review for exam one. the scientific method scientists use the scientific method to test theories....
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Review for exam one
The Scientific method
• Scientists use the Scientific Method to test Theories.– Generate an Observation– Pose a Hypothesis– Perform Experiments– Analyze Results– Reach a Conclusion--does the date support or
refute our Theory?
The Scientific method
• Scientists use the Scientific Method to test Theories.– Generate an Observation– Pose a Hypothesis– Perform Experiments– Analyze Results– Reach a Conclusion--does the date support or
refute our Theory?
Why do Experiments in Labs?
• Controls! Controls! Controls!
• Lab Experiments can prevent “variables”– Variable: Factor that can cause observable change
and through results off.• Independent – what you vary during the experiment.
Usually this will be time.• Dependant – what you measure – what will change
during the experiment
– Control: Subject to all experimental steps EXCEPT the experimental Factor.
Animalia – development by means of an embryonic stageNo cell walls. Do not undergo photosynthesis
Plantae – contain a cell wall carry out photosynthesisNon-motile life stages.
Fungi - contain cell wallDo NOT photosynthesize
Protista – No cell walls reproduce by spores – motile
Monera – the bacteria: single-cell organisms
Box 6.2 (1)
Box 6.2 (2)
Components of a Cell
Components of a Cell• Nucleus--contained within a cell by nuclear
envelope. The nucleus contains DNA.• Ribosomes--these structures make protein.• Endoplasmic Reticulum--this is a membrane
network composed RER--rough has ribosomes makes proteins, and SER--smooth makes lipids.
• Golgi Apparatus--modifies proteins involved in secretion.
• Endomembrane system--Composed of nuclear envelope, ER, Golgi, Lysosomes and Vesicles, these organelles all work together to make protein sorting and protein secretion possible.
The Mitochondria • Contain their own DNA and
protein-synthesizing machinery
– Ribosomes, transfer RNAs, nucleotides.
– Thought to have evolved from endosymbiotic bacteria.
– Divide by fusion
– The DNA is in the form of circular chromosomes, like bacteria
– DNA replication is independent from DNA replication in the nucleus
The MitochondriaSite of Cellular Respiration
• This process requires oxygen.• Composed of three stages:
– Glycolysis--glucose splitting, occurs in the cell. Glucose is converted to Pyruvate.
– Krebs cycle--Electrons are removed--carriers are charged and CO2 is produced. This occurs in the mitochondrion.
– Electron transport--electrons are transferred to oxygen. This produces H2O and ATP. Occurs in the mito.
The Chloroplast• Contain their own DNA and
protein-synthesizing machinery
– Ribosomes, transfer RNAs, nucleotides.
– Thought to have evolved from endosymbiotic bacteria.
– Divide by fusion
– The DNA is in the form of circular chromosomes, like bacteria
– DNA replication is independent from DNA replication in the nucleus
The Chloroplast• Membranes contain chlophyll
and it’s associated proteins
– Site of photosynthesis
• Have inner & outer membranes
• 3rd membrane system– Thylakoids
• Stack of Thylakoids = Granum
• Surrounded by Stroma– Works like mitochondria
• During photosynthesis, ATP from stroma provide the energy for the production of sugar molecules
• Phenotype– An organism’s physical traits
• Genotype– An organism’s genetic makeup
Terms:
Allele• Allele: Alternate form of a gene at same
position on pair of chromosomes that affect the same trait.
• Dominant Allele: Capital Letter--O
• Recessive Allele: lowercase letter--o
• Homozygous Dominant--OO
• Homozygous Recessive--oo
• Heterozygous--Oo
Stages of Division• Prophase--nuclear envelope breakdown,
chromosome condensation, spindle formation.• Metaphase--chromosomes are lined up
precisely on the metaphase plate, or middle of the cell.
• Anaphase--spindle pulls sister chromatids apart.
• Telophase--chromatids begin to decondense and become chromatin. Spindle disappears.
• Cytokinesis--divide cell and organelles. Actin ring, or cleavage furrow splits cell.
Review: Comparing Mitosis and MeiosisMitosis
Duplicated chromosome(two sisterchromatids)
Prophase
Chromosomeduplication
2n = 4
MeiosisParent cell
(before chromosome duplication)
Pairing ofhomologouschromosomes
Chromosomeduplication
Site of crossing over Meiosis I
Tetrad formed by pairing of homologouschromosomes
Prophase I
MetaphaseTetradsalign at themiddle ofthe cell
Metaphase I
AnaphaseTelophase
2n
Chromosomesalign at the middle of the cell
Sisterchromatidsseparateduring anaphase 2n
Daughter cellsof mitosis
Daughtercells of
meiosis I
HomologouschromosomesseparateduringanaphaseI; sisterchromatidsremaintogether
n n n n
Meiosis II
Daughter cells of meiosis II
Anaphase ITelophase I
Haploidn = 2
No furtherchromosomalduplication;sisterchromatidsseparateduringanaphase II
Replicated pairs of chromosomes line up side by side.
These pairs are called Homologous--both have same gene order (gene for eye color, hair color, etc).
Sister chromatid from one pair interact with a Sister chromatid from another pair.
One sister is from father, one sister from mother, but they have same gene order.
Prophase -I
• This interaction is called Synapsis.
• Synapsis results in the formation of a Tetrad (4 sisters together).
• Crossing over swaps sections of homologous genes.
Prophase -I
•Meiosis IMeiosis I: Homologous chromosomes separate
Microtubules attached to Chromosomes
Sister chromatidsremain attached
Cleavagefurrow
Sisterchromatids
Tetrad Centromere
Anaphase I Telophase Iand Cytokinesis
Sites of crossing over
Spindle
Prophase I Metaphase I
Homologous chromosomespair and exchange segments
Two haploid cells form: chromosomes are still double
Tetrads line up Pairs of homologouschromosomessplit up
•Meiosis IIMeiosis II:
Sister chromatids separate
Anaphase II Telophase IIand Cytokinesis
Sister chromatidsseparate
Haploid daughter cellsforming
Prophase II Metaphase II
During another round of cell division, the sister chromatids finally separate; four haploid daughter cells result, containing single chromosomes
Sex Determination• All embryos start on a neutral or
"indifferent" path. The 4 week old embryo is indifferent
• By 7 weeks, the SRY (sex-related) gene encoded by the short arm of the Y chromosome begins to roar!
• Testis determining factor converts progesterone to testosterone
Sex Determination• Indifferent embryos have two sets of
ducts: • Müllerian ducts--will be come the
future oviducts--thus female.
• Wolfian ducts--will become the future vas deferens--thus male– dependent on testosterone for its
continued development
• The testes also produce an anti-Müllerian hormone that promotes regression of the Müllerian ducts– without SRY, the indifferent embryo
will naturally develop into a female
Figure 3.6aMutations
Mutations
Sex Chromosomal Disorders
• Turner Syndrome – XO only one sex chromosome
• Short, thick neck and stature• Do not undergo puberty, or menstruate, • no breast development
• Kleinfelter Syndrome – XXY• Testis and prostate underdeveloped• No facial hair• Brest development• Long arms and legs: big hands and feet• Can be mentally retarded
An XY Individual with Androgen Insensitivity
Syndrome
Androgen Insensitivity Syndrome is a sex reversal condition where XY individuals look female. These individuals have the Y chromosome and functional SRY. These individuals have testis which generate AMH and testosterone. However, the genetic mutation results in a lack of the testosterone receptor. Estrogens are made in the adrenal gland which drive phenotypic development. As adults, these individuals have testes in the abdomen and lack a uterus and oviducts.
DNA Replication• Each new double helix is composed of an old
(parental) strand and a new (daughter) strand.
• As each strand acts as a template, process is called Semi-conservative Replication.
• Replication errors can occur. Cell has repair enzymes that usually fix problem. An error that persists is a mutation.
• This is permanent, and alters the phenotype.
The structure of RNA• Formed from 4
nucleotides, 5 carbon sugar, phosphate.
• Uracil is used in RNA.– It replaces Thymine
• The 5 carbon sugar has an extra oxygen.
• RNA is single stranded.
Central Dogma of Molecular Biology
• DNA holds the code
• DNA makes RNA
• RNA makes Protein• DNA to DNA is called
REPLICATION• DNA to RNA is called
TRANSCRIPTION• RNA to Protein is called
TRANSLATION
Genes can lead to inherited diseases
• A gene which doesn’t function on an autosomal chromosome can lead to devastating diseases
• Autosomal chromosomes are 22 pairs of chromosomes which do not determine gender
• Such diseases can be caused by both a dominant or a recessive trait
Autosomal Recessive Disorders
• Tay-Sachs Disease:– Jewish people in USA (E. Euro descent)– Not apparent at birth– 4 to 8 months
• Neurological impairment evident
• Gradually becomes blind and helpless
• Develops uncontrollable seizures/paralyzed
• Allele is on Chromosome 15– Lack of enzyme hexosaminidase A (Hex A)
• Lysosomes don’t work, build up in brain
Autosomal Recessive Disorders
• Cystic Fibrosis– Most common in USA (Caucasian) – 1 in 20 caucasians is a carrier – Mucus in bronchial and pancreas thick/viscous– Breathing and food digestion problems
• Allele is on chromosome 7– Cl ions can not pass through plasma membrane
channels
• Cl ions pass –water goes with it. No water, thick mucus
Autosomal Recessive Disorders
• Phenylketonuria (PKU)– Affects in in 5,000 newborns– Most common nervous system disorder
• Allele is on chromosome 12– Lack the enzyme needed for the metabolism of the
amino acid phenylalanine– A build up of abnormal breakdown pathway
• Phenylketone
• Accumulates in urine. If diet is not checked, can lead to severe mental retardation
Autosomal Dominant Disorders
• Neurofibromatosis
• Very common genetic disorder
• Tan spots on skin
• Later tumors develop
• some sufferers have large head and ear and eye tumors.
• Allele is on chromosome 17– Gene controls the production of a protein called
neurofibromin– This naturally stops cell growth
Autosomal Dominant Disorders
• Huntington Disease
• Leads to degeneration of brain cells
• Severe muscle spasms and personality disorders
• Attacks in middle age
• Allele is on chromosome 4– Gene controls the production of a protein called
huntington– Too much AA glutamine. Changes size and shape of
neurons
GOOD LUCK NEXT WEEK!