Bio Sem 2 Final

Passive cellular transport

Passive cellular transport

Substances diffuse spontaneously down the concentration gradients crossing a membrane with no expenditure of energy by the cell

Active cellular transport

Some transport proteins act as pumps, moving substances across a membrane against their concentration gradients.  Energy for this work is usually supplied by ATP. 

Mitosis

Division of the nucleus

Cytokinesis

Division of the cytoplasm

DNA (Deoxyribonucleic Acid)

• Shape: Double Helix

• Molecule Type: Nucleic acid and polymer

• Building Block(Monomer): Nucleotide

• Nucleotide Composition: Deoxyribose Sugar, Phosphate Group, Nitrogenous Base (A:Adenine,T:Thymine,C:Cytosine,G:Guanine)

Purines

Adenine and Guanine

Pyrimidines

Thymine and Cytosine

RNA

1. Single helix

2. Ribose sugar

3. Uracil instead of thymine

mRNA (messenger)

Carries information specifying amino acid sequences of proteins from DNA in the nucleus to the ribosome in the cytoplasm

tRNA (transfer)

Carries amino acids to the ribosome for protein synthesis

rRNA (ribosomal)

Plays catalytic and structural roles within the ribosome

Central dogma of molecular biology

Transcription —> Splicing —> Translation —> Protein folding

Mutations

heritable changes in genetic information

Point mutations (substitution)

one change in DNA template, only one mRNA codon is shifted

Missense mutation

Mutation changes AA

Silent mutation

Mutation doesn’t change AA

Nonsense mutation

Mutation changes AA to “stop”

Frameshift mutation (insertion or deletion)

Mutation causes all mRNA codons to be shifted

DNA Replication Step 1

Helicase unwinds/unzips the DNA double helix by breaking the hydrogen bonds between the nitrogenous bases

DNA Replication Step 2

DNA polymerases continuously replicate the leading strand using free nucleotides in the 5’-3’ direction.

DNA Replication Step 3

The lagging strand is synthesized discontinuously in segments with the aid of DNA polymerases.  The lagging strand is synthesized in the opposite direction of the leading strand.

DNA Replication Step 4

DNA ligases induce the covalent bonding of the sugar phosphate backbone in the segments of the lagging strand.

Transcription

RNA polymerase unwinds the DNA double helix and adds free RNA nucleotides to the 3’-5’ strand of DNA(the gene) creating an RNA transcript

Transcription Step 1

The small subunit of the ribosome binds to the mRNA transcript to begin translation

Transcription Step 2

tRNA anticodons begin to matchup with the complementary codons from the mRNA transcript

Transcription Step 3

Each tRNA carries an amino acid which is peptide bonded to the newly created amino acid chain

Law of Segregation

Allele pairs separate during gamete formation and then randomly re-form as pairs during the fusion of gametes during fertilization.

Law of Independent Assortment

Each allele pair segregates independently during gamete formation when genes for two different characteristics are located on different pairs of homologous chromosomes. 

Monohybrid Cross (Incomplete Dominance)

Inheritance in which the F₁ hybrids have an appearance that is intermediate between the phenotypes of the parental varieties

Monohybrid Cross (Complete Dominance)

• A cross between parents which are homozygous for different alleles for the same trait.  

• The F₁ generation is all heterozygous

Dihybrid Crosses

•  A cross between parents homozygous for two different alleles.

• Results in an F₁ generation that is a hybrid for both traits

Homologous pairs of chromosome

Chromosome pairs that possess the same genes containing variations of the same trait.

Epistasis

One gene altering the expression of another gene

Sister Chromatids

Replicated forms of a each homologous chromosome

Pinky finger cause

Small population

Ring finger cause

Non-random mating

Middle finger cause

Mutation

Index finger cause

Migration

Thumb cause

Natural selection

Artificial Selection

The process by which human selectively breed organisms, so that they exhibit desirable traits.

Panspermia

The seeds of life exist all over the universe and they can be spread to any suitable planet throughout space

Abiogenesis

The idea that life originated from non-living substances that organized into the first cell

Evidence for Evolution

• Biogeography

• Fossil Record

• Embryology

• Genetic Differences

Biogeography

The continental drift and plate tectonics of the past and present influence the distribution and formation of species.

Embryology

Embryos across species from classes such as fish, amphibians, reptiles, mammals, and birds share similar features such as gill slits, yolk sacs, notochords, etc. which provides evidence that they all share a common ancestor.

Genetic Differences

The percentage differences between the genomes of species indicate evolutionary similarities.

Molecular Clock

A research tool which utilizes mutation rates to approximate the time which species divergence occurred

Homologous Structures

• Structures that look similar in different species but are used differently

• Different use may require modification but general plan is similar

• Evidence of Divergent Evolution

Adaptive Radiation

The process by which a single species or a small group of species evolves over a relatively short time into several different forms that live in different ways.

Analogous Structures

• Structures from unrelated species that may look different but are used for similar function/purpose

• Evidence of convergent evolution

Allopatric Speciation

Requirements: Geographic barrier and founder effect

Sympatric Speciation

Requirements: Competition pressures  within a population