bio 120 chapter 6

study of the heredity of the organism

genetics

the complete genetic information in a cell, the complete base sequences of chromosomes

genome

structures containing DNA, carry hereditary information, chromosomes contain genes

chromosome

segments of DNA that encode functional products, usually proteins

gene

the genetic makeup of an organism, codes for the genetic characteristics of the organisms

Potential characteristics

genotype

manifests genotype genetic makeup

actual expression of the genetic characteristic

phenotype

study of organism’s genome

genomics

smaller genomes but still has variety in cytoplasm

circular & singular DNA

bacterial chromosomes- circular or linear

plasmids provide survival advantages for bacteria, i.e.

prokaryotic cells

Larger genomes in nucleus

Human cell has approx. 24,000 genes

Chromosomes have histones to prevent tangling of DNA

DNA- antiparallel directionality of 5’ to 3’

Mitochondria & chloroplasts- own DNA-

eukaryotic cells

nitrogenous bases

adenine(purine), guanine(purine), thymine (pyrimidine), cytosine(pyrimidine)- (uracil in RNA)

what pairs with adenine

thymine

what pairs with guanine

cytosine

enzymes in DNA replication

helicase, DNA polymerase 111, DNA polymerase 1, ligase

unzips DNA helix

helicase

synthesizes new DNA strand, adds bases, proofreads

DNA polymerase 111

removes primer, repairs mismatches of bases

DNA polymerase 1

binds nicks in DNA, repairs

ligase

each daughter molecule is identical to the parent in composition- neither is completely new

the template strand is an original parental DNA strand

semi conservative replication

place in the helix where the strands are unwound, and replication is taking place

each DNA molecule has 2

replication fork

circular DNA, replication proceeds in opposite direction

progeny offspring cell receives one identical copy of the parental DNA & a new DNA strand

replication is highly accurate because of proofreading capability of DNA polymerase

bidirectional replication

old view of central dogma

DNA— RNA— protein

dna is used to synthesize rna

in eukaryotic cells in nucleus

section of DNA used as template to make mRNA

transcription

rna template used to produce proteins

occurs at ribosomes

determines phenotype

translation

new view of central dogma

RNA used in protein synthesis

regulatory RNA segments

regulate gene function

not found in genes proteins

DNA codes regulatory RNA

structures used in transcription and translation

Messenger RNA (mRNA)*

Transfer RNA (tRNA)*

Regulatory RNA (rRNA)*

ribosomes*

Several types of enzymes & raw materials

single-stranded nucleotide

5-carbon ribose sugar

Contains uracil (U) instead of thymine (T)

rna

integral part of ribosomes

Ribosomes are complexes of RNA and proteins called ribonucleoprotein

ribosomal rna, r- RNA

transports amino acids to ribosome during protein synthesis

Contains sequences of bases formed by hydrogen bonds with complementary tRNA strand

transfer rna, t RNA

carries coded information from DNA to ribosomes

A transcript of a structural gene or genes in the DNA

messenger rna, m- RNA

A series of triplet bases that hold the message of the transcribed mRNA

codons

first stage of gene expression

DNA code to mRNA Template strand- instructions for protein synthesis

3 stages • Initiation • Elongation • Termination

RNA polymerase binds DNA & copies template strand- mRNA

transcription

second stage of gene expression,

apparatus machine is small and large subunits

mRNA-template of DNA

tRNA- anticodon for amino acid

Resultant polypeptide chain protein

translation

the way mRNA nucleotides are read, specific to amino acids

codon

process of shifting the ribosome down the mRNA strand to read new codons

translocation

potential targets of protein synthesis by antibiotics

Target RNA polymerase to block initiation step of transcription, possibly bind to human DNA

Target ribosome to affect functionality and prevent protein synthesis

Target translation by interfering with attachment of mRNA to ribosomes

Selectivity toxicity of antibiotics- treat infection with least damage to eukaryotic cells

exchange of genetic material between two cells resulting in the new combination of genes.

Offspring has new genetic code different from parent cells, genetic diversity

genetic recombination

donor DNA inserted into cell’s chromosome, shuffled and DNA is recombined with donor DNA.

crossing over

DNA acquired from unrelated individuals

horizontal gene transfer

DNA inherited from parental organism

vertical gene transfer

Transformation, Conjugation, Transduction, Transposons

types of horizontal gene transfer

Donor cell with pilus, fertility plasmid in donor, both donor and recipient alive, bridge forms between cells to transfer DNA\

direct contact

produces drug resistance, toxins

conjugation

form of horizontal transfer

The acceptance by a bacterial cell of small fragments of soluble naked DNA from the surrounding environment, not direct

produces polysaccharide capsules

transformation

type of horizontal transfer where bacteriophages carry DNA from one bacterium to another

no direct contact

produces toxins, sugar for fermentation, drug resistance

transduction