GeneticsChapters 9 and 12

Introduction to Genetics• Genetics is the science

of heredity and variation in living organisms.

• Every living thing has inherited a set of characteristics from its parent or parents.

• Traits – genetically determined variant of a characteristic

Francis Crick's first sketch of the deoxyribonucleic acid

double-helix

• At its most fundamental level, inheritance in organisms occurs by means of discrete traits, called “genes”.

• This property was first observed by

Gregor Mendel

Introduction to Genetics

http://en.wikipedia.org/wiki/Genetics Chapter 12: Day One

Introduction to Genetics

The molecular basis for genes is: deoxyribonucleic acid.

http://en.wikipedia.org/wiki/Genetics Chapter 12: Day One

DNA

Good thing to know.

Gregor Mendel

• Called the father of genetics for his study of the inheritance of traits in pea plants.

Chapter 11: Day Five Start Herehttp://en.wikipedia.org/wiki/Gregor_Mendel

Gregor Mendel

• Used garden peas and studied 7 specific traits

• These different varieties of peas are called true-breeding because they always pass on their traits to their offspring

Chapter 11: Day Fivehttp://en.wikipedia.org/wiki/Gregor_Mendel

Gregor Mendel

• Normally the flowers of pea plants self-pollinate: the pollen (male sex cells) and the ovum (female sex cells) come from the same flower

Chapter 11: Day Five

pollen

ovum

Gregor Mendel

• He studied 7 specific traits

• Each trait had 2 possible forms (alleles)

• Allele- one of a number of different forms of a gene

P generation Cross

P generationOriginal true-breeding plants

F1 generation

Hybrid plants- offspring that have inherited 1 trait from each parent

Chapter 11: Day Five

r r

r r r r

P generation Cross

• Mendel concluded that each P1 parent had 2 identical genes for each trait AND that 1 allele must be DOMINANT and the other RECESSIVE

Chapter 11: Day Five

Why are the F2 hybrids all red?

r r

r r r r

• Genotype- the letter combinations showing possible alleles

• Identical alleles are homozygous

• Opposite alleles are heterozygous

• Phenotype is the form of the trait that shows up in what the organism looks like

rr = homozygous white

Rr = heterozygous red

RR = homozygous red

white redor

Chapter 11: Day Five

F1 generation

F2 generation

Chapter 11: Day Five

3:1 ratio

r r r r

r

r

RR

rrRr

Rr

3:1 ratio, why is that?

When each F1 plant flowers and produces gametes, the 2 alleles segregate from each other so that each gamete carries only a single copy of each gene.

Therefore, each F1 plant produces 2 types of gametes- those with the allele for redness and those with the allele for whiteness.

Mendel’s Results & Conclusions

• Law of Segregation – a pair of factors is segregated, or separated, during the formation of gametes

• Law of Independent Assortment - factors separate independently of one another during the formation of gametes

Gregor Mendel Review

• The inheritance of biological characteristics is determined by individual units known as genes. Genes are passed from parents to their offspring.

• The principle of dominance states -some alleles are dominant and some others are recessive.

• During gamete formation, alleles segregate from each other so that each gamete carries only a single copy of each gene.

• Principle of independent assortment –alleles segregate independently

Inheritance Patternand Human Genetics

Chapter 12

Chromosomes

• Sex chromosomes– Contain genes that determine the sex of an

individual• Autosomes

– All the other chromosomes

This is old news.

Sex Determination

Sex-Linked Trait• A trait that is coded for an allele on a sex

chromosome

Most X-linked alleles have no counterpart on the Y chromosome.

Bigger, has more

information

r

Is something

missing here?

Linked Genes• Pairs of genes that tend to be inherited

together, found on same chromosome

Dude, I ain’t

going nowher

e!!

Don’t leave me,

man!!

Chromosome Map• A diagram that shows the linear order of

genes on a chromosome.

Mutations• A change in the nucleotide-base sequence.• Involve an entire chromosome or a single

nucleotide.

Germ cell:Occurs in the organism’s gametes.

Passed onto offspring.

Somatic-cell:Take place in

organism’s own body cell

Lethal:Cause death.

Chromosome Mutations

• Deletion– Loss of a piece of chromosome

• Inversion– Segment breaks off, flips, and reattaches

• Translocation– Piece breaks off and reattaches to different chromosome

• Nondisjunction– Chromosome fails to separate from its homologous

partner during meiosis

Gene Mutations• Point mutations

– Change that occurs within a single gene or other DNA segment

• Substitution– One nucleotide replaces another

• Frameshift mutation– Loss of nucleotides cause incorrect grouping of codons

• Insertion mutation– One or more nucleotides are added to a gene, which can

also result in a frameshift mutation

See page 240

Pedigree

• A diagram that shows how a trait is inherited over several generations.

Genetic Traits and Disorders

• Genetic disorders– Diseases or disabling conditions that have a

genetic basis

• Complex characters– Characters that are influenced strongly by the

enviroment and by genes

Beyond Gregor Mendel

• Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes.– Incomplete dominance– Codominance– Multiple alleles– Polygenic traits

Polygenic

• Characteristics are influenced by several genes

Multiple Alleles

• Genes with 3 or more alleles

Codominance

• Both alleles are expressed

Incomplete Dominance

• A trait that is blended

Genetic Engineering

• Genetic engineering, recombinant DNA technology, genetic modification/manipulation (GM) and gene splicing are terms that are applied to the direct manipulation of an organism's genes.

Chapter 13: Day Seven

http://en.wikipedia.org/wiki/Genetic_engineering http://www.foxnews.com/images/330367/0_61_121207_cat.jpg

Cloned glow in the dark cats.

Genetic Engineering

There are a number of ways through which genetic engineering is accomplished. Essentially, the process has four main steps.

1) Isolation of the gene of interest

2) Insertion of the gene into a vector

3) Transformation of cells of organism to be modified

4) Tests to isolate genetically modified organism (GMO)

Chapter 13: Day Seven

http://en.wikipedia.org/wiki/Genetic_engineering

Lab Assignment

• In your team, begin discussion on what you think genetic engineering is and your position on stem cell research.

Chapter 13: Day Seven Stop Here

AFP / Getty Images