MENDELIAN AND modern genetics

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MENDELIAN AND modern genetics
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Vocabulary

• Alleles
• Dominant
• Gene
• Genetics
• Genotype
• Heterozygous
• Homozygous
• Incomplete Dominance
• Phenotype
• Recessive

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What is genetics?

• The study of heredity.

• Transferring information from 1 generation to the
  next.

Who is Gregor Mendel?
1. A monk, gardener, scientist 19th century
2. Conducted experiments of heredity using pea
plants
3. Developed the principles of dominance,
segregation, independent assortment
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More about Gregor Mendel..
4. He really loved math and statistics (you may
ask yourself why??!!)
5. Mendel began to notice a pattern in his pea
plants.

• In each generation some of the plants looked like
  the others, but some were different! (hmmm)

• He came up with the laws of genetics.

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Why use pea plants?

• Easy to grow

• Mature quickly

• Lots of offspring

• Only 2 alleles/gene

What did he do first?

• Carried out a controlled, scientific study.

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POSSIBLE PEA PLANT ALLELES
Seed Shape
Flower Position
Seed Coat Color
Seed Color
Pod Color
Plant Height
Pod Shape
Axial
Round
Yellow
Gray
Smooth
Green
Tall
Wrinkled
Green
White
Constricted
Yellow
Terminal
Short
Round
Yellow
Gray
Green
Smooth
Axial
Tall
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Mendels Hypothesis

• There are alternative forms of the same gene
  alleles
• Each organism has 2 alleles for each trait one
  from each parent heterozygous and homozygous
• Dominant alleles can mask the expression of the
  lesser allele dominant and recessive
• Alleles segregate during gametogenesis. Each
  gamete has only 1 allele law of segregation

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How many copies of each gene?

• 2 -- 1 gene from mom 1 gene from dad

Then what is an allele?

• The trait (characteristic) found on a gene.

Where do they come from?

• 1 gene from mom 1 gene from dad

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2 alleles for color in pea plants

• Green G

• yellow g

2 alleles for height in pea plants

• Tall T

• short t

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What does dominant mean?

• One allele is more powerful than the other.
• TT or Tt

What does recessive mean?

• One allele is overpowered by the other.
• tt

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What does homozygous mean?

• Both alleles from the parents are the same.
• Either TT or tt

What does heterozygous mean?

• The alleles from the parents are different.
• Tt

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What is genotype?

• The genetic makeup of an individual.
• The letters (ex TT, Tt, tt)

What is phenotype?

• The physical makeup of an individual.
• The description (ex Tall or
  Short)

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Name some possible genotypes and phenotypes for
the height of a pea plant
Genotype Phenotype
Tall
TT
Tt
Tall
short
tt
Mendels law of dominance
The dominant trait overpowers the recessive.
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Law of Segregation and Recombination
Mendel explained that factors which occur in
pairs are separated from each other during
gamete formation and recombined at fertilization.
Law of Independent Assortment
Mendel concluded that different traits are
inherited independently of one another (genes
for different traits are separated distributed
to gametes independently of one another when
they are on different chromosomes).
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Phenotypes Brown white
What will be the percentage of Phenotypes?
What will be the percentage of Genotypes?
B
b


Genotypes BB Bb bb
B
b
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ANSWER
Phenotypes 75 Brown 25 white
B
b
B B B b
B b b b
B
Genotypes 25 BB 50 Bb 25 bb
b
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What is a test cross?

• Used to find out the genotype of an unknown
  individual.

• Ex a black dogis it pure or hybrid?
• BB or Bb? (BBlack bbrown)

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What is incomplete dominance?

• AKA Intermediate Inheritance

• The result is a blending of traits.

What is codominance?

• Both alleles are equally dominant

• The result is a streaking affect.

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Test Cross Consider a phenotypically tall
organism. What is its genotype? Is it TT or
Tt? To answer this question, you would do a test
cross definition By observing the
phenotypes of the offspring, we can trace back to
the genotype of the parent If the genotype
If the genotype of the
parent was of the parent was homozygous (TT),
heterozygous (Tt), all the offspring
are tall 50 of the offspring are
tall and 50 are short

when an organism showing the dominant trait is
crossed with a pure recessive to determine if
that dominant organism is homozygous or
heterozygous
T t
Tt tt
Tt tt
t t
T T
Tt Tt
Tt Tt
t t
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What are multiple alleles?

• When there are more than 2 alleles for a gene in
  an entire population.

• Ex hair color, eye color, blood type

Alleles A B O
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Multiple Alleles when there are more than 2
(multiple) alleles for a trait example
Human blood groups have 3 alleles IA where
I is dominant IB and i is recessive i t
he possible combinations of these 3 blood alleles
are as follows





Blood type genotype Phenotype A B AB O
IAIA or IAi
IBIB or IBi
IAIB
ii
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Polygenic Inheritance

• Poly Many

• Genic Genes

• More than one gene influences a single trait

• Ex) Height skin color

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Does the environment influence the expression of
a phenotype?

• Available Nutrition
• Affects growth health
• Exercise / Activity
• Affects growth health
• Temperature
• Affects many characteristics
• Skin color, health, etc

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Mendels Principles
Meiosis explains Mendels principles
Chromosome Theory of Inheritance

• Genes are located on chromosomes
• The behavior of chromosomes during meiosis
  fertilization explains inheritance patterns

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What is gene linkage?

• When 2 genes are found on the same chromosome.
  (Genes A-E are linked)

What does this tell you about inheritance of
traits A E?
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Crossing over

• To recombine the alleles when the genes are far
  apart
• The exchange of genetic material between
  homologous chromosomes

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How is gender determined?

• It is a 50/50 chance to get a boy or a girl

Girls XX Boys XY
XX x XY Mom x Dad
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Punnett Squares Gender Determination
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Sex Determination there are 2 types of
chromosomes sex chromosomes (1 pair)
autosomes (all other pairs) in each
diploid human cell this looks like sex
chromosomes 1 pair autosomes 22
pairs 23 homologous pairs or
_____chromosomes The genotype XX represents a
_______________ The genotype XY represents a
_______________ The sex of an individual is
determined by the _______________ at the
time of________________________. The human
egg contains only ______ chromosomes while the
human sperm can contain either ______ or
_______ chromosomes.
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female
male
sperm
fertilization
X
X
Y
X X
Every time a man and woman have a child there is
a ________ chance it will be a boy or girl.
XX XX
XY XY
X Y
50 / 50
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Sex Linkage sex-linked traits are caused by
genes found on the X chromosome sex-linked
traits are recessive since they are recessive,
fewer females are afflicted with these
traits because they have another X
chromosome which is dominantly normal.
Males have only one X chromosome so when they
have a sex-linked gene, theyll display the
trait. the genotype of a sex-linked trait is
represented as_________ females with one
gene for the trait ( X X ) are
called_____________ examples of sex-linked
traits hemophilia, color- blindness
X or X (can also be represented as Xh, where h
is the trait)
carriers
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Pedigree charts used to show he presence or
absence of a certain trait
in families through several
generations. theyre kind of like a genetic
family tree
Bb
Bb
Bb
Bb
bb
bb
bb
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Monohybrid Cross

• What is a hybrid? Offspring of parents that have
  different forms of a trait- ex). Tall and short.

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Dihybrid Cross- cross with two traits
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Modern Genetics
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(not in notes)
How is Genetics used in everyday life?

• Name some foods that you eat.

• How many of them do you think are genetically
  altered?

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• Not in notes
• Genetically Modified Foods

What are the Benefits?
What are the Risks?
Believe It or Not,
YOU are the generation
that will decide
how to use this technology!!!!
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Genome

• Is the complete set of genetic material in an
  organism- the order of the bases in the DNA
• Can fit into the nucleus of a single cell because
  of the packing system

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• The Human Genome Project

• Mapping the sequence of nucleotides
• ACCGTTTAACCGTATAGGACCACT
• for the entire amount of DNA in our cells

• This info is then entered into a computer database

• Researchers then compare the data to find genes,
  evolutionary links, and more

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• Recombinant DNA
• Combines genes from different sources into a
  single DNA molecule

• Why is this useful?
• Organisms can be modified to produce products
  that benefit everyone

• Examples
• Bacteria that could clean up oil spills or toxic
  waste sites
• Vaccine production
• Insulin production Pure human form
• 4. Gene cloning
• 5. Genetically modified plants and animals

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• Biotechnology
• The use of organisms to perform practical tasks
  for humans- to analyze and manipulate the genomes
  of organisms

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• Plasmids
• A small circular DNA molecule separate from the
  much larger bacterial chromosome.

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• Plasmids BIG DEAL
• What can they be used for?

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• Restriction Enzymes
• These are tools used to cut DNA in specific
  locations

AAAATTCCGAGACGAATTCAATACGAATTCGGGTTAAACCCCCGAATTCG
GGCCTCA

• How many times do you see GAATTC?
• Draw a line between the GA (in these sections)

• So how many sections of DNA do you have now?

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The Good With the Bad The manipulation of DNA
allows scientists to do some interesting things.
Scientists have developed many transgenic
organisms, which are organisms that contain genes
from other organisms.
Recently, scientists have removed a gene for
green fluorescent protein from a jellyfish and
tried to insert it into a monkey.
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1. Transgenic animals are often used in
research.

• What might be the benefit to medical research of
  a mouse whose immune system is genetically
  altered to mimic some aspect of the human immune
  system?

2. Transgenic plants and animals may have
increased value as food sources.

• What might happen to native species if transgenic
  animals or plants were released into the wild?

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Nucleic Acid Probe

• A complimentary strand of DNA that has been
  radioactively labeled

Lets say we want to find the sequence TAGGCT
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What is it How is it done When?
Plants
Animals
Animal Cloning
Use of plasmids from the soil to introduce new
genes

• To delay ripening
• Improved nutritional content
• Resistance to spoilage or disease

To improve the characteristics of the plants

• Extract an egg cell
• Sperm fertilizes the egg
• Desired gene is injected into the fertilized egg

Same as plants- better quality wool Or to
mature in a shorter time

• To make vaccines
• Growth hormones

The nucleus from a single cell replaces the
nucleus of an unfertilized egg from another
animal- the egg develops into an animal that has
the same genome as the nuclear donor
Cloning can offer the potential to mass produce
an animal
Entire genomes can be cloned Dolly
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Polymerase Chain Reaction (PCR)

• A method for amplifying a DNA base sequence.

How?

• The newly synthesized DNA strands can serve as
  templates for making more DNAamplifying the
  desired sequence.

When?
Can detect viral genes infected with the virus
that causes AIDS
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PCR
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Genetic Markers- particular stretches of DNA
that are variable among individuals Ex.) DNA
fragments that include certain disease alleles
have distinct genetic markers
DNA fingerprinting- a particular banding
pattern produced by your restriction fragments
- Unless you have an identical twin, it is
unlikely to have the exact same fingerprint
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Gel Electrophoresis

• A method of separating large molecules (such as
  DNA fragments or proteins).

• How?
• An electric current is passed through a medium
  containing the mixture
• Each kind of molecule travels through the medium
  at a different rate, depending on its electrical
  charge and size.
• Separation is based on these differences.

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Gel Electrophoresis
DNA plus restriction enzyme
Power source
Longer fragments
Mixture of DNA fragments
Shorter fragments
Gel
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Stem cells

• -Cells with the potential to turn into an
  undifferentiated cells
• -Have the potential into various types of cells

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DNA Sequencing

• Any lab technique used to find out the sequence
  of nucleotide bases in a DNA molecule or fragment.

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DNA Sequencing
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Gene Therapy

• The process of introducing new genes into the DNA
  of a person's cells to correct a genetic disease
  or flaw

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Making Recombinant DNA
Section 13-3
Gene for human growth hormone
Recombinant DNA
Gene for human growth hormone
DNA recombination
Human Cell
Sticky ends
DNA insertion
Bacterial Cell
Plasmid
Bacterial cell containing gene for human growth
hormone
Bacterial chromosome
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Flowchart
Cloning
A body cell is taken from a donor animal.
An egg cell is taken from a donor animal.
The nucleus is removed from the egg.
The body cell and egg are fused by electric shock.
The fused cell begins dividing, becoming an
embryo.
The embryo is implanted into the uterus of a
foster mother.
The embryo develops into a cloned animal.
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Cloning of the First Mammal
A donor cell is taken from a sheeps udder.
Donor Nucleus
These two cells are fused using an electric shock.
Fused Cell
Egg Cell
Cloned Lamb
The nucleus of the egg cell is removed.
An egg cell is taken from an adult female sheep.
Embryo
The fused cell begins dividing normally.
The embryo develops normally into a lambDolly
The embryo is placed in the uterus of a foster
mother.
Foster Mother
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