Yr 11 biology sac work

Eukaryotes + Prokaryotes :

• eukaryotes are cells of animals, plants and fungi and they contain membrane bound organelles.

• Prokaryotes are bacterial cells that lack membrane bound organelles

• Differences: Eukaryotes have a defined nucleus, while prokaryotes have no true nucleus and their genetic material is located in the nucleoid region.

• Reproduction: Eukaryotes reproduce through mitosis and meiosis whereas prokaryotes reproduce through binary fission

Chromosomes and DNA :

• Chromosome are just long strands of DNA

• Different segments of DNA are called genes which code for particular proteins that make up your body.

• Chromosomes are found in the nuclues of a cell.

• In order of size it goes: nucleotides - genes - long strand of DNA - chromosome - nucleus - cell

• The position of a gene on a chromosome is called the locus.

• Histones are DNA wrapped in protein

• 8 histones with DNA wrapped around them are known as nucleosomes

• Exons = gene coding region

• introns = non coding region

• chromatid = strand of DNA

• centromere a protein that holds sister chromatids together and where the spindle fibres attach during mitosis.

• telomere: a region of repetitive nitrogenous bases at the ends of chromosomes

• gene loci = the location of a certain gene, the same across all organisms of the same species.

Sex chromosomes and autosomes :

• Humans have 22 pairs of homologous chromosomes called autosomes and 1 pair of sex chromosomes.

• Sex Chromosome : XX = female and XY= Male

• Karyotype is a map of an individual set of chromosomes that can be used to identify chromosomal abnormalities and determine the sex of the individual based on the presence of XX or XY.

• Humans have 23 pairs of chromosomes (46 chromosomes)

• They are all organised by size apart from sex chromosomes

• Diploid : A cell or organism that contains 2 complete sets of chromosomes, each side inherited by each parent. (our autosomal cells are diploid containing 46 chromosomes)

• Haploid : A haploid is a cell or organism that contains one complete set of chromosomes. (our sex cells such as sperm or egg cells has a total of 23 chromosomes)

Mitosis:

• Mitosis starts with the cell cycle

• The first step is the interphase G1 or gap 1 where cell growth, protein synthesis and duplication of organelles

• The next step is S or synthesis were DNA is replicated and chromosomes duplicated

• The last step before mitosis is G2 or gap 2 where the cell prepares for mitosis and division

• Mitosis goes through 4 stages PMAT

• First is prophase where chromatin condenses into chromosomes condense so that they are visible showing 92 chromatids or 46 chromosomes

• Next is metaphase where chromosomes line up along the metaphase plate

• Next is anaphase chromosomes break at centromeres and sister chromatids (identical chromatids) move towards opposite poles of the cell

• Lastly, before cytokensis is telophase where nuclear membranes reform around the seperated chromatids which begin to de condense back into chromatin.

• Cytokensis is the last part of the cell cycle where cell division occurs at the cleavage furrow of the parental cell to make 2 daughter cells.

• In plant cells a cell plate froms as the point of seperation

• Cell division is useful for 5 things : reproduction, growth, regeneration, replacement and development

• Interphase takes up 90% of the time and mitosis takes up 10% of the time during the cell cycle

• Cell cycle is the lifespan of a cell

Genes + Alleles =

• Genes are a unit of inheritance

• DNA comes from both parents

• Genes are portions of DNA that code a specific protein

• The Stronger gene controls the trait in the human that is present

• Eukaryotic genes are made up of 2 different regions which or exons or coding regions and introns or non coding regions

• A genome is a collection of all genes

• Genes are a segment of DNA that codes protein

• Alleles are a specific type of gene that controls the trait or an alternate form of genes

• offspring recieve one chromosome from each parent

• Proteomes are a complete set of protein expressed by a cell

• when a dominant allele is paired with a recessive allele the dominant allele determines the characteristic. For a recessive allele to produce a recessive phenotype the individual must have 2 copies one from each parent.

• genotype is the combination of alleles from a gene in our DNA responsible for a particular trait and phenotype is the physical trait that is present.

• Homozygous : When both alleles are the same

• Heterozygous : when both alleles are different

• AA = homozygous dominant, Aa = heterozygous, aa = homozygous recessive

DNA:

• DNA or deoxyribonucleic acid is a long molecule that is comprised of 2 strands that form a double helix making them intertwine.

• DNA is made up of nucleotides (monomers) which have the structure of sugar, phosphate group and nitrogenous base

• There are 4 nitrogenous bases which are: adenine, cytosine, guanine and thymine

• Adenine and thymine pair together and cytosine and guanine pair together with hydrogen bonds

• Purines are Adenine and guanine and they have a 2 ring structure

• Pyrimidines are Cytosine and thymine and they have a singular ring structure

• A must pair with T because they both have the structure for 2 hydrogen bonds

• G must pair with C because they both have the structure for 3 hyrdrogen bonds

• Phosphodiester bonds are the lines connecting the sugar to the phosphate group in a nucleotide which are made up of deoxyribose sugar

Bioethics:

• there are 3 types of ethics

• Consequence based: consideration of the consequences of an action with the aim to achieve maximisation of positive outcomes and minimisation of negative effects.

• Duty/Rule based: consideration of the obligation people have to act in a particular way regardless of the consequences that may be produced

• virtues based: consideration of what a morally “ good “ person would do when carrying out an action

  Bioethics article analysis:

• Integrity : commitment to knowledge, understanding and honest reporting whether results are favorable or not

• Justice: Commitment to consideration of competing claims and the fair access to the benefits of an action

• Beneficence : commitment to maximisation of benefits and minimisation of harm

• Non-maleficence : commitment to not causing harm that is disproportionate to the benefit.

• Respect : commitment to consideration of beliefs, customs and cultural heritage

ACED or area of study, content limits, ethics, data

Karyotypes:

• is a picture of an individuals full set of chromosomes arranged in homologous pairs

• 22 pairs of autosomes and 1 pair of sex chromosomes

• Homologoues pairs : 2 chromosomes that share 3 structural and functional similarities. same size, same gene loci, same centromere position

Cells:

• somatic cells: any cell that isn’t a sperm or egg cell, described as 2n or diploid and has 46 chromosomes

• Gamete cells: formed in gerline cell, sperm and egg cells, are described as n or haploid, have 23 chromosomes

Meiosis:

• meiosis is a process where a single cell divides to produce 4 different cells containing half the original amount of genetic information.

• the daughter cells created are haploid

• recombinant chromosomes are a mixture of parental chromosomes

• Meiosis occurs in germline cells to produce gametes and it has 2 consecutive divisions meiosis 1 and meiosis 2

• Prophase 1: chromosomes condense and become visible. homologous chromosomes pair up and under go crossing over where they switch genetic material which increases genetic diversity

• Metaphase 2 : Homologous chromsome pairs align along the metaphase plate.

• Anaphase 1 : Homologous chromosomes are pulled to opposite poles of the cell

• Telophase 1: Nuclear membranes reform around the seperated chromosomes, followed by cytokinesis, resulting in two haploid daughter cells, each containing one chromosome from each homologous pair.

• Prophase 2 : The chromosomes condense again, and spindle fibers begin to form in both haploid cells.

• Metaphase 2 chromosomes line up individually along the metaphase plate.

• Anaphase 2: sister chromatids are pulled apart to opposite sides of the cell.

• Telophase 2: nuclear membranes reform around the chromatids, followed by cytokinesis. this results in four genetically diverse haploid gemetes.

Genetic variation:

• genetic variation is the diversity present in the DNA of a population

• genetic variation is advantageous as it allows populations to adapt to changing environments.

• if a population has more genetic variation it is more likely that some individuals in a population will possess advantageous traits for their environment

• Sources of genetic variation: genetic recombination which is regrouping of genes during the formation of gametes (during meiosis), sexual reproduction - reproduction involving the fusion of a male and female haploid gene and mutation - environmental changes.

• Crossing over : chromosomal segments are exchanged between a pair of homologous chromosomes

• independent assortment: random distribution of alleles occurring during gamete formation

• The production of sperm and egg cells is called gametogenesis (sperm production = spermatogenesis, egg production = oogenesis)

Non-disjunction:

• non disjunction is the failure of homologous chromosomes or sister chromatids to seperate properly during anaphase 1 or 2 this is because the Centromere hasn’t divided. This could result in cells that have an abnormal number of chromosomes, one having 2 many while the other cell has none. An abnormal number of chromosmes inside of a cell is called aneuploidy.

Sex linked:

• meaning it must be carried on a x or y chromosome

• typically there are more x linked conditions because the x chromosome is much bigger than the y chromosome and therefore can carry more genes

• Sex linked punnett square (x - linked) recessive trait cannot be hidden since there is no second allele, whereas females with their 2nd X get a second chance, only females can be carriers.

• (y - linked) only males are affected, not dominant or recesseve ; have or have not.

Mendelian inheritance :

• law of dominance: in cross of parents that are pure for contrasting traits only one form of the trait will appear in the next generation, offspring that are hybrid for a trait will have only the dominant type trait in the phenotype.

• Law of segregation : During the formation of gametes (eggs or sperm) the 2 alleles responsible for a trait separate from each other. Alleles for a trait are their “recombined” at fertilisation, producing the genotype for the traits of the offspring.

• Law of independant assortment: alleles for different traits are distributed to sex cells and offspring independently of one another.

• Some traits don’t follow the dominant/recessive rules like : codominance, incomplete dominance, multiple alleles, lethal alleles, multiple genes(polygenic) and environmental factors (epigenetic)

• Incomplete dominance : incomplete dominance is where a heterozygous genotype produces a mixed phenotype, influencing the expression of traits as it isn’t clearly one parental gene or the other but a mixed phenotype affecting the offspring.

• codominance : Hetrozygote produces a third phenotype that is a mix of both parental phenotypes and can be clearly seen.

Types of Mendelian inheritance:

• autosomal dominant: only need one copy of the dominant gene for the characteristic to be present e.g AA or Aa

• Autosomal recessive: need both copies of the specific gene for the characteristic to be present e.g aa

• X linked dominant: The dominant gene is located on the x chromosome. only need one copy of the dominant gene to be present e.g XA XA or XA Xa or XA Y

• X linked recessive: the recessive gene is located on the x chromosome, both copies of the gene are required in females but only 1 for males for the characteristic to be present e.g Xa Xa or Xa Y

• Autosomal: meaning that is carried on chromosomal pairs 1-22

• Sex linked: meaning it is carried on either the X or Y chromosomes. Most Sex linked conditions occur on the X linked chromosome as it is bigger and able to carry more genes there fore X linked.

Genetic Crosses:

• Monohybrid cross: a cross between individuals differing in one trait

• Dihybrid cross: a cross between individuals different in 2 traits.

  

Pedigrees:

• Pedigrees are family trees that show the appearance and occurrence of a particular phenotype of a particular gene and how it’s inheritance differs throughout a families generations.

• It allows scientists to track particular traits in a family.

• The roman numerals stand for the generation that that line of descendant is in

• The line of descendant per generation is ordered from left to right in oldest to youngest

Bioethics:

• Consequence Based: The consideration of the consequences of an action with the aim to achieve the maximisation of positive outcomes and minimisation of negative effects.

• Duty/rule Based: The consideration of the obligation people have to act in a particular way regardless of the consequences that may be produced.

• Virtues Based: Consideration of what a “morally” good person would do when carrying out an action

• The 5 values of ethics:

  • Integrity: Commitment to knowledge, understanding and honest reporting whether results are favourable or not.

  • Justice: Commitment to consideration of competing claims and the fair access to the benefits of an action.

  • Beneficence: Commitment to maximisation of benefits and minimisation of harm.

  • Non-Maleficence: Commitment to not causing harm that is disproportionate to the benefit.

  • Respect: Commitment to consideration of beliefs,customs and heritage.

Asexual and Sexual Reproduction:

• Sexual reproduction: Not necessarily by having intercourse; Sexual reproduction is the fertilisation(fusion of male and female gametes) of gametes between 2 parents.

• Hence, making the offspring genetically different because of genetic variation over a long time

• In animals, gametes are sperm and egg

• In plants gametes are pollen and sperm

• Asexual Reproduction: There are no gametes involved, as there is only 1 parent, meaning that there is also no genetic variation, hence making the offspring all genetically identical clones.

• Plants and fungi (some animals) achieve asexual reproduction through mitosis (eukaryotes)

• Bacteria achieves asexual reproduction through binary fission.

Advantages + Disadvantages of Asexual Reproduction:

• Asexual reproduction benefits: Only one parent is needed and it is faster than meiosis.

• Asexual Reproduction Downsides: All offspring are clones with no genetic variation making them more susceptible to disease and there are also less chances for adapting to new conditions.

• Sexual Reproduction Benefits: The offspring can adapt to the environment and there is lots of genetic variation.

• Sexual Reproduction Downsides: It requires finding a suitable partner for mating and it takes a longer amount of time.

Cloning and Reproduction:

• Cloning: The process of producing genetically identical cells, groups of cells or organisms asexually.

• Reproductive Cloning: The process which a human or other organisms is produced which is genetically identical to another human/organism

• Therapeutic Cloning: The first step of reproductive cloning. Carried out by the somatic cell nuclear transfer. Embryonic stem cells from the cloning can be instructed to form bone marrow.

• Ethical Implications:

  • Positives: Treats patients with disease or cancer, failed IVF can be used for treatment, taken prior to the development of embryos so it doesn’t feel pain, risk of tissue rejection reduced.

  • Negatives: Possibly leads to reproductive cloning, destroys embryos, may cause tumours, embryos should have the chance to be a human.

Biological Complexity:

• Living Organisms can be studied at different levels of complexity

  • Biosphere

  • biome

  • Ecosystem

  • Community

  • Population

  • Organism

• Biotic: Living

• Abiotic: Non-Living

• Habitat: A physical place where something lives.

• Niche: A particular role in the environment

Ecological Grouping:

• Producers (Autrophs) : Are organisms capable of producing complex organic compounds from simple inorganic molecules. Through the process of photosynthesis (gaining energy from light) or chemosynthesis (Using chemical energy)

• Consumers (Heterotrophs): Gets energy from outside source. Organisms that receive energy by consuming other organisms. All animals, fungi, protozoans and most bacteria are heterotrophic.

• Decomposers: Organisms that break down organic matter to simple mineral nutrients. Common examples include fungi, worms and bacteria.

• Energy In Food Chains: As you move up in the food chain you progressively get less energy in each trophic level(by 10%)

• Keystone Species: A species that plays a crucial role in the way an ecosystem functions, disproportionate to its abundance.

• Competition: Species compete with each other for finite resources. Occurs when one organism is more efficient in gains that resources.

• Interspecific (Competition between different species)

• Intraspecific (Competition between same species)

• Predation: A predator prey relationship is one in which one species (The predator) kills and eats another living animal (The prey)

• Symbiosis:

  • Parasitism: Relationship where one species the parasite, benefits at the expense of the other the host.

  • Mutualism: An interaction which both species benefit.

  • Commensalism: Relationship in which one organism benefits whilst the other is neither benefited or harmed.

  • Amensalism: relationship in which one organism is inhibited or destroyed while the organism is neither benefited or harmed.

Populations:

• A population is all of the organisms of the same species, which live in a particular area that have the capability of interbreeding.

• Characterizations:

  • Abundance or density

  • Distribution (clumped, random or uniform)

  • Age structure of population

  • Rate of growth

  • Size

• Abundance: Is defined as the number of individuals of a given species per unit area. Can be expressed qualitatively (Scarce, frequent, abundant) or quantitatively (54 tasmanian devils living in an area of 80 square Kms would have an abundance of 0.7 animals per Km squared)

• Distribution: Refers to the spread of members of a population over space. May be described as clumped, uniform or random

• Age Structure: Identifies the proportion of its members that are pre-reproductive, reproductive or post reproductive.

• Population dynamics: the study of changes in population size over time. Birth rate death rate and migration rate (either in or out of the population)

• Limiting factors: Things that prevent a population from growing

• Density Dependant: Factors whose impact is related to population size

• Density independent: Factors affecting population size which aren’t related to population size.

Adaptations:

• An adaptation is a characteristic of an organism developed overtime that improves it’s chances of surviving and/or reproducing in its specific environment.

• Occurs because a gene mutates. Not always a good thing (can be good)

• Natural selection: Is the process by which biological traits become either more or less common in a population due to reproductive success of organisms this is due to environmental factors affecting the survival of this organism

• Structural Adaptations: Physical differences in biological structure (e.g neck length of a giraffe) also external.

• Behavioural Adaptations: Differences in pattern of activity.

• Physiological Adaptations: Variations in detection and response by vital organs to maintain homeostasis. also internal.

Sympatric Speciation:

• It occurs in the same environment/habitat/place within the same population; if they were geographically isolated/separated that would be allopatric speciation.

• Mutations over time cause differences so 2 populations are created within the original population.

• Set response:

  • There was natural variation in the Howea belmoreana palms on lord howe island.

  • They subsequently started to grow in different areas of the island, where there were differences in soil pH

  • Some palms of the Howea belmoreana adapted to neutral and acidic soils (low pH) while other palms Howea belmoreana colonized alkaline soil (high pH).

  • In the Howea belmoreana palms that inhabited the alkaline soil, physiological differences, including changes in flowering times, emerged as reproductive isolation mechanisms (lack of gene flow)

  • After several generations and as differences (mutations) continued to accumulate, the two populations could no longer interbreed to form viable and fertile offspring, and new species (howea forsteriana) was formed via sympatric speciation.