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 mutations1. 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 affected1. 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 IDb. Recessive allele-Heterozygous will give a carrierEx 1- cystic fibrosisFF- normal Ff- carrierff- normalEx 2- sickle cell anemiaAA- normal Aa- carrieraa- 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 Xr = red eyed females
XrXr = white eyed femalesXRY = red eyed malesXrY = white eyedmales
Morgan’s 2nd 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 TraitsAllele on X chromosome• 2 needed for female phenotype• 1 allele for male phenotype• Ex- color blindness, hemophilia and Duchenne MD3. 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 recessive4 Phenotypes : Possible genotypes
Type O OOType A AO, AAType B BO, BBType AB AB
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 bornA. Amniocentesis- takes sample of amniotic
fluid. - can only be done
week 14-16B. 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 246-247
• http://www.youtube.com/watch?v=goEZ7feoZVk
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