Genetic Breakdown

Study of genets goes back to ancient times

Heredity & Genetics:
Gregor Mendel (Father of Genetics) & peas: used peas to study traits(alleles) and characters (genes)

Mendels 4 hypotheses (and 2 laws):

  1. Alternative versions of genes called alleles, acc. for variations
  2. Organisms inherit 2 alleles of a gene, one from each parent.
  3. If the 2 alleles differ, the visible one is dominant & the nondominant is recessive.
  4. Sperm & eggs only carry 1 allele for each inherited character, called the law of segregation.

Homozygous: two identical alleles
Heterozygous: two different alleles

Punnet square: all possible combinations of alleles that can occur when gametes combine

Designate dominant allele (upper-case)
Designate recessive allele (lower-case)
Genotype: letters representing phenontype (ex. Gg)
Phenoytype: Physical attributes (ex. purple)

Monohybrid cross: one pair of alleles
Dihybrid cross: two pair of alleles

Mendel's law of independent assortment states that gametes only carry one allele for a gene.

Dominant:

  • Polydactyly
  • Achondroplasia
  • Huntington's
  • Hypercholesterolemia

Recessive:

  • Cystic fibrosis
  • Albinism
  • Phenylketonuria
  • Sickle-cell
    Tay- Sachs

A single gene an affect many phenotypic characters.

Pleiotropy: The production by a single gene of two or more apparently unrelated effects.
ex. sickle-cell disease

The chromosome theory of inheritance:

  • genes occupy specific loci (positions) on chromosomes
  • chromosomes undergo segregation and independent assortment during meiosis

Mendel's laws correlate with chromsome separation in meiosis

  • Linked genes violate Mendelian genetics, because the genes are not inhereted independently.

Sex chromsomes: x always there and y determines male or not
SRY gene: sex-determining region y
sex linked genes: mostly x-linked, meaning mostly in men

Ex. of recessive x-linked disease: Duchenne muscular dystrophy, and hemophilia

Y chromosomes have an evolution connection, giving clues abt human male evolution, they have a common ancestry

Molecular Biology of the Gene

Genetic Material:

  • Only 4 nucleic acids
    Proteins:
  • 20 amino acids

Fredrick Griffith 1928:

  • Streptoccous pnemonia (causes pneumonia)
  • worked with mice, using a rough strain (nonvirulent) and smooth strain (virulent)

Alfred Hershey & Martha Chase

  • Bacteria phages/phages have only protein and DNA
  • discovered DNA holds genetic information

macromolecule: nucleic acids
monomers: nucleotides
polymers: polynucleotides

2 types:

  • DNA (deoxyribose nucleic acid) adenine, thymine, guanine, and cytosine
  • RNA (ribose) adenine, uracil, guanine, and cytosine

Pyrimidines: thymine and cytosine
Purines: adenine and guanine

nucleotides are joined covalent bonds: sugar-phasphate

Rosalind Fanklin: Mother of the double helix/backbone, Watson & Frick were given the credit

5 prime end is the phosphate, 3 prime is the sugar end of the nucleotide

DNA replication:

  1. Parent molecule of DNA
  2. Parental strands separate and use as template
  3. two identical DNA strands

Topoisomerase: snips DNA, lets it unwind, then reconnects it

SSB (single strand binding): keeps DNA single stranded

leading strand is always 5' to 3'
lagging strand is 3' to 5'

helicase: opens up DNA by breaking hydrogen bonds

DNA polymerase: replicates DNA molecules to build a new strand of DNA from the parent strand

Primase: makes the primer so the DNA polymerase knows where to start (made of primers)

Ligase: helps glue DNA fragments together between the okazaki fragments

Okazaki fragments: the short lengths of DNA that are produced on the lagging strand

Mutations can be spontaneous, and mutagens cause mutations

Can be caused by radiation, chemicals, or infectious agents

DNA gets transcripted into RNA in the nucleous, then is translated by changing the entire molecule (protein)

triplet code: every 3 nucleotides (codon), 1 amine acid

RNA is processed before leaving the nucelus as mRNA (messenger RNA)

RNA splicing;

  • get rid of introns
  • connect exons
  • add cap and tail

translation: (in cytoplasm)

  • ribosome
  • transfer RNA (tRNAs)
  • anticodon on one end
  1. initiation
  2. elongation
  3. termination

Ribosomes: ribosomal RNA's and proteins, binding sites for tRNAs and mRNA

Mutations:
silent: has no effect on the protein sequence
missense: results in amino acid substitution
nonsense: results in amin acid substitution

Prions: misfolded proteins

chronic wasting disease, kuru, and creutzfeldt

Bacteria moves genes from cell to cell

  1. transformation, DNA enters cell
  2. transduction, fragments of DNA from another cell
  3. conjugation, makes another bacterial cell

How genes are controlled

gene expression: genotype --> pheontype

  • gene regulation: regulates genes
  • operons: promoter, operator, multiple genes together
  • regulatory proteins
  • regulatory gene makes repressor protein

repressors stop operons from working

eukaryotic cells: differentiated cells (specialized cells)

  • chromosome structure level
  • epigenetic inheritance
  • to turn off DNA, attach methyl groups to chromatids
  • packed up DNA = no expression
  • x chromosome inactivation (barr bodies)

Eukaryotes usually use activators

  • most are by default turned off

Transcription factors: proteins that together help make RNA polymerase

Alternative RNA splicing

humans are over 90% protein-coding genes

Other regulation forms

  • breakdown of mRNA (speed up time)
  • regulatory proteins for translation
    protein processing

noncoding RNA's play more than one role in gene expression:

  • 1.5% of human genomes code for proteins
  • another small fraction is genes for rRNA and tRNA
  • little functional RNAs

miRNAs:

  • degrade complementing mRNAs
  • block translation of partially complementing mRNAs

siRNAs:

  • RNA that interferes with translation
  • formation of centromere
  • methyl for gamete formation

Eukaryotic only: flow the nuclear envelope, cap & tail, splicing, DNA unpacking

Prokaryotes ) eukaryotes: transcription, translation, mRNA breakdown, modifying proteins, break down of proteins

Homeotic genes: one gene that controls many other genes

cloning: genetically identical

plants: totipotent cells: can turn into any cell necessary

animals: nuclear transplation: transplanting nucleus (w/ eggs)
reproductive cloning: placing the egg cell in a uterus

humans: therapeutic cloning: regrowing instead of replacing

  • embryos have totipotent cells
  • adult stem cells are programmed to make certain cells

Cancer: cells dividing rapidly

photo-oncogene: normal version of the gene, and helps control cell division

tumor supressor gene: helps control cell division and prevent tumor

  • faulty proteins can interfere with normal signal transduction pathways
  • affects cell cycle control system
  • oncogene

carcinogens: turnoff tumor-suppressors, increases likelikhood to make oncogenes

Chapter 9

Chapter 10

Chapter 11

DNA technology and Genomics

Biotechnology

  • DNA technology
  • GMOs
  • Recombinant DNA

Genes can be cloned in recombinant plasmids

Bacterial plasmids (vector) w/ recombinant DNA

Complementary DNA (cDNA): results in DNA from a mRNA from a eukaryotic cell

genetically modified organisms (GMOs): one or more genes by artificial means

GMOs can help make vaccines:
ex. waiting for plants to grow, secreting the virus, then turning it into a pill

ethical questions arise w/ GMOs because they can potentially effect environments

CRISPR-Cas9 system- target a gene in a living cell for removal or editing

Polymerase chain reactio in (PCR) w/ primers
PCR is used to amplify DNA sequences

Electrophoresis helps sort DNA samples

  • the smaller the faster, uses electric currents to flow between negative and positive charges

Bacteria can be used for DNA profiling

  • fingerprints
  • blood samples
  • hair folicles
  • skin cells

Chapter 12