Animal Reproduction: Sexual and Asexual Methods

• Reproduction ensures the continuity of a species through sexual and asexual methods in various organisms

Reproduction

• A fundamental feature of life where each individual exists because of this process
• Breeding is a biological process that produces new individual offspring from parents through either sexual or asexual reproduction
• Allows individuals to be better suited for survival and selective adaptation

Sexual Reproduction

• Achieved through combining reproductive cells (gametes) from two individuals
• Involves the union of a male gamete (sperm) and a female gamete (egg or ovum) to form a unique individual through a zygote
• Genetic variation is only possible through this type of reproduction

Asexual Reproduction

• The simplest way for an organism to reproduce, producing identical offspring from one parent through mitosis
• Includes fission, budding, and fragmentation

Animal Fertilization

• Male and female gamete union occurs either outside the body (external fertilization) or inside the body (internal fertilization)
• Successful ova fertilization relies on gametes meeting and not dehydrating, each being a single haploid cell surrounded by a cell membrane
• External fertilization suits organisms in aquatic or moist environments

Advantages of External Fertilization

• Usually more rapid
• Females can reproduce without the male while the first young develop
• Parents do not expend energy for gestation and caring for the young
• Young are widely dispersed, reducing competition with parents

Disadvantages of External Fertilization

• More gametes need to be produced
• No control over the gametes once released
• Decreased fertilization chance, improved via synchronized gamete releases (spawning events)
• Takes place in aquatic environments where gametes and zygotes face predation and disease

Advantages of Internal Fertilization

• Occurs on dry land
• Fewer gametes are produced by the female
• Gametes are more likely to be successful due to close proximity in the female reproductive tract
• Gametes and zygotes are protected from predation and disease
• Developing young are fed and protected increasing survival chances

Disadvantages of Internal Fertilization

• Slower with fewer gametes produced from the female
• Mating actions are more complex for copulation
• There is potential to spread sexually transmitted diseases throughout a population
• Energetically costly, requires parental input, especially from the female
• Parental care of young is lengthy and demanding

Examples of Animal Fertilization

• Bullfrogs: External fertilization where the male frog grabs the female's back during egg release, fertilizes the eggs, with the females depositing 20,000 eggs in a protected environment
• Tiger salamanders: Internal fertilization where males produce spermatophores attaching them to underwater rocks; females fertilize their eggs with these spermatophores at night after courtship

Sexual Reproduction in Plants

• Relies on successful fusion of male and female gametes, but plant immobility makes this difficult
• Plants evolved the use of external agents to carry the gametes from one parent to another, using pollinating agents
• They also rely on external agents to disperse seeds and have survival strategies for extreme temperatures

Plant Reproductive

• For fertilization, male gametes must be carried from the anthers to the stigma
• Gamete transfer is called pollination where pollen deposition on the stigma leads to pollen tube germination containing the male gamete to an ovule in the ovary
• Fertilization occurs within the ovary in flowering plants

Plant Fertilization

• The sperm cell transferred by the pollen tube fuses with the egg cell within the ovule inside the female part of the flower
• The fertilized ovule develops, protected within the ovary, forming a seed, and the surrounding ovary becomes fruit

Plant Pollination

• Plants depend on agents (wind, water, animals) to transfer their pollen from the anthers of one flower to the stigma of a flower on another plant (cross-pollination) or the same plant (self-pollination)

Cross-pollination

• Ensures greater variation in offspring by relying on external agents
• These agents can be abiotic (wind, water) or biotic (insects, birds, mammals)
• Flowers become more specialized, with their association with pollinating agents

Self-pollination

• Requires less energy as there is no need for the plant to produce structures to attract pollinators

Stamen

• Anther: Where pollen grains are formed
• Filament: Stalk that carries the anther, this determines if the anthers are contained inside the petals for insect pollination or hang outside for wind pollination

Mammal Reproduction

• Gametes undergo internal fertilization, divided into monotremes, marsupials, and eutherians (placental mammals)

Monotremes

• Platypus and echidna are examples of animals that lay eggs (oviparous)
• Following internal fertilization, females lay eggs that develop outside the mother's body

Marsupials

• Young marsupials develop internally shortly after fertilization, continuing embryonic development in a pouch
• Young marsupials are born very young and crawl up the mother's abdomen to the pouch

Eutherians

• Dingoes, rabbits, mice, and humans are examples that fall into this category

• Young complete embryonic development inside the mother's uterus after internal fertilization and the uterus nurtures and protects the offspring

• One or more fertilized eggs implant into the uterine wall where a placenta develops, connecting the young to a nutrient and oxygen supply from the mother's bloodstream

• Placental mammals produce one to a few young at a time and invest heavily in parental care, increasing the young's survival

Hormones

• Three types of sex hormones: androgens, oestrogen, and progestogens

Androgens

• Control the development and action of male sex organs and secondary characteristics like deepening the male voice, increase in growth and thickness of hair and size of muscles and bone
• Cells in the testes secrete the androgen testosterone for sperm production (spermatogenesis)
• Present in both males and females, but at much higher levels in males

Oestrogen

• Controls the action of the female reproductive system and secondary characteristics (enlarged breasts, pubic hair, and widening of hips)
• Main function is ovarian functioning and therefore fertility in females

Progestogens

• Progesterone is the most common, with a primary role in pregnancy and stimulating with milk secretion

Cell Replication

• Inquiry question: "How important is it for genetic material to be replicated exactly?"

Cell Replication Processes

• Includes Mitosis and Meiosis, and DNA Replication

Mitosis

• Produces two identical daughter cells for growth, repair, and asexual reproduction
• Maintains genetic stability by ensuring precise chromosome distribution

Meiosis

• Produces gametes (sex cells) with half the number of chromosomes, introducing genetic variation through independent assortment and crossing over
• Is essential for sexual reproduction

DNA Replication

• Uses the Watson and Crick DNA model: Double helix structure with nucleotide base pairing (Adenine-Thymine, Guanine-Cytosine) held by hydrogen bonds

DNA Replication Process

• Unwinding: Helicase unwinds the DNA double helix, creating a replication fork
• Primer Binding: Primase adds RNA primers to initiate replication
• Elongation: DNA polymerase synthesizes new DNA strands by adding nucleotides complimentary to the template strands on leading and lagging strand
• Termination: RNA primers are replaced with DNA, and DNA ligase joins Okazaki fragments
• Enzymes: DNA polymerase, helicase, primase, ligase, exonuclease
• Directionality: Replication proceeds 5' to 3'
• DNA mismatch repair corrects errors via DNA polymerase I

The Cell Cycle

• Phases: G1, S, G2, and M phase

G1 phase

• Cell growth, protein synthesis, and organelle duplication

S phase

• DNA replication occurs

G2 phase

• Further growth, protein synthesis, and preparation for mitosis and checks for errors

M phase

• Nuclear division followed by cytokinesis (division of cytoplasm)

Mitosis

• Includes Interphase/Early Prophase, Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis

Interphase/Early Prophase

• DNA replicates, centrosomes divide, nuclear membrane begins to disintegrate and chromatin condenses

Prophase

• Chromosomes condense, nuclear envelope disappears, centrosomes move to opposite poles, spindle fibers form

Metaphase

• Chromosomes align at cell's equator, spindle fibers attach to centromeres

Anaphase

• Centromeres divide, sister chromatids are pulled to opposite poles by spindle fibers

Telophase

• Chromosomes arrive at poles, spindle disintegrates, nuclear envelopes reform, cytokinesis begins

Cytokinesis

• Cytoplasm divides, resulting in two daughter cells (cell plate formation in plants, cleavage furrow in animals)

Telomeres

• Protective caps at the ends of chromosomes
• Prevent chromosome fusion and protect genetic information
• Shorten with each cell division, eventually leading to cell death (apoptosis) when they reach a critical length

DNA Structure

• Is made of Nucleotides which are basic units that are composed of a sugar (deoxyribose), a phosphate group, and a nitrogenous base (A, T, G, C)
• Base Pairing: A always pairs with T, and G always pairs with C
• Function: Carries hereditary information, Undergoes crossing over (meiosis) for genetic diversity and replicates to pass on genetic information
• Is subject to Mutations that can lead to variations and new species

RNA Structure

• Types: mRNA (messenger RNA), rRNA (ribosomal RNA), and tRNA (transfer RNA)
• Is single-stranded nucleic acid with uracil (U) substituting thymine (T)

mRNA

• Transfers genetic information from DNA to ribosomes

rRNA

• Component of ribosomes and involved in protein synthesis

tRNA

• Carries amino acids to ribosomes during translation

Central Dogma

• Describes the flow of genetic information: DNA → RNA → Protein

Genetic Continuity

• Ensures the preservation of genetic information across generations, depending on the accuracy of DNA replication and distribution during cell division
• Is essential for species to continue because it ensures new cells and organisms have the necessary genetic information to survive
• Can be disrupted, leading to disease, cell death, and even extinction

Polypeptide Synthesis

• Why is polypeptide synthesis important?

Key Concepts

• Central Dogma of Molecular Biology: DNA->RNA->Protein

Polypeptide Synthesis

• Turns genes into proteins, is a chain of many amino acids linked by peptide bonds, can incorporate 20 different amino acids and the amino acid sequence is determined by genes (DNA triplets)

Transcription

• mRNA moves out of the nucleus and into the cytoplasm
• RNA polymerase binds to the DNA promoter region, and DNA unzips
• RNA polymerase uses the non-coding DNA strand as a template to assemble a complementary mRNA molecule (Uracil replaces Thymine)

Translation

• mRNA is broken down into nucleotides for reuse
• Ribosomes bind to the mRNA
• tRNA molecules, each carrying a specific amino acid and an anticodon, bind to the mRNA codons (three-nucleotide sequences)
• Amino acids are linked together by peptide bonds, forming a polypeptide chain
• tRNA detach and return to the cytoplasm to pick up more amino acids
• The polypeptide chain is further processed and folded into a functional protein

mRNA messenger RNA

• Carries the genetic code from DNA in the nucleus to the ribosomes in the cytoplasm

tRNA transfer RNA

• Carries specific amino acids to the ribosomes during translation, based on the mRNA codon sequence

Importance of Polypeptide Synthesis

• Genes determine an organism's traits (phenotype) by coding for specific proteins
• Serves structure, enzymes, transport, signalling and defense and essential for growth, development, and cellular processes

Terminology

• Phenotype: Observable characteristics of an organism (structure, behavior, physiology)
• Alleles: Different versions of a gene
• Gene expression: expression: The process by which the information in a gene is used to synthesize a functional gene product (protein)
• Genotype: Genetic makeup of an organism
• Both genes and environment influence phenotype

Environmental Effects on Gene Expression Exmaples

• Human height is linked to nutrition and toxins
• Hydrangea flower color (soil pH)

Protein Structure

• Primary: Linear sequence of amino acids
• Secondary: Localized folding patterns
• Tertiary: Overall 3D shape of a single polypeptide chain
• Quaternary: 3D structure of a protein composed of multiple polypeptide chains
• Protein shape is vital for its function

Protein Types

• Structural/Fibrous example is Collagen
• Functional/Globular (functional): Enzymes, transport proteins (hemoglobin)

Protein Functions

• Provides support, enzymes, transport, signal and defense

Genetic Variation

• Inquiry question: "How can the genetic similarities and differences within and between species be compared?"
• Meiosis has two divisions following the same stages as mitosis with an interphase where DNA is replicated
• Modeling the formation of new combinations of genotypes produced during meiosis, including: interpreting examples of autosomal, sex-linkage, co-dominance, incomplete dominance, and multiple alleles

Meiosis 1

• Reduces chromosomes, homologous chromosomes form bivalents, crossing over occurs
• Crossing over, the fibers attach to the bivalents from opposing angles
• Align along at cell's equator, spindle fibres contract and split the bivalent and splits the fibers until chromosomes decondense and two haploid daughter cells are formed

Meiosis 2

• Is identical but second division that separates sister chromatids chromosomes
• P fibers divide, spindle fibres attach, chromosomes condense, fibers separate
• Membrane decondenses, forming four haploid daughter cells perpendicular to equator

Fertilization

• Ensure variations of phenotype by having additional sources, such as fusion of different gametes and mutations

Mutation Types

• Autosomal inheritance
• Sex-linkage
• Co-dominance
• Incomplete dominance
• Multiple alleles

Key Definitions

• Genome: Information of sequence in the chromosoome of the nucleus
• Centromere: Region attached to spine during cell division
• Nucleosomes: DNA wound packaging
• Autosomes: Homologous pairs to transfer between parents and offspring
• Sex Chromosomes: Human pairs

Terminology

• Chromosome: Threadlike carries genetic from genes
• Genes: That determine the characteristics are inherited, genes from father and mother
• Alleles: Different forms of genetics- Paternal, Maternal
• Loci: Genes inherited
• Phenotype: Result of the trait

Genetic Configuration

• Genotype: Of an individual
• Dominant: Trait that is
• Recessive, recessive or not always seen
• Traits such as homo and heterozygous, hap and diploid
• Autosomal is 1 pair

Mendel's Experiment

• The study of each trait in pairs of factors, phenotypes may depend on factors
• Follow a model to represent
• Follow dominance laws
• Cross breeds create phenotypes
• When bred create genotypes

Second Law- Independent Assortment

• That studies multiple factor pairs and assumes genes are on different chromosomes

Pedigree Analysis

• Can be defined as a presentation of the inheritance patterns of a particular trait in
• related individuals over a number of generations
• Analysis of the pedigree chart is carried out to record to analysis affected individuals, patterns, and disorder
• Make predictions on how this affects

Sex Determination

• Is the way in which sex chromosomes separate during meiosis and then
• recombine during fertilisation to determine whether the offspring will be male or female.

Sex Linkage

• Some genes can affect by what is carried out
• Recissice are more frquent in makes and disrders are inherited with a lack of sex
• Haemmopilia: A bleeding disorder

Symbols

• XHXH = normal female
• XHXh = carrier female (heterozygous)
• XhXh = haemophiliac female (homozygous = lethal)
• XHY = normal male

Co Dominance

• Creates a new phenotype

Incomplete Dominance

• With unique genes

Multiple Alleles

• Usually two alleles, however this has multiple
• Ex- Humans
• Blood transfusions can lead to problems
• Body will recognize if these happen

Examining Frequency Data

• Frequency of gene

Inheritance Patterns in a Population

• Be accurately examined on a population level- what are the most popular methods to examine?

Technologies to Analyze

• Sequencing is a crucial method in understanding that variation
• DNA sequences tell a lot about genes. DNA profiling is one way to track

Management

• Description, the food source in the habitat etc of animals
• Risks via isolation and conservation

Studies relating to disorders

• Alkaphonuria

Populations in evolution

• Can change genes overtime
• These are essential ways to study

Mutation

• Alters population from new to allele

Sources

• Defined as agents to cause it and results
• Carcinogenses are an example

Radiation Sources

• Can make harmful

Mutations

• High frequrncy of mutations on chromosomes

Mutation Types

• Viruses
• Bacteria
• Fungi
• Metals

Mutation

• Defined as a process of deleting
• Can be changed due to error

Phases

Mutation has phases

• Substitution: Change
• Silent: Is similar
• Nonsense: No change

Cromosomic Mutation

• Can affect sections of mutations from radiation and can duplicate
• BEAST- Duplication, Inversion, Sections

Germaline vs Somatic

• Somatic is less, germline has much more

DNA segments

• Coding mutations

Variation Factors

• Meosis: Replication and crossover to make genetics by segregation
• Fertizalation: Mixing
• Mutation: A variation, and a error

Pool Facts

• Can be caused by bottleneck and drift
• Effects on gene

Allele Info

• mutation, flow- the effect of gene pool

Biotech

• Helps improve futures for everyone

Defintions

• Help with technology to improve it. Applications are agriculture and environment

Ethics

• Principles
• Rights to safety

Genetics Future

• Trends
• Biotech is leading us

Genetic benefits

• Can help medicine and decrease many diseases
• Increased yield can boost resources for food and water
• Increase products
• Improve materials and biodegradable tools

Genetic change

• Less breeding
• Potentional
• Increase resources