Chapter 12 Mutations, Xs, and Inheritance

Mutations= changes in organisms DNA Beneficial- lead to adaptations and aid evolution of a species Harmful- the worst are lethal

Types of Mutations 1.cellular mutations; a. germ cell mutation-change is in the gametes so it affects the offspring and not the parent organism b. somatic cell mutation-change is in an organism’s body cells will affect the organism but not the offspring ex; certain types of skin cancer, leukemia

Chromosome mutations 1.Deletion- loss of part of X so missing genes and lack info 2.Inversion- one X breaks off a part and attaches in a reverse pattern 3.Translocation- X part breaks off and reattaches to a non-homologous X 4. Nondisjunction- Xs do NOT separate during anaphase of meiosis so one gamete gets too many Xs and gets too few

Gene mutations- (DNA---mRNA---aa---protein) point mutation- if only 1 base is affected 1.Substitution 2.Insertion 3.Deletion –#2 and #3 cause a change in the codon sequence- called frameshifts Ex. THE CAT ATE THE RAT TTH ECA TAT ETH ERA T TEC ATA TET HER AT

Genetics Traits 1.Single allele traits; a. Dominant allele Ex- Huntington’s Disease -HH or Hh will develop disorder -hh is normal -genetic marker used to ID b. Recessive allele -Heterozygous will give a carrier Ex 1- cystic fibrosis FF- normalFf- carrier ff- normal Ex 2- sickle cell anemia AA- normalAa- carrier aa- diseased

Genetic researcher Thomas Morgan Worked with fruit flies, Drosophila melanogster Why fruit flies? 1.chromo. # = 8 (4 pairs) 2.Reproduce quickly 3.Males and females look differentt Observations 1.males not like females 2.females had 2 XX and males had 1 X and 1Y 3.called this the sex determining pair 4.other 3 prs. alike in both sexes (autosomes) 5.Had either red or white eyes

Morgan’s experiment with eye color Took a male with white eyes and crossed it with a red eyed female. Result was that ALL offspring had RED eyes!!!(F1) Crossed 2 offspring together and got 3 Red eyed:1 white eyed; however ALL white eyed flies were males this time!!! Why did that happen????

The Answer Sometimes a gene appears only on the X or Y chromosome These genes are called sex linked genes Ex-Drosophila eye color, 2 possible alleles red (R) or white (r) Allele only on the X chromo. Genotypes= X R X R or X R X r = red eyed females X r X r = white eyed females X R Y = red eyed males X r Y = white eyedmales

Morgan’s 2 nd Experiment Hypothesized that genes that are inherited together are found on the same chromosome Studied body color (GRAY vs. black) and wing length (LONG vs. short) Crossed GGLL x ggll What do you think he got???

Answer to GGLL x ggll In the F1 all were GgLl (GRAY, LONG wings) Morgan then crossed GgLl x GgLl Results were 3 GRAY, LONG :1 black, short Expected 9:3:3:1, instead results are always 3:1 for two characteristics So Morgan concluded that these were “Linked Genes”

Linked Genes If known linked genes do NOT follow a predicted pattern they may have crossed over during meiosis Ex.- pigmentation of human eye, hair, and skin color Chromosome maps- Determine how far apart genes are on a chromosome Geneticists use frequency (%) of cross-overs in offspring to determine distance between genes called map unit Rule; for every 1% of crossovers the genes are 1 map unit apart (p.224)

Chromosome Mapping Geneticists use frequency(%) of cross-overs in offspring to determine distance between genes called map unit Rule; for every 1% of crossovers the genes are 1 map unit apart (p.224)

12-2 Pedigrees used to study the inheritance of a trait through many generations patterns of phenotypes can be followed using a chart

Genetics Traits 2. X-linked Traits Allele on X chromosome 2 needed for female phenotype 1 allele for male phenotype Ex- color blindness, hemophilia and Duchenne MD 3. Sex Influenced Traits Phenotype affected by sex hormones Ex- Baldness BB is bald in male and female Bb is bald only when testosterone present bb- no baldness

Genetic Traits 4. Multiple Allele Traits Determined by three or more alleles Ex- ABO blood type Alleles- A and B (codominant) O recessive 4 Phenotypes :Possible genotypes Type OOO Type AAO, AA Type BBO, BB Type ABAB

Genetic Traits 5. Polygenic Traits Controlled by 2 or more genes Ex- melanin amounts In Hair, skin, eye color Genotypes- AABBCC- darkest AaBbCc- lt brown aabbcc- lightest

Genetic Testing Before a fetus is born A.Amniocentesis- takes sample of amniotic fluid. - can only be done week B. Chorionic villi- taken from chorionic villi - can only be done week 8-10 Both require a karyotype be done after cells are samples.

Genetic Diseases and Counseling Refer to page eoZVkhttp:// eoZVk

Gene Therapy Gene Therapy – a technique that replaces a defective gene with a healthy gene. -has been used to treat cystic fibrosis 2 types of gene therapy 1. somatic cell- body cells are changed 2. germ cell- changes to egg and sperm