BIO100 Exam 2

Chromosome number

23 pairs, 46 total

chromosome

most condensed version of DNA

homologous pairs

matched pairs of chromosomes

diploid/haploid

Diploid: somatic cell with two matched sets of chromosomes 2n

Haploid: cell that contains one set of 23 chromosomes

sex chromosome vs autosome

sex: x and y chromosomes

autosome: any chromosomes that is not a sex chromosome

G₁, S, G₂, M phases

G1: Interphase - normal processes while also preparing for cell division

S: Interphase - DNA replicates into two copies of each chromosome(sister chromatids) that are attached at the centromere, the two centrosomes create the mitotic spindle connected to centrioles

G2: Interphase - cell replenishes energy, some cell organelles are duplicated

M: many phases, results in division of the cell nucleus

chromatin

what DNA is packaged as between cell division

Cancer

uncontrolled cell division

proto‑oncogenes

normal genes that can become oncogenes- act like a stuck gas pedal and promotes cell-cycle progression, only one needs to be mutated

tumor suppressor genes

halt the cell cycle if DNA is damaged, both alleles need to mutate

Prokaryotic division

they divide by binary fission, asexual, identical offspring

origin of replication

replication of prokaryotic chromosome begins at origin of replication and continues in both directions

replication fork

region in a cells DNA double helix that has been unwound and separated

Meiosis I

homologous chromosome pairs line up and cross over DNA

crossing over

forming recombinant chromatids in meiosis I

independent assortment

during metaphase I, alleles of different genes independently separate

Meiosis II

sister chromatids separate

nondisjunction

failure of chromosomes to separate during meiosis, leads to games/zygotes with missing or extra chromosomes

inversions

chromosome inverts 180

translocations

one part of a chromosome breaks off and connects to another

alleles

one or two or more variants of a gene that determines a particular trait for a characteristic 

dominant vs recessive traits

dominant traits mask the expression of another trait when both versions of the gene are present in an individual

genotype vs phenotype

genotype- genetic makeup

pheno- observable traits

Incomplete dominance

in a heterozygote, expression of two contrasting alleles such that the individual displays an intermediate phenotype (blending)

Codominance

in a heterozygote, complete and simultaneous expression of both alleles for the same characteristic (Blood) (crosses- 1:2:1 but all phenotypes appear)

Multiple alleles

more than two alleles exist in a population, each individual still only carries two alleles

Epistasis

interaction between genes where one gene masks another, ex. a recessive allele at one locus might prevent pigment production regardless of allele at another locus

Sex-linked traits

genes on sex chromosomes have unique patterns. X linked recessive conditions appear more often than males

basic ratios (e.g. a heterozygote × homozygote recessive cross yields ~50:50 phenotypes

DNA structure

DNA nucleotides consist of a deoxyribose sugar (not ribose), a phosphate, and one of four bases (A, T, G, C) DNA strands are anti-parallel and form a double helix with sugar-phosphate backbones outside and base pairs inside

DNA packaging

DNA wraps around histone proteins into nucleosomes → solenoids → chromatin fiber.

Replication

helicase unwinds the double helix; primase lays RNA primers; DNA polymerase adds nucleotides to the 3′ end of the new strands

replication origins open replication “bubbles” and both strands are copied simultaneously

leading and landing strand

new strands (one strand synthesized continuously, the leading strand, and one in Okazaki fragments, the lagging strand)

Replication proofreading

DNA polymerase proofreads new DNA and mismatches can be fixed by mismatch repair. Understand that template strand guides complementary synthesis.

Transcription

DNA → mRNA. RNA polymerase binds a promoter and builds an mRNA transcript 5′→3′ complementary to the DNA template strand (T→U)

occurs in the nucleus (eukaryotes) and involves processing of mRNA (cap, tail, splicing of introns)

Translation

mRNA codons → amino acids using ribosomes and tRNAs

Each codon (3 bases) specifies an amino acid or stop

Central dogma

DNA → RNA → Protein.

DNA is transcribed to mRNA, which is translated to protein (amino acids)

PCR (Polymerase Chain Reaction)

technique used to make multiple copies of DNA

Denaturation

PCR step 1- Heat (~95 °C) separates (denatures) the DNA strands

Annealing

PCR step 2- Cool (~50–60 °C) so primers hybridize (anneal) to target sequences

Extension

PCR step 3- Warm (~72 °C) for Taq DNA polymerase to extend primers and copy DNA. Repeat cycles exponentially amplify the target

Recombinant DNA

DNA fragments are inserted into vectors (like plasmids) using restriction enzymes (which create sticky ends) and DNA ligase

molecular cloning

plasmids with foreign DNA are introduced into bacteria. As bacteria divide, they replicate the plasmid (and foreign gene), producing many copies

Reproductive cloning

Recreating an entire organism from one cell (like Dolly)

Gene therapy

including a healthy gene to cure a genetic defect, usually functional gene is carried by viral vector into patient cells to replace faulty gene

Transgenic organisms

organism with a foreign gene stably inserted, ex. mice with fluorescent protein genes

Vaccines vs. antibiotics

Vaccine- stimulate immunity, use microbes and clones genes to produce an antigen in bacteria or yeast, which is then purified when injected

Antibiotics- chemicals from fungi/bacteria that kill or inhibit bacteria, ineffective against viruses

Recombinant protein drugs

genes for human proteins can be clones into bacteria or yeast to produce large quantities of human proteins (insulin or growth hormone)

vector

a DNA molecule that is used as a vehicle to carry a particular DNA segment into a host

plasmid

small circular pieces of DNA that replicate independently from the host’s chromosomal DNA, prokaryotic

restriction enzyme

protein that cleaves DNA at specific sites, can be used to eliminate infections or manipulate fragments of DNA in a lab

ligase

catalyzes the formation of chemical bonds between DNA strands, glue

cloning (molecular vs. reproductive)

molecular- copying short strands of DNA and create multiple copies of genes

reproductive- make a clone or an identical copy of an entire multicellular organism

transgenic

carrying genes from another species

genome editing (CRISPR)

alteration of the genetic material of a living organism by inserting, replacing, or deleting a DNA sequence

CRISPR-Cas9

modern gene editing tool

somatic gene therapy vs germline modification differ ethically and technically

somatic- genetic material in somatic cell is altered, not genetically transferred

gremlin- gametes altered through germ, transferred to offspring