SBI3U Exam Review

all the things learned in SBI3U

START OF GENETIC UNIT

What is DNA coposed of?

5 Carbon Sugar (Deoxyribose), Negatively charged phosphate group, a nitrogenous base

What are the 4 nitrogenous bases?

Adenine, Guanine, Cytosine, Thymine

What is the difference between Primidines and Purines?

Purines are Double Ringed while Pyrimidines are single ringed

What is Chargaffs rule?

Always hydrogen bonds betweeen base pairs. 2 Between A-T and 3 Between G-C There is two sugar phosphate backbones

Describe the DNA replication process

1. Unzipping: H Bonds are Broken
2. Base Pairing: Free nucleotides that come from food and nutrients that we consume


1. H Bonds Reform: Reformed H Bonds

Why do Cells need to divide?

Restriction with Diffusion: If the cell gets too big it can no longer diffuse nutrients properly nor lose waste

Restrictions with Command Control: One nucleus is incapable of controlling a cell if it’s too big

Restrictions with SA to V Ratio: SA = A of All Faces V: lwh The surface area to volume ratio will get smaller. THis means that the volume is growing faster than the surface area which requires more nutrients but cannot get it because of the lack of surface area to absorb

What is the funtions of mitosis?

1. To allow growth for a multicellular organism
2. To allow repair for damaged cells
3. To replace dead cells

What is DNA?

Deoxyribonucleic Acid, double helix of S-P backbones

What is Chromatin

Long thin strands of DNA scattered through the nucleus

What is a chromsome?

Coiled, condensed, replciated strands of chromatinW

What is a chromatid?

One half of the replicated chromsoome and two sister chromatids are indetical

Explain Prophase in Mitosis

1. Chromosomes coil & condense
2. Nuclear membrane disappears
3. Two pairs of centrioles move towards the poles and genetre spindle fibres

Explain Metaphase in Mitosis

1. Spindle fibres attached to centromemere


1. Allign in the middle

Explain Anaphase in Mitosis

1. SPindle fibres shorten and pull sister chromatids apart to oppsoite poles

Explain Telophase in Mitosis

1. Chromosomes begin to uncoil & produce chromatid
2. Spindle fibres disappear and nuclear membrane reappears


1. Pinch in the middle for cell division

Explain Cytokinesis in Mitosis

New cytoplasm is formed

What is the purpose of Meiosis

produce gametes that each contain 23 chromosomes.

What is Gonad Cells?

(Reproductive Cells)

23 homologous pairs

What is the difference bteween diploid and haploid?

Diploid cells (2n) are cells that contain pairs of chromosomes while haploid cells (n) are only one member of each pair.

What is Interphase I

DNA replicates, homologus pairs beigin to migrate towards eachother

What is Prophase I

Centrioles & Spindle fibres appear and synapsis

The procress of synapsis is where they warmthemselves around eachother (crossing over) where segements of non-sister chromatids are exchanged

What is Metaphase I

Tetrads line up in two rows, randomly. Independent assortment means that chromosome five from mom mayu be in left column while father might be to the right

What is Anaphase I

Tetrads are pulled apart as the spindle fibres shorten

Variation in Prophase/Metaphase causes in variation in the gametes

Telophase I

Chromosomes reach poles and cells split two cells present

Interphase II

Rest phase

Prophase II

Centrioles and spindle fibres reform

Metahphase II

Chromosomes line up at the equator

Anaphase II

Chromatids seperate as the spindle fibres shorten

Cytokensis II:

Chromosomes reach the poles, nuceoli and nuclear membrane. 4 haploid cells each containing 23un replicated chromosomes

What is Heredity

The study of how traits are passed from generation to generation

What is a gene?

A part of the chromosome and it expresses traits by producing specific proteins.

What is an allele

Egg and sperm cells donate one set of chromosomes. Defined as the form a gene can take

What is Homozygous

2 alleles are the same

What is heterozygous

2 alleles are different

Genotype vs Phenotype

Combination of letters = genotype and pheatures = phenotype

What are punnett squares?

Shows the alles in the parents gametes along the top

What is amonohybrid cross?

Single trait, 1:1 Phenotypic / Genotypic Ratio

What is a dihybrid cross?

Two traits, Pheno 9:3:2:2, Geno no ask

Simple / Complete Dominance

Dominant allele will block out the recesssive allele

Incomplete Dominance

Prime symbol used, one allele doesn’t mask the other. Known as alleles that are blended

Codominance

Superscript used, heterozygote fully exxpressed

Mulitple Alleles - Blood

ABO blood type, Rh factor (protein that is found on the red blood cell

What is sex linkage?

X linked recessive traits are not fullyr elated to the feminine body characteristics

What are pedigrees

Shows mulitple generations of a genetic trait. Males = squares and females = circles Shaded symbols = affected half shaded carrier, unshaded is affected. Horiziontal line between man adn woman resprent marriage/mating

Start of Evo

Who was Malthus?

A demographer that wrote “Essay on the Principle of Population” He also stated that factors that would limit human population, aka population “checks” create gaps where the weak die out and the strong live.

Who was Wallace?

An optimisitc writer who coined “struggle for existence” and developed that the “fittest would survive” He believed that over generations natural selection of inheirted traits could rise to new species

Who was Lyell?

A geologist who sugessted that rather than \~8,000 y/o the Earth was 100s of millions of years old. He stated that the formation of the Earth’s crust took place through countless small changes over vast periods of time.

Who was E. Darwin?

The grandfather of Charles Darwin, he was a physician and philosopher. He believed that “Everything from shells” meaning all organisms evolve from simple to complex . Partially true as all organisms become more complex overtime because they adapt through natural selelction.

Who was C. Darwin?

Often acredited to developing the theory of Evolution, he coined the term natural selection. He published “On the Origin of Species by Means of Natural Selection” where it explains how natural selection occurs and that new species come from pre-existing species as they all share a common ancestor.

What is a Fossil Record?

deceased organisms preserved in rock; compressed over millions of years, so older fossils are found deeper than younger ones

Hole In Fossil Record?

gaps where fossils explaining likely links between species are missing

What are analogous structures?

Analogous structures are two unrelated structures that have a comparative purpose and Same traits evolved by different species that do not share a common ancestor

What is convergent Evolution?

unrelated species develop similar traits for the same purpose

What is Vestigial Structures?

Body parts that once performed an important function that have been reduced to or incompletely developed structure.

What are Homologous Structures?

Similar physical features in organisms that share a common ancestor, but features serve different functions

What is biogeography

How and When species may have evolved. Distrubution of life forms across geographical regions as a result of plate tectonics and habitats changing

What are the DNA similarities?

% of genes/DNA thar organisms share records to similarities

Artifical Selection

Indentification by humans of desirable traits

What are Ring species

Illustrate what happens over time as poplation genetically diverge. Pockets of overlapping species are able to interbreed, but if they converge they cannot

What is compartive embyrology?

Study of embryos to indetify similarities and differences bteeween species

What are HOX genes?

Similar genes in organisms the formation of body structures in early embryonic development.

What is resistance?

When germs develop the abilkity to dtect the drugs designed to kill them

What is the formula X = (1/4)^n stating

N is the number of genes that are difference, x will represent the proportion of F2 that look like parents

What is Natural Selefction?

A procress where random variation within INDIVIDUALS are selected for by nature in a NON-RANDOM way.

What does Natural Selection Result in?

a population of organisms changing over many generations

What are selective pressures?

Result of abiotic or biotic factors that put pressure on a population

What are mutations?

Changes in the DNA (genetic material) that result in new forms of genes (Alleles).

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What is the only source of new genetic variation?

Mutations are and they are random and continous

When are gene mutations?

Genes mutations occur during DNA replication

When are chromosomal mutations?

During Meiosis

What is selective Advantage?

Characteristic that enables it to survive and reproduce better than others in a population in a given ennvironment

What is variation?

Variation is the different DNA among individuals/populations. The variation in a species that creates a range of successful/unsuccessful gene

Adaptations - Behavioural

Affects the organism naturally due to a new predator or new environment

Adapations - Physiological

Adaptations that involve a physical aspect that cannot be seen in their appearance, an example would be hibernation

Adapatations - Structural

Visible aspect of the organism. Two common examples are mimicry; where a harmless species resembles a harmful one or camoflage; colouration to avoid being preyed on

Variation - Conclusion

Mutations cause a new gene combination that result in variations and adaptations. Natural Selection will then “feeds on” these variations and will select for the best adapted individuals

Natural Selection

Does not anticipate changesi n the environment, it is the result of variety of selective forces

Mutation → Natural Selection

Mutation → Variation/Adaptation → Selective Pressure → Natural Selection

What rule does Genetic Drift Break?

Population is Very Large Rule

What is Genetic Drift?

Change in frequency in alleles of an existing gene variant in small populations due to random change. T

Why does Genetic Drift impact smaller populations the most?

by leading to the fixation of alles, and reducing it’s genetic diversity

What is the Founder Effect?

Reduction in genomic variability that occurs when a small group of individuals becomes seperated from a large population

What is bottleneck Effect?>

When a population is greatly reduced in size, which limits genetic diversity of species because only a small part survives

What rule does gene flow break?

No migration rule

What is gene flow

When genes transfer from one population to another. (MIGRATION)

What rule does sexual selection break?

Mating opportunities are equal

What is sexual selection

Favours a trait that influences mating success

Female choosing mates

Most colorful

Male Vs Male Competition

Males defend a terriotry against other males

What is sexual dimorphism

When the male and female counterparts look different

What rule is broken from Patterns of Natural Selection

No Natural selection + No mutation

What is directional selection

Individuals with more extreme traits are favoured

What is stablizing selection

Stable seltive pressures staht are long term

What is disrusptive selection

Variations at opposite extremes

What is cumulative slelection?

Complex organisms arise and favourable mutations build up over time

What rule does artifical selection break?

random mating

What is artifical selection

When a human chooses an organisms genes that can be passed down

5 conditions of H-W

* Population is Large - Fluctuations can change allele frequencies
* Mating Opportunities are Random - must pair by chance
* No Mutations - New alleles may occur creating new frequencies
* No Migrations - Remove alleles from one population and add to the other
* No Natural Selection - Equal Allele chance