Genetics Chapter 11.1,11.2,11.3, and Chapter 14

Complex Inheritance Patterns Incomplete Dominance—When one allele for a gene is not completely dominant over another allele. The hybrid displays an intermediate phenotype. Ex: In snap dragons (flowers) the red allele is incompletely dominant over the white allele. RR=red, WW=white, RW=pink

Incomplete Dominance

Complex Inheritance Patterns Codominance—When both alleles for a gene are expressed. The hybrid displays both phenotypes. Ex: In chickens the alleles for black and white feathers are codominant. BB=black, WW=white, BW=speckled (both b and w feathers)

Roan cattle display co dominance

Co dominance in humans Sickle Cell Anemia—a human genetic disorder associated with codominance Sickle cell is more common in people of African or Mediterranean decent About 1/12 African Americans are heterozygous for the disorder SS Normal blood cells ss Sickle shaped red blood cells Ss ½ normal red blood cells, ½ sickle cells

Red blood cells and Sickle cells

Complex Inheritance Patterns Multiple alleles—when there are more than two possible alleles for a trait within a population. (Each individual still receives only two alleles for each trait.) Ex: Human blood types

Human Blood Types 3 possible alleles: A, b and O Blood Types Genotypes Can donate Blood to Can receive blood from O OO Eveeryone AB everyone A AA or AO A, AB A, O B BB or BO B, AB B, O

Complex Inheritance Patterns Polygenic Inheritance—when traits are controlled by many genes Ex: AAbbCcddEeFFgg x AaBbCCDdEeFfGg The genes can be on different chromosomes or the same chromosome (linked) Traits controlled by polygenic inheritance have a wide variety of phenotypes Ex: human skin color

Pedigree—a genetic family tree

Determining the sex of the offspring Males have the sex chromosomes XY Females have the sex chromosomes XX. The female’s egg always has an X chromosome 50% of sperm have an X and the other 50% have a Y. (So it is the sperm that decide the sex of the offspring)

Determining the sex of the offspring

Complex Inheritance Patterns Sex-linked traits—traits that are controlled by alleles located on the X chromosome. (most sex-linked genetic disorders are recessive) Females need two recessive alleles to exhibit the disorder Males only need one recessive allele to exhibit the disorder Examples: Hemophilia and Red-green colorblindness are fairly common sex-linked traits

Colorblindness Punnett Square This is a cross between a “carrier” female and a normal male

Environmental Influences Genes only determine potential Environmental factors can determine whether genes are expressed Internal factors—hormones, age External factors—temperature, nutrition, light, chemicals, viruses

Environmental Influences Nature vs. Nurture (genetics) (environment) Genes set the range/scale for a particular trait, and your environment determines the rest

Karyotyping Karyotype—a picture of an organism’s chromosomes Karyotypes are used to diagnose genetic disorders like: *Monosomy (having only one copy of one type of chromosome) *Trisomy (having three copies of one type of chromosome) Ex: Trisomy 21, called Down Syndrome XXY Syndrome, also called Klinefelter’s

Normal Female Karyotype

Normal Male Karyotype

Trisomy 21 Karyotype

Klinefelter's Karyotype

To review… Normal female – 22 pairs and 2 X chromosomes -> 23 pairs Normal male – 22 pairs and an X and a Y - > 23 pairs Down’s syndrome – trisomy 21 Klinefelter's – male with an extra x Turner’s – female with only 1 X

DNA Technology Cloning—producing cells or entire organisms that are genetically identical to the original. Applications of cloning: Creating stem cells to create new organs Producing new organisms genetically identical to their parents Using information from cloning to see what happens when certain genes are turned on or off

THE LAMB IS GENETICALY IDENTICAL TO SHEEP A Cloning an organism 56 chrom 56 chrom No DNA In a lab THE LAMB IS GENETICALY IDENTICAL TO SHEEP A

DNA Technology Since ancient times humans have used selective breeding to obtain desired traits in plants and animals. Inbreeding—when two closely related organisms are mated in order to maintain the desired traits in the offspring. Inbreeding helps create “purebred” organisms that are homozygous for many traits. Inbreeding is dangerous for the offspring because recessive genetic disorders are much more common in organisms that are homozygous for most of their traits.

DNA technology Genetic Engineering—When scientists genetically modify the DNA of an organism to obtain desired traits. Transgenic organisms—Organisms that have DNA from other species inserted into their genome Ex: Plants with deep sea fish genes inserted to prevent crop damage by frost Fish with inserted genes to make them grow year-round Transgenic plants and animals have the potential to improve people’s diets worldwide

Alba, the albino rabbit with jellyfish gene

Transgenic Organisms Disadvantages of transgenic organisms: Ethical questions: are we playing God? We don’t know what would happen if these organisms were released into the wild and started breeding with the natural species. These new, genetically modified species could reproduce, spread, and do damage to the natural ecosystem.

DNA technology Gel Electrophoresis—A technique that allows researchers to identify similarities and differences in the genomes (genes) of different organisms.

Gel Electrophoresis

DNA technology DNA Fingerprinting—a technique in which scientists examine a person’s DNA. From your DNA bases scientists can determine if: Two people are related A suspect could have been involved in crime A person carries a gene for a genetic disorder

DNA technology Gene Therapy—a technique used by scientists to change the DNA in a person’s cells in order to cure genetic disorders. Scientists use genetically modified viruses to infect cells and change DNA.

Steps of gene therapy Steps: 1. Identify the faulty gene that causes the disease 2. Use restriction enzymes to cut out the normal gene from DNA 3. Splice the normal gene into viral DNA 4. Allow recombinant viruses to infect human cells.