Biology Heredity

Cell Cycle

Cell Cycle

life of a cell from the time it is first formed from a dividing parent cell until its own division into two cells

Mitosis

asexual reproduction, growth, repair/replace of damaged cells, unicellular organisms need cell division to reproduce while multicellular organisms need to replace dead cells, divide somatic cells, form 2 identical diploid daughter cells, 1 cellular division, same # of chromosomes as parents, chromsomes MUST duplicate

Growth Factors

cells respond to specific molecular signals, both internal and external, protein released by certain cells that stimulate cells to divide

Differentiation

cells stop dividing to specialize in structure, ex. neurons

Apoptosis (cell death)

process that eliminates unnecessary cells during development and removes unhealthy or damaged cells in a mature organism

Cell Cycle Regulators

molecular signals that may stimulate or halt cell division, instruct cells to differentiate or initiate cell death

Too Little Cell Division

harmless hair loss, warts

Too Much Cell Division

life-threatening tumor

G1 Phase

newly divided cell enters and increases in size to prepare to replicate DNA, checkpoint: no dna damage, sufficient resources

Interphase

most of cell cycle, G1, Synthesis, G2

Synthesis

cell replicates its dna (chromosomes), two sets of chromosomes, checkpoint: no errors in replication

G2 Phase

continues to grow and prepare for division, checkpoint: no damage, chromosome set complete, enough cell components

G0

resting, nondividing state, cells may exit to resting state if they receive signal to differentiate or when resource are insufficient, depends on stage of development, type of cells and resources, some mature cells never leave G0 and some enter to repair

Somatic Cells

all body cells besides gametes, diploid (46 chromosomes in humans)

Sister Chromatids

when chromosomes replicate, each duplicated chromosome consists of TWO sister chromatids held together by sister chromatid cohesion and attached by a centromere, each chromatid has a copy of DNA

Prophase in Mitosis

chromatin condenses to form chromosomes, nucleoli disappear, mitotic spindle (consists of microtubules from two centrosomes) begins to form

Prometaphase in Mitosis

nuclear envelope begins to fragment so microtubules attach to chromosomes, two chromatids held together by centromere which contains protein kinetochores on each chromatid where microtubules attach

Metaphase in Mitosis

microtubules move chromosomes to metaphase plate, microtubule complex is the spindle, kinetochores of chromatins are attached to kinetochore microtubules

Anaphase in Mitosis

sister chromatids begin to separate, cell elongates, opposite ends of cells contain equal sets of chromosomes

Telophase in Mitosis

nuclear envelope reforms and chromosomes become less condensed, two new nuclei form

Cytokinesis in Mitosis

division of cytoplasm, cleavage furrow in animal cells, cell plate in plant cells, creates two identical diploid daughter cells

Binary Fission

process by which prokaryotes replicate their genome

Cyclin-dependent Kinase

protein complex of kinases and cyclins, cyclins activate kinases which stimulate the cell cycle through phosphorylation, also growth factors

Protein Kinase

activate or deactivate other proteins through phosphorylation, control cell cycle, exist at all times

Cyclins

regulatory proteins that interact with kinases

Cell Cycle Control System

cyclically operating set of molecules in the cell that trigger and coordinate key events in the cell cycle

Checkpoint

control point where stop and go-ahead signals can regulate cycles

G1 Checkpoint

most important, if cell receives go-ahead, it will most likely go through every other phase into division

Density-dependent Inhibition

phenomenon in which crowded cells stop dividing

Anchorage Dependency

normal cells must be attached to substratum to divide

Transformation

cells that acquire ability to divide indefinitely undergo transformation causing them to behave like cancer cells

Cancer Cells

exhibit number of key mutations that affect the cell cycle, mutations generally accumulate over time, explaining why people generally get cancer as they age, do not exhibit density-dependent inhibition or anchorage dependency, no limit to number of times they can divide

Tumor

mass of abnormal cells

Benign Tumor

abnormal cells remain at original site if genetic and cellular changes do not allow them to move or survive

Malignant Tumor

cells whose genetic and cellular changes enable them to spread to new tissues and impair functions of organs based on ability to divide indefinitely

Metastasis

spread of cancer cells to location distant from original cells

Genes

segment of Dna that code for basic units of heredity, transmitted from one generation to another

Locus

location of gene on chromosome

Homologous Chromosomes

pair of similar chromosomes, one chromosome is inherited from each parent (maternal and paternal), both chromosomes carry genes that control same inherited characteristics, similar in length and centromere position

Karyotype

picture of an organism’s complete set of chromosomes arranged in pairs of homologous chromosomes from largest pair to smallest pair

Sex Chromosomes

X and Y chromosomes, NOT homologous, females- XX, males -XY

Autosomes

nonsex chromosomes, all except X and Y

Gametes

sperm and egg, haploid (n, 23 chromosomes in humans), contain one chromosome of each homologous pair

Meiosis

sexual reproduction, create gametes, end in 4 haploid unique daughter cells, 2 cellular divisions, one chromosome of each pair will be randomly distributed to gametes, ends in half as many chromosomes, chromosomes MUST duplicate

Fertilization

fusion of sperm (23 chromosome) and egg (23 chromosome) cell to create a diploid zygote, contributes to genetic variability as unique sperm and unique egg fuse

Prophase 1 in Meiosis

chromosomes condense, sister chromatids attached at centromeres, synapsis and crossing over, nuclear envelope disappears, spindle microtubules attach to kinetochores to move chromosomes to metaphase plate

Synapsis in Prophase 1

joining of homologous chromosomes on top of each other (tetrad), aligns chromosomes gene by gene to prepare for next step

Crossing Over in Prophase 1

DNA from one homolog (non-sister chromatid) is cut and exchanged, increases genetic variation, where it occurs- chiasma forms which holds homologs together

Metaphase 1 in Meiosis

homologous pairs are lined up at metaphase plate

Anaphase 1 in Meiosis

homologous pairs separate and move toward poles, spindle apparatus helps move chromosomes toward ends of cells, sister chromatids stay connected

Telophase 1 in Meiosis

homologous chromosomes reach opposite poles, cleavage furrow in animal cells, cell plate in plant cells, 2 new nuclei form, nuclear envelope reforms

Cytokinesis 1 in Meiosis

divides cytoplasm to form 2 haploid daughter cells, genetic variability, sister chromatids still attached but homologous chromosomes separated (each cell has one chromosome)

Law of Segregation

supported by 3:1 ratio in F2 generation, anaphase, alleles for each character are segregated so each gamete receives one parental allele, provides genetic diversity

Law of Independent Assortment

supported by 9:3:3:1 ratio in F2 generation, anaphase, each pair of alleles segregate independently (on non-homologous chromosomes) into gametes, provides genetic diversity, 50% chance daughter cell gets paternal chromosome or maternal chromosome, ex. chromosome 1, 2, 3 from mom and chromosome 4 from dad

Possible Genetic Combinations

2^23

Prophase 2 in Meiosis

spindle apparatus forms, nuclear envelope disappears, sister chromatids are moved to metaphase plate

Metaphase 2 in Meiosis

haploid number of chromosomes lined up on metaphase plate, sister chromatids not genetically identical, kinetochores are attached to microtubules from opposite poles

Anaphase 2 in Meiosis

centromeres of sister chromatids separate and individual chromosomes move to opposite ends

Telophase 2 in Meiosis

2 nuclei appear, nuclear envelope reforms, chromatids on opposite ends

Cytokinesis 2 in Meiosis

division of cytoplasm, results in 4 haploid UNIQUE gametes

Egg

larger gamete, 1 of 4 produced in meiosis, contains all organelles and mitochondrial DNA

Sperm

smaller gamete, 3 of 4 produced in meiosis, contains DNA, determines sex of zygote

True-Breeding

parental (P) generation

F1 Generation

first offspring generation, reveals dominant trait

F2 Generation

second offspring generation, can be many different phenotypic ratios

Allele

alternative version of genes, account for variations in inherited characteristics among offspring, ex. flower color, every sexually reproducing organism receives one allele from each parent, two alleles separate during law of segregation

Dominant Trait

expressed if allele is inherited, not necessarily most prevelent

Recessive Trait

expressed only if both alleles inherited

Homozygous Dominant

AA, two of same alleles for dominant trait

Homozygous Recessive

aa, two of same alleles for recessive trait

Heterozygous

Aa, two different alleles

Testcross

determines if individual showing a dominant trait is homozygous or heterozygous, done between unknown and homozygous recessive- if RRxrr, all will be dominant, but if Rrxrr, some will be recessive

Monohybrid Cross

intended to study only one character

Dihybrid Cross

studies two characters at once

Rule of Multiplication

if finding the probability of A AND B, multiply them

Rule of Addition

if finding the probability of A OR B, add them

Incomplete Dominance

neither allele is completely dominant and phenotype is somewhere between (in heterozygous), ex. snapdragons, 1:2:1 phenotype, heterozygous are pink

Complete Dominance

heterozygote and homozygote for the dominant allele are completely indistinguishable

Codominance

two alleles affect the phenotype in separate, distinguishable ways in heterozygous, ex. roan cattle is red and white, blood type can be AB

Multiple Alleles

more than 2 possible alleles, but person has 2 because parents contribute 2, ex. blood type ABO

Polygenic Inheritance

additive effect of two or more genes on a single phenotypic character, ex. height, every dominant allele adds 2 inches

Quantitative Characters

characters that are not one of two discrete characters, but instead vary in the population in gradations along a continuum

Multifactorial Characters

environment contributes to quantitative nature of characters, both environment and genetics influence phenotype

Phenotypic Plasticity

people with same genotype may express it differently in phenotype due to environmental influences, ex. skin tone

Chromosome Theory of Inheritance

Mendelian genes have specific loci along chromosomes and chromosomes undergo segregation and independent assortment

Sex-linked Genes

gene located on either sex chromosome, can be both X-linked or Y-linked, females only express genes if homozygous recessive (carrier if heterozygous), male passes mutant allele only to daughters, female can pass allele to sons and daughters

SRY

sex-determining region of Y, required for development of testes

Hemizygous

males only have one locus so any male receiving recessive gene will express it, results in many more men with mutant allele

Sex-linked Disorders

color-blindness, Duchenne muscular dystrophy, hemophilia

Linked Genes

genes located near each other on same chromosome, tend to be inherited together, the farther apart, the more likely to cross over

Recombination Frequency

how likely genes are to cross over

Independent Genes

genes on separate chromosomes that do not inherit together, NO crossing over

Map Units

how far apart alleles are on the same chromosome

Nondisjunction

members of a pair of homologous chromosomes do not separate properly during meiosis 1, one gamete receives 2 copies and the other none, ex. down syndrome, klinefelter syndrome

Mitochondrial DNA

from mother’s egg

Genetic Map

ordered list of genetic loci along particular chromosome

Pedrigee

diagram that shows relationships between parents and offspring across two or more generations, helps determine genome and predict future genomes

Autosomal Dominant Pedigree

males and females both likely, two recessive parents WILL not have a dominant child, traits do not skip generations, trait is present whenever corresponding gene is present, male-to-male transmission, dom/hetero parents give trait to child, ex. Huntington’s disease

Autosomal Recessive Pedigree

males and females both likely, both parents of offspring who have trait are heterozygous/carriers, traits skip generations, recessive parents have recessive kids, homozygous individuals have trait, ex. sickle cell anemia- RBC shape is sickled and builds up in arteries, carriers less susceptible to malaria

Sex-linked Recessive Pedigree

all daughters of male who have trait are carriers, carrier female passes recessive X to 50% of sons, skip in generation, no male-to-male transmission, primarily in males, ex. colorblindness, hemophilia