Genetics

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Genetics
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Vocabulary

• Segregation Trait
• Gametes
• Genes
• Alleles
• True breeding
• Hybrids
• Homozygous
• Heterozygous
• Phenotype
• Genotype

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Traits

• Traits are qualities, features or other things
  that distinguish the organism. Traits can include
  things like hair color, tooth shape, beak shape,
  bone size, or muscle structure.
• Traits come in two varieties acquired and
  inherited.

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Acquired Traits

• Animals can acquire usesful abilities.
• These acquired traits can not be passed on
  genetically. You can't inherit your uncle's
  knowledge, skills, ideas or memories and it
  doesnt' work that way with other organisms
  either.
• Acquired traits include things such as calluses
  on fingers, larger muscle size from exercise or
  from avoiding predators.
• Behaviors that help an organism survive would
  also be considered acquired characteristics most
  of the time. Things like where to hide, what
  animals to hide from.

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Inherited Traits

• In organisms, inherited traits must come from a
  parent or other ancestor.
• A trait may seem to skip a generation or even two
  or three, but if a trait shows up it must have
  been present in an ancestor.
• Inherited traits include things such as hair
  color, eye color, muscle stucture, bone
  structure, and even features like the shape of a
  nose.
• Inheritable traits are traits that get passed
  down from generation to the next generation. This
  might include things like passing red hair down
  in a family.

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The basics

• Gregor Mendel "father of genetics"
• Blending Theory of Inheritance - offspring of two
  parents "blend" the traits of both
  parentsParticulate Theory of Inheritance -
  traits are inherited as "particles", offspring
  receive a "particle" from each parent.
• Evidence for Particulate Theory of Inheritance A
  plant with purple flowers is crossed with another
  plant that has purple flowers. Some of the
  offspring have white flowers (wow!). Mendel set
  out to discover how this could happen.

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Mendel

• parents were farmers
• he became ordained as a priest
• studied science and mathemathics at the
  University of Vienna
• Mendel's Experiments - chose pea plants as his
  experimental subjects, mainly because they were
  easy to cross and showed a variety of contrasting
  traits (purple vs white flowers, tall vs short
  stems, round vs wrinkled seeds)

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• _______________ was the father of genetics.
• Charles Darwin b. Gregor Mendel
• c. Charles Watson
• What did he use in his research?
• Corn b. Fruit flies
• Peas
• Hidden characteristics show up in_________ of the
  second generation.
• One half b. One quarter
• c. One third d. All of them

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Mendels Procedure

• 1. Mendel chose true-breeding lines of each
  plant/trait he studied (true breeding lines
  always produced offspring of the same type)
• 2. He crossed a true breeding plant with a plant
  of the opposite trait (purple x white). He called
  this the Parental (P) generation.
• 3. He recorded data on the offspring of this
  cross (First Filial, F1)
• 4. He self pollinated the F1 offspring
• 5. He recorded data on the offspring of the
  second generation, calling it the Second Filial
  generation (F2)

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Mendels Analysis

• The F1 generation always displayed one trait (he
  later called this the dominant trait)
• The F1 generation must have within it the trait
  from the original parents - the white trait
• The F2 generation displayed the hidden trait, 1/4
  of the F2 generation had it (he later called this
  hidden trait the recessive trait)
• Each individual has two "factors" that determine
  what external appearance the offspring will have.
  (We now call these factors genes or alleles)

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Mendels Conclusion

• Mendel established three principles (or Laws)
  from his research
• 1. The Principle of Dominance and Recessiveness -
  one trait is masked or covered up by another
  trait
• 2. Principle of Segregation - the two factors
  (alleles) for a trait separate during gamete
  formation
• 3. Principle of Independent Assortment - factors
  of a trait separate independently of one another
  during gamete formation another way to look at
  this is, whether a flower is purple has nothing
  to do with the length of the plants stems - each
  trait is independently inherited

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The Law of Segregation

• The Law of Segregation two alleles separate
  during gamete formation (a Tt parent can produce
  both T sperm, and t sperm)
• A punnet square is a representation of this law,
  showing how gametes separate and then come
  together during fertilization

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A simpler look at Mendels generations
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Modern Genetics

• Mendel's factors are now called ALLELES. For
  every trait a person has, two alleles determine
  how that trait is expressed.
• We use letters to denote alleles, since every
  gene has two alleles, all genes can be
  represented by a pair of letters.
• PP purple, Pp purple, pp white

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• ALLELES (WARNING - THIS WORD CONFUSES PEOPLE
  READ SLOW) alternative forms of the same gene. 
  Alleles for a trait are located at corresponding
  positions on homologous chromosomes. Remember
  just a second ago when explaining genotypes I
  said that "one code (letter) comes from ma one
  code (letter) comes from pa"? Well "allele" is a
  fancy word for what I called codes.
• For example, there is a gene for hair texture
  (whether hair is curly or straight).  One form of
  the hair texture gene codes for curly hair.  A
  different code for of the same gene makes hair
  straight.  So the gene for hair texture exists as
  two alleles --- one curly code, and one straight
  code. Let's try illustrate with a diagram.
• In this picture the two "hot dog" shapes
  represent a pair of homologous chromosomes. 
  Homologous chromosomes are the same size have
  the same genetic info (genes).  Each letter in
  the diagram stands for an allele (form of a
  gene).  What's important to notice is that the
  letters can be in different forms (capital or
  lowercase) --- that is what we mean by allele ---
  and that the letters are lined-up in the same
  order along each hot dog --- homologous
  chromosome. The "a-forms" are in corresponding
  positions, so are the "B-forms", the "c" alleles,
  the "d" alleles, etc. etc. Reread that "allele"
  definition again study the picture.
• back to our abbreviations, we could use a "C" for
  the curly allele, and a "c" for the straight
  allele.  A person's genotype with respect to hair
  texture has three possiblilties CC, Cc, or cc. 
  So to review some vocab, homozygous means having
  two of the same allele in the genotype (2 big or
  2 little letters --- CC or cc).  Heterozygous
  means one of each allele in the genotype (ex
  Cc).

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Important Terms

• Homozogyous when the alleles are the same, the
  individual is said to be homozygous, or true
  breeding. Letters designating a homozgyous
  individual could be capital or lowercase, as long
  as they are the same. Ex. AA, bb, EE, dd
• Heterozygous when the alleles are different, in
  this case the DOMINANT allele is expressed. Ex.
  Pp, Aa
• Monohybrid cross a cross involving one pair of
  contrasting traits. Ex. Pp x Pp
• Punnet Square used to determine the PROBABILITY
  of having a certain type of offspring given the
  alleles of the parents

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Homozygous vs. Heterozygous

• Homozygous involves traits where both alleles are
  the same , either dominant or recessive. If we
  were talking about round or wrinkeled seeds we
  could use the letter R. RR would be homozygous
  dominant and rr would be homozygous recessive
• Heterozygous involves traits where one inherited
  allele is dominant and the other is recessive
  such as Rr

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Indicate whether the following are homozygous
dominant, homozygous recessive or heterozygous

1. HH _________________
2. Hh
3. hh
4. Rr
5. rr
6. RR

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Genotype vs. Phenotype

• Genotype letters used to denote alleles (BB, Pp,
  etc.)
• Phenotype what an organism looks like (brown,
  purple..) Its physical appearance.
• If we donate PP for purple flowers and p for pink
  flowers, fill in the genotype and phenotype of a
  
• 1. homozygous dominant flower
• 2. homozygous recessive flower
• 3. heterozygous flower

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Answers

• Homozygous dominant flower
• genotype - PP
• phenotype purple
• Homozygous recessive flower
• genotype pp
• phenotype pink
• Heterozygous flower
• genotype Pp
• phenotype - purple

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PUNNETT SQUARES

• In pea plants, round seeds are dominant to
  wrinkled. The genotypes and phenotypes are
• RR roundRr roundrr wrinkled

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Punnett Squares Monohybrid cross
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Punnett Squares Monohybrid cross
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Punnett Squares Monohybrid cross

• PARENTS One is tall TT (homozygous) and one is
  short tt (homozygous)

T
T
t
Tt Tt
Tt Tt
t
All offspring are tall!
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Punnett Squares Monohybrid cross

• In the previous slide the two homozygous parents
  had all tall children who were heterozygous. Now
  we cross the offspring Tt x Tt

T
t
TT Tt
Tt tt
T
t
Now the probability of having a tall child is
lower It is 31, because three are tall one one
is short
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How to make a punnett square

• 1. Determine the genotypes (letters) of the
  parents. Bb x Bb2. Set up the punnett square
  with one parent on each side.3. Fill out the
  Punnett square middle4. Analyze the number of
  offspring of each type.
• In pea plants, round seeds are dominant to
  wrinkled. The genotypes and phenotypes areRR
  roundRr roundrr wrinkled

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• If you get stuck make a "key". Sometimes the
  problems won't give you obvious information.
  Example In radishes, a bent root is a dominant
  trait, though some roots are straight (which is
  recessive). If a straight rooted plant is crossed
  with a heterozyous bent root plant, how many of
  the offspring will have straight roots?
• Say what? First of all, this problem doesn't make
  it easy. Start by assigning genotypes and
  phenotypes. Pick the letter of the dominant
  trait. B for bent
• BB bentBb bentbb straightNow use the key
  to figure out your parents. In this case you have
  a straight root plant (bb) crossed with a
  heterozyous bent plant (Bb). Once you've figured
  that out, the cross is simple!

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Incomplete dominance

• Some alleles are neither dominant nor recessive,
  and many traits are controlled by mulitple
  alleles or multiple genes
• Incomplete dominance is when one allele is not
  completely dominant over another results in
  blended traits

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Incomplete Dominance

• There is no dominant or recessive, the
  heterozygous condition results in a "blending" of
  the two traits. Example Snapdragons can be red,
  white, or pink (heterozygous)

R allele for red flowers W allele for white
flowers red x white ---gt pink RR x WW ---gt 100
RW
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Now you try

• 1. A cross between a blue blahblah bird a white
  blahblah bird produces offspring that are
  silver.  The color of blahblah birds is
  determined by just two alleles. a) What are the
  genotypes of the parent blahblah birds in the
  original cross? b) What is/are the genotype(s)
  of the silver offspring? c) What would be the
  phenotypic ratios of offspring produced by two
  silver blahblah birds?

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• 1. A cross between a blue blahblah bird a white
  blahblah bird produces offspring that are
  silver.  The color of blahblah birds is
  determined by just two alleles. a) What are the
  genotypes of the parent blahblah birds in the
  original cross?
•   Since there are only 2 alleles three
  phenotypes (blue, white, silver), we must be
  dealing with incomplete dominance.  So the blue
  parent is homozygous blue (BB) the white parent
  is homozygous white (WW).
• b) What is/are the genotype(s) of the silver
  offspring? 
• The silver offspring are hybrids (BW), one blue
  allele one white allele, neither one dominating
  the other.  Instead, we get a blending of blue
  white, i.e. silver. c) What would be the
  phenotypic ratios of offspring produced by two
  silver blahblah birds?    silver x silver BW
  x BW
• The p-square would look like what you see here.

As you can see, 25 (1/4) of the offspring are
homozygous white (WW), 25 (1/4) are homozygous
blue (BB), 50 (2/4) are hybrid therefor have
the silver phenotype.
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Codominance

• Both alleles attribute to the phenotype
• Trait is not blended (as in the pink snapdragons)
  rather they are both expressed example would be
  spotted coats
• R allele for red flowers W allele for white
  flowers
• red x white ---gt red white spotted RR x WW
  ---gt 100 RW

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Now you try

• 1. A cross between a black cat a tan cat
  produces a tabby pattern (black tan fur
  together). a) What pattern of inheritence does
  this illustrate? b) What percent of kittens
  would have tan fur if a tabby cat is crossed with
  a black cat?

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• a) What pattern of inheritence does this
  illustrate?  Codominance, two phenotypes
  together at the same time
• b) What percent of kittens would have tan fur if
  a tabby cat is crossed with a black cat?   Tabby
  cats are the hybrids (because they have both
  colors) a black cat must be homozygous black. 
  So the cross for this problem is BB (black) x BT
  (tabby).
• The results show that 50 of the offspring will
  be BB (black) 50 will be tabby (BT).  So to
  answer the question, 0 of the kittens will be
  tan.

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Multiple Alleles

• Genes which have more than two alleles does not
  mean that the individual has more than two, just
  means that more than two possiblities exist in
  the population. Examples include different color
  coats, blood types in humans
• Blood type in humans is controlled by three
  alleles A, B, and O

Phenotype Genotype
A AA or AO
B BB or BO
AB AB only
O OO only
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Examples of Blood type crosses

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Polygenic Traits

• Traits controlled by two or more genes
• Wide variety of phenotypes
• Example skin color in humans

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Punnett Squares Dihybrid cross

• Monohybrid crosses are used to determine only ONE
  trait.
• Dihybrid crosses involve TWO traits

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Dihybrid crosses

• Crosses that involve 2 traits
• For these crosses your punnet square needs to be
  4x4
• In any case where the parents are heterozygous
  for both traits (AaBb x AaBb) you will get a
  9331 ratio.

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Now you try

• If you cross other combinations, you will need to
  do a square.
• Try RrYy x rryy

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Meiosis Warm Up 1 pg. 43 HonorsPg. 41 regulars

1. What is the main goal of meiosis?
2. What is a gamete?
3. How many cells are produced through mitosis?
4. How many cells are produced through meiosis?
5. 2n30, what is the haploid number?

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Did you know?

• A group of ravens is called a murder.
• A group of bears is called a sleuth.
• Twelve or more cows is called a flink.
• A baby oyster is called a spat.
• A group of unicorns is called a blessing.
• A group of kangaroos is called a mob.

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Did you know?

• By some unknown means, an iguana can end its own
  life.

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Did you know?

• It was discovered on a space mission that a frog
  can throw up. The frog throws up its stomach
  first, so the stomach is dangling out of its
  mouth. Then the frog uses its forearms to dig
  out all of the stomachs contents and then
  swallows the stomach back down again.

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Did you know?

• The woodland frog is the only animal able to
  survive being completely frozen. These frogs
  live north of the arctic circle and can be frozen
  for weeks their cells dont freeze but the
  water outside their cells does. The heart can
  also stop, but once the temperature rises they
  come back to life

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Did you know?

• The bagpipe was originally made from the whole
  skin of a sheep.

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Did you know?

• More people are killed annually by donkeys than
  in airplane crashes.

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Did you know?

• When a horned toad is angry, it squirts blood
  from its eyes.

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Did you know?

• The average garden-variety caterpillar has 248
  muscles in its head.

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Chapter 14 Human Genome