bio 2
Incomplete Dominance: neither of the two alleles is dominant, and the heterozygote phenotype is intermediate between that of the two homozygotes. Ex. Red + white = pink
Co-dominance: phenotypes of both alleles are exhibited in the heterozygote (the heterozygote is not an intermediate) Cow spots (roan) Multiple alleles: more than just two alleles for a single gene in the population. Ex. humans have A, B, AB, or O blood type Red blood
type of genes, Homologous chromosomes have the same structure and cells have various antigen protein molecules on their surface (cell membrane) depending on a person’s blood type A person makes
their genes are in the same relative position. homozygous: same or hetero: diff antibody proteins to attack “foreign” antigens if the wrong blood type is used in transfusion.
Human diploid cell (zygote or somatic): 46 chromosomes, 23 homo pairs. Rhesus(Rh) factor: red blood cell surface antigen protein with only two alleles: Rh + is dominant to the Rh – allele Individuals with the
Karyotypes for chromosomal abnormalities: amniocentesis; amniotic fluid. “+” (pos) phenotype may have either Rh+Rh+ or Rh+Rh- genotypes Individuals with the “-” (neg) phenotype must have the Rh-Rh- genotype
Chorionic villus sampling: from placenta, faster. Pleiotropy: 1 locus influences more than one trait. Ex.) frizzle feather causes organ enlargement, low fertility, odd body temp. incomplete dom
Cell division: reproduction of cells, tissue renewal, growth + development Polygenic trait= 1 trait controlled by multiple genes. Ex. Continuous traits like height, wide range of phenotypes.
S phase: longest, replication Epistasis: expression of 1 gene alters or modifies the expression of a second gene. Involves at least 2 genes at different loci ex. Gene a and b
Mitosis: nuclear division, ^ # cells Produces: 2 ident. Daughter cells, same # chromo ex. Lab coat color, The synthesis gene is epistatic to the color gene. The “ee” genotype results in golden retrievers, regardless of
as parent, same dna sequence. the color gene genotype (BB, Bb, or bb), because no pigment will be deposited.
G1: growth phase, start of cell cycle, ^ protein+organelle production Phenotypic plasticity: role of environment in gene expression, different colors grasshoppers, plant shorter with begin bothered.
S phase: synthesis, dna replication + cell growth (cells copied before g2 & prophase) anisogamous: different in morphology (most sexually reproducing gametes) sperm=smaller, egg=bigger so some loci unpaired
# chromo stays same, dna amount doubles *cell must have s to have replicated chromo XX= female XY= male, sex chromo carry loci that determine if gonads become ova or testes. females produce test but have no
G2: growth, check + prep for mitosis SRY locus: responsible for testosterone receptors on gonads (indifferent until 8 weeks) receptors so they develop ovaries
Centrosome: microtubule organizing center, assembly of spindle microtub. (replicates) produces regulatory protein that induces production of cell surface receptors for testosterone, causing cell differentiation
Chromosomes are replicated but not condensed XX= homogametic, only produces X gamete XY= heterogametic, produces X or Y (determine sex of offspring)
M(mitotic phase):nuclear division (mitosis), cytoplasmic division via cytokinesis Aneuploidy= abnormal chromosome # bc nondisjunction during meiosis= failure of homo chromosomes or sis chrom. to separate.
Replication has already occurred, 1 chromosome Can result in daughter cells w too many or too little chromosomes.
Prophase:dna is replicated+condensed, nuclear division begins, mitotic spindle begins forming, X-linked traits: genes only on the X chromosome, XY individuals are hemizygous for X-linked traits (have only 1 allele)
Centrosomes, microtubules, asters; Centrosomes move to opposite sides, replicated chromo condense - if they have the allele they will have the trait. Ex. Color blindness X^c = colorblind, X^+ = normal vision (dom)
Each replicated chromosome = two identical sis chromatids (joined at centromeres & X- chromosome inactivation: 1 of an XX individual’s X chromosomes is inactivated in every cell as dosage
Joined by cohesions, have same allele for each gene compensation between the XX and XY individuals (barr body) . If 50% of cells express normal x, carriers wont show disease
Pro-metaphase: nuclear envelope fragments, sister chromatids distinct + bound at An XX individual who is a heterozygote for X-linked genes will be a mosaic of phenotypes because it is RANDOM which X gets
centromere to spindle fibers. Each sis chrom. has kinetochore: protein complex assembled at centromere inactivated in each of their cells. Ex. Torti cats, X^BX^O, some orange some black. Ex. Calico bc piebalding
kinetochore captured by microtubules. Mitotic spindle complete. Y- linked traits: only expressed in XY individuals, can contribute to sexual function.
Nonkinetochore microtubules: extend from each pole, contact plasma membrane Plants: some have XY sex determination. Mechanisms of sex determination not evolutionarily conserved.
Kinetochore microtubules: each pole, connect to kinetochore on sis chrom. Fruit flies: XY determination, sex determined by ratio of autosomes to X chromosomes. F: 2 sets autosomes, 2 X’s M: 2 auto, 1 X
Aster: microtubules anchor centrosome to cell membrane, provide anchorage, microtubules dev. here X0 (cricket, roaches, grasshoppers): m: X0, F:XX, no Y, probably lost evolutionarily.
Metaphase: kineto. mic. Line up sis chrom. in single file on midline (metaphase plate) sister chrom face opposite poles ZW: (Birds, butterfly, fish): M: ZZ (homogametic) F: ZW (heterogametic)
Anaphase: cohesins cleaved by separase, once sis chrom. now indiv. Daughter chromo., kinet micro. shorten Hap. Dip. Sex determination: does not involve sex chromosomes. Some insects, F: dip M: hap, fert= f
Telophase:mitotic spindle disassembles, nuc. Membrane forms * mitosis over non- chromosomal sex determination: enviro.: temp dependent. Age/size: plants can start m & become f
Cytokinesis: cell membrane pinches at cleavage furrow * cytoplasmic division complete when large enough. Social control of sex determination: m mate w/ f, when m lost, largest f become f & fert rest
sexual life cycles: haploid+diploid phases, meiosis (dip to hap) and fertilization Parthenogenesis: asexual reproduction where f produce offspring from unfert. Eggs. Ex.) all lizards female
fertilization: activates egg + restore chromo # and only need sperm to stimulate egg development and expel sperm after egg activation. (before fert)
meiosis: form 4 haploid gametes, add genetic variation. 1 round dna replication, 2 rounds cell division Pedigree analysis: examining trait over several generations to determine type of inheritance
meiosis 1: reduction (2n > n). prophase 1: sis chrom held by cohesions, homologues (parent chrom.) line up genes (synapsis) = male = female row left to right: offspring in order of birth, L to R. Shaded shape = have trait ex.) color blind
makes tetrad (made of 4 sister chromatids) Chiasmata= points of crossing over Consanguineous mating: mating among relatives, causes homozygous for recessive alleles.
crossing over: dna molecules of non sis chrom. are broken by proteins + rejoined, exchange dna ^ Blue people: recessive autosomal allele, causes increase in methemoglobin, results in blue skin.
leads to new allele combos, makes genetic variation Analyzing pedigrees: pick letters that represent alleles for trait (gene) in question. Figure out genotype of the
tetrads line up on metaphase plate, in pairs next to each other, eggs and sperm don’t have to be on same side individuals in the pedigree using symbols. Ex.) If autosomal dominant = B If autosomal recessive = b
law of indep. Ass.: each allele pair sep. independently of eachother in gamete formation, leads to assort. If X-linked dominant = X^B. If X-linked recessive = X^b (If Y-linked = look for the trait that ONLY shows up in XY
Gametes haploid bc: each cell gets 1 allele from mom OR dad. individuals and is ALWAYS passed from fathers to all sons)
Now cell is n, 1 copy each chromo. *skips g1 and s, goes to meiosis 2 Aneuploidy: can lead to down syndrome, extra #21 chromosome. Has maternal likelihood increase w mom age
Meiosis 2: (separates sister chromatids) metaphase 2: attached sis chrom. line up @ midline Anaphase 2: sis chrom Chronic myelogenous leukemia (CML): a cancer of blood and bone marrow, caused by translocation
Separate Results: 4 haploid (n=3), w/ 1 set of chromosomes. Between human chromosomes 9 and 22. Abl gene is an oncogene.
Cell cycle control system: cyclin operated set of molecules, triggers+ coordinates events in cell cycle Sickle cell trait: caused by autosomal S/s allele. SS genotype= normal RBC, Ss= when blood o2 low
Johnson and Rao (1970): g1 fused w s or m phase immediately moved into that phase RBC become sickled + reduced malaria. ss= sickle cell anemia + malaria resistance.
G1 check: if cell can get through g1 it should get through the rest ;Cell checks everything, dna is fine, Congenital generalized Hypertrichosis: abnormal amount of hair growth, caused by X-linked dominant allele