Somatic cell

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Somatic cell

• Body cells other than egg or sperm

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Chromosome Number is fixed in each species
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Sexual Reproduction

• Combining the monoploid chromosomes of two
  individuals to make a new diploid organism

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sperm

• Male gamete

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egg

• Female gamete

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Pollination

• Male pollen is combined with female ovules to
  form embryo-seed

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zygote

• Fertilized egg or gamete

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meiosis

• Chromosome division for production of monoploid
  or haploid cells

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tetrad

• Chromosome arrangement in prophase of meiosis-
  homologous pairs lie side by side in synapsis

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• Gene- a single unit of inheritance
• Gene map- show the location of genes on a
  chromosome
• Gene linkage- when genes are located near each
  other on a chromosome

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Principles of Heredity

• Alternative versions of genes (alleles) account
  for variations in a trait.
• For each character, an organism inherits two
  alleles, one from each parent.
• If alleles differ, then the dominant will be
  fully expressed over the recessive.
• The two alleles segregate (separate) during
  gamete formation.
• Alleles on different chromosomes segregate
  independently of one another

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segregation

• Genes( alleles) separate on chromosomes during
  anaphase of meiosis

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Independent assortment

• Gene alleles separated independently on
  homologous chromosome during anaphase of meiosis

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Genetic recombination

• Genes come together in a random fashion as
  chromosomes pair following fertilization

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Gametes- sex cells---egg, sperm or pollen

• Monoploid or haploid
• Half of the diploid number

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allele

• An alternate form of a gene
• A a
• B b

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Alleles

• Dominant
• Yellow seeds
• Axial flowers
• Tall Plants
• Smooth seeds/Round

• Recessive
• Green seeds
• Terminal flowers
• Short Plants
• Wrinkled Seeds

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Punnet Square

• Shows a genetic cross between two individuals
  alleles

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dominant

• A gene which can express itself when in the
  presence of a recessive

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Recessive

• A gene which is unable to express itself when
  with a dominant
• Can only be expressed when homozygous recessive

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Homozygous

• Both alleles are the same either both dominant or
  both recessive

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Heterozygous

• Both of the alleles are different
• One dominant and one recessive

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Genotype

• Actual gene present
• Not visible
• AA, Aa, aa

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Phenotype

• The expression of a genotype, what is seen in the
  individual
• eye color
• hair color
• disease present

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Mendel

• Made genetics quantifiable
• Experimental crosses
• Character- detectable inherited feature
• Trait-variation of a character

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• True breeding or pure bred- always produced the
  same trait
• Hybrids produced different variants
• WHY

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Autosomal Complete Dominance
b
b

• One gene is able to dominate the other recessive
  allele
• Example all offspring express B as black fur over
  b white

B
Bb
Bb
B
Bb
Bb
All black offspring
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Autosomal Recessive Pattern
Gene is unable to express itself unless it is in
a homozygous condition.
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Incomplete dominance- heterozygotes are
intermediate in expression
B
B

B
In this cross BB results in black fur, BB
results in white fur, and BB results in gray.
BB
BB
B
BB
BB
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CODOMINANCE- each gene of the allele is expressed
iA
iA
The A,B, O Blood type shows Codominance genotypes
iAiA, iBiB, iOiO, iAiB, iAiO ,and iAiO
iAiB
iAiB
iB
iAiB
iAiB
iB
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Multiple Alleles

• In this pattern more than two alleles are
  possible for a trait.
• Blood Groups or types are an example of this
  also.

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Test Cross- used to determine the genotype of an
unknown

• If a dominant trait is expressed how could you
  tell if the individual is heterozygous or
  homozygous
• Cross the unknown with a homozygous recessive and
  if the ratio is 50/50 you can be certain the
  unknown was heterozygous

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Polygenic

• More than one pair of genes control the trait
• Genes working together
• Expression is varied
• Race is an example
• Most common form of inheritance

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Polygenic Inheritance

• Additive effect of two or more genes on
  phenotypic expression
• Phenotypic expression varies along a continuum
• Skin and eye pigmentation

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Multifactorial

• Influenced by both environment and heredity.

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• Sex or X linked
• Inheritance- genes that are carried on the X
  chromosome

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Sex-Linked Disorders

• Genes carried on the X chromsome
• Males only have one- more likely to have trait
• Females can be carriers
• Most important diseases are recessive
• Red-green color blindness, hemophilia

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Nondisjunction

• Chromosomes fail to separate properly during
  meiosis.
• Age is a factor
• results in Downs Syndrome
• results in Turners Syndrome
• results in Klinefelters Syndrome

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Aneuploidy

• Too many or too few chromosomes.

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Mutations-any sudden change in genetic material
that can be passed on to the next generation
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Deletion

• A fragment of a chromosome is missing
• ex. Cri-du-chat syndrome or deletion of the short
  arm of the b group
• chromosome results in a sever form of autism

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Translocation- exchange of genetic material from
one location on a chromosome to another
non-homologous chromosome.
Ex. D_G translocation causes a form of
Downs Syndrome
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Chromosomes

• Autosomes
• First 44
• Same for male as female

• Sex Chromosomes
• Determine sex
• XX or XY

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Mutations-any sudden change in genetic material
that can be passed on to the next generation
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Translocation- exchange of genetic material from
one location on a chromosome to another
non-homologous chromosome.
Ex. D_G translocation causes a form of
Downs Syndrome
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• Amniocentesis-withdraw amniotic fluid ( amniotic
  sac )14th-16th week

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• chorionic vili sampling biopsy remove a piece of
  chorionic (fetal/maternal) tissue

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Ultrasonography

• Use of Ultrasound, sonar to determine shape and
  position of fetus