Genetic Information Transmission and Reproduction

• Genetic information transmission is a unifying theme in biology and is essential for reproduction
• Species transmit specific genetic information at the cellular level
• During cell division, the parent cell duplicates its chromosomes
• The resulting daughter cells are genetically identical to each other and the parent cell
• Offspring cell inherits an identical set of chromosomes from the original parent cell
• Cell division results in whole organism reproduction, especially in single-celled organisms
• Asexual reproduction occurs when a single parent produces genetically identical offspring (no sperm and egg)
• Multicellular organisms such as sea stars and house plants can reproduce asexually from fragmented pieces
• In asexual reproduction, the lone parent and its offspring have identical genes
• Sexual reproduction requires gamete fusion (egg and sperm)
• Sexual reproduction involves a specific type of cell division in reproductive organs
• Gametes have half the chromosomes of the parent cell, carrying unique gene combinations
• Offspring from sexual reproduction are not identical to their parents or each other (except identical twins)
• Sexually reproduced offspring inherit a unique gene combination from both parents resulting in significant variation

Cell Division Roles

• Cell division allows sexually reproducing organisms to develop from a single fertilized egg (zygote) into an adult
• Cell division enables growth, renewal, and repair by replacing cells that die or are damaged
• Millions of cells divide every second to replace damaged or lost cells
• Mitosis is the cell division responsible for multicellular organism growth, maintenance, and asexual reproduction
• Meiosis is the cell division involved in egg and sperm cell production

Terms

• Chromosomes: gene-carrying structure in the nucleus of eukaryotic and prokaryotic cells
• Chromosomes main gene-carrying structure, consisting of a DNA molecule and associated proteins
• Cell division: reproduction of a cell through genome duplication and cytoplasm division
• Binary fission: asexual reproduction where a parent organism divides into two genetically identical individuals of equal size
• Cell division plays a role in reproduction, development, growth, and repair within an amoeba, a single-celled protist, and the human body

Prokaryotes and Binary Fission

• Prokaryotes reproduce through "binary fission" (dividing in half)
• Most prokaryotic genes are carried on a single circular DNA molecule, forming a single chromosome
• Accurately replicating the prokaryotic chromosome to daughter cells is complex
• Escherichia coli (E. coli) chromosome is 500x longer than the cell itself when stretched out
• During binary fission, the chromosome duplicates with one copy moving to opposite cell end as the cell elongates
• Once chromosome duplication is complete, the plasma membrane pinches inward and more cell wall is made, dividing the parent cell into two daughter cells

Asexual Reproduction by Binary Fission

• Binary fission is classified as asexual reproduction because genetically identical offspring inherit the single parent DNA

Eukaryotic Chromosomes

• Eukaryotic cells are generally more complex and larger than prokaryotic cells
• Eukaryotic cells have more genes (human cells have just under 21,000 while bacterium have about 3,000)
• eukaryotic cell, genes are mostly in the nucleus and grouped into chromosomes
• Exceptions include genes in mitochondria and chloroplasts of plants
• Eukaryotic species has a characteristic number of chromosomes in each cell nucleus
• Human body cells have 46 chromosomes, dogs have 78, and hedgehogs have 90
• Eukaryotic chromosome consists of a long DNA molecule bearing genes and proteins
• Proteins help in maintaining and controlling a chromosome's structure gene activity
• DNA and protein complex is called chromatin
• Chromatin typically exists as a diffuse mass of long, thin fibers that are too long to fit in a cell's nucleus if stretched out
• Total DNA length in one stretches out to be longer than a human's height
• Chromatin is too thin to be seen with a light microscope
• A cell prepares to divide its chromatin coils into tight, distinct chromosomes
• Compaction is necessary to organize and transport DNA efficiently
• Chromosome consists of a single DNA molecule tightly wrapped around proteins
• Before cell division, chromosomes are duplicated, and the DNA molecule of each chromosome is replicated
• After replication, new protein molecules attach to maintain the structure and regulate genes
• Each chromosome now consists of two copies called sister chromatids, joined along their lengths by proteins, with the centromere being the most closely attached region

Cell Dividing

• Sister chromatids separate and become individual chromosome identical to the original when a cell divides
• Humans have 46 duplicated chromosomes (92 chromatids), resulting in each daughter cell having 46 chromosomes
• Chromosome consists of two identical chromatids when the cell is preparing to divide, and chromosomes have duplicated but before they separate
• Chromatin is a complex of DNA and proteins that makes the eukaryotic chromosomes, usually in a diffuse, very extended non-dividing form
• Sister chromatids are identical parts of a duplicated chromosome in a eukaryotic cell
• Before mitosis, sister chromatids remain attached to one another at the centromere
• The centromere is the region where the duplicated chromosome sister chromatids are joined and where spindle microtubules attach during mitosis and meiosis
• The centromere divides at the onset of anaphase during mitosis and anaphase II

Cell Cycle

• Chromosome duplication and cell division are essential for cell and organism life and is fundamental to reproduction, growth, and replacing cells
• Millions of cells divide every second to maintain the body's total number of about 200 trillion cells
• Some cells divide daily while others do so less, and specialized cells like muscle and nerve do not divide at all
• Damage such as that done to cardiac muscle tissue during a heart attack or to brain cells during strokes can't be reversed because these specialized cells do not divide at all
• The process of cell division is a part of the cell cycle, from formation to division into two cells
• The cell cycle has two main stages, interphase (cell doubles its cytoplasm and replicates DNA) and the mitotic phase (cell division occurs)
• The cell cycle is spent in interphase when the activity level is at its highest and it can perform normal functions
• A small intestine releases digestive enzymes
• The cell grows bigger, supplies more digestive proteins, and creates various organelles like ribosomes
• The cell also duplicates its chromosomes during this period
• Interphase typically lasts for at least ninety percent of the total cell cycle time
• Interphase can be divided into three phases: G1 phase (first gap), S phase (synthesis of DNA), and G2 phase (second gap)
• The cells are active during interphase and grow
• The chromosomes are duplicated during the synthesis phase that lasts for half of the interphase
• Chromosomes are single, and by the end, they are doubled, consisting of two sister chromatids at the beginning of the S phase
• The cell completes preparations for division in the second gap phase
• Mitotic phase (M phase) is cell division that accounts for only ten percent of the cell cycle
• It has two overlapping stages that consist of mitosis and cytokinesis
• The nucleus and duplicated chromosomes are divided into two daughter nuclei during mitosis
• The cytoplasm divides, resulting in two genetically to each other
• Two daughter cells proceed with a single nucleus, cytoplasm, organelles, and a plasma membrane during cytokinesis before repeating the cycle
• Mitosis, unique to eukaryotes, ensures that each daughter cell receives an identical set of chromosomes
• It is shown that the error in chromosome distribution occurs only once in about 100,000 cell divisions
• Mitotic cell division makes sure all the body cells receive copies of the 46 chromosomes
• Every one of the trillions of cells in bodies trace its ancestry back through mitotic divisions to mother and father cells
• Chemicals that prevent DNA synthesis from starting would trap the cells in the first gap section of the cell cycle
• Cell cycle ordered sequence of events
• Interphase :the period in the eukaryotic cell not actually dividing
• Mitosis: division into two nuclei

Dynamic Changes

• The cell grows and synthesizes new molecules and organelles during interphase
• The image shows a cell in (G2) with doubled contents and two centrosomes in late interphase.
• Chromosomes are formed when Chromatin fibers become tightly coiled
• Each duplicated chromosome appears as two identical sister chromatids joined
• The mitotic spindle begins to form as microtubules grow out from the centrosomes
• The nuclear envelope fragments as the cell enters into prometaphase
• Microtubules from the centrosomes can extend to the nuclear region around the chromosomes.
• A protein structure(kinetochore) is on each sister chromatid
• Some spindle microtubules attach to the kinetochores
• Chromosomes move toward cell's center.
• Mitotic is formed during metaphase
• Sister are attached to microtubules from opposite poles
• Anaphase begins when the two centromeres of each chromosome come apart
• Motor proteins "walk" the newly separated daughter chromosomes toward poles of the cell.
• Telophase: Daughter nuclei appear at the two poles of the cell as nuclear envelopes form around the chromosomes
• Cytokinesis: The cytoplasm divides simultaneously with telophase
• In animal cells, a cleavage furrow forms
• Mitosis relies on the mitotic spindle, a protein fiber that help sets of daughter chromosomes apart

Cytokinesis

• Cytokinesis, overlapping with telophase, differs based on plants and animals
• Due to the stiff cell wall in plant cells, it prompts distinct processes for cytokinesis in different celled organisms
• In animal cells, cytokinesis occurs in a process called cleavage
• First sign of cleavage forms from a cleavage furrow on the surface of the cell.
• A ring of actin microfilaments forms and contracts
• Plant cells walls gather a cell plate that expands outward and fuses with plasma membrane, forming daughter cells with individual cell wall and plasma membrane

Know the Terms

• Cytokinesis: cytoplasm divides, resulting in two daughter cells
• Cleavage: present in animal and protist characterized by a plasma membrane pinching
• Pair of homologous duplicated shows chromosomes during mitosis

Chromosomes

• Humans somatic all has 46 chromosome
• Chromosomes are arrange and is view with two pairs of sister chromatin
• Sommatic cell under goes 23 sets of chromosome

Terms

• Homologous: make pair of diploid cell such as centromere and possessing same character
• Locus: a spot where jeans is found on a chromosome
• Fertilization: fusion of the nucleus of a sperm cell and egg
• Diploid cell: contains 2 homologous set
• Zygote: produced with union and creates a diploid cell

Meiosis

• Meiosis follows stages of chromosome fertilization that produces offspring's
• A life cycle begins with a haploid sperm cell that fertilizes with the egg
• Offspring has haploid sperm
• Somatic cells contain pairs of homologous chromosomes that are diploid
• Gametes make the single exception with autosomes

Chromosomes and Divisions

• Gametes, are not produced by cell divison
• Meisosis is the type of cell division that occurs in reproductive organs
• Meiosis halves number of the chromosomes that mitosis produces chromosomes
• chromosome duplicate in interphase
• homologous chromosomes in sepearte Haploid daughter cells

Reducing the chromosome number

• Gametes can combine through fertilization to form a diploid
• Meisosis is preceded by chromosome duplication and shares the same stages as mitosis but occurs in tow cell divisons
• In tetrads the chromosomes coil tightly and nuclear envlope moves

ProphaseI Homologous Chromosomes.

Patterns of Inheritance Begins

• Heredity is the transmission of traits from one generation to the next
• The field of genetics began in the 1860s with Gregor Mendel, an Augustinian monk
• Mendel deduced the fundamental principles of genetics by breeding garden peas
• Mendel's research was influenced by his studies in physics, mathematics, and chemistry
• These fields helped him design rigorous experiments, and he lived and worked in an abbey in Brunn, Austria (now Brno, Czech Republic).

Groundbreaking Publication

• In 1866, Gregor Mendel published a paper arguing that parents pass discrete "heritable factors" (now known as genes) to their offspring.
• These genes retain their individuality across generations, much like playing cards in a shuffled deck
• This publication, appeared seven years after Darwin's The Origin of Species, marked a significant milestone in modern biology

Mendel's Garden

• Mendel likely favored garden peas for their short generation times
• Peas produce many offspring per mating, and come in easily distinguishable varieties (purple and white flowers)
• A heritable feature that varies among individuals constitutes a character, with each variant being a trait
• Pea plants allow strictly controlled matings due to petals enclosing reproductive organs
• Petals enable manipulation of breeding experiments

Pea Plant Fertilization

• Pea plants typically self-fertilize with stamens pollen landing on the carpel of the same flower
• Mendel ensured self-fertilization by covering flowers with small bags that prevent external pollen
• Mendel cut off immature stamens for cross-fertilization to prevent self-pollination and dusted the carpel with pollen from another plant
• The carpel then developed into a pod containing seeds with Mendel planting to grow offspring plants (F1)
• Mendel's method allowed parentage control/verification of new plants

Mendel's Success

• Mendel's success was partly due to his experimental approach, choice of organism, and selecting characters for study
• Mendel observed seven characters, each with two distinct traits
• Mendel used true-breeding varieties, which consistently produced the same traits over generations of self-pollination
• A true-breeding plant with purple flowers would always produce offspring with purple flowers

Observed Offspring

• Mendel crossed different true-breeding varieties to observe offspring called hybrids
• Known as hybridizations, this genetic-cross process involved true-breeding parents (P generation) and their hybrid offspring (F1 generation)
• When F1 plants self-fertilize or fertilize each other, their offspring are the F2 generation
• Mendel's analysis of F2 plants from thousands of genetic crosses helped him deduce the fundamental principles of heredity
• Grandparents are the P generation, parents are the F1 generation, and you (and any siblings) are the F2 generation

Terms

• **Self-fertilization: Plant fertilization-process resulting in genetically identical offspring from parent
• F2 generation: Offspring of the F1 generation abbreviated
• Cross-fertilization: Mating of two sexually reproducing individuals, for genetics experiments involving controlled mating ("genetic cross")
• Hybrids: Offspring from mating individuals from different species or true-breeding varieties differing in traits
• P generation: Parent individuals in inheritance studies, "P" represent parental
• F1 generation: Offspring of two parental (P generation) individuals, "F1" implies filial
• Hybridization: Crossing two true-breeding varieties to produce offspring with mixed traits, used to study trait inheritance patterns

Mendel's Law

• Mendel conducted experiments to track character inheritance
• Examined two forms, like flower color, leading to hypotheses about inheritance
• Mendel crossed true-breeding pea plants with purple and white flowers, resulting in F1 plants with only purple flowers
• To determine if the white-flower trait was lost, he mated the F1 plants with each other, observing a 3:1 ratio (705 purple, 224 white / 929 plants) in the F2 generation
• The white-flower factor was masked by the purple-flower factor in F1 plants
• It was deduced that F1 plants carried two flower-color factors
• From these observations, Mendel developed four hypotheses about inheritance

Hypotheses of Inheritance:

• Alternative Versions of Genes: Genes have alternative versions called alleles, which account for variations in inherited traits
• Inheritance of Alleles: Organisms inherit two alleles for each gene, one from each parent
• Homozygous: Two identical alleles
• Heterozygous: Two different alleles
• Dominant and Recessive Alleles: When alleles differ, the dominant allele determines appearance
• The recessive allele has no noticeable effect

Law of Segregation

• During gamete production, allele pairs separate, with each sperm/egg carrying only one allele
• At fertilization, alleles from each parent combine, restoring the paired condition
• The 3:1 ratio is accounted for in the F2 generation: allele pairs separate during gamete formation; each gamete carries one allele
• F1 generation plants have one purple allele (P) and one white allele (p)
• Gamete Formation: Half of gametes receive P, and the other half receive p
• Random Fertilization: Gametes unite randomly ensuring the F1 plant generation has an equal chance of being fertilized by sperm with P or p

Possible Combinations

• There are four equally likely sperm/egg combinations in the F2 generation:
• PP = purple flowers
• Pp = purple flowers
• pP = purple flowers
• pp = white flowers
• Since three of the four have purple, and only one has white, the expected purple:white ratio is 3:1
• Punnett squares visually represent the four gamete combinations
• Squares show an equal/probable fertilization product
• The upper right shows the genetic combination from a p sperm fertilizing a P egg

Appearance of F2 offspring

• According to the Punnett square:
• 25% have two alleles for purple flowers (PP), resulting in purple
• 50% have one allele for purple (Pp), yielding purple because purple are the dominant trait
• 25% have two alleles for white flowers (pp), yielding white flowers
• The 3:1 ratio of purple to white flowers observed in F2 corresponds to the observed result
• Observable traits are a phenotype, and genetic makeup is a genotype

How can phenotypically identical plants have different genotypes?

• It corresponds to whether the dominant allele is in a homozygous or alleleterozygous configuration

Homologous Chromosomes

• Every diploid cell that exists has pairs of chromosomes
• The pairs of homologous chromosomes contains alleles for the same and are located in the same loci
• One chromosome in each pair comes from the female parent and the other comes from the male parent
• Labeled bands on the chromosomes exhibit the gene loci
• It is where alleles of a reside along the chromosomes
• The chromosomes may be identical at each loci which is (homozygous)
• They may be different alleles (heterozygous)
• Segregation by Medel's Law
• The basis of Medel's Law
• An individual is heterozygous, Bb, for a gene with each gamete has one or the other alleles and where they separate during Meiosis I

Additional Terms

• Heterozygous: having two different alleles for a gene
• dominant allele: the allele that determines the phenotype of a gene when the individual is heterozygous for that gene
• punnett square: a diagram used in the study of inheritance to show the results of random fertilization
• Homozygous: having two identical alleles for a gene
• principle of segregation: individuals contain two alleles and when gametes produces by meiosis the two alleles separate which is also and end result ending up with only one allele
• Phenotype: expressed traits of an organism
• recessive allele-an allele that has no noticeable effect on the phenotype of a gene when the individual is heterozygous for that gene.
• monohybrid cross-mating of and individual that are either self pollen or a heterozygous plants
• Genotype: genetic make up

Character assortment

• A summarized: Through out is experiment, his observations and data lead to law of character assortment.
• Mono-bybrid: where two sets of individual are heterogenous
• Medel observed that the set is dominated that certain are dominant
• Mendel wondered that both set different or same

Medel Crossing

• Mendel crossed by hybrid and homo- zygotes which create ry gamete also create different f1 generate due hybrids known as dihybrid
• dependent assortment and cross the genes color and shape would be transmitter in the parental and independently
• Mendle cross with to hypothesis two spem
• However Medle did did match its observation leading to some wrong info
• Different games were created in the ratio 9:3:3:1 result the others

F1 Generator

• Monohybrid focus was focus
• Medel observes dominant and recessive allele

F2 Generators

• Focus expand traits
• Medel examines through assortment ratio in the generation independent

Independent assortment

• 12 set that wrinkled others reduce it
• 4 to Green other reduce to other character

Heterozygous Labrador retrievers

• Black Labs will always contain one dominant allele
• Homozygous chocolate labs also include nn bindness
• The test include to also included

Additional Terms

• Main concept and inheritance that when games creates the for the particular pair which helps to create a sorting also create test-cross
• Main point the different point
• The genetics helps to create this
• How to to determine

The laws of Mendel

• Created results in after later in the late 1800 which scientist had to learn from this

• To observe is from one self after another each games end through

• The test also helps to create others test

The law of segregation

• Where a two test create to help another in the test through

The laws of test

• The theory of the test is determine the pattern that test can also
• How it helps
• The laws the the assortment

Heterozygous plant are the the main to producer

Genes

• Tend to test together
• Basted and punter test found is that the laws can only be on it

Linckeages

• To help better test and the linckeages are located by
• By testing them for it

Meissos

• During miosis they are some genetic diversity that test it them

Linkages genes

• When to genetics link together also called linked genes were also and are located by eachother

Explore the transmission of genetic information, a cornerstone of biology essential for reproduction. During cell division, chromosomes duplicate, creating daughter cells genetically identical to the parent. Asexual reproduction yields identical offspring from a single parent, while sexual reproduction involves gamete fusion, resulting in offspring with diverse genetic combinations.