Monday3/19/12

• AIM: What is heredity?

• Homework: Handout Section 11.2 Read pages 288-291. Reading check on page 288.

• 2- Use figure 11.7 and in your own words, summarize steps A-C

• 3- Answer question 1 page 295 of the handout

Transcribe and translateDNA: TACGTTTGCGACACCACT

What do genes do?

Units of heredity that are passed down from generation to generation

Hold the code to build physical traits

Where are genes located?

On DNA which builds chromosomes which are in the

nucleus

How many codons are there in total? 64

How many amino acids are there in total? 20

Why is it a good thing to have multiple codons specify the same

amino acid?Because if the gene is mutated there is

still a chance the protein therefore physical trait will be unaffected!

• If a person with brown eyes has a baby with a person with green eyes? What color eyes do you think their baby will have and why do you think that?

Light blue 0 dominant alleles

Blue 1 dominant allele

Blue-green 2 dominant alleles

hazel 3 dominant alleles

Light brown 4 dominant alleles

Brown 5 dominant alleles

Dark brown / black 6 dominant alleles

What is Heredity?

• The transfer of characteristics from one generation to the next

Human heredity

• Chromosomes are built from DNA wrapped around proteins

• Genes are parts of DNA– Specific nucleotide sequences

• Therefore genes are found on chromosomes

• One chromosome might have 1000 genes on it

• Your cells have more genes than chromosomes

Thursday 3/22/12

• AIM: Why is Gregor Mendel the “father of Genetics”?

• DO NOW: If a person with brown eyes has a baby with a person with green eyes? What color eyes do you think their baby wil have and why do you think that?

• HOMEWORK: Text page 265 Inquiry Lab. Page 266 using words question 2

What are Traits?

• A characteristic that is determined by your genes

• A pair of genes will determine the trait

– Examples:• Tongue rolling• Earlobes• Widow’s Peak• Hair Whorl• Dimples

What is genetics?

• The science of how traits are inherited

Who is Gregor Mendel?

• “Father of Genetics”

• Studied pea plants

• He crossed pea plants with different characteristics and studied their offspring

• He was able to determine how

traits get passed on from

generation to generation

Gregor Mendel

• Father of genetics• Looked at the pea

plant• Specifically 7 visible

traits• Followed their

inheritance over many generations

• The pea plant displayed one of 2 possible characteristics for each trait

How did Mendel experiment with the pea plant?

Mendel’s pea plant

• Key feature: reproduction can be controlled and manipulated

• Self- fertilization and cross-fertilization were easily obtained

Fertilization

• Self-fertilization: egg in the flower is fertilized by the sperm of the same flower

• Cross-fertilization: sperm from a foreign plant fertilizes an egg

Friday 3/23/12

• AIM: How did Gregor Mendel develop his 3 laws of heredity?

• DO NOW: Explain the difference between self and cross fertilization.

• Homework: Complete any assignment you missed this week

• Last nights hw. 1- Page 265 Inquiry Lab

• 2- page 266 Understanding words # 2

Mendel’s work

• At first Mendel self fertilized plants in order to create true breeds

• True breed or pure breed has only one trait to pass on– Ex: Seed color

– Yellow seed yellow seed

• True breeds are homozygotes

Monday 3/26/12

• AIM: How did Gregor Mendel develop his first two laws of heredity?

• DO NOW: Explain why Mendel choose to work with pea plants

• HOMEWORK: textbook read pages 267-269. questions 1 and 3 on page 270

Mendel’s work

• Mendel did not know anything about dominant or recessive behavior

• He did know how to make pea plants reproduce

Definitions

• Genes: instructions to build physical characteristics

• Chromosome: large unit of DNA and protein that carry genes on them

• Human cells:– Somatic cells: body cells: diploid(2n)– Gametes: sex cells: haploid(n)

Somatic Cells

• ALL somatic (body cells) have the same 46 chromosomes

• Each cell is different due to the genes that get turned on or off

How is a cell’s DNA like a library?

Wednesday 3/28/12

• AIM: How did Gregor Mendel develop his law of dominance?

• DO NOW: Explain the difference between diploid and haploid and give an example of each

• HOMEWORK: Textbook page 270 questions 2 and 4

• I AM CHECKING 1-4 TOMORROW

Diploid (2n) vs haploid (n)

Mendel’s work

• He self fertilized plants for several generations to ensure that all were pure breeds

• True breed or pure breed: plants with a trait such as purple flowers that is always inherited by all offspring– Only have 1 type of allele for a specific gene

(homozygous)

Mendel’s work

• Cross fertilized plants that were true breeding for 7 specific traits

• Hybrid: The offspring of a cross fertilization– 2 parents similar to sexual reproduction– Has genetic information from both parents

Mendel’s work

• Crossed two true breed parents that displayed opposite traits.(P or Parental generation)

• All First filial or F1 offspring were purple

Genetics vocabulary

• Gene: part of DNa which holds the instructions to build a protein

• Allele: copy of a gene– Specific directions

• Genotype: genetic makeup of an organism

• Phenotype; resulting physical characteristics

What happened to the white color?

Self-fertilized F1

• Second filial or F2 generation yielded about ¼ white and ¾ purple

Mendel’s conclusion

• When the white flowered plants showed up in the F2 generation, Mendel concluded that the white characteristics must have been hidden in the F1

Self-fertilized F2

• Saw that all white flowered F2 yielded all white F3 but the purple still yielded 3:1 ratio of purple to white

• Therefore the white allele was not lost but rather hidden or masked by the purple allele

From these experiments, Mendel concluded:

• Traits are determined by physical unit that come in pairs

• Pairs are separated during gamete formation• Gametes only 1 allele each• The particular allele that ends up in a gamete is

caused by chance• One allele is dominant and one recessive• From Mendel’s Monohybrid cross he developed

the law of dominance and the law of segregation

3/29/12 Thursday

• AIM: how did Mendel develop his law of Independent assortment?

• DO NOW: Explain why ALL of the F1 generation had purple flowered plants.

• Homework: Textbook

Mendel’s Law of segregation

• Pairs of alleles on homologous chromosomes separate from each other during gamete formation

• Gametes receive only one allele from a homologous pair.

• Fertilization produces offspring with a copy of one allele from mom and one from dad

Mendel’s Law of dominance

• When two different alleles are present, the dominant alleles gives the resulting trait and masks the trait of the recessive allele

• However the recessive allele is still present

Friday 3/30/12

• AIM: how did Gregor Mendel develop his law of independent assortment?

• DO NOW: Explain the difference between genotype and phenotype

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• Which two laws did Mendel Develop from his Monohybrid crosses?

Answer

• Law of segregation: alleles separate during gamete formation

• Law of Dominance: when two different alleles for a trait are present, one is expressed (dominant) the other is masked

According to Mendel why do homozygote dominant and

heterozygote genotypes show the same phenotype?

Both have a copy of the dominant allele

Monohybrid cross

• ONLY tracks one physical trait at a time.

• From Mendel’s monohybrid crosses, he developed:– Law of segregation– Law of dominance

Mendel was not satisfied

• He wanted to see if alleles could be inherited together

• He looked at two traits at the same time

• Ex: seed shape and seed color

• His results were inconclusive

• • R-round• r-wrinkled• Y-Yellow• y-green

•

Mendel’s dihybrid cross

• P: true breed RRYY x rryy

• All F1: RrYy

• Allowed F1 to self-fertilize which yielded the following phenotypic ratio

• F2: 9:3:3:1 ratio of

Round Yellow: Round green: wr Yellow: wr,green

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Law of independent assortment

• Multiple traits are inherited independently of each other because alleles of genes are distributed independently during gamete formation

• Genes for different traits are inherited independently

•

Mendel’s laws

• Law of segregation

• Law of Dominance

• Law of independent assortment

• Still used today they paved the foundation for genetics

• Although his observations and laws explain the simplest form of genetics

Monday 4/3/12

• AIM: What are some exceptions to Mendel’s laws?

• DO NOW: Why did Mendel perform his di hybrid cross and what were his results?

• Homework: Textbook read page 282-284. questions 1-3 page 284. Write out the question followed by the answer

• Mendel gave us a foundation to build on genetics

• Without his experiments and discoveries, we may not have known anything about heredity

According to Mendel, phenotypically how does a

homozygote dominant and a heterozygote react?

Answer: Law of dominance: if the dominant allele is present it will be expressed

They will both display the same phenotpye

Incomplete Dominance

• Incomplete dominance is basically just a blending of traits

• The heterozygous form is a blend of the dominant and the recessive traits

Wednesday

• AIM: how can more than one allele code for the same trait?

• DO NOW:Explain how the pink snap dragon defies Mendel’s law of dominance

How does this happen?

Usually the law of dominance: if the dominant allele is present it is

expressed. So the Rr snapdragon would be Red BUT instead it is pink

due to incomplete dominance.The heterozygote Rr is a combination

of the dominant R and recessive r phenotypes

• Usually alleles code for enzymes which in turn code for chemical reactions to occur.

• In the case of the snap dragon, R allele codes for an enzyme which catalyzes a reaction which makes the red pigment

• r- white pigment• Both are made and mix

just like mixing red and white paint

Homozygous Dom

Homozygous recessive

Heterozygous

•

Tuesday 4/3/12

• AIM: How are two alleles expressed at the same time?

• DO NOW: Explain HOW the snap dragons of a red and white cross yielded all pink snap dragons

• HOMEWORK: Textbook page 284 questions 4-6

Wednesday 4/4/12

• AIM: How does human blood type defy Mendel’s laws?

• DO NOW: Explain how human blood type is determined.

• HOMEWORK: Read page 284. reading

Check on 284

•

Question

• 1- A woman with blood type A and a man with blood type B have a child with blood type O. How did this happen?

• 2- Baby daddy DRAMA! A woman claims her son is Mr. Clide’s. The woman has blood type O Mr. Clyde has blood type AB and the child also has blood type O. Is Mr. Clyde the boy’s father Explain why or why not

•

Codominance

• There is more than one dominant allele

• Ex: Human blood Type

• There are 3 alleles that code for the antigen protein found on the surface of the Red Blood Cell

Blood type is an example of codominance

• A person with blood type AB is showing the results of having both the IA and IB codominant genes

• 3 alleles code for blood type

• Specifically blood typing alleles code for antigens

• Antigen: specific recognition protein found on the surface of red blood cells

Antibody

• A protein that defends the body against foreign antigens

• In relationship to blood type, each antigen has the opposite antibody floating in the plasma

•

Rh factor

• Determines if blood is + or –

• It is a completely different protein and has NO connection to antigens

List and explain the 2 exceptions to Mendel’s laws we have

discussed so farIncomplete Dominance

COdominance

Monday 4/16/12

• AIM: How does one gene control several characteristics?

• DO NOW: Explain the difference between codominance and incomplete dominace

• HOMEWORK: textbook page 280 sex linked traits. Answer the Reading check on page 280

• Incomplete dominance;• The heterozygote is a

combination of the dominant and recessive allele

• Codominance: There is more than one dominant allele and both are fully expressed when present at the same time

SO FAR

• EXCEPTIONS to Mendel’s 3 laws of Inheritance– Incomplete dominance (pink snap dragons)– Codominance (Blood type AB)– Multiple allele inheritance: more than one

allele determines a trait. (human blood type)

Polygenic Inheritance

• More than one gene coding for the same trait

• Eye color is known to have a polygenic inheritance pattern, possibly governed by 6 or more genes.

• There are also 6 different described eye colors.

• Basically, dark is dominant at each of the 6 genes. The more dominant alleles that you have the darker your eyes are.

Light blue 0 dominant alleles

Blue 1 dominant allele

Blue-green 2 dominant alleles

hazel 3 dominant alleles

Light brown 4 dominant alleles

Brown 5 dominant alleles

Dark brown / black 6 dominant alleles

•

Pleiotropy

• Single gene influences several traits

• Ex: SRY gene on the Y chromosome

• Sex determining region• SRY gene: initiates

sequence of events that affects many different body structures

• Specifically during development it turns the gonads into testis and is responsible for all male charatceristics

Chromosomes are inherited

• Mendel did not know the difference between a gene and chromosome

• Thomas Hunt Morgan: worked with Drosophila fruit flies– He figured out that genes are the inherited

unit

Remember

• Chromosomes are the inherited unit– Humans have 22 pairs of Autosomes– 1 sex pair– Totaling 23 pairs = 46

• Genes are carried on chromosomes and contain the directions to build a protein

• One gene codes for one protein

The chromosomal basis of inheritance

• Genes are located on chromosomes

• Inheritance pertains to the behavior of chromosomes during meiosis and fertilization

• Gene locus: the actual position of an allele on a chromosome

Some gene loci are very close together

Tuesday 4/17/12

• AIM: How are some traits inherited together?

• DO NOW: Explain the difference between polygenic inheritance and pleiotropy.

• Homework: textbook Read page 335.Explain how DNA helped to identify unknown individuals whose coffins floated out of burial sites

What did Mendel’s Law of independent assortment say

• According to Mendel, genes or alleles found on different chromosomes cannot be inherited together

Remember Mendel’s Law of Independent assortment

• Independent Assortment of Alleles

Wednesday 4/18/12

• AIM: How can genes be inherited together?

• DO NOW: List ALL of the exceptions to Mendel’s laws that we discussed.

• HOMEWORK: Reading check page 283 and Monday’s Reading check page 280 will be collected tomorrow

Gene linkage

• Some alleles are so close to each other on a chromosome that they are inherited together

• This defies Mendel’s law of independent assortment

• Gene linkage only occurs when loci is close

Genetic linkage

• When two genes are very close on the same chromosome they do not segregate independently, they are said to be linked.

• Linkage is a powerful tool in modern genetic counseling.

• Autosomes (chromosomes 1-22) do display linkage however it is most understood in the sex chromosomes(X and Y)

• Since most X-linked traits are seen in males

Sex-linked genes

• Found on the X chromosome

• Are easy to track because traits are often seen in males due to males having only one X chromosome

Thursday 4/19/12

• AIM: What are some of the human genetic disorders?

• DO NOW: Explain why sex linked disorders are easier to trace in males over females

• Homework: textbook page 339-340 questions: 1,2,3,4,5,6,9,14,17. write out the question followed by the answer except for # 14.

Sex-linked genes

• Found only on X chromosome

• Specifically Y chromosome holds only about 20 genes

• Where as the X chromosome has about 1500 genes

How do our chromosomes determine sex?

Formation of a zygote

Genetic makeup of your cells

• Whatever chromosomes and genes the zygote receives, EVERY cell is genetically identical to it

• Cell differentiation: when cells become specialized

Friday 4/20/12

If all of our cells are genetically identical, then why does a neuron transmit electrical impulses while

a muscle cell provides movement?

Cells become specialized by turning on specific genes while turning other

genes off

Apoptosis

• Programmed cell death

Mutation• Any change in the coding sequence that

causes a change in the physical characteristic.

• Chromosomal mutations: loss or gain of a complete chromosome– Usually chromosomal mutations lead to

miscarriage• The baby does not develop to be born

– There are only a few chromosomal mutations that will lead to full term development but the child will have severe abnormalities

Mutations continued

• Genetic mutations: occur at a single gene– Change in the “reading frame” or nucleotide

sequence that causes a change in the physical characteristic

– Much more common than chromosomal mutations

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Human Genetic disorders

• Sex-linked genetic disorders– Only on the X chromosome– Seen more in males than females

• Examples:– Red-green colorblindness– Hemophilia

Red Green Colorblindness

Hemophilia:

• Inability for blood to clot

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

Females exhibit normal dominant or recessive

expression• As long as the

dominant allele is present, it will be expressed

•

Sex Linked traits

• Females must be homozygote recessive in order to display the sex linked disorder

Sex-linked dominant disorder

• Vitamin D resistant Rickett’s

• Ingestion of Vitamin D is ineffective

• Causes bone deformity and bow leggedness

Human Recessive Genetic disorders

• Homozygote Recessive is the only way to display

• Heterozygotes are carriers

• Sickle Cell Anemia

• Albinism

• Cystic fibrosis

Sickle cell anemia

• Homozygote recessive disorder

• Causes the hemoglobin protein to sickle in shape

• Hemoglobin can not carry oxygen

Cystic Fibrosis• European descent• 1:2500• Lack of a membrane

protein that transports Cl-

• Accumulation in the extracellular matrix leads to cells producing a thick sticky mucous

Renal cystic fibrosis

Albinism

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

Human Dominant Disorders

• Both Homozygote Dominant and Heterozygote display trait

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

Huntington’s disease: dominant allele causes slow deterioration of brain

and nervous system

Achondroplasia

• Dwarfism• “without cartilage

formation”• the defect is not in

forming cartilage but in converting it to bone

HypertrichosisExcessive 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 and Down’s syndrome

• • In Down syndrome, 95% of all cases

are caused by this event: one cell has two 21st chromosomes instead of one, so the resulting fertilized egg has three 21st chromosomes.

• Recent research has shown that in these cases, approximately 90% of the abnormal cells are the eggs.

• The cause of the nondisjunction error isn't known, but there is definitely connection with maternal age

Trisomy

• Trisomy 13 • Trisomy 18

Nondisjunction

•

Nondisjunction leads to abnormal numbers of

chromosomes• Turner’s syndrome: XO: no 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

• At puberty may experience mixed secondary sex characteristics such as 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

Genetic testing and counseling

• Punnett squares, testcrosses and genetic screening helps to determine the genotype of parents

• You can then predict the probability of zygote receiving traits

• Medical tests that identify changes in chromosomes, genes and proteins

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 Sampling8th-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

• Treated with diet regulation

Hemophilia: the inability to clot blood

• Sex-linked disorder found on the X chromosome

• It is a recessive trait therefor a female can have one copy of the allele and not display the trait however a male will always display the trait

Females exhibit normal dominant or recessive

expression• As long as the

dominant allele is present, it will be expressed

Because males have only 1 X chromosome, if they receive the recessive allele from mom they

show the recessive trait•