HeredityState Objective: 3d

DNA (Deoxyribonucleic acid)

• Chemical inside cell that contains hereditary information

• Controls how an organism will look & behave

• Shaped like a twisted ladder• Rungs hold genetic information that is

a pair of bases

Reproduction

• Reproduction is the process of producing a new organisms

• The purpose is to transfer DNA

Sexual Reproduction

• New organisms is produced from the combined DNA of TWO different cells called sex cells. – Male is called sperm & Female is called egg

• Fertilization occurs when an egg and sperm unite to form a new organism with half of each parent’s DNA

• Plants sexually reproduce from male and female parts of a flower

• Sex cells are formed by the process of Meiosis

Meiosis• During meiosis, the chromosome pairs separate and

are distributed to 4 different cells. The resulting sex cells have only half as many chromosomes as the other cells in the organism.

Heredity

• The passing of traits from parent to offspring

• Traits: physical characteristics of an organism

–Example: eye color, hair color, & height

Passing Traits to Offspring

• Sex cells have 23 chromosomes and the two sex cells combine to form a zygote with 46 chromosomes

• During fertilization the offspring receives half of its genetic information from its mother and the other half from its father.

Genetics

• The study of how traits are passed from parent to offspring by looking at genes– Genes are small sections of DNA on a

chromosomes that has information about a trait

• Each chromosome has a gene for the same trait (eye color from mom & eye color from dad)– Traits are determined by alleles on the

chromosomes

• Each gene of a gene pair is called an allele– Inherited traits are determined by the alleles on

the chromosome

The DNA Code• Chromosomes are made of DNA. • Each chromosome contains thousands of genes.• The sequence of bases in a gene forms a code

that tells the cell what protein to produce.

Genes on a Chromosome

• Chromosomes are made up of many genes joined together like beads on a string.

• The chromosomes in a pair may have different alleles for some genes and the same allele for others.

Genome• Scientist map a genome to identify all the

organisms genes & figure out where they are located– A Genome is the complete sequence of

an organisms DNA

The Sex Chromosomes

• The sex chromosomes carry genes that determine whether a person is male or female. – also carry genes that determine other traits.– XX = female– XY = male

Inheritance of Blood Type• Blood type is determined by a single gene

with three alleles.

Group Time

Put the following terms in the correct circle to show the hierarchical structures of DNA

• Gene• 1 Allele from each parent• 46 Chromosomes• Nucleus

DNA

Types of Alleles

• Dominant Alleles describe a genetic factor that is always expressed. – It prevents a recessive trait from showing

up in offspring.– Represented by capital letters (B)

• Recessive Alleles describe a genetic factor that is not always expressed. – It only expresses itself when both of the

recessive traits are inherited – Represented by lowercase letters (b)

Group Time

Use a double-bubble map to compare and contrast Dominant & Recessive

Alleles

Examining & Studying Traits

• Two ways scientist study traits– Phenotype: outside expression of a gene

• Blue Eyes– Genotype: the two alleles a person has

inherited that can only be seen on the DNA• BB, Bb, or bb

• Two categories of genotypes– Homozygous: inherited two identical alleles

• BB (pure dominant) or bb (pure recessive)– Heterozygous: inherited two different alleles

• Bb (hybrid)

EXTRA CREDIT

• Bring separate pictures of you and parents or some other relative to whom you look similar.

• These will be on a bulletin board in the hall.

• You will receive 5 extra points on your test.

Group Time

• Use a double-bubble map to compare and contrast genotype & phenotype• Use a tree map to classify the

following genotypes: DD,Dd,dd,ee,LL,Ll,Hh,HH,Ss,tt,

Punnett Squares• Shows all possible

combinations of alleles that children can inherit from parents

• Mom’s genotype for brown eyes (Bb)

• Dad’s genotype for brown eyes (Bb)

• Offspring’s Phenotype– 75% brown, 25% blue

• Offspring’s Genotype– 25% BB, 50% Bb, 25% bb

B b

B BB Bb

b Bb bb

MomMom

DDaadd

brownbrown

blueblue

brownbrown

brownbrown

Punnett Square Practice

• What is the genotype and the phenotype for each parent?

• What are the possible genotypes and the phenotypes for the offspring?

Codominance• In codominance, the alleles are neither dominant

nor recessive. As a result, both alleles are expressed in the offspring.

• FW FB = black & white

• FB FB = black

• FW FW = white

Incomplete Dominance• In incomplete dominance, one allele is not

completely dominant over the other allele . As a result, both alleles have a blended expression.

• RR = red

• WW = white

• RW = pink

Pedigree• Geneticist use pedigrees to follow a human trait to

learn how the trait was inherited • A pedigree is a chart or “family tree” that tracks the

members of a family that have a certain trait.• Circles stand for female• Squares stand for males• A line connecting a square & circle shows they are

married• Shaded = person has the trait• Half-shaded = carries one allele for the trait but does

not have the trait• No shading = person does not have or carry the trait

Pedigree Practice

• What does this symbol stand for? Male or female• What does the shading of this symbol represent?

A Hemophilia Pedigree

• The chart below follows hemophilia in a family. Hemophilia is a genetic disorder that does not allow the blood to clot normally. How many males have hemophilia?

Biotechnology

• Biotechnology is the manipulation of living things to make useful products– Causes changes in an organism

• Examples of genetic biotechnology– Selective Breading

– Genetic Engineering

• Gene Therapy

Selective Breeding

• Selective Breeding is an intentional mating of organisms to produce offspring with specific traits – Two types:

• Pure bred• Hybrid

Selective Breeding: pure bred

• Pure breeding– Crossing two individuals that have identical

or similar sets of alleles.

• Example: breeding only fast horses, breeding only labs

– Con – decreases genetic variety therefore makes it harder to adapt, resist diseases, and higher chance of genetic disorders

Selective Breeding: hybrid

• Hybridization– Crossing two genetically different individuals. The

Hybrid organism is bred to have the best traits from both parents.

• Example: Labradoodles, corn produces lots of kernels with one resistant to disease

– Con – doesn’t always turn out the planned way & is time consuming

• Can not easily predict weather the dominant or recessive trait will appear

Thad Cochran National Warm-water Aquaculture Center

• Diseases in catfish farming are prevalent and costly, particularly the bacterial disease Enteric Septicemia of Catfish.

• The Aquatic Center uses selective breeding in a multi-trait process to increase the natural disease resistance of the fish through selective breeding.

Genetic Engineering

• Genetic engineering changes the genetic material of a living organism by removing genes from one organism then transferring them into the DNA of another organism. (gene splicing)

• Uses:– Make medication and treat diseases– cure human genetic disorders– Improve crops

• Bacteria were the first success with genetic engineering because they are one celled and not as complex.

• Ex. Insert bacteria DNA into rice, wheat, and tomatoes to enable plants to survive in colder temps, poor soil conditions, and resist insect pests.

Genetic Engineering• Scientists use genetic engineering to

create bacterial cells that produce important human proteins such as insulin.

Gene Therapy• Gene therapy is an experimental technique that

uses genes to treat or prevent disease by inserting working copies of a gene directly into the cells of a person with a genetic disorder

• Researchers are testing several approaches to gene therapy, including:– Replacing a mutated gene that causes disease with a

healthy copy of the gene.– Inactivating, or “knocking out,” a mutated gene that is

functioning improperly.– Introducing a new gene into the body to help fight a

disease.

• Several studies have already shown that this approach can have very serious health risks, such as toxicity, inflammation, and cancer.

Gene Therapy Examples

• People with CF don’t produce the protein to control mucus production. Both genes are defected (recessive). Scientist insert working copies of gene into harmless viruses. The engineered viruses can be sprayed into the lungs of the patients.

• Gene therapy works in hemophilia by using DNA as the drug and viruses as the deliverer. A virus containing the gene that produces Factor VIII or Factor IV is injected into a large group of cells in the patient. The hope of the gene therapy is to have the cell produce more of the cured cells and spread throughout the rest of the body..

Animal Functional Genomics Lab

• Located at Mississippi State University• Deals with Bovine (Cow)• Animal Biotechnology - Our laboratory’s research

interests include efficient production of genetically enhanced livestock and animals for biomedical studies.

• They selectively breed bovine that exhibit good traits such as higher milk production, resistance to diseases, better tasting milk, etc.– Example: Cattle type 1 doesn’t get sick from a certain

infection. Cattle type 2 does. They will no longer breed Cattle type 2. They will select to only breed cattle type 1 to produce offspring.

Animal Functional Genomics Lab

• They also explore the secrets of animal genomes to determine genes involved in important phenotypes in reproduction and growth.– map the genome of bovine to located certain genes

that control desirable traits.

– hopes to genetically engineer, better offspring by changing the DNA not just selecting better parents.

Stoneville Pedigreed Seed Co.

• Located in Stoneville, MS• Deals with plants• Soybeans, corn and cotton have been genetically

engineered to provide herbicide tolerance, insect resistance or both are widely grown in the United States and several other countries– That technique does not involve altering crops by putting in

foreign genes. Rather it uses genetic tests to help choose which plants to use in conventional cross-breeding, vastly speeding up the process.

Comparing and Contrasting

Cystic fibrosis Body produces abnormally thick mucus.

Recessive allele due to removal of three DNA bases

Disorder Description Cause

Sickle-cell diseaseRed blood cells are sickle-shaped and have reduced ability to hold oxygen.

Codominant allele

Hemophilia Blood clots slowly or not at all.

Recessive allele on X chromosome

Down Syndrome Mental retardation and heart defects

An extra copy of chromosome 21