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!