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Genetics: all the rage in bio One of the fastest changing fields in biology People started studying it back to ancient Greece but they were limited to.

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Presentation on theme: "Genetics: all the rage in bio One of the fastest changing fields in biology People started studying it back to ancient Greece but they were limited to."— Presentation transcript:


2 Genetics: all the rage in bio One of the fastest changing fields in biology People started studying it back to ancient Greece but they were limited to PHENOTYPE: what something looks like Due to our great new knowledge (human genome project and much more) we can now get meaningful information form the GENOTYPE: the genes/ versions that individuals contain

3 Historically it was easy to see We all already know too… You look like both of your parents. Each feature is a one or the other kind of thing… not a blend Ie. I have my dad’s eyes, my dads mouth shape and my mom’s hands. I am a blend but my features are not It took Gregor Mendel to start truly understanding WHY

4 Mendel changed the world with his peas Mendel had a hypothesis that all of our features were controlled by heritable factors (genes) He set out to prove it but needed a model organism… something that was easy to work with and showed what he needed it too He chose the pea plant

5 Why garden peas? 1. Easy to control fertilization. Insure self fertilization and cross fertilization For cross he removed the stamen before the pollen was mature

6 Why garden peas? 2. Had a variety of characters to explore

7 What Mendel did… First he let the peas self- fertilize so they would be pure He then crossed a purple flowering plant with a white flowering plant (cross- fertilization or hybrid) This was the _________________ P (parental) generation The progeny from that generation are F 1 When the F 1 are crossed… their progeny produce what is referred to as F 2

8 How he did it Started with plants that differ in only one characteristic (monohybrid cross) Flower color (purple vs white) The F1 progeny were all _______ Oh no! Did the white disappear?!? Few… in the F2 generation the white reappeared in a ratio of _____ _______ to _______________ So the white was not lost just covered for a while

9 What he concluded 1. There are different forms of each unit that determine heritable traits (alleles) 2. Principle of __________: During the formation of egg and sperm the parental alleles segregate then the diploid status of the offspring is restored at fertilization 3. Principle of Independent assortment: Each trait is inherited _________ from _____________. They segregate on their own 4. Law of dominance and recessiveness: Within each pair of alleles, there is an option for a ________ (fully expressed) and ______________ (largely unexpressed) variations

10 How we can use it First, each trait is named for the _________ version (P for purple because it is dominant) The recessive is just ______ ______ of the (p for white) Each parent can be either homozygous (both alleles the same) or heterozygous (one dominant and one recessive) We track their succession using a Punnett square

11 Genes v Look The genetic makeup of an individual trait is the _________ (heterozygous, homozygous dominant, homozygous recessive) The look of the individual is it’s __________ (purple or white) You can use the genotype to tell the phenotype and sometimes the phenotype to tell the genotype

12 Monohybrid cross: pod color (2 generations)

13 Test Cross If an individual is __________, it is impossible to determine its genotype (could be ___________ __________or _____________) Use a test cross… breed it with a known ____________ ____________ What would the F1 look like if the unknown were homozygous dominant?… heterozygous?

14 Dihybrid crosses Looks at _____ different characters… seed color and seed shape. If they were inherited together we would see a dominant seed color/shape combo and a recessive combo As it is the most characters exhibit _____________ ______________.

15 Dihybrid example If yellow is dominant to green and round to wrinkled You cross a yellow round seed with a green wrinkled. What do you get? ** need a bigger Punnett square!

16 Ratios… memorize instead of huge Punnett squares! Heterozygous dihybrid cross always yields a phenotype ratio of _:_:_:_ (dominant both: dominant one: dominant one: recessive both) Homozygous dominant- recessive cross gives all the ______________ (phenotypically the dominant character)

17 Incomplete dominance (blend) Not all traits are a one or the other thing With __________ _________both alleles work together to determine the final phenotype Take a cross for two flowers… One red (RR) and one white (WW) With incomplete dominance the heterozygote is an ___________ between the two homozygotes Now both the genotypic and phenotypic ratios are 1:2:1 in a heterozygote cross

18 Codominance Each allele is __________ _________in different regions or cells Calico cat, rone horse Neither one is totally dominant and the two traits co-exist without bothering each other, each controlling their own area

19 Blood types are codominant A or B or both or neither may be expressed If you have __antigens you recognize things with ___ and fight anything with ___ If you have AB you recognize _________ If you have O you recognize no one but they don’t detect you A donates to __ B donates to __ AB can receive from anyone but only donate to AB O can donate to _______ but only receive O

20 Linked traits Some traits do not independently assort We know that chromosome have loci, all the loci on the same ___________ HAVE to be inherited together (unless crossover moves them) Genes on the same chromosome are inherited together!

21 Sex linked traits Sometimes the link is with a sex chromosome. The __ is notorious for being linked… color blindness, hemophilia, and MANY other things in other animals Who would be more likely to be affected? Why?

22 Sex-Linked continued _______ are usually affected more often because they get only one X… so good gene or bad gene automatically shows up A female has another chance for a second X to cover the bad (or just recessive trait) Females are often ________

23 Deletion: a portion is _____________ Where is the dog?  Where the dog? ____________: a portion is doubled Where is the dog?  Where is the the dog? __________: If a deleted piece reattaches in the wrong orientation Where is the dog?  Where is dog?  Where is dog eht? Translocation: removed from chromosome and added ___________ to another Where is the dog? The dog is in the backyard.  Where is dog? The dog is in the backyard the. Changes in DNA during replication

24 Human Genetic Analysis We can display human inheritance using a display called a _______. In a pedigree, _______ are represented by ________ and females by circles. An individual who exhibits the trait is represented by a _____ symbol. A _____________ line between two symbols represents a mating. The ________ are connected to each other by ___________ line above the symbols and to the ________ by _________ lines. Roman numerals (I, II, III, etc.) symbolize generations. Autosomal Recessive Autosomal dominant

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