Biology MCAT

Nucleoid Region

DNA Region in prokaryotes

Nucleolus

Makes ribosomes

Peroxisomes

Collect and breakdown material

Rough ER

Accepts mRNA to make proteins

Smooth ER

Detox and makes lipids

Golgi

Modify and distribute proteins and only in eukaryotes
COPII → forward COP1 → return

Centrioles

9 groups of microtubules that pull chromosomes apart

Lysosomes

Demo & Recycling center. Made by Golgi. Single membrane

Plasmids

In prokaryotes

Obligate Aeroba

Need oxxygen

Obligate Anaerode

Dies in oxygen

Facultative Anaerobe

Toggle between aerobic and anaerobic

Aerotolerant Anaerobe

Does not use O2 but tolerates it

Gram postive

Thick peptidoglycan cell wall

Gram negative

Thin cell wall and an outer membrane

Microfilaments

Made of actin

Microtubules

Made of tubulin

Intermediate filamets

Keratin = Vitamin D

Epithelia tissues

Parenchyma (functional parts of organ).

Simple: One layer.

Stratified: Multiple layers.

Pseudostratified: One layer (looks mult, but really just 1). Cuboidal: Cube shape.

Columnar: Long and narrow.

Squamous: Flat, scale-like.

Connective tissues

Stroma. Bone cartilage, tendon, and blood

Eukaryote

With mitochondria, large ribosomes, and reproduce with mitosis

Prokaryotes

Cell membrane, small ribosomes, and plasmids carry DNA material

Prions

Infectious proteins

Viroid

Plant pathogens

Transformation

Gets genetic info from environment

Conjugation

Transfer of genetic info via conjugation bridge

Transduction

Transfer using pacteriophase

Transposons

Genetic info that can insert/remove themselves

Virus Capsid

Protein coat

Virus Envelope

Some have lipid envelope

Virion

Individual virus particles

Bacteriophase

Bacteria virus. Tail sheath injects DNA/RNA

Viral Genome

May be DNA or RNA. Single or double stranded

If single strand

Positive Sense: Can be translated by host cell.

Negative Sense: RNA replicase must synthesize a complimentary strand, which can then be translated.

Retrovirus

Single stranded RNA. Reverse transcriptase needed to make DNA

Bacteriophage life cycles

Lytic: Virions made until cell lyses.

Lysogenic: Virus integrates into genome as provirus or prophage. Goes dormant until stress activates it.

G1

Make mRNA and proteins to prep for mitosis

G0

Termination of division

G1 checkpoint

Decides if it should divide which is determined bt P53

S

DNA replicated

G2

Cell growth. Make organelles

G2 checkpoint

Check cell size and organelles

M

Mitosis and cytokinesis

Positive growth

1) CDK + Cyclin create a complex

2) Phosphorylate Rb to Rb + P

3) Rb changes shape, releases E2F

4) Cell division continues

Negative growth

1) CDK inhibitors block phosphorylation of Rb

2) So, E2F stays attached

3) Cell cycle halts

X-linked disorders

Males express, female carriers

Y chromosome

Little genetic info

Mitosis steps

1. prophase

2. metaphase

3. anaphase

4. telophase

Meiosis steps

Double the steps as mitosis

Nondisjunction

when sister chromatids don’t separate properly during anaphase. Results in aneuploidy

Alleles

Alternative forms of a gene. Dominant allele only requires 1 copy in order to be expressed. Recessive allele requires two copies in order to be expressed

Genotype

The combination of alleles one has at a given locus. Homozygous: Having two of the same allele.

Heterozygous: Having two different alleles.

Phenotype

Observable traits

Dominance

Complete: Only one dominant allele.

Codominance: More than one dominant allele.

Incomplete: No dominant alleles; heterozygotes have intermediate phenotypes.

Penetrance

The proportion of individuals carrying a particular allele that also express an associated phenotype

Expressivity

The varying phenotypic outcomes of a genotype

Genetic leakage

Flow of genes between species via hybrid offspring.

Genetic Drift

When the composition of the gene pool changes as a result of chance.

Founder effect

Bottlenecks that suddenly isolate a small population; inbreeding.

Taxonomic Rank

Kingdom, phylum, class, order, family, genus, species.

Law of segregation

An organism has two alleles for each gene, which segregate during Anaphase I. Because of this, gametes carry only one allele for a trait

Law of Independent Assortment:

The inheritance of one allele does not influence the probability of inheriting a given allele for a different trait (except for linked genes).

Griffith

Demonstrated transformation. Heat-killed smooth (virulent) strain of bacteria still transformed rough strain into smooth.

Avery-MacLeodMcCarty

Degradation of DNA led to a cessation of bacterial transformation. Degradation of proteins did not.

Hersey-Chase

Confirmed DNA is the genetic material because only radiolabeled DNA could be found in bacteriophageinfected bacteria.

Point Mutations

The substituting of one nucleotide for another.

Frameshift mutations

Moving the 3 letter reading frame.

Types of mutations

Silent: No effect on the protein.

Missense: Replace one amino acid with another.

Nonsense: A stop codon replaces an amino acid. Insertion/Deletion: Shift in the reading frame, leading to a change in all downstream amino acids.

Chromosomal mutations

Deletion: A large segment of DNA is lost.

Duplication: A segment of DNA is copied multiple times. Inversion: A segment of DNA is reversed.

Insertion: A segment of DNA is moved from one chromosome to another.

Translocation: A segment of DNA is swapped with a segment of DNA from another chromosome.

Punnett Squares

Monohybrid cross accounts for 1 gene. Dihybrid crosses account for two genes. Sex-linked cross is linked to the X chromosome.

Recombination Frequency

The likelihood of two alleles being separated during crossing over in meiosis. Farther = more ­likely

Hardy-Weinberg Principle

If a population meets certain criteria (aimed at a lack of evolution), then the allele frequencies will remain constant.

Hardy-Weinberg Equation

P + q = 1
P²+2Pq+q²=1

Natural selection

Mechanism for evolution

Modern synthesis model

Neo-Darwinism. Mutation and recombination are mechanisms of variation. Differential reproduction.

Inclusive fitness

If a population meets certain criteria (aimed at a lack of evolution), then the allele frequencies will remain constant

Punctuated equilibrium

Considers evolution to be a very slow process with intermittent rapid bursts of evolutionary activity.

Mode of natural selection

Stabilizing Selection: Keeps phenotypes in a narrow range, excluding extremes.

Directional Selection: Moves the average phenotype toward an extreme.

Disruptive Selection: Moves toward two different phenotypes at the extremes, can lead to speciation.

Adaptive Radiation: Rapid emergence of multiple species from a common ancestor, each has a niche.

Isolation

Reproductively isolated from each other by pre- or postzygotic mechanisms.

Molecular clock model

The degree of difference in the genome between two species is related to the amount of time since the two species broke off from a common ancestor