Bio1A Exam 3 Prep

G1 checkpoint

most important, check for DNA damage, cell size, adequate reserves, etc.

G0 phase

non dividing state if failure to pass G1 checkpoint

G2 checkpoint

cell size and reserves re-check including newly duplicated DNA from S phase

M checkpoint

kinetochores not attached to spindle microtubes send a signal to delay anaphase. Prevents division of unequal chromosomes.

Positive regulation

drives a phenomenon

Negative regulation

suppresses phenomenon

Cyclins & cyclin-dependent kinases (Cdks)

Positive regulator; Cyclin binds to Cdk, P-donating kinase adds a P, Cyclin-Cdk complex donates P to target protein, continues cell cycle (refer to cyclin D, E, A, B)
D - Mid G1 transition. Phosphorylation of retinoblastoma gene product (Rb, tumor suppressor protein)
E - G1/S transition.
A - S/G2 transition
B - M phase transition

Cyclin

Family of proteins that regulate cell progression in cell life cycle.

Retinoblastoma protein (Rb)

Negative regulator; binds to E2F, preventing DNA binding. E2F is a transcriptional activator.

p53

Negative regulator; apoptosis if cellular damage is too far gone. >1/2 cancers have mutated p53.

p21

Negative regulator; upstream regulator activated by p53. Inhibits CDK complexes activity.

Proto-oncogenes

promote cell growth (oncogenes when mutated)

Sexual reproduction

Two haploid cells fuse to form a unique diploid cell.

Meiosis I

homologous pairs separate, 2n -> n

Meiosis II

sister chromatids separate - n -> n

Independent assortment

tetrads line up randomly at metaphase I plate

Interkinesis

Some species enter a brief interphase (interkinesis) before meiosis II (lacks S phase)

Crossing over

DNA exchange between paired homologous chromosomes during meiosis.

homologous vs homozygous

Homologous chromosome - same genes, different alleles
Homozygous - Gene with same allele on chromosome.

Crossing over

Any combo of genes between two parents.

Sister chromatids

identical single duplicated chromosomes

Chiasmata

crossover over point

Tetrads

structure of homologous chromosomes

Meiosis I: Prophase I

Synapsis and crossing over, tetrads connect and exchange gene info.

Meiosis I: Metaphase plate

paired homologous chromosomes (tetrads) instead of individual replicated chromosomes.

Meiosis I: Anaphase I

homologous chromosomes separate instead of sister chromatids

Johann Gregor Mendel

set framework for genetics in 1800s, used quantitative analyses

Law of Segregation

Alleles segregate during Meiosis

"and" rule

p that 2 events will occur together, multiply

"or" rule

p that either of ≥2 will occur, add

Dihybrid cross

cross between two parents with two phenotypes controlled by two distinct genes.

Law of Independent Assortment

Allele pairs of different genes segregate independently

Test cross

dominant plant crossed with homozygous recessive to reveal parent's genotype
All D offspring - homozygous D parent
1:1 ratio offspring - heterozygous parent

Linked genes

inherited together b/c located near each other on same chromosome

Parental types

offspring w/phenotype matching one of parental phenotypes

Recombinant types

offspring with nonparental phenotypes, 50% recombination frequency for any 2 genes on different chromosomes.

Centimorgans (cM)

maternal and parental alleles for these genes recombine in 17% of offspring on average

Karotype

All chromosomes isolated and labeled for display.

Nondisjunction

occurs in meiosis I/II if:
homologous chromosomes fail to separate in meiosis I
sister chromatids fail to separate in meiosis II

Aneuploid

too few/too many chromosomes

Trisomy

three copies of one of the chromosomes

Monosomy

only one copy of chromosomes

Down Syndrome

(Trisomy 21), frequency occurs as mother ages.

Edward's Syndrome

(Trisomy 18)

XXX

(Trisomy X Syndrome) - taller than average, normal fertility

XXY

(Klinefelter's Syndrome) - infertility, poor func testes, often unaware

XYY

(Jacob's Syndrome) - taller than average, learning disabilities and behavioral problems

Tuner Syndrome

(Monosomy X) - sterile females, only known viable monosomy in humans

Polyploid

More than the correct number of chromosome sets, sterile b/c meiosis cannot proceed normally. Commonly plants, more robust and larger than euploids.

Deletion

removes a segment

Duplication

repeats a segment

Inversion

reverses a segment within chromosome

Translocation

moves a segment from one chromosome to nonhomologous chromosome.

Anueploidies

Anueploidies describe genetic conditions where an individual
does not have the normal chromosome number. Aneuploidies
usually exhibit a range of phenotypes that can be severe or even
lethal.

Variable regions

made variable during biosynthesis for new antibodies with with binding capabilities

Fluroophore

a probe molecule, used in immunostaining to bind to secondary antibody

Sry gene

only Y chromosome, controls differentiation of testes if on the Y chromosome

XY-Sry

lacks Sry gene in Y but a transgenic gene from an autosomal chromosome can fix it.

Reprimo

p53-dependent candidate tumor suppressor gene