RNA: ribonucleic acid

• Large nucleic acid built from many nucleotides bonded together

• Remember a nucleotide consists of a phosphate group, 5 carbon sugar and nitrogen containing base

RNA nucleotide

• The 5-Carbon sugar is ribose

• The 4 nitrogen containing bases:– Adenine– Uracil– Cytosine– Guanine

3 types of RNA

• mRNA: messenger RNA: carries the genetic code from the nucleus to the ribosome

• rRNA: ribosomal RNA: builds ribosomes

• tRNA: transfer RNA: carries amino acids to the synthesizing polypeptide

Wednesday 4/3/13

• AIM: How is mRNA translated?

• DO NOW: Explain the importance of messenger RNA. Where does the message come from?

• HOMEWORK: Text read page 306 answer the reading check question

Modification of RNA

• The rough draft is called the primary transcript

• Before it leaves the nucleus it gets modified

• Addition of 5’cap and Poly-A tail

• The most important is RNA splicing

RNA modification

• 5’ cap and Poly A tail protect the RNA from being broken down by cellular enzymes

• They also help the ribosome recognize the RNA

RNA splicing

• Introns: junk DNA that does not code for proteins

• Exons: good DNA codes for protein• Splicesome: enzymes that catalyze the

removal of introns and the connection of exons

• Allows the human genome to produce a variety of polypeptides

• One gene codes for one polypeptide

• How do your cells know which amino acids it wants or needs?

• ANSWER: the genetic code determines the polypeptide (sequence of amino acids)

Now the mRNA is ready to leave the nucleus and enter the

cytoplasm

Quick Review

• What are the 3 major events that occur during transcription?

• Why is it important to modify the primary RNA before leaving the nucleus?

The Genetic code

• Codon: sequence of 3 nucleotides that specify an amino acid

• There are 20 amino acids that build ALL polypeptides

• It is the unique sequence of amino acids that build polypeptide chains

• It is the unique folding of polypeptides that build proteins

Codon: sequence of 3 nucleotides that specify an amino

acid

Period 7 Thursday 4/4/13

Friday 4/5/13

• AIM: How is the mRNA molecule translated?

• DO NOW: In your own words explain how the primary transcript is modified before it leaves the nucleus.

• Why is it modified?

Codons to know

• AUG

• UAA

• UAG

• UGA

• So we know DNA can replicate and transcribe. But what happens next?

Translation: RNA to amino acid sequence

• Involves mRNA, tRNA, rRNA and ribosomes

• Before mRNA leaves the nucleus, proteins called splicesomes cut out and paste together coding regions of the primary mRNA transcript

• Plays a major role in polypeptide diversity

• Now it is ready for translation

RNA:ribonucleic acid

• Polymer made up of small subunits called nucleotides

• Each nucleotide has a 5 C sugar, nitrogenous base and phosphate group

• The 5 carbon sugar in RNA is ribose

• The four possible nitrogenous bases are

• Adenine, uracil, cytosine and guanine

• Instead of thymine, adenine attracts a uracil nitrogenous base

mRNA: messenger RNA

tRNA: Transfer RNA carries amino acids to the mRNA-ribosome complex

mRNA: messenger RNA

mRNA: codon

tRNA anticodon• 3 base pair sequence complementary to the mRNA

codon • Anticodon-codon complex allows amino acids to

bond in proper sequence

Ribosomal RNA builds ribosomes

• AIM: How are codons translated into polypeptides?

• DO NOW: Handout. Label 1-10

• Homework: Handout

Translation- mRNA and tRNA interact at a ribosome

Translation continued

Translation Stage of Protein Synthesis

• Rectangles = amino acids

• Crooked Cross = transfer RNA with an amino acid on top and anticodon at bottom

• X = messenger RNA molecule with codons

• Double oval = ribosome

What I want you to know about translation

• Process that builds a polypeptide chain from a mRNA molecule

• The original message comes from the DNA template

• tRNA anticodon bonds to mRNA codon bringing an amino acid into its proper place

• Translation occurs in the ribosome

Translation

• There is a specific start AUG codon

• There are 3 possible stop codons that terminate UAA,UAG or UGA

Reading frame

• Each codon specifies an amino acid

• The reading frame is the sequence of codons in a gene

• If the reading frame is changed, the amino acid sequence may be changed

• Possibly resulting in a dis-functional protein

Lets build a protein

DNA : TACCCTCAACTCTCAACT

mRNA: AUGGGAGUUGAGAGUUGA

tRNA: UACCCUCAACUCUCAACU

aa: met - gly- val- glu- ser

Amino acid sequence

• MET-GLY-VAL-GLU-SER

• We got a polypeptide but is this a functional protein?

• NO! Remember it is the unique shape of a protein that gives it a specific function

http://press2.nci.nih.gov/sciencebehind/snps_cancer/snps_cancer/images/21.jpg

Assessment

• Handout 1-5 and A-E

Wednesday 4/27/2011

• AIM: How is the reading frame effected if the base pair sequence changed?

• DO NOW: How would mRNA and amino acid sequence change if the following DNA template changed?

Original DNA: TACCCTCAACTCTCAACT

Changed DNA: TACCCTCATTCTCAAC

DO NOW ANSWER

• If the gene sequence is changed and causes a change in the amino acid sequence (polypeptide), the physical characteristic changes

Homework• Textbook Read Page 266. Using Science

graphics questions 1-3

Are all genes in each cell expressed in every cell?

NO!

All of the 30,000 genes are in each body cell but only specific genes are

expressed in specific cells

Differentiation

• The regulation of gene expression

• Different genes are expressed in different cells

• Different cells build different proteins

Thursday 4/28/11

• AIM: How is human phenotype effected by genetic mutations?

DO NOW: 1- How many base pairs make up a single codon?

2- How many amino acids build all human proteins?

Homework: Read 267-269. Reading Check pages 267 and 269

DO NOW ANSWER

• 3 nitrogen bases=codon• 64 codons in total• 20 amino acids build all

proteins• More than one codon for

a single amino acid• This is why some

mutations have NO effect on the polypeptide chain

How do you make a polypeptide?

Gene-mRNA-ribosome-codon/anticodon bonding which makes a long

chain of amino acids

How are polypeptides related to physical characteristics?

Polypeptides build proteins which lead to chemical reactions that

cause physical traits

Functional protein

• Polypeptide: Long chain of amino acids– Combine with other

polypeptides– Folds into a unique shape– This makes a functional

protein– The shape of a protein is

unique to its function– If you change the shape, you

change the function

Denaturing a protein

• Changes the shape of the protein

• If the shape of the protein changes the function changes or it does not function at all.

• How would a protein get denatured?– Gene mutation– Mistake in mRNA modification– Mistake in translation– Mistake in polypeptide folding

• If my DNA makes a mistake, how will the protein behave?

– The protein will have a different shape, and without its shape, it cannot function properly

– Proteins are shape specific– Denature: changes the shape of a protein

GENE Mutations

• Change in nucleotide sequence of bases in a DNA molecule (gene)

• May or may not change the amino acid sequence

• Nonsense mutation: gene sequence changes but amino acid does not

• EX: normal DNA CTT mutated DNA: CTC

Assessment

How many amino acids build all of the human proteins?

20

How many nitrogen bases build RNA? 4

How many nitrogen bases make up a codon? 3

How many codons are there?

64

Gene Mutations

• Nucleotide substitutions: single base pair is replaced with a different incorrect pair

• Insertion: addition of 1 or more base pairs

• Deletion: removal of one or more base pairs

Mutations

• How is the polypeptide changed if the reading frame of an mRNA molecule is changes from GGC to AGC?

• amino acid in the polypeptide chain is changed from SER to GLY

• Mutation in reading frame of a gene could result in protein dysfunction

Sources of mutations

• Mutagen: any chemical that causes a change is nucleotide sequence of a gene– Chemicals– Medication– Vaccine– Radiation– carcinogens

How are mutations inherited?

• If a mutation is in a gamete (sperm or egg), it will be inherited by the zygote

Wednesday 3/10/10

• AIM: How can a genetic mutation effect the phenotype of a human being?

• DO NOW:

How is the human genome organized?

Autosomes: 1-2223 pair sex chromosomes

XX=femaleXY=male

Sex genetic disorders

Found on Y chromosome• Deletion of SRY• Deletion of DAZ

Found on X chromosome• Red-green

colorblindness• Hemophilia

Deletion of the SRY gene can lead to XY females

• SRY: sex determining region

Deletion of DAZ gene leads to infertility in males

Sex-linked disorder

• found on the X chromosome

• female can have one copy of the allele and be a carrier

• a male with one copy always display the trait

Red Green Colorblindness

Hemophilia: on the X chromosome

• Inability for blood to clot

• People do not produce one of the proteins necessary for proper blood clotting

Autosomal Genetic Disorders

• Found within Chromosomes 1-22

• If you mutate a gene, it may change the shape of the protein that it codes for

Human Recessive Autosomal Genetic disorders

• Homozygote Recessive is the only way to display

• Heterozygotes are carriers

• Ex:A

chondroplasia (Dwarfism)

Sickle cell anemia

Cystic fibrosis

Albinism

PKU

Tay Sachs

Achondroplasia

• Dwarfism• “without cartilage

formation”• the defect is not in

forming cartilage but in converting it to bone

Sickle cell anemia

Sickle cell anemia

Sickle cell anemia

Sickle Cell Anemia

• Effects mostly South African Descendants• Hemoglobin: protein in the red blood cell

that carries oxygen• People with Sickle Cell Anemia make a

sickled shape hemoglobin protein• Symptoms:

– Inability to carry oxygen– Shortness of Breath– Pain in Joints– Coagulation of RBC’s

Cystic Fibrosis

• European descent

• 1:2500

• Lack of a cell membrane protein

• Causes cells to produce a thick sticky mucous

Renal (kidney) cystic fibrosis

Albinism

• Albinism: homozygous recessive allele for the enzyme tyrosine which builds melanin

• Melanin: protein that gives skin pigment

Phenylketonuria (PKU)

• Base substitution( G-A)– Changes amino acid from ARG-GLU

Changes the shape of hydrooxylase enzymeEnzyme cannot break down the amino acid PHE

(Phenylalanine)

• increases the levels of a substance called phenylalanine in the blood– Causes mental retardation and other serious

health problems

• If detected early, it can be treated by dieting

Phenylketonoria PKU

• Accumulation of the amino acid phenylaline in the blood

• Mental Retardation

• Abnormal skin color

Tay Sachs disease

• Lipid accumulation in brain cells

• Mental deficiency• Blindness• Death in childhood• Blue stain shows

swollen neurons

Period 2 Friday 3/12/10

• AIM: How do chromosomal disorders differ from genetic disorders?

• DO NOW: Explain why a heterozygote does not display albinism but could have a child with albinism.

• HOMEWORK:

• Textbook read pages 650-651. Observe fig 22.13. Is that child a male or female? How do you know?

Human Dominant Disorders: Huntington disease

• Genetic duplication: repeat of CAG codon

• Causes string of glutamines (glu) in the polypeptide chain of the huntington protein

• Causes change in shape of huntington protein

• Slow deterioration of brain and nervous system

Huntington’s disease

Huntington Disease

• People usually have symptoms for up to 10 years before they find out they have Huntington's disease.

• Most people are diagnosed between the ages of 30 and 50, although this can happen much earlier or later.

• Symptoms are often overlooked, as they are mild and commonly experienced by well people• mild tremor • clumsiness • lack of concentration • difficulty remembering things • mood changes, including depression • sometimes, aggressive antisocial behavior

per 6 Friday 3/12/10

• AIM: How are gene mutations different from chromosomal mutations?

• DO NOW:Explain why a heterozygote does not display albinism but could have a child with albinism.

In your own words, explain the relationship between genes and

chromosomes.

Gene vs chromosome

• Genes are on chromosomes

• Gene mutations: occur at the single gene

• Chromosomal mutations: loss or gain of entire chromosome

Hypertrichosis: genetic disorderexcessive hair growth

over and above the normal for the age, sex and race of an individual

Exact cause is unknown but has been linked to a spontaneous mutation

Nondisjunction:• Uneven distribution of chromosomes during

gamete formation

• Usually leads to spontaneous abortion or severe disorders

Autosomal Disorders

• Trisomy 21

• Trisomy 8

• Trisomy 13

• These are the only trisomy’s that will lead to full term fetal development

• Any other trisomy will cause spontaneous abortion (miscarriage)

Nondisjunction and Down’s syndrome

• • one gamete has two 21st the resulting fertilized egg has three 21st chromosomes.

• 90% of the abnormal cells are the eggs

• Trisomy 21

Mental retardation

Physical abnormalities

Down’s syndrome

Trisomy 8 and 13

Trisomy 8• low-set or abnormally shaped ears and a

bulbous-tipped nose, eye abnormalities

• bone and tissue abnormalities,

• various structural heart problems,

• palate abnormalities

• mild to moderate mental delays

• deep hand and feet creases.

Trisomy 13• Cleft lip or palate • Close-set eyes -- eyes may actually fuse

together into one • Decreased muscle tone • Extra fingers or toes (polydactyly) • Hernias: umbilical hernia, inguinal hernia • Hole, split, or cleft in the iris (coloboma) • Low-set ears • Mental retardation, severe • Scalp defects (absent skin) • Seizures • Single palmar crease • Skeletal (limb) abnormalities • Small eyes • Small head (microcephaly) • Small lower jaw (micrognathia) • Undescended testicle (cryptorchidism)

Nondisjunction of sex chromosomes

•

Turner’s syndrome:

• XO: no sex hormones lead to no menstruation and no secondary sex characteristics

• Infertility• Short stature, folds on

neck, more X linked recessive disorders, color blindness, hemophilia etc.

Trisomy X

• 1 in every 1000 woman have 3 X chromosomes

• Very tall

• Below normal intelligence

Klinefelter syndrome

• 1 in every 1000 males have XXY

• Most never even know they have it

• partial breast development, widening of the hips and small testis

• These men are usually infertile

XYY males

• High levels of testosterone

• Severe acne

• More than 6 feet tall

• Lower IQ

Per 7

• AIM: How can pregnant woman get tested for genetic and chromosomal disorders?

• DO NOW: In your own words, explain what would happen to a zygote if it contained 3 autosome 3’s.

How are genetic disorders different from chromosomal

disorders?

Fetal Testing

• Ultrasound

• Amniocentesis

• Chorionic Villus Sampling

• Fetoscopy

• Newborn Screening

Ultrasound

• Sounds waves are used to produce an image

Fetoscopy

• Viewing scope is placed into the uterus creating an image

• Enables blood samples to be taken

• Detects Spina bifida• Only done if there is a

history of birth defects

Amniocentesis• 14th-16th week• 10 mL of amniotic fluid• Looks at chemicals and molecules

present• chromosomal disorders, including

Down’s syndrome, trisomy 13,18,Turner’s syndrome, Kleinfelter’s syndrome

• Sickle Cell, Tay Sachs• spina bifida and anencephaly

Chorionic Villus Sampling

8th-10th week• Insert through the cervix

into the uterus• Take a tissue sample

from the placenta• Contain fetal cells which

divide more rapidly than amniotic cells

New born Screening

• Examines newborn blood to detect genetic disorders

• PKU: phenylketonoria

• Tay Sacs

• Treated with diet regulation

End Friday notes

Viruses: Genes in packages

• Basically is a piece of nucleic acid surrounded by a protein

• Survives by infecting other cells with its nucleic acid and taking over the cell

• Using the cells organelles to produce new viral cells

Animal viruses

• Such as influenza or the mumps

• Surrounded by protein coat

• Protein coat attaches to cell membrane and injects its nucleic acid in to the cell cytoplasm

• New viral proteins and mRNA are synthesized and often the animal cell is destroyed

HIV: Human Immunodeficiency virus

• Virus that causes AIDS: autoimmunodeficiency syndrome

• Similar to the flu and mumps in that it is surrounded by a protein coat

• Its nucleic acid is RNA: it is called a retrovirus

• An RNA virus that reproduces by means of a DNA molecule

HIV a retrovirus

• Carry molecules of RNA and a specific enzyme called reverse transcriptase

• Reverse transcriptase: cause the synthesis of a DNA strand from an RNA template

Steps in HIV infection

• Reverse transcriptase makes a single strand of DNA from an RNA template

• The new strand of DNA then builds a second complementary strand

• The resulting double strand then enters the nucleus and inserts itself into the genome: provirus

• NOW EVERY TIME THE CELL DIVIDES THE VIRAL DNA IS REPLICATED AND TRANSCRIBED

HIV

• Infects and eventually kills several kinds of white blood cells

• Causing the body to become susceptible to many diseases

• SECONDARY infections cause the development of AIDS

• AIDS: collection of symptoms

Treatment for HIV and AIDS

• Drugs interfere with the reproduction of the virus

• AZT: blocks the synthesis of the HIV DNA by binding to reverse transcriptase during transcription. – Structurally similar to Thymine

• Proteases: inhibit the synthesis of HIV proteins making the virus unable to be transmitted