CHARACTERISTICS OF LIFE

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CHARACTERISTICS OF LIFE
All Living Things reproduce!!!!!
All Living Things Have DNA!!!!
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Cladogram
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WHY ARE WE ALL DIFFERENT?
We all inherited different genes from our parents
which determines our traits.
Heredity Passing on of traits from parents to
offspring.
23 chromosomes from each parent.
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Autosomal vs. Sex Chromosomes
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• ALL OF THE TRAITS THAT MENDEL STUDIED WERE
  AUTOSOMAL TRAITS. THAT IS WHY PEA PLANT WAS AN
  EASY STUDY. NO WEIRD TRAITS LIKE BLENDING!!!

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Genes Pieces of DNA that carry
heredity instructions and are passed from parents.
Traits A distinguishing characteristic that is
passed from parents to offspring.
Genetics Study of heredity(passing on of genes)
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JOHANN Gregor Mendel was born July 22, 1822.
Mendel became a friar at the Augustinian
monastery in Brno, Czechoslovakia. From 1868
until his death, Mendel was the abbot of the
monastery. Mendel was experimenting with
flowers in the monastery's gardens. He wondered
how traits were passed from parent to offspring.
He studied the relations between parents and
children with mathematical symbols.
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Father of Modern Genetics

• The first person to trace the characteristics of
  successive generations of a living thing

• He was not a world-renowned scientist of his day.
• Rather, he was an Augustinian monk who taught
  natural science to high school students.

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Family

• Second child of Anton and Rosine Mendel
• They were farmers in Brunn
• They couldnt afford for him to attend college
• Gregor Mendel then attended the Augustinian
  Monastery and became a monk

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The Monastery Garden with the greenhouse
whichGregor J. Mendel, O.S.A., had built in
1870. Its appearance before 1902.Courtesy of
Villanova University Archives.
Gregor J. Mendel, O.S.A., experimental garden
(35x7 meters) in the grounds of the Augustinian
Monastery in Old Brno.Its appearance before 1922.
Courtesy of Villanova University Archives.
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The Birth of the idea Heredity

• On a walk around the monastery, he found an
  atypical variety of an ornamental plant.
• He took it and planted it next to the typical
  variety.
• He grew their progeny side by side to see if
  there would be any approximation of the traits
  passed on to the next generation.
• This experiment was "designed to support or to
  illustrate Lamarck's views concerning the
  influence of environment upon plants.

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GREGOR MENDAL
He chose to study 7 different traits,only one at
a time, so he could understand the mathematical
results.(tall, flower color and position, pod
color and shape, etc.)
He learned that each plant had two genes for each
trait. One from each parent.
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He Argued!!!!

• Parents pass on their offspring heritable
  traits(genes) SO two alleles for every trait. One
  from each parent!!!
• Genes retain their individuality. There is no
  blending.

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Why Did He Chose Peas?

• Short generation times
• Large number of offspring
• Many different traits(varieties)

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Why did Mendal work with peas?

• Good choice for environment of monastery(food)
• Network provided unusual varieties for testing-
  several traits.
• Obligate self-pollination reproductive system
• Crosses easy to document
• Short life cycle
• Easy to track he traits.

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Character vs. trait

• Character heritable trait varies that varies
  among individual. Hair color, eye color, etc
• Trait Variant for a character brown , black,
  blonde hair

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Self- pollination Vs. Cross Pollination

• Self pollination plant pollinates itself.
  Peas do this. Mendel could decide on the test
  crosses.
• Cross pollination Mendel crossed one plant with
  another by taking pollen from one type of plant
  and placing it on the other.

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Mendel cross-pollinated pea plants

• He cut away the male parts of one flower, then
  dusted it with pollen from another
• He found that the plants' respective offspring
  retained the essential traits of the parents, and
  therefore were not influenced by the environment.

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Mendels 4 Conclusion

• There are alternative versions of gene that
  account for variations in inherited characters.
• Alleles Alternate versions of a gene!!!

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Mendels 4 Conclusion

• For each character, an organism inherits two
  alleles. They can be the same or different.
• Homozygous identical alleles
• Heterozygous two different alleles.

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Mendels 4 Conclusion

• If the 2 alleles of an inherited pair differ,
  then one determines the organisms appearance.
  It is called DOMINANT.
• Recessive no affect on organism unless dominant
  is not present.

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Mendels 4 conclusions

• A sperm or egg carries only one allele for each
  inherited character because allele pairs separate
  from each other during gamete formation.
• Law of segregation Sperm and egg carries only
  one allele which separate during meiosis.

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MENDALS EXPERIMENT
PART 1- He bred a pure tall pea plant with a
pure short pea plant. ALL the offspring
were TALL. TT X tt Tt
PART 2 - F1 He crossed 2 of the offspring from
the above cross. Results 75 Tall 25
Short Tt X Tt TT, Tt, tt
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Mendelian genetics

• Character (heritable feature, i.e., fur color)
• Trait (variant for a character, i.e., brown)
• True-bred (all offspring of same variety)
• Hybrid (crossing of 2 different true-breds)
• P generation (parents)
• F1 generation (first filial generation)

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Parent Generation
F1 Generation
F2 Generation, 31 ratio
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Three Conclusions to His Research

• Principle of Dominance and Recessiveness
• One allele in a pair may mask the effect of the
  other
• Principle of Segregation
• The two alleles for a characteristic separate
  during the formation of eggs and sperm
• Principle of Independent Assortment
• The alleles for different characteristics are
  distributed to reproductive cells independently
  of the other genes on the chromosome.

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Independent Assortment
This means all gametes will be different!

• Chromosomes separate independently of each other

B F
Bb Ff
b f
Bb Ff
B f
Bb Ff
B F
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Independent Assortment

• Genes for different traits can segretate
  independently during the formation of gametes
  without influencing eachother
• Question How many gametes will be produced
  for the following allele arrangements?
• Remember 2n (n of heterozygotes
• 1. RrYy
• 2. AaBbCCDd
• 3. MmNnOoPPQQRrssTtQq

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Mendals Death

• Died in 1884 of Nephritis(kidney inflammation).
  After his death, his papers were burnt by his
  abbott because they went against beliefs of the
  times.
• His work was lost for 50 years!!

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Genetic vocabulary.

• Punnett square
• Gene point on a chromosome that controls the
  trait
• Allele an alternate form of a gene A or a
• Homozygous identical alleles for a character
• Heterozygous different alleles for a gene
• Phenotype physical traits
• Genotype genetic makeup
• Testcross breeding of a recessive homozygote X
  dominate phenotype (but unknown genotype)

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Vocabulary

• Diploid Full number of chromosomes in a somatic
  cell
• Haploid Half number of chromosomes in a gamete.

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Dominant and Recessive alleles

• Dominant alleles upper-case
• a. homozygous dominant
• (BB Brown eyes)
• Recessive alleles lower case
• a. homozygous recessive
• (bb blue eyes)
• b. Heterozygous (Bb Brown eyes)

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Dominant gene Stronger of the two traits and
masked(hides) the recessive trait. Recessive gene
Weaker trait.
For these reasons, he is called the Father of
Genetics.
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GENETICS RULES
GENETIC SYMBOLS
Use symbols to represent different forms of
a gene.
Capital Letters Represents dominant trait.
Lower Case Letters Represents recessive trait.
Examples- B Brown eyes b blue eyes
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GENETIC RULES
Every organism has TWO forms of every gene. One
from each parent. Each form is called an ALLELE.
You could have got a blue eye gene from mom and
a brown eye gene from dad.
Examples Bb, WW, gg, Rr
An organism can have the same gene for the trait
or they can have two different genes.
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If the genes are the same, then they are called
HOMOZYGOUS or purebred.
Examples aa(one antenna), AA(2 antenna),
LL(different colored legs), ll(clear legs),
TT(curly Tail), tt(straight tail)
If the genes are different, then they are called
HETEROZYGOUS or hybrid
Examples Aa(2 antenna), Ll(different color
leg), Tt(curly tail)
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Phenotype vs. Genotype

• Outward appearance
• Physical characteristics
• Examples
• 1.Brown eyes 2.blue eyes

• Arrangement of genes that produces the phenotype
• Exmple
• 1. TT, Tt
• 2. tt

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GENETIC PROBABILITY
Mendal crossed yellow and green pea plants and
discovered that 1 out of 4 were green.

He was using probability.
Probability The possibility or likelihood
that a particular event will occur.
Used to predict the results of genetics crosses.
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The squares contain the gene combinations that
could occur in the cross.
The genotype is the letter combination or gene
combinations in the squares. Example Tt, Aa,
bb,or Ll
The phenotype is the actual appearance of the
organism. Example curly tail, 2 antennas, 3
body Segments, different color legs
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PUNNETT SQUARES
A Punnett square is a special chart used to show
the possible gene combinations in a cross
between 2 organisms.
Developed by an English genetists by the name of
Reginald Punnett.
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5 Steps of Punnett Square

1. Determine the genotypes of parents.
2. Set up your Punnett Square. Dads genotype on top
   and Moms on side.
3. Fill in squares by combining sperm with egg.
4. Write out possible combos(genotype).
5. Determine phenotype ratio.

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How does a Punnett Square Work?
1. Draw a square and divide it into 4 sections.
2. Write the gene pairs across the top of the
box, then the other down the side 3. In each
box, place the correct gene to see the possible
combinations.
Each square represents a 25 possibility of
getting that trait.
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PARTS OF A PUNNETT SQUARE
Male Genes
Female Genes
Offspring Combinations
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Cross between homozygous dominant and recessive.
Tt
Tt
Tt
Tt
What are the percent of the offspring? What are
the genotypes? What are the phenotypes?
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Cross between two heterozygous parents.
TT
Tt
tt
Tt
What are the percentages of offspring? What are
the genotypes? What are the phenotypes?
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Mathematical Computations
In a Punnett Square where both parents are
Hybrids the percents are listed below 25
purebred(homozygous) black BB
50 hybrid(heterozygous) black - Bb
25 purebred(homozygous) white - bb
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of same genotype as parents -
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of same phenotype as parents -
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What about 2 Traits?

• BbTt x BbTt
• The Gametes contain one of each of the alleles.
  (BT).
• Each of the offspring contain four alleles
  exactly like the parents.(BbTt).
• Notice the number of possible offspring has
  increased.
• The phenotypic ratio is 9331

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Steps of Dihybrid Cross
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Dihybrid Cross
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Dihybrid Cross
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Dihybrid Cross
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Dihybrid Cross

• Example cross between round and yellow
  heterozygous pea seeds.
• R round
• r wrinkled
• Y yellow
• y green

RrYy x RrYy
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Genetics Beyond Mendel

• Sex linked
• Incomplete dominance
• Codominance
• Pedigrees

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Incomplete Dominance

• One allele is not completely dominant over
  another. THEY BLEND TOGETHER!!

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INCOMPLETE DOMINANCE
Sometimes, you may notice that traits can blend
Together. The blending of two traits is call
incomplete dominance. Two capital letters are
used. For example, from baby marmellow RY
orange nose, RR red nose, and RY yellow
nose Examples palomino in horses, pink color
in flowers are red and white combined.
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Cat Examples

• Black cat mated to a white cat can get a gray
  cat!!!

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What is meant by MULTIPLE ALLELES?

• A trait that is controlled by more than two
  alleles is said to be controlled by multiple
  alleles
• Traits controlled by multiple alleles produce
  more than three phenotypes of that trait.
• Codominance situation where both alleles are
  expressed.

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Multiple Alleles and Codominance

• Ex )Blood type
• Blood type A and B are co-dominant, while O is
  recessive.
• Forms possible blood types of A, B, AB, and O.

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Codominance

• Both alleles are expressed
• 1. type A IAIA or IAi
• 2. type B IBIB or IBi
• 3. type AB IAIB
• 4. type O ii

Black cow white cow spotted cow
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Blood Also Shows Codominance
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Where are Disorders Located?

• Autosomal chromosomes 1 - 22
• The disorder is caused by a gene or
  nondisjunction of chromosomes 1 - 22.
• Sex Linked disorders Located on the X or Y
  chromosomes.

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Sex Linked Genes

• Sex Linked Traits or Disorders - The X and Y
  chromosomes carry the genes that determine gender
  traits so the genes located on X and Y are called
  sex linked.
• X 1098 genes
• Y 26 genes much smaller!!!

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Sex Linked Genes

• The genes that are on the X are expressed in the
  phenotype of the male because it is the only gene
  they carry. If the gene is a recessive for a
  disorder, the male will have the disorder.
• Ex hemophilia, duchene muscular, fragile-X
  syndrome, high blood pressure(some), night
  blindness, and red-green color blindnesss.

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Sex-Linked Inheritance

• Traits that are only found on the X chromosome
• Colorblindness and Hemophilia are examples of
  sex-linked traits.
• These genes are recessive and found only on the X
  chromosome.

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How Would a Female Have a Sex Linked Disorder?

• She would have to receive a recessive gene from
  both parents.

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Queen Victoria of England

• Carrier of hemophilia
• X-linked traits to one of her sons. He died but
  all of her daughters were carriers.
• They married into the Russia royal families and
  spread it to the Russian royality.
• By 20th century, 20 of her descendants had
  hemophilia.

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History

• Her daughter Alexandra married Tsar Nicholas of
  Russian. Finally had a son Alexei. He had
  hemophilia. He was the only son and only heir to
  become Tsar. To keep people from learning of his
  disease, they withdrew from society. The people
  mistook this as they did not care. Alexei had
  som internal bleeding and a man by the name of
  Rasputin stopped the bleeding. He was let into
  the inner circle. Many thought he led to
  revolution.

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Why do Pedigrees?

• Punnett square tests work well for organisms
  that have large numbers of offspring and
  controlled matings, but humans are quite
  different
• 1. small families. Even large human families
  have 20 or fewer children.
• 2. Uncontrolled matings, often with
  heterozygotes.
• 3. Failure to truthfully identify parentage.

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Today... Pedigree analysis

• In humans, pedigree analysis is an important tool
  for studying inherited diseases
• Pedigree analysis uses family trees and
  information about affected individuals to
• figure out the genetic basis of a disease or
  trait from its inheritance pattern
• predict the risk of disease in future offspring
  in a family (genetic counseling)

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Goals of Pedigree Analysis

• 1. Determine the mode of inheritance dominant,
  recessive, partial dominance, sex-linked,
  autosomal, mitochondrial, maternal effect.
• 2. Determine the probability of an affected
  offspring for a given cross.

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Basic Symbols
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More Symbols
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Today... Pedigree analysis

• How to read pedigrees
• Basic patterns of inheritance
• autosomal, recessive
• autosomal, dominant
• X-linked, recessive
• X-linked, dominant (very rare)
• Applying pedigree analysis - practice

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Sample pedigree - cystic fibrosis
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Dominant vs. Recessive

• Is it a dominant pedigree or a recessive
  pedigree?
• 1. If two affected people have an unaffected
  child, it must be a dominant pedigree D is the
  dominant mutant allele and d is the recessive
  wild type allele. Both parents are Dd and the
  normal child is dd.
• 2. If two unaffected people have an affected
  child, it is a recessive pedigree R is the
  dominant wild type allele and r is the recessive
  mutant allele. Both parents are Rr and the
  affected child is rr.
• 3. If every affected person has an affected
  parent it is a dominant pedigree.

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Assigning Genotypes for Dominant Pedigrees

• 1. All unaffected are dd.
• 2. Affected children of an affected parent and an
  unaffected parent must be heterozygous Dd,
  because they inherited a d allele from the
  unaffected parent.
• 3. The affected parents of an unaffected child
  must be heterozygotes Dd, since they both passed
  a d allele to their child.
• 4. Outsider rule for dominant autosomal
  pedigrees An affected outsider (a person with no
  known parents) is assumed to be heterozygous
  (Dd).
• 5. If both parents are heterozygous Dd x Dd,
  their affected offspring have a 2/3 chance of
  being Dd and a 1/3 chance of being DD.

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Autosomal Dominant

• Assume affected outsiders are assumed to be
  heterozygotes.
• All unaffected individuals are homozygous for the
  normal recessive allele.

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Autosomal dominant pedigrees

• Trait is common in the pedigree
• Trait is found in every generation
• Affected individuals transmit the trait to 1/2
  of their children (regardless of sex)

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Dominant Autosomal Pedigree
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Autosomal dominant traits

• There are few autosomal dominant human diseases
  (why?), but some rare traits have this
  inheritance pattern

ex. achondroplasia (a sketelal disorder causing
dwarfism)
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Assigning Genotypes for Recessive Pedigrees

• 1. all affected are rr.
• 2. If an affected person (rr) mates with an
  unaffected person, any unaffected offspring must
  be Rr heterozygotes, because they got a r allele
  from their affected parent.
• 3. If two unaffected mate and have an affected
  child, both parents must be Rr heterozygotes.
• 4. Recessive outsider rule outsiders are those
  whose parents are unknown. In a recessive
  autosomal pedigree, unaffected outsiders are
  assumed to be RR, homozygous normal.
• 5. Children of RR x Rr have a 1/2 chance of being
  RR and a 1/2 chance of being Rr. Note that any
  siblings who have an rr child must be Rr.
• 6. Unaffected children of Rr x Rr have a 2/3
  chance of being Rr and a 1/3 chance of being RR.

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Autosomal Recessive

• All affected are homozygotes.
• Unaffected outsiders are assumed to be homozygous
  normal
• Consanguineous matings are often (but not always)
  involved.

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Autosomal recessive traits

• Trait is rare in pedigree
• Trait often skips generations (hidden in
  heterozygous carriers)
• Trait affects males and females equally

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Recessive Autosomal Pedigree
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Autosomal recessive diseases in humans

• Most common ones
• Cystic fibrosis
• Sickle cell anemia
• Phenylketonuria (PKU)
• Tay-Sachs disease
• For each of these, overdominance (heterozygote
  superiority) has been suggested as a factor in
  maintaining the disease alleles at high frequency
  in some populations

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Y-Linked Inheritance

• We will now look at how various kinds of traits
  are inherited from a pedigree point of view.
• Traits on the Y chromosome are only found in
  males, never in females.
• The fathers traits are passed to all sons.
• Dominance is irrelevant there is only 1 copy of
  each Y-linked gene (hemizygous).

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X-linked recessive pedigrees

• Trait is rare in pedigree
• Trait skips generations
• Affected fathers DO NOT pass to their sons,
• Males are more often affected than females

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X-linked recessive traits
ex. Hemophilia in European royalty
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X-linked recessive traits

• ex. Glucose-6-Phosphate Dehydrogenase deficiency
• hemolytic disorder causes jaundice in infants and
  (often fatal) sensitivity to fava beans in adults

• the most common enzyme disorder worldwide,
  especially in those of Mediterranean ancestry
• may confer malaria resistance

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X-linked recessive traits

• ex. Glucose-6-Phosphate-Dehydrogenase deficiency

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X-linked dominant pedigrees

• Trait is common in pedigree
• Affected fathers pass to ALL of their daughters
• Males and females are equally likely to be
  affected

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Sex-Linked Dominant

• Mothers pass their Xs to both sons and daughters
• Fathers pass their X to daughters only.
• Normal outsider rule for dominant pedigrees for
  females, but for sex-linked traits remember that
  males are hemizygous and express whichever gene
  is on their X.
• XD dominant mutant allele
• Xd recessive normal allele

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Sex-Linked Recessive

• males get their X from their mother
• fathers pass their X to daughters only
• females express it only if they get a copy from
  both parents.
• expressed in males if present
• recessive in females
• Outsider rule for recessives (only affects
  females in sex-linked situations) normal
  outsiders are assumed to be homozygous.

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X-linked dominant diseases

• X-linked dominant diseases are extremely unusual
• Often, they are lethal (before birth) in males
  and only seen in females
• ex. incontinentia pigmenti (skin lesions)
• ex. X-linked rickets (bone lesions)

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Pedigree Analysis in real life complications
Incomplete Penetrance of autosomal dominant
traits gt not everyone with genotype expresses
trait at all
Ex. Breast cancer genes BRCA-1 and BRCA-2
many genetic tendencies for human diseases
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What is the pattern of inheritance? What are
IV-2s odds of being a carrier?
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What is the inheritance pattern? What is the
genotype of III-1, III-2, and II-3? What are the
odds that IV-5 would have an affected son?
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Sample pedigree - cystic fibrosis
What can we say about I-1 and I-2? What can we
say about II-4 and II-5? What are the odds that
III-5 is a carrier? What can we say about gene
frequency?
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III-1 has 12 kids with an unaffected wife 8
sons - 1 affected 4 daughters - 2 affected
Does he have reason to be concerned about
paternity?
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Breeding the perfect Black Lab
How do we get a true-breeding line for both
traits??
black individuals fetch well grey individuals
dont drool