us,Cs,Gs) read in group of threes called codons
Gene mutations
To do with base pair sequence
- substitution: wrong base match
- insertion: extra base added
- Deletion: base is removed
Chromosomal mutations
- Duplication
- Deletion
- Inversion
- Translocation
Mutations
Changes in DNA and or RNA sequence is called a mutation. Mutations may be beneficial, detrimental or have no effect
Cause of mutations
Occur when mistakes are made during DNA replication or transcription
Anything in the environment that can cause a mutation is called a mutagen
Body-cell vs Sex-cell mutations
Somatic (body) cell mutations are not passed in to the next generation
Mutations that occur in sex cells are passed on to the organisms offspring and will be present in every cell of the offspring
Chromosomal mutations occur
The process when chromosome 21 does not seperate from its duplicate partner meaning during meiosis it leaves one cell with too many cells and another with not enough
Proteins
Responsible for the physical expression of genes and the phenotypic characteristics or traits such as eyecolour
Alleles
Genes occupying the same position on homologous chromosomes
Homologous chromosomes
A set of one maternal and one paternal chromosome that pair up with each other inside a cell during fertilisation
Maternal
Chromosome from mum
Paternal
Chromosome from dad
One allele comes from the mother and the other from the father
Traits
Treats can be expressed as either being heterozygous or homozygous
Homozygous traits
An organism carries two of the same alleles
Heterozygous traits
An organism carries one of each type of Allele for a particular trait
Genotype
Refers to its genetic make up
Phenotype
The phenotype of an organism refers to its observable features or traits
Recessive
Lowercase letter
The allele that is dominated over is called the recessive gene
Dominant
Uppercase letter

What determines the phenotype
Most gene pairs exist with one of the pair being dominant over the other
Punnet square
Is a chart that allows you to determine the expected percentage of different genotypes in the offspring of two parents each parent provides two gametes for the grid
Haemophilia
When clotting factors don’t work and someone bleeds continuously
Pedigree chart
Square= male circle= female Shaded= a trait that is being tracked
Modes of inheritance
Autosomal dominant
Autosomal recessive
X-linked dominant
X-linked recessive
Autosomal dominant
The gene is dominant and is located on one of the autosomes (non-sex chromosomes)
If both parents are affected (shaded)and an offspring is affected the trait must be dominant (both parents are heterozygous)
All affected individuals must have at least one affected parent
Autosomal recessive
Inheritance the gene is recessive and is located on one of the autosomes (non-sex chromosomes)
If both parents are unaffected and an offspring is unaffected the trait must be recessive (parents are heterozygous carriers)
X-linked dominant
If a male shows a trait so too must all daughters as well as his mother
And unaffected mother cannot have affected sons (or an affected father)
X-linked recessive
If a female shows a trait so too must all sons as well as her father
An unaffected mother can have affected sons if she is a carrier (heterozygous)
X-linked recessive trait tend to be more common in males
How to determine mode of inheritance on a pedigree
- Determine if it is dominant or recessive
- Determine if it is autosomal or sex linked
- Assign genotypes to affected (shaded) individuals first
- Double check your work (use a punnet square) does the pedigree make sense

Evolution
All species of organisms arise and develop through the natural selection of small inherited variations that increase the individuals ability to compete, survive and reproduce
Microevolution
Describes a change in gene frequency within a population over a succession of generations. it is responsible for minor changes within species
Macroevolution
The change in the variation of allele frequencies at or above the level of species over geological time. it is responsible for the long-term development of new species
Darwins key observation
- All living things produce more offspring then survive to adult hood
- in spite of this population size remain roughly constant
- variation exist among species
- Characteristics can be passed on from one generation to the next
Darwins conclusion
Species evolve over a long period of time by a mechanism called natural selection the main evidence for this is from fossil records
Process of natural selection
1) each species shows variation
2) there is a competition within each species for food living space water mates
3) The better adapted members of the species are more likely to survive survival of the fittest
4) The survivors will pass on the better genes to their offspring who will also show this beneficial variation
Phenotypic selection
Two concepts are basic to the modern theory of evolution
mutations cause variability in the phenotype of a population
natural selection acts on the phenotypic variability of a population
Natural selection
The more viable an organism the greater chance it has to survive and therefore produce offspring this means an organism that is more fit for the environment is able to produce a greater number of viable offspring they have greater fecundity (enhanced production)
Biological fitness
Determined by not how long they live but by how many offsprings they have
Effects of a new allele on the fitness of a population
No effect
negative effect
positive effect
Do you alleles does appear as a result of natural selection
No they become recessive
Stabilising phenotypic selection
Natural selection by particular characteristic that maintains consistency of a population occurs in times of environmental stability they give a normal distribution curve and favours the intermediate types of traits
Directional phenotypic selection
Favours the emergence of new phenotypes it will shift the normal distribution in either direction
Distributive phenotypic selection
A situation where there is an increase in the frequencies of the extreme types in a population and the intermediate types are limited it will shift the normal distribution into a bimodal distribution
Cladogram
A diagram used to illustrate common ancestry and evolution however it does not show how ancestors are related to descendants
Patterns of diversity
Populations and species involve not individuals changes in the gene pool are the evidence of evolution not mutations within a gene pool
Divergent evolution
Occurs when a population of interbreeding organisms diverges into two or more descendent species
Two forces can drive divergent speciation a mass extinction that provides new niches for surviving species and geographic isolation
Convergent evolution
Different species demonstrate similar adaptions to similar ecological niches in different locations they have evolved similarities in phenotype but remain distinct species that do not interbreed
Parallel evolution
Occurs when two species that once shared a common ancestor are exposed to similar environmental pressures despite the geographical isolation as a result similar phenotypic features are selected
Parallel vs convergent
Common ancestor vs two different ancestors
Coevolution
Result in simultaneous phenotypic adjustments between community members. When two species are very reliant on each other each species exert a strong selective force on the other these interactions are mainly between predator or parasite and pray
Speciation
The process by which new species are formed
The modes of speciation
allopatric
Sympatric
Pararpatric
allopatric speciation
when two populations of the same species become isolated from each other due to geographic changes
parapatric speciation
Occurs when subpopulations of the same species are mostly isolated from each other but have a narrow area where their ranges overlap
Sympatric speciation
New species emerge from populations living in highly overlapping or even identical areas
