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Understanding Genes' Role in Cellular Processes and Diseases, Exams of Biology

Walden University Biology

An overview of various cellular processes, focusing on the roles of genes and proteins in motility, communication, inheritance, and growth. Topics include the functions of dynamin in neuron communication, the cell cycle and inheritance, griffith's experiments, and dna structure. Additionally, it covers gene functions in fruit flies, dna as the inheritance molecule, and the mechanisms of dna replication and repair.

Typology: Exams

2022/2023

Available from 03/18/2024

ClemBSC 🇺🇸

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BIOL SCI 215 GENETICS STUDY NOTES 2024

Introduction to Genetics

20,000 genes in the human genome

•

Two main branches

o Prokaryotic cells

▪

Bacteria

▪

Unicellular

▪

“Bag of molecules”

o Eukaryotic cells

▪

Plants, animals

▪

Unicellular or multicellular

▪

Focus on nucleus, mitochondria, etc.

•

Proteins are a linear sequence of polymers called amino acids

o Formed through the dehydration reaction

o 20 different amino acids, each have particular R group thus giving them

varied chemical properties.

o This is the reason why proteins can carry out different functions

•

Proteins fold into 3-D shapes

o 3-D orientation + amino acid sequence leads to varying chemical properties

•

Proteins perform complex functions due to high chemical complexity

•

Enzymes catalyze particular chemical reactions by bind to subspecific area

o Protein binding to another protein

o Protein binding with specific DNA sequence

•

Most cellular functions are performed by proteins

o Motors move along scaffolds to transport materials within the cells

o Receptors allow for communication between inside and outside of cells

•

Mutation in dynamin gene → sequence change in dynamin protein (now slightly

unstable as high temperature unfolds) → neuron communication requires dynamin

•

Lower temperature leads to restoration of synaptic connection

•

Model organisms allow rapid identification of gene functions relevant for mammalian

biology → hippo gene in fruit flies is a common gene used for suppression of tissue

growth

o Identification of gene led to a discovery of control of growth in humans and

animals

•

Have to start learning inheritance first before understanding mechanism as

transmission of disease

Discover Exams of Biology Walden University

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BIOL SCI 215 GENETICS STUDY NOTES 2024

Introduction to Genetics 20,000 genes in the human genome

Two main branches o Prokaryotic cells ▪ Bacteria ▪ Unicellular ▪ “Bag of molecules” o Eukaryotic cells ▪ Plants, animals ▪ Unicellular or multicellular ▪ Focus on nucleus, mitochondria, etc.
Proteins are a linear sequence of polymers called amino acids o Formed through the dehydration reaction o 20 different amino acids, each have particular R group thus giving them varied chemical properties. o This is the reason why proteins can carry out different functions
Proteins fold into 3 - D shapes o 3 - D orientation + amino acid sequence leads to varying chemical properties
Proteins perform complex functions due to high chemical complexity
Enzymes catalyze particular chemical reactions by bind to subspecific area o Protein binding to another protein o Protein binding with specific DNA sequence
Most cellular functions are performed by proteins o Motors move along scaffolds to transport materials within the cells o Receptors allow for communication between inside and outside of cells
Mutation in dynamin gene → sequence change in dynamin protein (now slightly unstable as high temperature unfolds) → neuron communication requires dynamin
Lower temperature leads to restoration of synaptic connection
Model organisms allow rapid identification of gene functions relevant for mammalian biology → hippo gene in fruit flies is a common gene used for suppression of tissue growth o Identification of gene led to a discovery of control of growth in humans and animals
Have to start learning inheritance first before understanding mechanism as transmission of disease

Blended inheritance idea

Traits could blend together in a fluid fashion
Idea pre-dated Mendel, traits blend in each generation Why was Mendel successful?

1. Used a good model organism

1. Pea plants grown and analyzed in large numbers and several varieties had

been found

2. Have good offsprings

3. Easy to grow

4. Plants can cross-fertilize or self-fertilize

1.1. Plant gametes: Pollen (Male) + ovule (female)

1.2. Self: Can occur with a brush or a bag - transfer pollen to

stigma which leads to progeny and plant grows into an adult

1.3. Cross: Transfer pollen from one plant to another by removing

anthers of the other plant → progeny → adults

2. Examined “discontinuous character traits”

1. Two distinct phenotypes: appearance/characteristic or trait that can be

measured

2. True-breeding strains / Pure-breeding strains/lines

1. Cross it with itself and same population and the generations would be the

same

2. Wrinkliness or roundness of a pea

2. Quantified the data

1. First breeding: F0/P(parental generation) - Pure breeding of round and pure

breeding of wrinkly leading to the first generation (F1) being round peas

2. These round peas self fertilize and this leads to F2 being round:wrinkly (3:1)

Mendel builds a model by:

1. Defining players: Round pea gene having 2 alleles: R and r - round = R and wrinkly =

r

1. Homozygous - same allele such as rr and RR

2. Heterozygous - different allele = Rr

1.1. Only one of the alleles is typically “expressed” ==

shown/displayed

1.2. This is denoted by dominant and recessive

1.3. [taken as an assumption till later chapters]

2. Need an experiment to determine whether alleles are dominant or recessive

3. You can only know by looking at the phenotype of heterozygotes

F0 or P: RR x rr P gametes: 100% R, 100% r F1: Rr x Rr Mendel’s first law

Adults have two versions of each gene (allele)

4/6 Meiosis, Mitosis and Aneuploidy

Each adult will have 2 alleles in a gene
Equal segregation of alleles in the gene
Humans have 23 pairs of chromosomes, 2n= o Colors used to distinguish the different chromosomes o Most human cells are diploid, but the gametes are haploid o Body made up of somatic cells [diploid so they would have 23 copies of the chromosomes] n= ▪ Mitosis creates this ▪ Sperm and egg create a zygote which grow bigger and bigger and become an adult. Part of the zygote has been put aside for reproduction and this creates sperm/egg ▪ Zygote = Diploid cell resulting from fusion of two haploid gametes, a fertilized ovary ▪ Trillions of somatic cells in adults and almost all have the same DNA content ▪ Mitosis takes 2n cells and makes 2n cells ▪ How does mitosis ensure all daughter cells are genetically identical? ▪ Cells have to replicate DNA (S phase) prior to cell division (M phase) ▪ Stages of the cell cycle: M=mitosis, S=DNA synthesis, G=gap ▪ Interphase (S and G1 and G2) (Chromosome all spread out) ▪ Mitosis ▪ Prophase ▪ Early: Chromosome condensation compacts DNA into a small volume ▪ Centromere: Connecting sister chromatids, which are identical, to form a chromosome ▪ Chromatid: 1 DNA double helix ▪ 2 homologous chromosomes: Similar not identical in DNA sequence so they contain two different alleles ▪ Metaphase: Attachment of spindle to centromeres, there are two centrosomes on each chromosome ▪ Centrosome: Spot where microtubules are extended and the place where microtubules connect between sister chromatids are centromere ▪ Anaphase: Chromosomes move apart to opposite poles of the spindle: separation of sister chromatids ensures each new cell will receive one copy of each homolog ▪ Centromere splits apart ▪ Telophase: Reassemble nucleo envelope and form two nuclei ▪ Cytokinesis is division of the cytoplasm after the nucleus divides o Gametes [Germ line, haploid (n), half the genetic content in the somatic cells] ▪ Human: sperm and egg, Plants: pollen and ▪ Meiosis creates this

DNA Structure and Replication

Morgan’s model: genes are like beads on a string o Gene sometimes called a “locus” (plural - loci) o A location on a chromosome and its a particular stretch of DNA sequence
Griffith’s experiments: Something can transform R cells into S cells o Possible Inheritance o DNA was the inheritance molecule / transforming agent
Hershey- Chase experiment: virus bacteriophage DNA not protein is transferred into infected cell o Differentiate with radio-labeled atoms/isotopes o Shows that radiolabeled DNA was transferred not proteins
Chargaff’s rule - for each organism, A and T are in equal abundance as well as C and G are in equal abundance
Crystallography - DNA crystallized into lattices and a diffraction pattern is produced in the X ray after they hit the sample, showing the 3D arrangement of atoms o Suggests that DNA is a double helix through the diffraction pattern
Overall structure of DNA (Deoxyribonucleic acid) o Sugar phosphate backbone (outer part of DNA) ▪ Don’t need to know major and minor grooves ▪ Molecule adopts helix because of interaction between successive base pairs o DNA is a polymer composed of nucleotide monomers (nucleotide bases) ▪ Deoxy refers to lack of - OH hydroxyl group at 2’ position ▪ Hydrogen bonding in DNA composed of Purines (A,G 2 rings) and Pyrimidines (C,T, U 1 ring), T and U are almost similar ▪ Deoxynucleotide Triphosphate (NEED TO KNOW), OH group at 3’ position ▪ 3 Phosphates connected to a 5 - member carbon ring with a base ▪ Structure of four DNA nucleotides (Just need to know that it is a nucleotide) o Detailed structure of DNA ▪ Purine and Pyrimidines are able to hydrogen bond to each other ▪ Each Phosphate carries a negative charge and thus DNA is negatively charged ▪ Each strand has a directionality ▪ Important features: ▪ Phosphate backbone is negatively charged ▪ Middle of double helix is hydrophobic ▪ Two strands held together by hydrogen bonding ▪ Anti-parallel notice 5’ - 3’ polarity on the strands ▪ Complementary strand of DNA ▪ Switch base pairs o Melting temperature ▪ Heat will separate strands of DNA ▪ CG base pairs have 3 hydrogen bonds, AT has two hydrogen bonds ▪ Longer strand = more hydrogen bonds o Three models for DNA replication ▪ Semi- conservative ▪ Labeling experiment shows “semi-conservative” replication occurs ▪ Conservative

Primers: Helicase, Primase, DNA pol, Ligase

DNA is a polymer, its monomer is called dNTP
Triphosphate is a high energy bond which helps to facilitate the reaction, taking 3’ Hydroxyl (from the base) and make a covalent bond
Primer is made of RNA
Lagging strand - with Okazaki fragment going backwards for 5’ to 3’, whereas for leading strand, you can just continue
End replication problem for linear chromosomes o Solution: Generate arbitrary sequence which will add the base pairs to the ends of the sequence using polymerase o Telomere lengthening: RNA held within telomerase which is able to bind to the base sequence. Enzyme does a reverse step making them complementary DNA. Transcription in Reverse o End is synthesized with primase
Every eukaryote has a telomerase - important in cancer progression. WIthout it, chromosomes will become smaller than coding genes will become lost Transcription
Problem 1: DNA is in nucleus but proteins are synthesized in the cytosol [Solve by making intermediate RNA]
Problem 2: Nearly all cells in an organism have identical DNA content but can express different proteins due to a developmental program or in response to their environment [A selectively produced messenger: RNA] RNA is same as DNA but is a form that can be read out by ribosome to create proteins
RNA has a NTP (Has a 2’ Hydroxyl and U instead of T) while DNA has a dNTP. o Ribonucleic used instead of Deoxyribonucleic
To make RNA through transcription, you would need a template strand, similar to DNA polymerization. o 5’ → 3’ of the new strand o RNA is synthesized by RNA polymerases o Top strand is called the coding strand [Same as DNA], mRNA is called the template strand (Opposite bases as RNA) o mRNA - goes on to make proteins o rRNA - Forms part of ribosomes and are involved in protein synthesis (Translation) o tRNA - Adaptors used in protein synthesis (translation) o Small RNAs - used for splicing
Promoter sequences specify transcription initiation, terminator sequences end transcription [RNA polymerase to stop]
On bacteria: Sigma factor binds to promoter, DNA and reproofs RNA polymerase and RNA polymerase starts transcription o Promoter sequences: - 35 and - 10, specific DNA sequences which the sigma factor recognizes Already starting transcription Elongation:

Telomere - appears at the end of the lagging strand at both ends of the chromosome
- makes the full copy of top strand that would add on sequences, helps solve lagging strand synthesis
Telomerase synthesizes DNA starting from an RNA template - performs a reaction that forms more DNA at the end by using piece of RNA to make a template so that a specialized sequence will form - reverse transcriptase activity
RNA monomer has 2’ Hydroxyl counting base from the first C of sugar attached to base
DNA monomer does not have 2’ Hydroxyl
Regulation of transcription enables control of protein expression levels o Promoter - 2 short sequences, 6 nucleotides each - 35 and - 10, within double strain DNA, and landing sites for protein sigma factor o +1 first Nucleotide made in the RNA, proceeds to the right as a bottom strand as the template o Hairpin loop prevents polymerase from continuing
RNA polymerase is a housekeeping gene because its useful for generic use
DNA in eukaryotes is kept in nucleus so there would be more elaborate interactions. o Processing such that it becomes RNA before it leaves the nucleus and is transported o TATA box with TATA binding protein TBP which recruits many factors such as RNA polymerase so that transcription starts o 3D space such that TBP will be able to recognize the TATA box o Transcription involves activating sequences far away from the start site ▪ Enhancers: DNA sequences /landing sites upstream before the TATA box which allow for regulated expression of transcripts e.g. muscle transcription ▪ Protein bound to them called the activator (Tf) ▪ Mediator proteins binds to activator proteins and allow for RNA polymerase II binding to start the transcription o mRNA synthesis in eukaryotes is more complex than in prokaryotes ▪ Make transcript, cut areas in it called splicing 1) 5’ end: Capping - Made first - Capping special enzyme called 7 - methylguanosine 2) 3’ end: Polyadenylation (adds a long set of As) - Special sequence toward the end that would direct an endonuclease cleavage, an enzyme that would cut an RNA at the downstream of the signal - Poly-A polymerase adds polyA “tail” which signals sequence determines effective end of a transcript - RNA looks more mature - Longer tail = longer survival - 3’ polyA formation effectively terminates synthesis of mRNA - Why do eukaryotic mRNAs have a cap and polyA tail? o Protect mRNAs from degradation (so that 5’ to 3’ or vice versa exonuclease does not eat up the mRNAs and this would then maintain stability) o Facilitates translation 3) Splicing - Processed by splicing to remove introns and retain exons in the mRNA

Introns stay in the nucleus and exons are exported to the cytoplasm
The multi-component spliceosome removes introns o 2’ Hydroxyl present in A at the Branch Point o Lariat structure loops on itself when 2 exons join together o Spliceosome made of protein and RNA ▪ snRNP - Small nuclear ribonucleic particles depart of the recognition of Extron and Intron sequences by using base pairing with the target mRNA
RNA has catalytic activity to make 3D structures

Nuclear Exports

mRNA must be exported to be translated in eukaryotes
Exported through pores in the membrane Alternative Splicing
Different mRNAs encode different proteins and thus alternative splicing can create many different proteins from the same gene
Produces related but distinct protein isoforms.. Different domains which can bind to different ligands FGFs
In disease: Splicing that would include the red region which allows normal functioning and some tumor cells have mutations such that the red region is not included and this leads to skin cancer cells for example
In Human genome, introns are much bigger than exons Almost all introns start in GU and end in AG Lariat is the loop

The genetic code is universal: all organisms use the same code, it evolved early
Types of single base mutations: Insertion, deletion and substitution (changing the nucleotide letter within the two different strands)
Point mutations: o Silent: change to DNA sequence but does not have any effect on the protein function o Missense: changes identity of the amino acid thus affecting the protein’s function (might) o Nonsense: Substitutes a stop codon for an amino acid: likely inactivates protein
Frameshift mutation: o Insertions or deletions of nucleotides may result in a shift in the reading frame of insertion of a stop codon and this then likely activates the protein o Combining frameshift mutations together on same gene showed that code is triplet
How was the genetic code deciphered: Chemically synthesize simple mRNAs and translate polyU (UUU codon) - Phe etc, then they would make slightly more complex RNAs
Typical human mRNA is 2000 bp = 2kb
Human protein ~
Frameshifts and nonsense mutations almost always inactivate encoded proteins but sometimes a single missense mutation has a big consequence e.g. sickle cell amenia

Protein translation and theories of computing Turing machine - uses tRNA to code the message and catalytic acid to take the amino acids and then join together to make proteins Wobble - alternate base pairing between tRNA and mRNA and it occurs at the 3’ end of the codon Wrinkled peas - frameshift Find first AUG, protein needs 7 amino acids, if there is another AUG that would be an inframe, and then you stop at the codon Ribosome- complex of proteins and ribosomal RNA

Prokaryotic o 70S ribosome with 50S and 30S subunit and they have RNA at the core o 16S rRNA is important o Specialization of subunits: large forms peptide bond formation and small is involved with holding the mRNA o Use special sequence called the Shine-Dalgarno sequence which binds to the 16S rRNA by base pairing and that is before the start codon AUG o More than 1 protein per mRNA
Eukaryotic o 80S ribosome with 60S and 40S subunit o 18S rRNA is important o Specialization of subunits: large forms peptide bond formation and small is involved with holding the mRNA o Involves scanning through the 5’ untranslated region (5’ UTR) ▪ Recognizes the capping, scans along till it recognizes the first AUG which is when there is tRNA-Met o Only 1 protein made from any eukaryotic protein ORF: Open reading frame “S” Svedbergs, a measure of size for large molecules Ribosomal RNA folds by intramolecular base-pairing - extensive with itself X- ray crystallography: structure of ribosome shows that the active site is exclusively RNA
Active site in the middle, ribosome RNA completes chemistry of peptide bond formation
Ribosime - enzyme made of RNA Assembling peptide chain after above is the same for Pro and Euk - translation elongation tRNAs have to be charged such that it is compatible with the genetic code
Aminoacyl-tRNA Elongation factor G binds to the ribosome - pushing the ribosome and RNA is opposite directions, and then the tRNA that is uncharged is released Termination

Gene regulation

“Some are always on” - constitutive [expressed]
Some can be turned on or off - regulatable
Gives organism ability to respond to environment or generate complexity
Two possible ways for regulation: o Positive regulation: Activator is facilitating transcription by binding to DNA and in absence, transcription does not occur o Negative regulation: DNA binding factor - DNA repressor binding prevents transcription ▪ E.coli - single cell bacteria, consumes glucose and lactose [two 6 member rings] ▪ Plasma membrane is hydrophobic and thus galactoside permease helps lactose enter the cell ▪ Key step to metabolize this lactose is beta- galactosidase in which it breaks down lactose to glucose and galactose ▪ Permeates protein only when lactose is present

1. Before exposure to lactose, they do not express enzyme beta-

gal or permease

2. Add lactose and the beta is expressed and encoded from the

lacZ gene

Fool cell that there is lactose by having IPTG compound which increases the beta-gal abundance and it is not consumed. Since IPTG can’t be degraded, beta-gal remains expressed
Mechanism of translation: Prok have shine delgano which binds to 16S, allowing them to translate ORF which are internal so they can have multiple sequences on the mRNA
Polycistronic gene structure: Bacteria houses genes that have the same sequences
Lac operon: Beta gal is the enzyme that takes lactose and breaks it down
DNA Binding factor called Lac-I has its own promoter and terminator - constituitively expressed so it makes an mRNA that forms a protein that has a structure which allows for recognition of gene sequences
LacI binds to LacO - prevents polymerase from moving forward and transcribing the genes
When lactose is present, LacI is still present and transcribed. But because lactose enters the cell and changes the lacI shape, thus preventing it from binding to lac o, and thus the whole sequence lacZ, lacY and LacA ORFs will be read and transcribed. Each lac have their shine dalgarno start and stop codons.
LacI is needed for operon function and is known as the repressor because it represses expression of LacZYA. Also its prime function is regulating expression of genes o Promoter can be located anywhere in the genome
LacI repressor encodes a protein that binds the lacO DNA
LacI binds to LacO (the operator) by recognizing specific bases What happens if the different parts were missing? Wildtype situation and 2 mutant phenotypes [Beta gal expression is always on/ never on] LacI
LacI cant bind and doesnt matter if lactose is present and will never get LacZ expression LacO
LacI cant bind and thus we will always have LacZ expressed in the individuals

LacZ

Gene that makes betagal and thus it is uninducible never on If u look at mutations you wont be able to know just from phenotype, f the mutation is encoding a regulatory sequence or a protein coding gene thus the cis/trans test helps
Arrangement of alleles if we are looking at heterozygous
Regulatory/protein coding sequence using information which comes about by whether alleles function in cis or trans
Trans: mutation that affects any DNA strand, affecting something whose product diffuses around
LacO will act in cis and LacI will act in trans because it is capable of affecting protein o Allows for restoration of inducible characteristic for the normal phenotype o LacO can’t act in trans. LacI protein made from the genome and can bind to the trans LacO+ but it doesnt matter because the LacO must be linked and upstream of LacZ o Have to add the thing back to the cell and if it can rescue the wild type phenotype then that can occur in cis/trans Plasmids are circles of DNA that can replicate in bacteria and in some cases transfer between strains
Genome has a single origin and plasmid has origins of replication, useful for biotechonology. Genome is too big to transfer from one cell to another but u can for plasmid

5/11 Eukaryotic Regulation

Lac operon: system in bacteria o Need a carbon source such as lactose to start the reaction
Regular arrow: Positive interaction
---| arrow: Negative Interaction
Lactose (Metabolite/Inducer which means it has a positive influence)--| LacI(which binds to DNA) → LacO which is a DNA sequence (landing site) → regulate LacZ expression o No LacI means that LacZ will be constitutively expressed o LacI conformational shape changed by Lactose as recognition that lactose is present
Glucose and cAMP levels inversely proportional
CAP, a protein, binds to DNA with high cAMP, facilitates binding for RNA polymerase
When glucose is high and lactose is present, there still won't be any CAP binding because there is no activator present o Cell prefers to metabolize glucose over lactose mRNA synthesis in eukaryotes is more complex than in prokaryotes
mRNA translated in the cytoplasm
In order to activate transcription: Promoter (TATA box) upstream of the coding sequence, Enhancers located downstream of genes where they bind to protein transcription factors called activators where activators recognizes bases on enhances and bring it to mediator, and then the mRNA polymeraese will start the transcription. Positive and negative signals modulate the probability of transcription initiation Organization/Characterization of DNA
In eukaryotes but not bacteria, DNA is wrapped around histones
First level: DNA wrapped around nucleosomes, at a distance apart from each other
Nucleosomes made up of Histones and DNA
Several configurations
Heterochromatin: regions of the genome that are silent because the chromosome is so compact by the nucleosomes
When histones are methylated, they are inactivated for expression that would create heterochromatin
Histones can carry through many generations
Each histone has a tail and is together as a bunch, Galactose binds to enhancers upstream of UAS sequences Gal4 activated only when Galactose is near the cell. In absence of Galactose, it is inactive but Gal80 binds to UAS gAL3 is a sensor but does not bind

Regulatory system that would act to express GAL genes using protein, GAL 4, a transcription factor that binds to UAS sequence. This UAS lies upstream of many genes o UAS is a landing site
In the absence of gal, Gal80 will bind to gal4 which will bind to UAS and the rna polymerase
Galactose activates gal 3 which has a negative effect on 80, negative effect on 4 which binds to UAS allowing for expression of Gal 1 - 10
is missing, there would be no expression of Gal1 and thus uninducible
UAS changed, landing site changes, leading to uninducible as well
UAS active in Cis Dosage compensation in humans
Need an equal dose of proteins encoded on X linked genes between males and females
In females, one X is epigenetically silenced at random in each cell leading to an inactive X as a barr body Model for X-chromosome inactivation
Xist transcription region
Chromatin modifying enzymes
RNA is bringing particular proteins to the particular chromosome
Xist RNA recruits chromatin modifying factors which creates heterochromatin
Inactive chromatin spreads leading to inactivating X chromosome
X-inactivation can make females phenotypically mosaic Translational control by miRNAs and RNAi interference by siRNAs microRNAs halt translation of specific genes by binding to 3’ UTR sequences in target mRNAs.
Code distinct sequences
Transcribed from genome
Dicer: takes hairpin precursor and cuts off the loop so that you are left with 2 small RNAs - 22 - 23 nucleotides long leading to them ending up in RISC (RNA induced silencing complex) and it is capable of base pairing
With the help of RISC, it is able to target particular genes
RISC prevents translation
Expression of miRNA can influence expression of a gene by binding to 3’ UTR RNA interference is a related antiviral system microRNA pathway is related to anti-viral response
Many viruses produce double-stranded RNA
Dicer chops this into 21 - 23 bp RNAs called siRNAs, then they are loaded into RISC
siRNA RISC complex binds to mRNA with perfect bp then RISC makes cut in RNA and RNA is degraded siRNAs are small RNAs that have 21 - 23 nucleotides, and are designed to match particular mRNAs, and then they will degrade them

Understanding Genes' Role in Cellular Processes and Diseases, Exams of Biology

Related documents

Partial preview of the text

Download Understanding Genes' Role in Cellular Processes and Diseases and more Exams Biology in PDF only on Docsity!

BIOL SCI 215 GENETICS STUDY NOTES 2024

1. Used a good model organism

1. Pea plants grown and analyzed in large numbers and several varieties had

2. Have good offsprings

3. Easy to grow

4. Plants can cross-fertilize or self-fertilize

1.1. Plant gametes: Pollen (Male) + ovule (female)

1.2. Self: Can occur with a brush or a bag - transfer pollen to

1.3. Cross: Transfer pollen from one plant to another by removing

2. Examined “discontinuous character traits”

1. Two distinct phenotypes: appearance/characteristic or trait that can be

2. True-breeding strains / Pure-breeding strains/lines

1. Cross it with itself and same population and the generations would be the

2. Wrinkliness or roundness of a pea

2. Quantified the data

1. First breeding: F0/P(parental generation) - Pure breeding of round and pure

2. These round peas self fertilize and this leads to F2 being round:wrinkly (3:1)

1. Defining players: Round pea gene having 2 alleles: R and r - round = R and wrinkly =

1. Homozygous - same allele such as rr and RR

2. Heterozygous - different allele = Rr

1.1. Only one of the alleles is typically “expressed” ==

1.2. This is denoted by dominant and recessive

1.3. [taken as an assumption till later chapters]

2. Need an experiment to determine whether alleles are dominant or recessive

3. You can only know by looking at the phenotype of heterozygotes

1. Before exposure to lactose, they do not express enzyme beta-

2. Add lactose and the beta is expressed and encoded from the