Biology Finals

Chromosomes

Structures that organize DNA in the cell, akin to aisles in a store like Target.

Chromatid

• Structure: One half of a duplicated chromosome

Centromere

The region where pairs of chromatids are joined together.

Spindle

A fanlike microtubule structure aiding in the separation of chromatids during cell division.

Eukaryotic Cell Cycle

The cycle comprising Interphase (G1, S, G2) and Cell Division (M phase).

G1 Phase (INTERPHASE)

DNA replication occurs, cells increase in size, synthesize new proteins or organelles

S phase (INTERPHASE)

new DNA is synthesized, chromosomes are replicated

G2 (INTERPHASE)

Preparing for Cell Division - many of the organelles and molecules required for cell division are produced

M Phase (CELL DIVISION)

occurs in two stages (Mitosis and cytokinesis) - prophase, metaphase, anaphase, telophase, cytokinesis

Prophase

The phase where the cell prepares for division, chromosomes condense, and the spindle forms.

Metaphase

Stage where chromosomes align in the middle of the cell with spindle fibers connecting them.

Anaphase

Phase where chromatids separate and move to opposite poles of the cell.

Telophase

Stage where chromosomes spread out, the nucleus reforms, and cytokinesis begins.

Cell Division in Plant Cells

difference: cell plates instead of membrane

Cyclins

Proteins regulating the timing of the cell cycle in eukaryotic cells.

Internal regulators

respond to events inside a cell — allow the cell cycle to proceed only once certain processes have happened inside the cell

External regulators

respond to events outside the cell - cells speed up or slow down the cycle

Growth factors

external regulators that stimulate the growth/division of cells, are important during eukaryotic development/wound healing

Apoptosis

Programmed cell death crucial for tissue development and organ shaping.

Cancer

Condition where body cells lose control over growth, leading to uncontrolled division.

Benign Tumor

non-cancerous, does not spread to healthy tissue

Malignant Tumor

cancerous, spread of cancer cells is metastasis (absorb nutrients needed, block nerve connection, prevent organs from functioning)

Treatments (for cancers and tumors)

chemotherapy, radiation, surgery

Causes (of cancers and tumors)

• defects in genes that regulate cell growth/division

• some sources of gene defects are smoking, radiation, defective genes, viral infection

• damaged p53 gene is common, causes cell to lose the information needed to respond to growth signals

Telomeres

like an angle of a chromosome, telomere get shorter as the chromosomes keep dividing

Meiosis

Cell division forming gametes with half the number of chromosomes.

2 Divisions of Meiosis

Meiosis 1 and 2

Homologous Chromosomes

Maternal and paternal chromosome pairs carrying genes for the same traits.

Sex Chromosomes

code for the sex of offspring;

• 2 X chromosomes = female

• 1 X chromosome + 1 Y chromosome = male

Interphase of Meiosis

GUESS WHAT??? SAME AS MITOSIS~

Meiosis

Cell division reduces chromosome number by head (can only give half of DNA)

Four phases of Meiosis 1

• Prophase 1: crossing over segments of non-sister chromatids break and reattach to the other chromatid (very good— genetic diversity) - like playing footsies

• Metaphase 1: similar to Mitosis

• Anaphase 1: similar to Mitosis

• Telophase 1: similar to Mitosis

Meiosis 2

Similar to Mitosis- same process (telophase 2 makes 4 haploid daughter cells)

Fertilization

fusion of sperm and egg to form zygote

Spermatogenisis

making of sperm

Oogenisis

making of egg

Trait

specific characteristic of an individual (MAY VARY)

True Breeding

Would process offspring with identical traits to themselves (the traits of each successive generation would be the same)

Gene

Inherited factors passed from parent to offspring determining traits.

Allele

different forms of genes

Gametes

sex cells

Probability

likelihood that a particular event will occur

Homozygous

organism that have 2 identical alleles for a particular gene

Heterozygous

organism that have 2 different alleles for the same gene

Phenotype

physical traits

Genotype

genetic makeup

Independent Assortment

Mendel performed an experiment that followed two different genes as they passes from 1 generation to the next

Principle of Independent Assortment

genes for different traits can segregate independently

Incomplete Dominance

one allele is not completely dominant over another/the heterozygous is a MIX

Multiple Alleles

gene with more than 2 alleles is said to have multiple alleles

Polygenic Traits

are controlled by two or more genes (many genes)/ often show a wide range of phenotypes (EX: skin color)

Sex-linked Inheritance

some traits are located on the sex chromosomes so the inheritance of these traits depends on the sex of their parent carrying the trait/affects males more than females/some associated with disorders (male pattern baldness or reel-green color blindess)

Autosomal Dominant Inheritance

Refers to those situations in which a single copy of allele is sufficient to cause expression of a trait (EX: progeria, Huntington’s disease)

Genes and the Environment

The characteristics of any organism are determined by the genes that organism inherits and the environment it lives in

Central Dogma of Biology

DNA —> RNA —> Protein

DNA stores information by order

A = T C = G

Transcription

Process of copying DNA into RNA.

Translation

Conversion of RNA into proteins.

Codon

3-letter “word” in mRNA / consists of 3 consecutive bases that specify a single amino acid (AMino acids make up proteins)

Process of Transcription

RNA polymerase makes mRNA —> mRNA has a message from DNA… it leaves the nucleus and goes in the cytoplasm

Reading mRNA (between)

Ribosomes (attaches to mRNA) reads message —> tRNA has an anticodon and places the corresponding amino acid

Process of Translation

Polypeptide chain continues to grow until the ribosome reaches a “stop” code on the mRNA molecule/ translated into sequences of amino acids on ribosomes/ tRNA carries individual amino acids to ribosomes according to anticodon

Gene mutations (point mutations)

Produces changes in a single gene (1 chromosome)

Substitutions

GENE MUTATIONS/substitute one base pair for another

Insertion/Deletion

GENE MUTATIONS/inserting extra nucleotide/take one nucleotide out

Insertion/Deletion

GENE MUTATIONS/inserting extra nucleotide/take one nucleotide out

Chromosomal mutations

Involves changes in the number or structure of chromosomes

Deletion

CHROMOSOMAL MUTATION / deletion of chunk of genes

Duplication

CHROMOSOMAL MUTATION / 2x

Inversion

CHROMOSOMAL MUTATION / switching, flipping

Translocation

CHROMOSOMAL MUTATION/rearranging (getting letters from another source)

Mutagens

Occurs naturally mistakes

Protein Folding

Primary, Secondary, Tertiary, Quaternary

Mutation

Changes in DNA, including gene mutations and chromosomal mutations.

Evolution

Involves changes in gene frequencies within populations over time.

Gene pool

All the genes in a population

Allele frequency

How often “B” and “b’ show up

Hardy-Weinberg Law

Conditions where allele frequencies remain constant, indicating no evolution.

• no mutations

• Populations are large

• Mating is random

• No immigration of other genes

• No selection pressure

Genetic Drift

In small populations, allele frequencies can change drastically!

Bottleneck Effect

event occurs —> reduces size of population —> only those left surviving will reproduce —> changes the population

Founder effect

a few colonize a new area —> only THEIR genes in the population —> could lead to new species! 😄

Species

a group that can mate and have fertile offspring

Allopatric Speciation

barrier PHYSICALLY separates the population

Sympatric Speciation

specialization to a specific habitat within the same location

Pre-mating Isolation Mechanism

before mating, prevent it (EX: breeding @ different times, incompatible reproductive structures, different courtship rituals)

Post-mating Isolation Mechanism

after mating, unfit offspring (EX: cannot fertilize, hybrids don’t survive, hybrids are sterile)

Sexual Selection

Females (usually) choose which males to mate with, only their genes go on to the next generation

Gene flow

Immigration/Emigration of individuals happens all the time, causing genes to MIX together

Stabilizing Selection

Middle phenotype is best, so that increase over time (EX: height- bell curve) (EX: Sickle cell anemia and Malaria)

Directional Selection

One of the extremes are the best, so the population shifts in one direction (EX: speed)

Disruptive Selection

Both extremes are good and the middle is bad (EX: peppered moths)

Hardy Weinberg Equation

• Allele frequencies remain constant over generations

• p^2 + 2pq + q^2 = 1

• p squared = frequency of dominant allele, q squared = frequency of recessive allele, 2pq = frequency of heterozygous (p and q are the alleles)

• Assumptions: no mutation, migration, natural selection, genetic drift, random mating

Adaptations

Structures or behaviors aiding organisms in survival and reproduction.

Morphological (anatomical) adaptations

Camouflage (blend in with surroundings), Mimicry (look like something you’re not), Defense Mechanisms (defend yourself from predators)

Physiological (internal) adaptations

poisons, temperature regulations

Behavioral

Sexual selection, tool use, hibernation/migration

Coevolution

When 2 species evolve in response to another/ work together = mutualism/ “arms race” predator and prey

Main evidence to support evolution!

Biogeography, homologous Structure, Similar Embryos, Molecular/DNA

Biogeography

Fossils = dead preserved organisms / if organisms live in similar environments —> similar selection pressures —> similar features!

Homologous Structures

Similar bones = same ancestor —> must share DNA