genetics. –the study of heredity heredity? –passing of traits from parents to offspring traits...

Genetics

Genetics

– the study of heredity

• heredity?

– passing of traits from parents to offspring

• Traits– Distinguishing characteristics that are inherited, ie

eye color, leaf shape, tail length

Genetics

Father of genetics

Gregor Mendel

• born in Austria, 1822

• monk, lived in monastery

• worked with pea plant

• work published in

1900’s,after his death

Genetics

Father of genetics

• Why was the pea plant so good?

– grow easily

– available

– self pollinating

– display traits easy

to see

– produce a large

number of offspring

Genetics

Father of genetics

• 7 main traits

Genetics

Generations

• Mendel would cross pollinate the pea plants with different traits and observe the offspring produced.

• cross between parents with different traits is called a hybrid

• P = parental generation

• F means filial

– F1 generation = offspring from the parent

– F2 generation = offspring from offspring from parents.

Genetics

Generations Genetics

Mendel’s Laws

• Cross between smooth x wrinkled seeds

– F1 = all smooth

Genetics

Mendel’s Laws

• Mendel concluded that alleles segregate from each other during the formation of gametes

• Law of Segregation

– Organisms inherit two copies of each gene, one from each parent.

– Organisms donate only one copy of each gene in their gametes, thus 2 copies of each gene segregate, or separate, during gamete formation.

Genetics

Mendel’s Laws

• Law of Segregation

– Ex GG plant will send an G allele while a gg plane will send a g allele

– What alleles can a Gg plant give?

– G or g

Genetics

The same gene can have many versions!

• Allele- any of the alternative forms of a gene that may occur at a specific locus.

• They may be HOMOZYGOUS-two of the same alleles at a specific (could both be white flowers)

• Or they may be HETEROZYGOUS-two different alleles at a specific locus. (one for white, one for purple!)

Genes influence the development of traits

• Genome-ALL of an organism’s genetic material

• Genotype-refers to the genetic makeup of a specific set of genes

• Phenotype-physical characteristics, or traits, of an individual – Hidden genes don’t matter in the phenotype

Mendel’s Laws

• Law of Dominance

– some alleles are dominate (CAPITAL letter) and some are recessive (lower case letter)

– ex the allele for tall

(T) pea plants is

dominant to the

allele for short (t)

pea plants

- An allele is dominant simply b/c it in a heterozygote it is expressed and the other allel is not.

Genetics

Punnett square

– A grid system for predicting all possible genotypes resulting from a cross.

• The axes represent the possible gamete genotypes of each parent

• Grid boxes show possible genotype of offspring from those two parents.

– find genotypes

of parents

– purple Pp

– purple Pp

• segregate alleles

– P p; P p

Genetics

Punnett square

Looking at results

• How many of each genotype are possible

– 1 PP, 2 Pp, 1pp

• know the phenotype of each genotype

Genetics

Punnett square

Looking at results

• How many of each genotype did you made

– 1 PP, 2 Pp, 1pp

• know the phenotype of each genotype

• 1PP homozygous dominant

• 2Pp heterozygous

• 1pp homozygous recessive

Genetics

Punnett square

Looking at results

• know the genotype ratio– 1 PP: 2 Pp: 1pp– 1:2:1

– A hybrid cross will always give you a 1:2:1 ratio

Genetics

Punnett square

Looking at results

• know the phenotype ratio

– 3 purple:1 white

– 3:1

Genetics

Mendel’s Laws

• Cross between

smooth x wrinkled

seeds

– F1 = all smooth

– F1 x F1

– F2 = 3 smooth,

1 wrinkled

• Monohybrid cross– Examine the inheritance

of only 1 specific trait.

Genetics

Mendel’s Laws

• Cross between smooth x wrinkled seeds

– F1 = all smooth

– F1 x F1

– F2 = 3 smooth, 1 wrinkled

• Where did the recessive trait in the F2 come from?

– some how they were carried but not expressed in the plant

Genetics

Mendel’s Laws

• Looking at two different traits at the same time, Mendel found they were not always paired together.

– ex yellow & round

do not always

show up together

in offspring

Dihybrid crosses-examine the inheritance of two different traits

Genetics

Mendel’s Laws

• Law of Independent Assortment

– alleles for different traits segregate independently of one another

• ex yellow seed color is independent of smooth seed texture

– getting one trait does not

guarantee you another

trait

Genetics

Mendel’s Laws

• Law of Independent Assortment

– made possible because of?

– Meiosis

Genetics

NON-MENDELIAN GENETICS

Patterns of Inheritance

incomplete dominance

• neither allele is dominant to the other

• both are expressed equally, often a blending of the two traits occurs

Genetics

Patterns of Inheritance

incomplete dominance

• CR is not

dominant to CW

Genetics

Patterns of Inheritance

codominance

• two or more alleles are expressed at the same time

• both are expressed in patches on the organism

Genetics

Patterns of Inheritance

codominance

• CS and CD

are both

expressed

in patches

Genetics

Patterns of Inheritance

codominance

• human blood types

– blood types code for protein on surface of red blood cells

– A, B, O, AB

Genetics

Patterns of Inheritance

codominance

• human blood types

Genetics

Patterns of Inheritance

codominance

• human blood types

Genetics

Patterns of Inheritance

codominance

• human blood types

– cross a father with AB blood with mother O blood

Genetics

Patterns of Inheritance

• human blood types also demonstrate multiple alleles

• multiple alleles refer to a trait (one gene) which is coded for by more than two alleles

– What alleles are present in human blood?

– IA, IB, i

Genetics

Patterns of Inheritance

Determining sex of offspring

• punnett square can help predict the sex of offspring

• female is – XX

• male – XY

Genetics

Patterns of Inheritance

sex-linked traits

– traits found on sex chromosomes, X or Y chromosome

(all non-sex chromosomes are autosomes)

• X chromosome is larger = more traits

• female is XX, male XY

– traits on the X chromosome are more likely to be expressed in males

– ex hemophilia, colorblindness

Genetics

Patterns of Inheritance

sex-linked traits

• sex-linked

dominant

Genetics

Patterns of Inheritance

sex-linked traits

• sex-linked

recessive

Genetics

Tracking inheritance

• pedigree

– traits can be tracked over several generations

– affected individuals

Genetics

Tracking inheritance

• karyotyping

– tool used to look at chromosomes of individuals to look for mutations

Genetics

Tracking inheritance

• nondisjunction

• failure of chromosomes to separate during cell division

Genetics

Tracking inheritance

• nondisjunction

Genetics

Frontiers of Biotechnology!

I. DNA manipulation

A. During recent years, scientists have developed a technique to manipulate DNA, enabling them to study DNA and genes.

B. A DNA molecule is too small for a scientist to cut themselves, so it is cut by special restriction enzymes.

II. Restriction Enzymes

A. Used by bacteria to cut up DNA of viruses.

B. Many different types that cut DNA at different sequences.

III. Copying DNA

A. Often, DNA samples are very small.

B. In order to get enough DNA to study,a polymerase chain reaction (PCR) is used to copy the same segment over and over.

IV. Separating DNA

A. Gel electrophoresis separates the cut DNA by length, using an electrical current.

V. How is the DNA used?

A. Genetic engineering- new genes can be added to an organisms DNA.

B. Mutations and genetic diseases can be shown through different DNA fragments.

C. A DNA fingerprint can identify a criminal, body, or missing person.

D. DNA from different species can be compared to determine their relationship.

I. Genetic Engineering

A. When humans make a change in an organism’s DNA code.

B. In recombinant DNA , genes from one species can be inserted into another.

C. Is frequently used in many of the foods we eat.

II. GM foods

A. These are crops that have been genetically engineered (modified).They are also called transgenic, because they have genes from another species.

B. GM crops make up 52% of the soybeans and 25% of the corn we eat.

III. How is it done?

A. In bacteria:1.A restriction enzyme is used to cut a gene.2. The gene is added to a bacterial plasmid using sticky ends. 3. The plasmid is added to a bacteria, which makes many copies of the plasmid.

B. In plants:

1. The bacteria is modified (see A)

2. The modified bacteria can be allowed to infect a plant

C. In animals:

1. A fertilized egg cell must be used.

2. The foreign DNA is inserted into the nucleus using restriction enzymes and sticky ends.

3. The egg is implanted in a female.

4. The female gives birth to the transgenic organism.